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Programming
with Java
Introduction to JDBC
Instructor: Daniel J. Hood
Northrop Grumman Corporation
1
Overview
What is JDBC?
JDBC Architecture
JDBC API
JDBC Drivers
A JDBC Example
 Loading the Driver
 Opening/Closing a Connection
 Creating/Closing a Statement
 Getting a ResultSet
 Object-Relational Mapping Tools
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What is JDBC
 Stands for Java DataBase Connectivity
 API consisting of Java classes, interfaces, exceptions and a
specification which driver vendors adhere to
 java.sql
 javax.sql
 JDBC is Sun's attempt to create a platform neutral interface
between various databases and the Java language
 Isolates program from database details
 For the most part you will use Interfaces defined in java.sql and
javax.sql, and the vendor specified JDBC driver will provide
classes which implement those interfaces
 So, if you are programming to an interface it should be trivial to
change the underlying driver without breaking anything.
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JDBC Architecture
4
JDBC API
 DriverManager
 Loads JDBC driver into JVM
 Used to obtain connections to a DataSource
 Connection
 Represents a connection with a DataSource
 Used to create Statement, PreparedStatement and
CallableStatement objects.
 Statement
 Represents a static SQL statement.
 Can be used to retrieve ResultSet objects.
 PreparedStatement
 Higher performance alternative to Statement object,
represents a precompiled SQL statement.
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JDBC API (continued)
 CallableStatement
 Represents a stored procedure. Can be used to
execute stored procedures in a RDBMS which
supports them.
 ResultSet
 Represents a database result set generated by using
a SELECT SQL statement.
 SQLException
 An exception class which encapsulates database
base access errors.
 DataSource
 Abstracts a data source. This object can be used in
place of DriverManager to efficiently obtain data
source connections
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JDBC Drivers
 Type 1 JDBC-ODBC bridge drivers
 Sits atop preexisting ODBC setup
 Type 2 Native-API partly Java drivers
 Uses native API as basis (wrapped via JNI)
 Type 3 Net-protocol All-Java drivers
 100% Java
 Connect to another machine which talks to the DB in
some fashion
 Type 4 Native-protocol All-Java drivers
 100% Java
 “Best” solution when available
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Obtaining a Driver for Your Database
 Each vendor must provide a JDBC driver to talk to their
database
 Typically the JDBC driver is distributed as a jarfile that needs to
be added to the classpath
 Various vendors JDBC Drivers
 MySQL
 http://dev.mysql.com/downloads/connector/j/
 Oracle
 http://www.oracle.com/technology/software/tech/java/sqlj_j
dbc/
 PostgreSQL
 http://jdbc.postgresql.org/
 Sybase
 http://www.sybase.com/detail_list?id=11662&multi=true&S
R=Y&show=1265
 MS Access
 JDBC-ODBC Driver
Loading the Driver
 The driver we are using will need to be registered with
the JDBC DriverManager
 Typically done via loading the class directly
 Class.forName(“com.oracle.jdbc.OracleDriver”);
 This method may throw a ClassNotFoundException,
so we must wrap it in a try/catch block
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
System.err.println("Failed to load the JDBC driver");
}
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JDBC URLs
 JDBC drivers use a JDBC URL to identify and connect
to a given database
 Typically specify
 Driver name
 Machine to connect to
 Database name
 Username (typically optional)
 Password (typically optional)
 General format like so:
 jdbc:driver:databasename
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Connecting to the Database
 To connect to the database we need to get a
connection off of the DriverManager

Connection conn = DriverManager.getConnection("url", "user", "password");
 We should also take some care to close the
connection when we are done with it to free up
resources
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Connecting to the Database (continued)
Connection connection = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection(
"jdbc:mysql://127.0.0.1:3306/test","username","password");
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
System.err.println("Failed to load the JDBC driver");
} finally {
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
System.err.println("Failed to close the connection.");
}
}
}
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Creating a Statement
 The next thing that we need to do is to create a SQL
Statement to issue to the database
 There are 3 different types of statements that are
supported
 Statement
 A basic SQL statement
 PreparedStatement
 A precompiled SQL statement
 CallableStatement
 Access to stored procedures
 Just like a connection, we should close the statement
when we are done with it
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Creating a Statement (continued)
Connection connection = null;
Statement statement = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection(
"jdbc:mysql://127.0.0.1:3306/test","username","password");
statement = connection.createStatement();
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
System.err.println("Failed to load the JDBC driver");
}
// continued on next slide
Creating a Statement (continued)
// continued from previous slide
finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
System.err.println("Failed to close the statement.");
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
System.err.println("Failed to close the connection.");
}
}
}
Obtaining a ResultSet
 We can get a ResultSet back which represents the
results of our query
 A ResultSet is returned from executing a query
 statement.executeQuery("select * from people");
 You can think of a result set as an iterator over a
collection of results that you can walk through
 next() – returns a boolean if there is more data and
advances to the next item in the collection
 There are a lot of methods to get data out of the results
set in the following format
 getType(int colNum)
 getType(String colName)
 i.e. String name = rs.getString(“first”);
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Obtaining a ResultSet (continued)
Connection connection = null;
Statement statement = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection(
"jdbc:mysql://127.0.0.1:3306/test","username","password");
statement = connection.createStatement();
ResultSet results =
statement.executeQuery("select * from people");
while (results != null && results.next()) {
System.out.println(results.getString("first") + " " +
results.getString("last") );
}
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
System.err.println("Failed to load the JDBC driver");
}
// continued on next slide
Obtaining a ResultSet (continued)
// continued from previous slide
finally {
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
System.err.println("Failed to close the statement.");
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
System.err.println("Failed to close the connection.");
}
}
}
Execution
 For the following database table
mysql> select * from people;
+-------+-------+
| first | last |
+-------+-------+
| John | Doe
|
| Jane | Smith |
+-------+-------+
2 rows in set (0.00 sec)
 Our code produces
John Smith
Jane Doe
Object-Relational Mapping Tools
 In recent years there has been a lot of work to reduce the
complexity of manually writing the SQL code to map Java
objects to a table in the database
 Tools like Hibernate (http://www.hibernate.org/) provide a
framework for persisting Plain Old Java Objects (POJOs) to a
relational database
 Typically all you need to configure is the following:
 Where the database is and who to connect as
 What JDBC driver to use
 Which Java objects map to which tables
 Which members map to which columns
 This way you can write simple Java Bean classes and hand
them off to a framework such as hibernate to persist them to the
database
 The framework manages all SQL – no SQL in your code
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