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1 25 Accessing Databases with JDBC 1992-2007 Pearson Education, Inc. All rights reserved. 2 25.1 25.2 25.3 25.4 25.5 Introduction Relational Databases Relational Database Overview: The books Database SQL 25.4.1 Basic SELECT Query 25.4.2 WHERE Claus 25.4.3 ORDER BY Claus 25.4.4 Merging Data from Multiple Tables: INNER JOIN 25.4.5 INSERT Statement 25.4.6 UPDATE Statement 25.4.7 DELETE Statement Instructions for installing MySQL and MySQL Connector/J 1992-2007 Pearson Education, Inc. All rights reserved. 3 25.6 25.7 Instructions for Setting Up a MySQL User Account Creating Database book in MySQL 25.8 Manipulating Databases with JDBC 25.8.1 Connecting to and Querying a Database 25.8.2 Querying the books Database 25.9 RowSet Interface 25.10 Java DB/Apache Derby 25.11 PreparedStatements 25.12 Stored Procedures 25.13 Transaction Processing 25.14 Wrap-Up 25.15 Web Resources and Recommended Readings 1992-2007 Pearson Education, Inc. All rights reserved. 4 25.1 Introduction Database – Collection of data DBMS – Database management system – Storing and organizing data SQL – Relational database – Structured Query Language 1992-2007 Pearson Education, Inc. All rights reserved. 5 25.1 Introduction (Cont.) RDBMS – Relational database management system – MySQL - Open source - Available for both Windows and Linux - dev.mysql.com/downloads/mysql/4.0.hml JDBC – Java Database Connectivity – JDBC driver - Enable Java applications to connect to database - Enable programmers to manipulate databases using JDBC 1992-2007 Pearson Education, Inc. All rights reserved. 6 Software Engineering Observation 25.1 Using the JDBC API enables developers to change the underlying DBMS without modifying the Java code that accesses the database. 1992-2007 Pearson Education, Inc. All rights reserved. 7 25.2 Relational Databases • Relational database – Table • Rows, columns – Primary key • Unique data • SQL queries – Specify which data to select from a table 2005 Pearson Education, Inc. All rights reserved. 8 Fig. 25.1 | Employee table sample data. 1992-2007 Pearson Education, Inc. All rights reserved. 9 Fig. 25.2 | Result of selecting distinct Department and Location data from table Employee. 1992-2007 Pearson Education, Inc. All rights reserved. 10 25.3 Relational Database Overview: The books Database • Sample books database – Four tables • authors – authorID, firstName, lastName • titles – isbn, title, editionNumber, copyright, publisherID, imageFile, price • authorISBN – authorID, isbn 2005 Pearson Education, Inc. All rights reserved. 11 Column Description authorID Author’s ID number in the database. In the books database, this integer column is defined as autoincremented—for each row inserted in this table, the authorID value is increased by 1 automatically to ensure that each row has a unique authorID. This column represents the table’s primary key. firstName Author’s first name (a string). lastName Author’s last name (a string). Fig. 25.3 | authors table from the books database. 1992-2007 Pearson Education, Inc. All rights reserved. 12 authorID firstName lastName 1 Harvey Deitel 2 Paul Deitel 3 Andrew Goldberg 4 David Choffnes Fig. 25.4 | Sample data from the authors table. 1992-2007 Pearson Education, Inc. All rights reserved. 13 25.3 Relational Database Overview: The books Database (Cont.) • Foreign key – A column • matches the primary key column in another table – Helps maintain the Rule of Referential Integrity • Every foreign key value must appear as another table’s primary key value 2005 Pearson Education, Inc. All rights reserved. 14 Column Description authorID The author’s ID number, a foreign key to the authors table. isbn The ISBN for a book, a foreign key to the titles table. Fig. 25.5 | authorISBN table from the books database. 1992-2007 Pearson Education, Inc. All rights reserved. 15 authorID isbn authorID isbn 1 0131869000 2 0131450913 2 0131869000 1 0131828274 1 0131483986 2 0131828274 2 0131483986 3 0131450913 1 0131450913 4 0131828274 Fig. 25.6 | Sample data from the authorISBN table of books. 1992-2007 Pearson Education, Inc. All rights reserved. 16 Column Description isbn ISBN of the book (a string). The table’s primary key. ISBN is an abbreviation for “International Standard Book Number”—a numbering scheme that publishers use to give every book a unique identification number. title Title of the book (a string). editionNumber Edition number of the book (an integer). copyright Copyright year of the book (a string). Fig. 25.7 | titles table from the books database. 1992-2007 Pearson Education, Inc. All rights reserved. 17 isbn title editionNumber copyright 0131869000 Visual Basic How to Program 3 2006 0131525239 Visual C# How to Program 2 2006 0132222205 Java How to Program 7 2007 0131857576 C++ How to Program 5 2005 0132404168 C How to Program 5 2007 0131450913 Internet & World Wide Web How to Program 3 2004 Fig. 25.8 | Sample data from the titles table of the books database. 1992-2007 Pearson Education, Inc. All rights reserved. 18 25.3 Relational Database Overview: The books Database (Cont.) • Entity-relationship (ER) diagram – Tables in the database – Relationships among tables • Rule of Entity Integrity – Primary key uniquely identifies each row – Every row must have a value for every column of the primary key – Value of the primary key must be unique in the table 2005 Pearson Education, Inc. All rights reserved. 19 Fig. 25.9 | Table relationships in the books database. 1992-2007 Pearson Education, Inc. All rights reserved. 20 Common Programming Error 25.1 Not providing a value for every column in a primary key breaks the Rule of Entity Integrity and causes the DBMS to report an error. 1992-2007 Pearson Education, Inc. All rights reserved. 21 Common Programming Error 25.2 Providing the same value for the primary key in multiple rows causes the DBMS to report an error. 1992-2007 Pearson Education, Inc. All rights reserved. 22 Common Programming Error 25.3 Providing a foreign-key value that does not appear as a primary-key value in another table breaks the Rule of Referential Integrity and causes the DBMS to report an error. 1992-2007 Pearson Education, Inc. All rights reserved. 23 25.4 SQL • SQL keywords – SQL queries and statements 2005 Pearson Education, Inc. All rights reserved. 24 SQL keyword Description SELECT Retrieves data from one or more tables. FROM Tables involved in the query. Required in every SELECT. WHERE Criteria for selection that determine the rows to be retrieved, deleted or updated. Optional in a SQL query or a SQL statement. GROUP BY Criteria for grouping rows. Optional in a SELECT query. ORDER BY Criteria for ordering rows. Optional in a SELECT query. INNER JOIN Merge rows from multiple tables. INSERT Insert rows into a specified table. UPDATE Update rows in a specified table. DELETE Delete rows from a specified table. Fig. 25.10 | SQL query keywords. 1992-2007 Pearson Education, Inc. All rights reserved. 25 25.4.1 Basic SELECT Query • Simplest format of a SELECT query – SELECT * FROM tableName • SELECT * FROM authors • Select specific fields from a table – SELECT authorID, lastName FROM authors 2005 Pearson Education, Inc. All rights reserved. 26 authorID lastName 1 Deitel 2 Deitel 3 Goldberg 4 Choffnes Fig. 25.11 | Sample authorID and lastName data from the authors table. 1992-2007 Pearson Education, Inc. All rights reserved. 27 Software Engineering Observation 25.2 For most queries, the asterisk (*) should not be used to specify column names. In general, you process results by knowing in advance the order of the columns in the result—for example, selecting authorID and lastName from table authors ensures that the columns will appear in the result with authorID as the first column and lastName as the second column. Programs typically process result columns by specifying the column number in the result (starting from number 1 for the first column). Selecting columns by name also avoids returning unneeded columns and protects against changes in the actual order of the columns in the table(s). 1992-2007 Pearson Education, Inc. All rights reserved. 28 Common Programming Error 25.4 If you assume that the columns are always returned in the same order from a query that uses the asterisk (*), the program may process the results incorrectly. If the column order in the table(s) changes or if additional columns are added at a later time, the order of the columns in the result would change accordingly. 1992-2007 Pearson Education, Inc. All rights reserved. 29 25.4.2 WHERE Clause • specify the selection criteria – SELECT columnName1, columnName2, … FROM tableName WHERE criteria • SELECT title, editionNumber, copyright FROM titles WHERE copyright > 2002 2005 Pearson Education, Inc. All rights reserved. 30 Portability Tip 25.1 See the documentation for your database system to determine whether SQL is case sensitive on your system and to determine the syntax for SQL keywords (i.e., should they be all uppercase letters, all lowercase letters or some combination of the two?). 1992-2007 Pearson Education, Inc. All rights reserved. 31 title editionNumber copyright Visual C# How to Program 2 2006 Visual Basic 2005 How to Program 3 2006 Java How to Program 7 2007 C How to Program 5 2007 Fig. 25.12 | Sampling of titles with copyrights after 2005 from table titles. 1992-2007 Pearson Education, Inc. All rights reserved. 32 25.4.2 WHERE Clause (Cont.) •WHERE clause condition operators – <, >, <=, >=, =, <> – LIKE • wildcard characters % and _ • SELECT authorID, firstName, lastName FROM authors WHERE lastName LIKE ‘D%’ 2005 Pearson Education, Inc. All rights reserved. 33 authorID firstName lastName 1 Harvey Deitel 2 Paul Deitel Fig. 25.13 | Authors whose last name starts with D from the authors table. 1992-2007 Pearson Education, Inc. All rights reserved. 34 Portability Tip 25.2 Read your database system’s documentation carefully to determine whether your system supports the LIKE operator. The SQL we discuss is supported by most RDBMSs, but it is always a good idea to check the features of SQL that are supported by your RDBMS. 1992-2007 Pearson Education, Inc. All rights reserved. 35 25.4.2 WHERE Clause (Cont.) • SELECT authorID, firstName, lastName FROM authors WHERE lastName LIKE ‘_i%’ 2005 Pearson Education, Inc. All rights reserved. 36 authorID firstName lastName 3 Andrew Goldberg Fig. 25.14 | The only author from the authors table whose last name contains o as the second letter. 1992-2007 Pearson Education, Inc. All rights reserved. 37 25.4.3 ORDER BY Clause • Optional ORDER BY clause – SELECT columnName1, columnName2, … FROM tableName ORDER BY column ASC • SELECT authorID, firstName, lastName FROM authors ORDER BY lastName ASC – SELECT columnName1, columnName2, … FROM tableName ORDER BY column DESC • SELECT authorID, firstName, lastName FROM authors ORDER BY lastName DESC 2005 Pearson Education, Inc. All rights reserved. 38 authorID firstName lastName 4 David Choffnes 1 Harvey Deitel 2 Paul Deitel 3 Andrew Goldberg Fig. 25.15 | Sample data from table authors in ascending order by lastName. 1992-2007 Pearson Education, Inc. All rights reserved. 39 authorID firstName lastName 3 Andrew Goldberg 1 Harvey Deitel 2 Paul Deitel 4 David Choffnes Fig. 25.16 | Sample data from table authors in descending order by lastName. 1992-2007 Pearson Education, Inc. All rights reserved. 40 25.4.3 ORDER BY Clause (Cont.) •ORDER BY multiple fields – ORDER BY column1 sortingOrder, column2 sortingOrder, … • SELECT authorID, firstName, lastName FROM authors ORDER BY lastName, firstName 2005 Pearson Education, Inc. All rights reserved. 41 authorID firstName lastName 4 David Choffnes 1 Harvey Deitel 2 Paul Deitel 4 Andrew Goldberg Fig. 25.17 | Sample data from authors in ascending order by lastName and firstName. 1992-2007 Pearson Education, Inc. All rights reserved. 42 25.4.3 ORDER BY Clause (Cont.) • Combine the WHERE and ORDER BY clauses • SELECT isbn, title, editionNumber, copyright, price FROM titles WHERE title LIKE ‘%How to Program’ ORDER BY title ASC 2005 Pearson Education, Inc. All rights reserved. 43 isbn title edition -Number copy-right 0132404168 C How to Program 5 2007 0131857576 C++ How to Program 5 2005 0131450913 Internet and World Wide Web How to Program 3 2004 0132222205 Java How to Program 7 2007 0131869000 Visual Basic 2005 How to Program 3 2006 013152539 Visual C# How to Program 2 2006 Fig. 25.18 | Sampling of books from table titles whose titles end with How to Program in ascending order by title. 1992-2007 Pearson Education, Inc. All rights reserved. 44 25.4.4 Merging Data from Multiple Tables: INNER JOIN • Split related data into separate tables • Join the tables – Merge data from multiple tables into a single view – INNER JOIN • SELECT columnName1, columnName2, … FROM table1 INNER JOIN table2 ON table1.columnName = table2.column2Name • SELECT firstName, lastName, isbn FROM authors, authorISBN INNER JOIN authorISBN ON authors.authorID = authorISBN.authorID ORDER BY lastName, firstName 2005 Pearson Education, Inc. All rights reserved. 45 firstName lastName isbn firstName lastName isbn David Choffnes 0131828274 Paul Deitel 0131525239 Harvey Deitel 0131525239 Paul Deitel 0132404168 Harvey Deitel 0132404168 Paul Deitel 0131869000 Harvey Deitel 0131869000 Paul Deitel 0132222205 Harvey Deitel 0132222205 Paul Deitel 0131450913 Harvey Deitel 0131450913 Paul Deitel 0131525239 Harvey Deitel 0131525239 Paul Deitel 0131857576 Harvey Deitel 0131857576 Paul Deitel 0131828274 Harvey Deitel 0131828274 Andrew Goldberg 0131450913 Fig. 25.19 | Sampling of authors and ISBNs for the books they have written in ascending order by lastName and firstName. 1992-2007 Pearson Education, Inc. All rights reserved. 46 Software Engineering Observation 25.3 If a SQL statement includes columns with the same name from multiple tables, the statement must precede those column names with their table names and a dot (e.g., authors.authorID). 1992-2007 Pearson Education, Inc. All rights reserved. 47 Common Programming Error 25.5 Failure to qualify names for columns that have the same name in two or more tables is an error. 1992-2007 Pearson Education, Inc. All rights reserved. 48 25.4.5 INSERT Statement • Insert a row into a table – INSERT INTO tableName ( columnName1, … , columnNameN ) VALUES ( value1, … , valueN ) • INSERT INTO authors ( firstName, lastName ) VALUES ( ‘Sue’, ‘Smith’ ) 2005 Pearson Education, Inc. All rights reserved. 49 authorID firstName lastName 1 Harvey Deitel 2 Paul Deitel 3 Andrew Goldberg 4 David Choffnes 5 Sue Smith Fig. 25.20 | Sample data from table Authors after an INSERT operation. 1992-2007 Pearson Education, Inc. All rights reserved. 50 Common Programming Error 25.6 It is normally an error to specify a value for an autoincrement column. 1992-2007 Pearson Education, Inc. All rights reserved. 51 Common Programming Error 25.7 SQL uses the single-quote (') character as a delimiter for strings. To specify a string containing a single quote (e.g., O’Malley) in a SQL statement, the string must have two single quotes in the position where the single-quote character appears in the string (e.g., 'O''Malley'). The first of the two single-quote characters acts as an escape character for the second. Not escaping single-quote characters in a string that is part of a SQL statement is a SQL syntax error. 1992-2007 Pearson Education, Inc. All rights reserved. 52 25.4.6 UPDATE Statement • Modify data in a table – UPDATE tableName SET columnName1 = value1, … , columnNameN = valueN WHERE criteria • UPDATE authors SET lastName = ‘Jones’ WHERE lastName = ‘Smith’ AND firstName = ‘Sue’ 2005 Pearson Education, Inc. All rights reserved. 53 authorID firstName lastName 1 Harvey Deitel 2 Paul Deitel 3 Andrew Goldberg 4 David Choffnes 5 Sue Jones Fig. 25.21 | Sample data from table authors after an UPDATE operation. 1992-2007 Pearson Education, Inc. All rights reserved. 54 25.4.7 DELETE Statement • Remove data from a table – DELETE FROM tableName WHERE criteria • DELETE FROM authors WHERE lastName = ‘Jones’ AND firstName = ‘Sue’ 2005 Pearson Education, Inc. All rights reserved. 55 authorID firstName lastName 1 Harvey Deitel 2 Paul Deitel 3 Andrew Goldberg 4 David Choffnes Fig. 25.22 | Sample data from table authors after a DELETE operation. 1992-2007 Pearson Education, Inc. All rights reserved. 56 25.5 Instructions to Install MySQL and MySQL Connector/J • Install MySQL – Platform-specific installation requirements: • dev.mysql.com/doc/refman/5.0/en/generalinstallation-issues.html – Download your platform’s installer from: • dev.mysql.com/downloads/mysql/5.0.html • Need only the Windows Essentials package on Microsoft Windows – Follow installation instructions for your platform: • dev.mysql.com/doc/refman/5.0/en/installing. html 2005 Pearson Education, Inc. All rights reserved. 57 25.5 Instructions to Install MySQL and MySQL Connector/J • MySQL Server Instance Configuration Wizard – Click Next > then select Standard Configuration and click Next > again. – Not necessary to install MySQL as a Windows service for our examples • Uncheck Install as a Windows Service • Check Include Bin Directory in Windows PATH – Click Next > then click Execute to perform the server configuration. – Click Finish to close the wizard. 2005 Pearson Education, Inc. All rights reserved. 58 25.5 Instructions to Install MySQL and MySQL Connector/J • Install MySQL Connector/J – Must install Connector/J JDBC driver from: • dev.mysql.com/downloads/connector/j/ 5.0.html – Download mysql-connector-java-5.0.4.zip – Extract mysql-connector-java-5.0.4.zip to your hard disk into the folder mysql-connector-java-5.0.4 – Documentation for MySQL Connector/J is in connector-j.pdf in the docs subdirectory of mysql-connector-java-5.0.4 – Docs also online at dev.mysql.com/doc/connector/j/en/ connector-j.html 2005 Pearson Education, Inc. All rights reserved. 59 25.6 Instructions on Setting MySQL User Account • Set up a user account – Start database server • mysqld-nt.exe on Windows – Start the MySQL monitor • mysql –h localhost –u root – Select the built-in database mysql • USE mysql; – Add the user account jhtp7 and specify privileges • create user 'jhtp7'@'localhost' identified by 'jhtp7'; • grant select, insert, update, delete, create, drop, references, execute on *.* to 'jhtp7'@'localhost'; – Exit the MySQL Monitor • exit; 2005 Pearson Education, Inc. All rights reserved. 60 25.7 Creating Database books in MySQL • Create books database – Open Command Prompt and change to the directory containing the SQL script books.sql – Start the MySQL monitor • mysql –h localhost –u jhtp7 –p – Execute the script • source books.sql; – Exit the MySQL Monitor • exit; 2005 Pearson Education, Inc. All rights reserved. 61 25.8 Manipulating Databases with JDBC • Connect to a database • Query the database • Display the results of the query in JTable 2005 Pearson Education, Inc. All rights reserved. 62 25.8.1 Connecting to and Querying a Database •DisplayAuthors – Retrieves the entire authors table – Displays the data in the standard output stream – Example illustrates • Connect to the database • Query the database • Process the result 2005 Pearson Education, Inc. All rights reserved. 1 2 // Fig. 25.23: DisplayAuthors.java // Displaying the contents of the authors table. 3 4 import java.sql.Connection; import java.sql.Statement; 5 6 import java.sql.DriverManager; import java.sql.ResultSet; 7 8 import java.sql.ResultSetMetaData; import java.sql.SQLException; 63 Outline Imports for the JDBC classes and interfaces from package java.sql DisplayAuthors .java 9 10 public class DisplayAuthors (1 of 3 ) 11 { 12 13 // JDBC driver name and database URL static final String DRIVER = "com.mysql.jdbc.Driver"; 14 static final String DATABASE_URL = "jdbc:mysql://localhost/books"; 15 16 // launch the application 17 public static void main( String args[] ) 18 { 19 20 21 22 Connection connection = null; // manages connection Statement statement = null; // query statement ResultSet resultSet = null; // manages results 23 24 // connect to database books and query database try 25 26 { 27 28 // load the driver class Class.forName( DRIVER ); Declare a String constant that specifies the JDBC driver’s class name Declare a String constant that specifies the database URL Loads the class definition for the database driver. 1992-2007 Pearson Education, Inc. All rights reserved. // establish connection to database connection = 29 30 DriverManager.getConnection( DATABASE_URL, "jhtp7", "jhtp7" ); 31 32 33 64 // create Statement for querying database statement = connection.createStatement(); 34 35 36 37 38 39 Invokes ConnectionDisplayAuthors method createStatement to .java obtain an object // query database Use theinterface Statement object’s that implements Statement. resultSet = statement.executeQuery( executeQuery to (2 ofmethod 3) "SELECT authorID, firstName, lastName FROM authors" ); execute a query that selects all the author information // process query results Obtains the metadata ResultSetMetaData metaData = resultSet.getMetaData(); from table authors. Uses ResultSetMetaData for the ResultSet. int numberOfColumns = metaData.getColumnCount(); System.out.println( "Authors Table of Books Database:\n" );method getColumnCount to retrieve the number of columns in the ResultSet. for ( int i = 1; i <= numberOfColumns; i++ ) Obtain column System.out.printf( "%-8s\t", metaData.getColumnName( i ) ); name using method System.out.println(); getColumnName Position the ResultSet cursor to the first while ( resultSet.next() ) row in the ResultSet with method next { 40 41 42 43 44 45 46 47 48 49 50 51 for ( int i = 1; i <= numberOfColumns; i++ ) 52 53 System.out.printf( "%-8s\t", resultSet.getObject( i ) ); System.out.println(); } // end while 54 55 Initialize a Outline Connection reference called connection. } Extract the contents of one column in the current row // end try 1992-2007 Pearson Education, Inc. All rights reserved. 56 57 58 catch ( SQLException sqlException ) { sqlException.printStackTrace(); 59 60 61 62 63 } // end catch catch ( ClassNotFoundException classNotFound ) { classNotFound.printStackTrace(); } // end catch 64 65 66 67 68 69 finally // ensure resultSet, statement and connection { try { resultSet.close(); Close the Statement statement.close(); 70 71 72 connection.close(); } // end try catch ( Exception exception ) 73 74 75 { Catch SQLException, which Outline is thrown if the query execution or ResultSet process fails 65 DisplayAuthors ClassNotFoundException is .java thrown if the class loader cannot locate the driver class are closed (3 of 3 ) and the database Connection. exception.printStackTrace(); } // end catch 76 } // end finally 77 } // end main 78 } // end class DisplayAuthors Authors Table of Books Database: authorID 1 2 3 4 firstName Harvey Paul Andrew David lastName Deitel Deitel Goldberg Choffnes 1992-2007 Pearson Education, Inc. All rights reserved. 66 Software Engineering Observation 25.4 Most major database vendors provide their own JDBC database drivers, and many third-party vendors provide JDBC drivers as well. For more information on JDBC drivers, visit the Sun Microsystems JDBC Web site, servlet.java.sun.com/products/ jdbc/drivers. 1992-2007 Pearson Education, Inc. All rights reserved. 67 Software Engineering Observation 25.5 Most database management systems require the user to log in before accessing the database contents. DriverManager method getConnection is overloaded with versions that enable the program to supply the user name and password to gain access. 1992-2007 Pearson Education, Inc. All rights reserved. 68 RDBMS Database URL format MySQL jdbc:mysql://hostname:portNumber/databaseName ORACLE jdbc:oracle:thin:@hostname:portNumber:databaseName DB2 jdbc:db2:hostname:portNumber/databaseName Java DB/Apache Derby jdbc:derby:dataBaseName (embedded) jdbc:derby://hostname:portNumber/databaseName (network) Microsoft SQL Server jdbc:sqlserver://hostname:portNumber;databaseName=dataBaseName Sybase jdbc:sybase:Tds:hostname:portNumber/databaseName Fig. 25.24 | Popular JDBC database URL formats. 1992-2007 Pearson Education, Inc. All rights reserved. 69 Software Engineering Observation 25.6 Metadata enables programs to process ResultSet contents dynamically when detailed information about the ResultSet is not known in advance. 1992-2007 Pearson Education, Inc. All rights reserved. 70 Common Programming Error 25.8 Initially, a ResultSet cursor is positioned before the first row. Attempting to access a ResultSet’s contents before positioning the ResultSet cursor to the first row with method next causes a SQLException. 1992-2007 Pearson Education, Inc. All rights reserved. 71 Performance Tip 25.1 If a query specifies the exact columns to select from the database, the ResultSet contains the columns in the specified order. In this case, using the column number to obtain the column’s value is more efficient than using the column name. The column number provides direct access to the specified column. Using the column name requires a search of the column names to locate the appropriate column. 1992-2007 Pearson Education, Inc. All rights reserved. 72 Common Programming Error 25.9 Specifying column number 0 when obtaining values from a ResultSet causes a SQLException. 1992-2007 Pearson Education, Inc. All rights reserved. 73 Common Programming Error 25.10 Attempting to manipulate a ResultSet after closing the Statement that created the ResultSet causes a SQLException. The program discards the ResultSet when the corresponding Statement is closed. 1992-2007 Pearson Education, Inc. All rights reserved. 74 Software Engineering Observation 25.7 Each Statement object can open only one ResultSet object at a time. When a Statement returns a new ResultSet, the Statement closes the prior ResultSet. To use multiple ResultSets in parallel, separate Statement objects must return the ResultSets. 1992-2007 Pearson Education, Inc. All rights reserved. 75 25.8.2 Querying the books Database • Allow the user to enter any query into the program • Display the results of a query in a JTable 2005 Pearson Education, Inc. All rights reserved. 1 // Fig. 25.25: ResultSetTableModel.java 2 // A TableModel that supplies ResultSet data to a JTable. 3 import java.sql.Connection; 4 import java.sql.Statement; 5 6 import java.sql.DriverManager; import java.sql.ResultSet; 7 8 import java.sql.ResultSetMetaData; import java.sql.SQLException; 76 Outline ResultSetTable Model.java 9 import javax.swing.table.AbstractTableModel; 10 (1 of 7 ) 11 // ResultSet rows and columns are counted from 1 and JTable 12 // rows and columns are counted from 0. When processing 13 // ResultSet rows or columns for use in a JTable, it is 14 // necessary to add 1 to the row or column number to manipulate 15 // the appropriate ResultSet column (i.e., JTable column 0 is 16 // ResultSet column 1 and JTable row 0 is ResultSet row 1). 17 public class ResultSetTableModel extends AbstractTableModel 18 { 19 private Connection connection; 20 private Statement statement; Class ResultSetTableModel extends 21 private ResultSet resultSet; class AbstractTableModel, which 22 private ResultSetMetaData metaData; 23 private int numberOfRows; implements interface TableModel. 24 25 26 27 // keep track of database connection status private boolean connectedToDatabase = false; Instance variable keeps track of database connection status 1992-2007 Pearson Education, Inc. All rights reserved. 28 // constructor initializes resultSet and obtains its meta data object; 29 // determines number of rows 30 public ResultSetTableModel( String driver, String url, String Constructor username, String password, String query ) Establishes a connection throws SQLException, ClassNotFoundException to the database. 31 32 33 34 35 { Class.forName( driver ); // connect to database connection = DriverManager.getConnection( url, username, password ); 39 40 41 42 statement = connection.createStatement( ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY ); 43 44 45 // update database connection status connectedToDatabase = true; 46 47 48 49 Outline accepts five String arguments—the driver class name, the database URL, the ResultSetTable username, the password and the Model.java default query to perform 36 37 38 // create Statement to query database 77 (2 of 7 ) Invokes Connection method createStatement to create a Statement object. Indicate that connect to database is successful // set query and execute it Invokes ResultSetTableModel setQuery( query ); method setQuery to perform } // end constructor ResultSetTableModel the default query. 1992-2007 Pearson Education, Inc. All rights reserved. 50 51 // get class that represents column type public Class getColumnClass( int column ) throws IllegalStateException 52 53 { 54 Verify database Override method getColumnClass to obtain connection status IllegalStateException( "Not Connected to Database" ); ResultSetTable a Class object that represents the superclass Model.java of all objects in a particular column Java class of column if ( !connectedToDatabase ) throw new 56 57 58 // determine try 61 62 63 Outline // ensure database connection is available 55 59 60 78 { String className = metaData.getColumnClassName( column (3 of 7 ) class Obtains the fully qualified +name 1 ); for the specified column. // return Class object that represents className Loads return Class.forName( className ); 64 } // end try 65 66 67 68 69 catch ( Exception exception ) { exception.printStackTrace(); } // end catch the class definition for the class and returns the corresponding Class object. Returns the default type. 70 71 return Object.class; // if problems occur above, assume type Object } // end method getColumnClass 72 73 // get number of columns in ResultSet 74 75 76 77 78 public int getColumnCount() throws IllegalStateException { // ensure database connection is available if ( !connectedToDatabase ) method throw new IllegalStateException( Override "Not Connected togetColumnCount Database" ); 79 to obtain the number of columns in the model’s underlying ResultSet 1992-2007 Pearson Education, Inc. All rights reserved. 80 81 // determine number of columns try 82 83 { 84 } // end try 85 catch ( SQLException sqlException ) 86 87 88 { 79 Obtains the number of columns in the ResultSet. return metaData.getColumnCount(); ResultSetTable Model.java sqlException.printStackTrace(); } // end catch 89 90 Outline (4 of 7 ) return 0; // if problems occur above, return 0 for number of columns 91 92 93 } // end method getColumnCount 94 public String getColumnName( int column ) throws IllegalStateException 95 96 97 98 99 { // get name of a particular column in ResultSet // ensure database connection is available if ( !connectedToDatabase ) method getColumnName throw new IllegalStateException( "NotOverride Connected to Database" ); 100 101 // determine column name try 102 103 { 104 105 106 107 108 } // end try catch ( SQLException sqlException ) { sqlException.printStackTrace(); } // end catch to obtain the name of the column in the model’s underlying ResultSet return metaData.getColumnName( column + 1 ); Obtains the column name from the ResultSet. 109 1992-2007 Pearson Education, Inc. All rights reserved. return ""; // if problems, return empty string for column name 110 111 112 } // end method getColumnName 113 // return number of rows in ResultSet 114 public int getRowCount() throws IllegalStateException 115 116 117 118 119 { 120 121 return numberOfRows; } // end method getRowCount 122 123 124 125 126 // obtain value in particular row and column public Object getValueAt( int row, int column ) throws IllegalStateException { Outline // ensure database connection is available if ( !connectedToDatabase ) Override method getColumnCount throw new IllegalStateException( "Not Connected to Database" ); to obtain the number of rows in the model’s underlying ResultSet 127 128 129 130 // ensure database connection is available Override method getValueAt to obtain if ( !connectedToDatabase ) the Object in a particular row and column throw new IllegalStateException( "Not Connected to Database" ); 131 132 133 // obtain a value at specified ResultSet row and column try { 134 135 136 80 ResultSetTable Model.java (5 of 7 ) of the model’s underlying ResultSet Uses ResultSet method absolute to position ResultSet cursor at a specific row. resultSet.absolute( row + 1 ); the return resultSet.getObject( column + 1 ); } // end try Uses ResultSet method getObject to obtain the Object in a specific column of the current row. 1992-2007 Pearson Education, Inc. All rights reserved. 137 138 catch ( SQLException sqlException ) { 139 140 sqlException.printStackTrace(); } // end catch 81 Outline 141 return ""; // if problems, return empty string object 142 143 144 145 } // end method getValueAt 146 147 public void setQuery( String query ) throws SQLException, IllegalStateException 148 149 150 { 151 152 153 154 155 156 // set new database query string (6 of 7 ) // ensure database connection is available if ( !connectedToDatabase ) throw new IllegalStateException( "Not Connected to Database" ); // specify query and execute it resultSet = statement.executeQuery( query ); Executes the query to obtain a new ResultSet. // obtain meta data for ResultSet Uses ResultSet method last to position the ResultSet cursor at ResultSet the last row in the ResultSet. 157 158 metaData = resultSet.getMetaData(); 159 160 // determine number of rows in resultSet.last(); // move to last row 161 162 163 164 165 numberOfRows = resultSet.getRow(); // get row number 166 ResultSetTable Model.java // notify JTable that model has changed fireTableStructureChanged(); } // end method setQuery Uses ResultSet method getRow Invokes methodthe fireTableAStructureChanged to obtain row number for the to notify any row JTable using this current in the ResultSet. ResultSetTableModel object as its model that the structure of the model has Education, changed.Inc. All rights reserved. 1992-2007 Pearson 167 // close Statement and Connection 168 169 public void disconnectFromDatabase() { 170 171 82 Verify whether the connection is already terminated Method disconnectFromDatabase Statement and Connection implement an appropriate termination method for class ResultSetTableModel if ( connectedToDatabase ) { 172 173 174 175 // close try { resultSet.close(); 176 177 178 179 180 statement.close(); connection.close(); } // end try catch ( SQLException sqlException ) { 181 182 183 184 185 186 sqlException.printStackTrace(); } // end catch finally // update database connection status { connectedToDatabase = false; } // end finally 187 188 189 } Outline } // end if } // end method disconnectFromDatabase // end class ResultSetTableModel ResultSetTable Model.java Close the Statement and Connection if a7 ) (7 of ResultSetTableModel object is garbage collected. Set connectedToDatabase to false to ensure that clients do not use an instance of ResultSetTableModel after that instance has already been terminated 1992-2007 Pearson Education, Inc. All rights reserved. 83 ResultSet static type constant Description TYPE_FORWARD_ONLY Specifies that a ResultSet’s cursor can move only in the forward direction (i.e., from the first row to the last row in the ResultSet). TYPE_SCROLL_INSENSITIVE Specifies that a ResultSet’s cursor can scroll in either direction and that the changes made to the ResultSet during ResultSet processing are not reflected in the ResultSet unless the program queries the database again. TYPE_SCROLL_SENSITIVE Specifies that a ResultSet’s cursor can scroll in either direction and that the changes made to the ResultSet during ResultSet processing are reflected immediately in the ResultSet. Fig. 25.26 | ResultSet constants for specifying ResultSet type. 1992-2007 Pearson Education, Inc. All rights reserved. 84 Portability Tip 25.3 Some JDBC drivers do not support scrollable ResultSets. In such cases, the driver typically returns a ResultSet in which the cursor can move only forward. For more information, see your database driver documentation. 1992-2007 Pearson Education, Inc. All rights reserved. 85 Portability Tip 25.4 Some JDBC drivers do not support updatable ResultSets. In such cases, the driver typically returns a read-only ResultSet. For more information, see your database driver documentation. 1992-2007 Pearson Education, Inc. All rights reserved. 86 Common Programming Error 25.11 Attempting to update a ResultSet when the database driver does not support updatable ResultSets causes SQLFeatureNotSupportedExceptions. 1992-2007 Pearson Education, Inc. All rights reserved. 87 Common Programming Error 25.12 Attempting to move the cursor backward through a ResultSet when the database driver does not support backward scrolling causes a SQLException. 1992-2007 Pearson Education, Inc. All rights reserved. 88 ResultSet static concurrency constant Description CONCUR_READ_ONLY Specifies that a ResultSet cannot be updated (i.e., changes to the ResultSet contents cannot be reflected in the database with ResultSet’s update methods). CONCUR_UPDATABLE Specifies that a ResultSet can be updated (i.e., changes to the ResultSet contents can be reflected in the database with ResultSet’s update methods). Fig. 25.27 | ResultSet constants for specifying result properties. 1992-2007 Pearson Education, Inc. All rights reserved. 1 // Fig. 25.28: DisplayQueryResults.java 2 // Display the contents of the Authors table in the books database. 3 import java.awt.BorderLayout; 4 5 import java.awt.event.ActionListener; import java.awt.event.ActionEvent; 6 import java.awt.event.WindowAdapter; 7 8 9 10 11 12 import import import import import import 89 Outline DisplayQuery Results.java java.awt.event.WindowEvent; java.sql.SQLException; java.util.regex.PatternSyntaxException; javax.swing.JFrame; javax.swing.JTextArea; javax.swing.JScrollPane; (1 of 8 ) 13 import javax.swing.ScrollPaneConstants; 14 import javax.swing.JTable; 15 import javax.swing.JOptionPane; 16 import javax.swing.JButton; 17 import javax.swing.Box; 18 19 20 21 22 import import import import import javax.swing.JLabel; javax.swing.JTextField; javax.swing.RowFilter; javax.swing.table.TableRowSorter; javax.swing.table.TableModel; 23 24 public class DisplayQueryResults extends JFrame 25 { 26 27 // JDBC database URL, username and password static final String DRIVER = "com.mysql.jdbc.Driver"; 28 29 30 static final String DATABASE_URL = "jdbc:mysql://localhost/books"; static final String USERNAME = "jhtp7"; static final String PASSWORD = "jhtp7"; Declare the database driver class name, database URL, username and password for accessing the database 1992-2007 Pearson Education, Inc. All rights reserved. 31 32 90 // default query retrieves all data from authors table 33 34 static final String DEFAULT_QUERY = "SELECT * FROM authors"; 35 private ResultSetTableModel tableModel; 36 private JTextArea queryArea; 37 38 39 // create ResultSetTableModel and GUI public DisplayQueryResults() 40 41 Outline Declare the default query Declare tableModel to be a reference to ResultSetTableModel DisplayQuery Results.java (2 of 8 ) { super( "Displaying Query Results" ); 42 43 44 // create ResultSetTableModel and display database table try 45 { // create TableModel for results of query SELECT * FROM authors tableModel = new ResultSetTableModel( DRIVER, DATABASE_URL, USERNAME, PASSWORD, DEFAULT_QUERY ); 46 47 48 49 50 // set up JTextArea in which user types queries 51 52 queryArea = new JTextArea( DEFAULT_QUERY, 3, 100 ); queryArea.setWrapStyleWord( true ); 53 54 queryArea.setLineWrap( true ); 55 56 57 58 59 JScrollPane scrollPane = new JScrollPane( queryArea, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER ); 60 JButton submitButton = new JButton( "Submit Query" ); Create TableModel for results of default query “SELECT * FROM authors” // set up JButton for submitting queries 1992-2007 Pearson Education, Inc. All rights reserved. 61 62 // create Box to manage placement of queryArea and 63 64 65 // submitButton in GUI Box boxNorth = Box.createHorizontalBox(); boxNorth.add( scrollPane ); 66 67 68 69 70 71 boxNorth.add( submitButton ); 72 73 74 final JTextField filterText = new JTextField(); JButton filterButton = new JButton( "Apply Filter" ); Box boxSouth = boxNorth.createHorizontalBox(); 75 76 boxSouth.add( filterLabel ); 91 Outline DisplayQuery Results.java // create JTable delegate for tableModel JTable resultTable = new JTable( tableModel ); Create JTable delegate for tableModel (3 of 8 ) JLabel filterLabel = new JLabel( "Filter:" ); 77 78 79 80 81 boxSouth.add( filterText ); boxSouth.add( filterButton ); 82 add( new JScrollPane( resultTable ), BorderLayout.CENTER ); 83 add( boxSouth, BorderLayout.SOUTH ); 84 85 // create event listener for submitButton 86 submitButton.addActionListener( // place GUI components on content pane add( boxNorth, BorderLayout.NORTH ); 87 1992-2007 Pearson Education, Inc. All rights reserved. 88 89 new ActionListener() { 90 91 // pass query to table model public void actionPerformed( ActionEvent event ) 92 93 94 95 { Register an event handler for the submitButton thatOutline the user clicks to submit a query to the database // perform a new query try { DisplayQuery Results.java 96 97 tableModel.setQuery( queryArea.getText() ); } // end try (4 of 8 ) 98 99 catch ( SQLException sqlException ) { 100 JOptionPane.showMessageDialog( null, sqlException.getMessage(), "Database JOptionPane.ERROR_MESSAGE ); 92 Invoke ResultSetTableModel method setQuery to execute error", the new query 101 102 103 104 // try to recover from invalid user query 105 // by executing default query 106 107 108 109 110 111 try { tableModel.setQuery( DEFAULT_QUERY ); queryArea.setText( DEFAULT_QUERY ); } // end try catch ( SQLException sqlException2 ) 112 113 114 115 { JOptionPane.showMessageDialog( null, sqlException2.getMessage(), "Database error", JOptionPane.ERROR_MESSAGE ); 116 1992-2007 Pearson Education, Inc. All rights reserved. 117 118 // ensure database connection is closed tableModel.disconnectFromDatabase(); 119 120 System.exit( 1 ); // terminate application 122 } // end outer catch 123 124 125 } // end actionPerformed } // end ActionListener inner class ); // end call to addActionListener 126 127 final TableRowSorter< TableModel > sorter = 128 129 130 new TableRowSorter< TableModel >( tableModel ); resultTable.setRowSorter( sorter ); setSize( 500, 250 ); // set window size 131 setVisible( true ); // display window 132 133 134 135 136 // create listener for filterButton filterButton.addActionListener( new ActionListener() { DisplayQuery Results.java (5 of 8 ) 137 138 // pass filter text to listener public void actionPerformed( ActionEvent e ) 139 140 { 146 93 } // end inner catch 121 141 142 143 144 145 Ensure that the database connection is Outline closed Set up TableRowSorter String text = filterText.getText(); if ( text.length() == 0 ) sorter.setRowFilter( null ); else { No filter initially try 1992-2007 Pearson Education, Inc. All rights reserved. 147 { 94 sorter.setRowFilter( RowFilter.regexFilter( text ) ); 148 149 150 151 } // end try catch ( PatternSyntaxException pse ) 152 153 154 155 { 156 157 158 159 160 JOptionPane.showMessageDialog( null, "Bad regex pattern", "Bad regex pattern", JOptionPane.ERROR_MESSAGE ); } // end catch } // end else } // end method actionPerfomed } // end annonymous inner class ); // end call to addActionLister 161 162 163 164 165 166 } // end try catch ( ClassNotFoundException classNotFound ) { JOptionPane.showMessageDialog( null, "Database Driver not found", "Driver not found", JOptionPane.ERROR_MESSAGE ); 167 168 169 System.exit( 1 ); // terminate application } // end catch Outline Set filter using regular expression DisplayQuery Results.java (6 of 8 ) 1992-2007 Pearson Education, Inc. All rights reserved. 170 171 172 173 catch ( SQLException sqlException ) { 95 JOptionPane.showMessageDialog( null, sqlException.getMessage(), "Database error", JOptionPane.ERROR_MESSAGE ); Outline 174 175 // ensure database connection is closed 176 177 178 tableModel.disconnectFromDatabase(); Ensure that the database connection is closed System.exit( 1 ); // terminate application DisplayQuery Results.java (7 of 8 ) 179 180 } // end catch 181 182 183 // dispose of window when user quits application (this overrides // the default of HIDE_ON_CLOSE) setDefaultCloseOperation( DISPOSE_ON_CLOSE ); 184 185 186 187 188 189 // ensure database connection is closed when user quits application addWindowListener( new WindowAdapter() { 190 191 // disconnect from database and exit when window has closed public void windowClosed( WindowEvent event ) 192 193 { 194 195 196 197 198 tableModel.disconnectFromDatabase(); System.exit( 0 ); } // end method windowClosed } // end WindowAdapter inner class ); // end call to addWindowListener } // end DisplayQueryResults constructor Ensure that the database connection is closed when window is closed 199 1992-2007 Pearson Education, Inc. All rights reserved. 200 201 // execute application public static void main( String args[] ) 202 { 203 new DisplayQueryResults(); 204 } // end main 205 } // end class DisplayQueryResults 96 Outline DisplayQuery Results.java (8 of 8 ) 1992-2007 Pearson Education, Inc. All rights reserved. 97 25.10 RowSet Interface • Interface RowSet – Configures the database connection automatically – Prepares query statements automatically – Provides set methods to specify the properties needed to establish a connection – Part of the javax.sql package • Two types of RowSet – Connected RowSet • Connects to database once and remain connected – Disconnected RowSet • Connects to database, executes a query and then closes connection 2005 Pearson Education, Inc. All rights reserved. 98 25.10 RowSet Interface (Cont.) • Package javax.sql.rowset – JdbcRowSet • Connected RowSet • Wrapper around a ResultSet • Scrollable and updatable by default – CachedRowSet • • • • Disconnected RowSet Cache the data of ResultSet in memory Scrollable and updatable by default Serializable – Can be passed between Java application • Limitation – Amount of data that can be stored in memory is limited 2005 Pearson Education, Inc. All rights reserved. 99 Portability Tip 25.5 A RowSet can provide scrolling capability for drivers that do not support scrollable ResultSets. 1992-2007 Pearson Education, Inc. All rights reserved. 1 // Fig. 25.29: JdbcRowSetTest.java 2 // Displaying the contents of the authors table using JdbcRowSet. 3 import java.sql.ResultSetMetaData; 4 5 6 7 8 import java.sql.SQLException; import javax.sql.rowset.JdbcRowSet; import com.sun.rowset.JdbcRowSetImpl; // Sun's JdbcRowSet implementation 100 public class JdbcRowSetTest 9 { 10 // JDBC driver name and database URL 11 12 static final String DRIVER = "com.mysql.jdbc.Driver"; static final String DATABASE_URL = "jdbc:mysql://localhost/books"; 13 static final String USERNAME = "jhtp7"; 14 15 16 static final String PASSWORD = "jhtp7"; // constructor connects to database, queries database, processes 17 18 // results and displays results in window public JdbcRowSetTest() 19 20 { Outline JdbcRowSetTest .java (1 of 3 ) // connect to database books and query database 21 try 22 23 24 { Class.forName( DRIVER ); 1992-2007 Pearson Education, Inc. All rights reserved. 25 26 27 28 29 30 31 32 // specify properties of JdbcRowSet JdbcRowSet rowSet = new JdbcRowSetImpl(); Use Sun’s reference Invoke JdbcRowSet method Outline rowSet.setUrl( DATABASE_URL ); // set database URL implementation of JdbcRowSet Invoke JdbcRowSet setUrl to specify(JdbcRowSetImpl) the method database URL rowSet.setUsername( USERNAME ); // set username interface to Invoke JdbcRowSet method setUsername to specify the username rowSet.setPassword( PASSWORD ); // set password JdbcRowSet method createInvoke a to JdbcRowSet object setUsername specify the password rowSet.setCommand( "SELECT * FROM authors" ); // set query setCommand to JdbcRowSetTest specify the query Invoke JdbcRowSet method rowSet.execute(); // execute query 101 .java execute to execute the query 33 34 // process query results ResultSetMetaData metaData = rowSet.getMetaData(); 35 36 int numberOfColumns = metaData.getColumnCount(); System.out.println( "Authors Table of Books Database:\n" ); (2 of 3 ) 37 38 39 40 41 // display rowset header for ( int i = 1; i <= numberOfColumns; i++ ) System.out.printf( "%-8s\t", metaData.getColumnName( i ) ); System.out.println(); 42 43 44 45 46 47 48 // display each row while ( rowSet.next() ) { for ( int i = 1; i <= numberOfColumns; i++ ) System.out.printf( "%-8s\t", rowSet.getObject( i ) ); System.out.println(); 49 50 51 52 } // end while 53 // close the underlying ResultSet, Statement and Connection rowSet.close(); } // end try 1992-2007 Pearson Education, Inc. All rights reserved. 54 catch ( SQLException sqlException ) 55 { 56 57 58 sqlException.printStackTrace(); System.exit( 1 ); } // end catch 59 catch ( ClassNotFoundException classNotFound ) 60 61 62 { 63 } // end catch classNotFound.printStackTrace(); System.exit( 1 ); 64 65 } // end DisplayAuthors constructor 66 67 // launch the application public static void main( String args[] ) 102 Outline JdbcRowSetTest .java (3 of 3 ) 68 { 69 JdbcRowSetTest application = new JdbcRowSetTest(); 70 } // end main 71 } // end class JdbcRowSetTest Authors Table of Books Database: authorID 1 2 3 4 firstName Harvey Paul Andrew David lastName Deitel Deitel Goldberg Choffnes 1992-2007 Pearson Education, Inc. All rights reserved. 103 25.11 Java DB/Apache Derby • As of JDK 6, Sun Microsystems now bundles the open-source, pure Java database Java DB (the Sun branded version of Apache Derby) with the JDK • We use the embedded version of Java DB • There is also a network version that executes similarly to the MySQL DBMS introduced earlier in the chapter 2005 Pearson Education, Inc. All rights reserved. 104 25.11 Java DB/Apache Derby • Java DB comes with several batch files to configure and run it • First set the environment variable JAVA_HOME to refer to the JDK’s C:\Program Files\Java\jdk1.6.0 installation directory • Open the batch file setEmbeddedCP.bat (located in C:\Program Files\Java\jdk1.6.0\db\frameworks\embedded\bin) in a text editor such as Notepad • Locate the line rem set DERBY_INSTALL= and change it to set DERBY_INSTALL=C:\Program Files\Java\jdk1.6.0\db • Also, comment out the line @FOR %%X in ("%DERBY_HOME%") DO SET DERBY_HOME=%%~sX by preceding it with REM • Save your changes and close this file 2005 Pearson Education, Inc. All rights reserved. 105 25.11 Java DB/Apache Derby • Change directories to C:\Program Files\Java\ jdk1.6.0\db\frameworks\embedded\bin\. Then, type setEmbeddedCP.bat and press Enter to set the environment variables required by Java DB. • Embedded Java DB database must reside in the same location as the application that manipulates the database – Change to the directory that contains the code for Figs. 25.30– 25.32 • Execute the command "C:\Program Files\Java\jdk1.6.0\db\frameworks\embedded\bin\ij" to start the command-line tool for interacting with Java DB. The double quotes are necessary because the path contains a space. 2005 Pearson Education, Inc. All rights reserved. 106 25.11 Java DB/Apache Derby • At the ij> prompt type connect 'jdbc:derby:AddressBook;create=true; user=jhtp7;password=jhtp7'; to create the AddressBook database in the current directory. This command also creates the user jhtp7 with the password jhtp7 for accessing the database. • To create the database table and insert sample data in the database type run 'address.sql'; • To terminate the Java DB command-line tool, type exit; 2005 Pearson Education, Inc. All rights reserved. 107 25.12 PreparedStatements •PreparedStatements execute more efficiently than Statement objects •PreparedStatements can specify parameters 2005 Pearson Education, Inc. All rights reserved. 108 25.12 PreparedStatements • PreparedStatement to locate all book titles for an author with a specific last name and first name, and to execute that query for several authors: – PreparedStatement authorBooks = connection.prepareStatement( "SELECT lastName, firstName, title " + "FROM authors INNER JOIN authorISBN " + "ON authors.authorID=authorISBN.authorID " + "INNER JOIN titles " + "ON authorISBN.isbn=titles.isbn " + "WHERE lastName = ? AND firstName = ?" ); • Question marks (?) are placeholders for values that will be passed as part of the query to the database 2005 Pearson Education, Inc. All rights reserved. 109 25.12 PreparedStatements • Program must specify the parameter values by using the PreparedStatement interface’s set methods. • For the preceding query, both parameters are strings that can be set with PreparedStatement method setString as follows: authorBooks.setString( 1, "Deitel" ); authorBooks.setString( 2, "Paul" ); • setString automatically escapes String parameter values as necessary (e.g., the quote in the name O’Brien) • More info at java.sun.com/javase/6/docs/api/ java/sql/PreparedStatement.html 2005 Pearson Education, Inc. All rights reserved. 110 Performance Tip 25.2 PreparedStatements are more efficient than Statements when executing SQL statements multiple times and with different parameter values. 1992-2007 Pearson Education, Inc. All rights reserved. 111 Error-Prevention Tip 25.1 Use PreparedStatements with parameters for queries that receive String values as arguments to ensure that the Strings are quoted properly in the SQL statement. 1992-2007 Pearson Education, Inc. All rights reserved. 1 2 3 // Fig. 25.30: Person.java // Person class that represents an entry in an address book. public class Person 4 5 { private String firstName; private String lastName; private String email; 9 10 private String phoneNumber; 11 // no-argument constructor 12 13 14 15 public Person() { } // end no-argument Person constructor 16 17 // constructor public Person( int id, String first, String last, Person.java (1 of 3 ) String emailAddress, String phone ) { setAddressID( id ); setFirstName( first ); 22 23 setLastName( last ); setEmail( emailAddress ); 24 setPhoneNumber( phone ); 25 26 Outline private int addressID; 6 7 8 18 19 20 21 112 } // end five-argument Person constructor 1992-2007 Pearson Education, Inc. All rights reserved. 27 28 // sets the addressID public void setAddressID( int id ) 29 { 30 31 32 33 34 35 36 addressID = id; } // end method setAddressID 37 38 } // end method getAddressID 39 40 41 // sets the firstName public void setFirstName( String first ) { 42 43 44 firstName = first; } // end method setFirstName 45 46 47 48 49 // returns the first name public String getFirstName() { return firstName; } // end method getFirstName 50 51 52 53 54 // sets the lastName public void setLastName( String last ) { lastName = last; 55 56 // returns the addressID public int getAddressID() { return addressID; 113 Outline Person.java (2 of 3 ) } // end method setLastName 1992-2007 Pearson Education, Inc. All rights reserved. 57 58 // returns the first name public String getLastName() 59 { 60 61 62 63 64 65 66 return lastName; } // end method getLastName 67 68 } // end method setEmail 69 70 71 // returns the email address public String getEmail() { 72 73 74 return email; } // end method getEmail 75 76 77 78 79 // sets the phone number public void setPhoneNumber( String phone ) { phoneNumber = phone; } // end method setPhoneNumber 80 81 82 83 84 // returns the email address public String getPhoneNumber() { return phoneNumber; // sets the email address public void setEmail( String emailAddress ) { email = emailAddress; 114 Outline Person.java (3 of 3 ) 85 } // end method getPhoneNumber 86 } // end class Person 1992-2007 Pearson Education, Inc. All rights reserved. 1 // Fig. 25.31: PersonQueries.java 2 3 // PreparedStatements used by the Address Book application import java.sql.Connection; 4 5 6 7 8 9 import import import import import import java.sql.DriverManager; java.sql.PreparedStatement; java.sql.ResultSet; java.sql.SQLException; java.util.List; java.util.ArrayList; 115 Outline All program to use PreparedStatements PersonQueries .java (1 of 7 ) 10 11 public class PersonQueries 12 { 13 private static final String URL = "jdbc:derby:AddressBook"; 14 private static final String USERNAME = "jhtp7"; 15 private static final String PASSWORD = "jhtp7"; 16 17 private Connection connection = null; // manages connection 18 19 20 21 private PreparedStatement selectAllPeople = null; private PreparedStatement selectPeopleByLastName = null; private PreparedStatement insertNewPerson = null; 22 23 24 25 26 27 // constructor public PersonQueries() { try { connection = 28 29 Note that we do not load the Java DB driver first. JDBC 4’s automatic DriverManager.getConnection( URL,driver USERNAME, PASSWORD discovery is used here. Declare PreparedStatements ); 1992-2007 Pearson Education, Inc. All rights reserved. // create query that selects all entries in the AddressBook selectAllPeople = 30 31 Outline connection.prepareStatement( "SELECT * FROM Addresses" ); 32 33 34 // create query that selects entries with a specific last name selectPeopleByLastName = connection.prepareStatement( "SELECT * FROM Addresses WHERE LastName = ?" ); 35 36 37 38 39 40 // create insert that adds a new entry into the database insertNewPerson = connection.prepareStatement( "INSERT INTO Addresses " + 41 42 43 "( FirstName, LastName, Email, PhoneNumber ) " + "VALUES ( ?, ?, ?, ? )" ); } // end try 44 45 catch ( SQLException sqlException ) { 46 47 48 49 50 sqlException.printStackTrace(); System.exit( 1 ); } // end catch } // end PersonQueries constructor 51 // select all of the addresses in the database 52 public List< Person > getAllPeople() 53 54 { 55 116 PersonQueries .java (2 of 7 ) Configure each PreparedStatement. Each ? represents a parameter. List< Person > results = null; ResultSet resultSet = null; 56 1992-2007 Pearson Education, Inc. All rights reserved. 57 58 59 try { // executeQuery returns ResultSet containing matching entries 60 61 resultSet = selectAllPeople.executeQuery(); results = new ArrayList< Person >(); 62 63 64 65 66 while ( resultSet.next() ) { results.add( new Person( resultSet.getInt( "addressID" ), 67 resultSet.getString( "firstName" ), 68 69 70 71 resultSet.getString( "lastName" ), resultSet.getString( "email" ), resultSet.getString( "phoneNumber" ) ) ); } // end while 72 73 } // end try catch ( SQLException sqlException ) 74 { 75 76 77 sqlException.printStackTrace(); } // end catch finally 78 79 80 { 81 82 117 Outline Executes the query in PreparedStatement selectAllPeople.PersonQueries .java Process the ResultSet. (3 of 7 ) try { resultSet.close(); } // end try 1992-2007 Pearson Education, Inc. All rights reserved. 83 84 85 catch ( SQLException sqlException ) { sqlException.printStackTrace(); 86 87 close(); } // end catch 88 89 90 91 92 118 Outline } // end finally PersonQueries .java return results; } // end method getAllPeople (4 of 7 ) 93 // select person by last name 94 95 96 97 public List< Person > getPeopleByLastName( String name ) { List< Person > results = null; 98 99 ResultSet resultSet = null; 100 try 101 102 103 { 104 105 106 107 Specify the parameter to PreparedStatement // executeQuery returns ResultSet containing matching selectPeopleByLastName. entries Executes the query in resultSet = selectPeopleByLastName.executeQuery(); PreparedStatement selectPeopleByLastName. results = new ArrayList< Person >(); selectPeopleByLastName.setString( 1, name ); // specify last name 108 1992-2007 Pearson Education, Inc. All rights reserved. while ( resultSet.next() ) { 109 110 results.add( new Person( 111 112 113 114 115 116 117 118 resultSet.getInt( "addressID" ), resultSet.getString( "firstName" ), resultSet.getString( "lastName" ), resultSet.getString( "email" ), resultSet.getString( "phoneNumber" ) ) ); } // end while } // end try 119 120 catch ( SQLException sqlException ) { 121 122 123 sqlException.printStackTrace(); } // end catch finally 124 125 126 { 127 128 129 130 131 132 133 134 135 136 137 138 Process the ResultSet. 119 Outline PersonQueries .java (5 of 7 ) try { resultSet.close(); } // end try catch ( SQLException sqlException ) { sqlException.printStackTrace(); close(); } // end catch } // end finally return results; } // end method getPeopleByName 1992-2007 Pearson Education, Inc. All rights reserved. 139 // add an entry 140 public int addPerson( String fname, String lname, String email, String num ) 141 142 143 144 145 146 147 148 149 120 Outline { int result = 0; PersonQueries .java // set parameters, then execute insertNewPerson try { insertNewPerson.setString( 1, fname ); insertNewPerson.setString( 2, lname ); 150 151 152 153 insertNewPerson.setString( 3, email ); insertNewPerson.setString( 4, num ); 154 155 156 result = insertNewPerson.executeUpdate(); } // end try catch ( SQLException sqlException ) 157 158 159 { 160 } // end catch (6 of 7 ) Specify the parameters to PreparedStatement insertNewPerson. // insert the new entry; returns # of rows updated Executes the insert operation in PreparedStatement insertNewPerson. sqlException.printStackTrace(); close(); 1992-2007 Pearson Education, Inc. All rights reserved. 161 121 return result; 162 163 164 165 166 } // end method addPerson 167 168 169 { 170 171 172 173 174 // close the database connection public void close() try { connection.close(); Outline PersonQueries .java (7 of 7 ) } // end try catch ( SQLException sqlException ) { sqlException.printStackTrace(); 175 } // end catch 176 } // end method close 177 } // end interface PersonQueries 1992-2007 Pearson Education, Inc. All rights reserved. 1 // Fig. 25.32: AddressBookDisplay.java 2 // A simple address book 3 import java.awt.event.ActionEvent; 4 5 import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; 6 import java.awt.event.WindowEvent; 7 8 9 10 11 12 import import import import import import java.awt.FlowLayout; java.awt.GridLayout; java.util.List; javax.swing.JButton; javax.swing.Box; javax.swing.JFrame; 122 Outline AddressBook Display.java (1 of 14 ) 13 import javax.swing.JLabel; 14 import javax.swing.JPanel; 15 import javax.swing.JTextField; 16 import javax.swing.WindowConstants; 17 import javax.swing.BoxLayout; 18 19 20 21 22 import javax.swing.BorderFactory; import javax.swing.JOptionPane; public class AddressBookDisplay extends JFrame { 23 24 25 private Person currentEntry; private PersonQueries personQueries; private List< Person > results; 26 27 private int numberOfEntries = 0; private int currentEntryIndex; 28 29 30 private JButton browseButton; private JLabel emailLabel; 1992-2007 Pearson Education, Inc. All rights reserved. 31 32 private JTextField emailTextField; private JLabel firstNameLabel; 33 34 private JTextField firstNameTextField; private JLabel idLabel; 35 private JTextField idTextField; 36 private JTextField indexTextField; 37 38 39 private JLabel lastNameLabel; private JTextField lastNameTextField; private JTextField maxTextField; 40 41 private JButton nextButton; private JLabel ofLabel; 42 43 44 private JLabel phoneLabel; private JTextField phoneTextField; private JButton previousButton; 45 private JButton queryButton; 46 47 48 49 50 private private private private private 51 52 private JButton insertButton; 53 54 // no-argument constructor public AddressBookDisplay() 55 56 57 58 59 { 123 Outline AddressBook Display.java (2 of 14 ) JLabel queryLabel; JPanel queryPanel; JPanel navigatePanel; JPanel displayPanel; JTextField queryTextField; super( "Address Book" ); // establish database connection and set up PreparedStatements personQueries = new PersonQueries(); 60 1992-2007 Pearson Education, Inc. All rights reserved. 61 62 // create GUI navigatePanel = new JPanel(); 63 previousButton = new JButton(); 64 65 66 indexTextField = new JTextField( 2 ); ofLabel = new JLabel(); maxTextField = new JTextField( 2 ); 67 68 69 nextButton = new JButton(); displayPanel = new JPanel(); idLabel = new JLabel(); 70 71 idTextField = new JTextField( 10 ); firstNameLabel = new JLabel(); 72 firstNameTextField = new JTextField( 10 ); 73 lastNameLabel = new JLabel(); 74 75 76 lastNameTextField = new JTextField( 10 ); emailLabel = new JLabel(); emailTextField = new JTextField( 10 ); 77 78 79 80 81 phoneLabel = new phoneTextField = queryPanel = new queryLabel = new queryTextField = 82 queryButton = new JButton(); 83 84 browseButton = new JButton(); insertButton = new JButton(); 85 86 setLayout( new FlowLayout( FlowLayout.CENTER, 10, 10 ) ); 87 setSize( 400, 300 ); 88 89 setResizable( false ); 124 Outline AddressBook Display.java (3 of 14 ) JLabel(); new JTextField( 10 ); JPanel(); JLabel(); new JTextField( 10 ); 1992-2007 Pearson Education, Inc. All rights reserved. 90 91 navigatePanel.setLayout( new BoxLayout( navigatePanel, BoxLayout.X_AXIS ) ); 92 93 94 95 96 97 98 99 previousButton.setText( "Previous" ); previousButton.setEnabled( false ); previousButton.addActionListener( new ActionListener() { public void actionPerformed( ActionEvent evt ) { 100 101 previousButtonActionPerformed( evt ); } // end method actionPerformed 102 103 104 } // end anonymous inner class ); // end call to addActionListener 105 106 107 navigatePanel.add( previousButton ); navigatePanel.add( Box.createHorizontalStrut( 10 ) ); 108 109 110 111 112 indexTextField.setHorizontalAlignment( JTextField.CENTER ); indexTextField.addActionListener( new ActionListener() { 113 114 115 116 117 118 119 125 Outline AddressBook Display.java (4 of 14 ) public void actionPerformed( ActionEvent evt ) { indexTextFieldActionPerformed( evt ); } // end method actionPerformed } // end anonymous inner class ); // end call to addActionListener 1992-2007 Pearson Education, Inc. All rights reserved. 120 121 navigatePanel.add( indexTextField ); navigatePanel.add( Box.createHorizontalStrut( 10 ) ); 122 123 124 125 ofLabel.setText( "of" ); navigatePanel.add( ofLabel ); navigatePanel.add( Box.createHorizontalStrut( 10 ) ); 126 127 128 maxTextField.setHorizontalAlignment( JTextField.CENTER ); 129 130 maxTextField.setEditable( false ); navigatePanel.add( maxTextField ); 131 navigatePanel.add( Box.createHorizontalStrut( 10 ) ); 126 Outline AddressBook Display.java (5 of 14 ) 132 133 134 135 136 137 138 139 140 141 nextButton.setText( "Next" ); nextButton.setEnabled( false ); nextButton.addActionListener( new ActionListener() { public void actionPerformed( ActionEvent evt ) { nextButtonActionPerformed( evt ); } // end method actionPerformed 142 143 } // end anonymous inner class ); // end call to addActionListener 144 145 navigatePanel.add( nextButton ); 146 add( navigatePanel ); 147 148 displayPanel.setLayout( new GridLayout( 5, 2, 4, 4 ) ); 1992-2007 Pearson Education, Inc. All rights reserved. 149 150 127 idLabel.setText( "Address ID:" ); 151 152 displayPanel.add( idLabel ); 153 154 idTextField.setEditable( false ); displayPanel.add( idTextField ); 155 156 firstNameLabel.setText( "First Name:" ); 157 158 159 displayPanel.add( firstNameLabel ); displayPanel.add( firstNameTextField ); 160 161 lastNameLabel.setText( "Last Name:" ); displayPanel.add( lastNameLabel ); 162 163 164 165 displayPanel.add( lastNameTextField ); 166 displayPanel.add( emailTextField ); 167 168 phoneLabel.setText( "Phone Number:" ); 169 170 171 displayPanel.add( phoneLabel ); displayPanel.add( phoneTextField ); add( displayPanel ); 172 173 174 queryPanel.setLayout( new BoxLayout( queryPanel, BoxLayout.X_AXIS) ); Outline AddressBook Display.java (6 of 14 ) emailLabel.setText( "Email:" ); displayPanel.add( emailLabel ); 175 1992-2007 Pearson Education, Inc. All rights reserved. 176 177 queryPanel.setBorder( BorderFactory.createTitledBorder( "Find an entry by last name" ) ); Outline 178 queryLabel.setText( "Last Name:" ); 179 180 181 queryPanel.add( Box.createHorizontalStrut( 5 ) ); queryPanel.add( queryLabel ); queryPanel.add( Box.createHorizontalStrut( 10 ) ); 182 183 184 185 queryPanel.add( queryTextField ); queryPanel.add( Box.createHorizontalStrut( 10 ) ); 186 187 188 189 queryButton.addActionListener( new ActionListener() { public void actionPerformed( ActionEvent evt ) 190 191 192 193 194 195 196 197 198 128 AddressBook Display.java (7 of 14 ) queryButton.setText( "Find" ); { queryButtonActionPerformed( evt ); } // end method actionPerformed } // end anonymous inner class ); // end call to addActionListener queryPanel.add( queryButton ); queryPanel.add( Box.createHorizontalStrut( 5 ) ); add( queryPanel ); 199 1992-2007 Pearson Education, Inc. All rights reserved. 200 browseButton.setText( "Browse All Entries" ); 201 browseButton.addActionListener( 202 new ActionListener() 203 204 205 { 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 129 Outline public void actionPerformed( ActionEvent evt ) { browseButtonActionPerformed( evt ); } // end method actionPerformed } // end anonymous inner class ); // end call to addActionListener AddressBook Display.java (8 of 14 ) add( browseButton ); insertButton.setText( "Insert New Entry" ); insertButton.addActionListener( new ActionListener() { public void actionPerformed( ActionEvent evt ) { insertButtonActionPerformed( evt ); } // end method actionPerformed } // end anonymous inner class ); // end call to addActionListener 223 1992-2007 Pearson Education, Inc. All rights reserved. 224 225 226 227 228 229 230 231 add( insertButton ); Outline addWindowListener( new WindowAdapter() { public void windowClosing( WindowEvent evt ) { personQueries.close(); // close database connection 232 233 234 235 System.exit( 0 ); } // end method windowClosing } // end anonymous inner class ); // end call to addWindowListener 236 237 setVisible( true ); 238 239 240 241 242 243 244 245 246 130 AddressBook Display.java (9 of 14 ) } // end no-argument constructor // handles call when previousButton is clicked private void previousButtonActionPerformed( ActionEvent evt ) { currentEntryIndex--; if ( currentEntryIndex < 0 ) currentEntryIndex = numberOfEntries - 1; 247 248 249 250 251 indexTextField.setText( "" + ( currentEntryIndex + 1 ) ); indexTextFieldActionPerformed( evt ); } // end method previousButtonActionPerformed 1992-2007 Pearson Education, Inc. All rights reserved. 252 // handles call when nextButton is clicked 253 254 private void nextButtonActionPerformed( ActionEvent evt ) { Outline currentEntryIndex++; 255 256 257 258 259 260 if ( currentEntryIndex >= numberOfEntries ) currentEntryIndex = 0; AddressBook Display.java indexTextField.setText( "" + ( currentEntryIndex + 1 ) ); 261 262 263 264 265 indexTextFieldActionPerformed( evt ); } // end method nextButtonActionPerformed 266 { 267 268 269 270 271 272 131 (10 of 14 ) // handles call when queryButton is clicked private void queryButtonActionPerformed( ActionEvent evt ) Executes the query in results = personQueries.getPeopleByLastName( queryTextField.getText()PreparedStatement ); selectPeopleByLastName numberOfEntries = results.size(); from class PersonQueries. if ( numberOfEntries != 0 ) { 273 274 275 276 277 278 currentEntryIndex = 0; currentEntry = results.get( currentEntryIndex ); idTextField.setText( "" + currentEntry.getAddressID() ); firstNameTextField.setText( currentEntry.getFirstName() ); lastNameTextField.setText( currentEntry.getLastName() ); emailTextField.setText( currentEntry.getEmail() ); 279 280 phoneTextField.setText( currentEntry.getPhoneNumber() ); maxTextField.setText( "" + numberOfEntries ); 1992-2007 Pearson Education, Inc. All rights reserved. 281 282 indexTextField.setText( "" + ( currentEntryIndex + 1 ) ); nextButton.setEnabled( true ); 283 284 previousButton.setEnabled( true ); } // end if 285 286 else browseButtonActionPerformed( evt ); Outline AddressBook Display.java 287 288 } // end method queryButtonActionPerformed 289 290 291 // handles call when a new value is entered in indextTextField private void indexTextFieldActionPerformed( ActionEvent evt ) { 292 293 currentEntryIndex = ( Integer.parseInt( indexTextField.getText() ) - 1 ); 294 295 296 297 if ( numberOfEntries != 0 && currentEntryIndex < numberOfEntries ) { currentEntry = results.get( currentEntryIndex ); 298 idTextField.setText("" + currentEntry.getAddressID() ); 299 300 firstNameTextField.setText( currentEntry.getFirstName() ); lastNameTextField.setText( currentEntry.getLastName() ); 301 302 303 emailTextField.setText( currentEntry.getEmail() ); phoneTextField.setText( currentEntry.getPhoneNumber() ); maxTextField.setText( "" + numberOfEntries ); 304 305 306 132 (11 of 14 ) indexTextField.setText( "" + ( currentEntryIndex + 1 ) ); } // end if } // end method indexTextFieldActionPerformed 307 1992-2007 Pearson Education, Inc. All rights reserved. 308 309 // handles call when browseButton is clicked private void browseButtonActionPerformed( ActionEvent evt ) 310 311 { 312 313 314 315 133 Outline try { results = personQueries.getAllPeople(); numberOfEntries = results.size(); if ( numberOfEntries != 0 ) { 316 317 Executes the query in PreparedStatementAddressBook Display.java selectAllPeople from class PersonQueries. (12 of 14 ) 318 319 currentEntryIndex = 0; currentEntry = results.get( currentEntryIndex ); 320 idTextField.setText( "" + currentEntry.getAddressID() ); 321 322 323 324 firstNameTextField.setText( currentEntry.getFirstName() ); lastNameTextField.setText( currentEntry.getLastName() ); emailTextField.setText( currentEntry.getEmail() ); phoneTextField.setText( currentEntry.getPhoneNumber() ); 325 maxTextField.setText( "" + numberOfEntries ); 326 327 328 329 330 331 indexTextField.setText( "" + ( currentEntryIndex + 1 ) ); nextButton.setEnabled( true ); previousButton.setEnabled( true ); } // end if } // end try catch ( Exception e ) 332 333 334 335 { e.printStackTrace(); } // end catch } // end method browseButtonActionPerformed 336 1992-2007 Pearson Education, Inc. All rights reserved. 337 // handles call when insertButton is clicked 338 339 private void insertButtonActionPerformed( ActionEvent evt ) { 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 134 Outline int result = personQueries.addPerson( firstNameTextField.getText(), lastNameTextField.getText(), emailTextField.getText(), Executes phoneTextField.getText() ); if ( result == 1 ) JOptionPane.showMessageDialog( this, "Person added!", "Person added", JOptionPane.PLAIN_MESSAGE ); the insert operation in PreparedStatement AddressBook insertNewPerson from class Display.java PersonQueries. (13 of 14 ) else JOptionPane.showMessageDialog( this, "Person not added!", "Error", JOptionPane.PLAIN_MESSAGE ); browseButtonActionPerformed( evt ); } // end method insertButtonActionPerformed // main method public static void main( String args[] ) { 357 new AddressBookDisplay(); 358 } // end method main 359 } // end class AddressBookDisplay 1992-2007 Pearson Education, Inc. All rights reserved. 135 Outline AddressBook Display.java (14 of 14 ) 1992-2007 Pearson Education, Inc. All rights reserved. 136 25.12 Stored Procedures • Stored procedures – Store SQL statements in a database – Invoke SQL statements by programs accessing the database • Interface CallableStatement – Receive arguments – Output parameters 2005 Pearson Education, Inc. All rights reserved. 137 Portability Tip 25.6 Although the syntax for creating stored procedures differs across database management systems, the interface CallableStatement provides a uniform interface for specifying input and output parameters for stored procedures and for invoking stored procedures. 1992-2007 Pearson Education, Inc. All rights reserved. 138 Portability Tip 25.7 According to the Java API documentation for interface CallableStatement, for maximum portability between database systems, programs should process the update counts or ResultSets returned from a CallableStatement before obtaining the values of any output parameters. 1992-2007 Pearson Education, Inc. All rights reserved. 139 25.13 Transaction Processing • Many applications require guarantees that a series of database insertions, updates and deletions executes properly before the applications continue processing the next database operation • Enables a program that interacts with a database to treat a database operation (or set of operations) as a single operation – Known as an atomic operation or a transaction – At the end of a transaction, decide to commit or roll back 2005 Pearson Education, Inc. All rights reserved. 140 25.13 Transaction Processing • Committing a transaction finalizes the database operation(s); all insertions, updates and deletions performed as part of the transaction cannot be reversed without performing a new database operation • Rolling back a transaction leaves the database in its state prior to the database operation 2005 Pearson Education, Inc. All rights reserved. 141 25.13 Transaction Processing • Methods of interface Connection – setAutoCommit specifies whether each SQL statement commits after it completes (a true argument) or if several SQL statements should be grouped as a transaction (a false argument) • If the argument to setAutoCommit is false, the program must follow the last SQL statement in the transaction with a call to Connection method commit or rollback – getAutoCommit determines the autocommit state for the Connection. 2005 Pearson Education, Inc. All rights reserved.