Download Java Database Connectivity (JDBC)

Java for Interfaces and Networks
Java for Interfaces and Networks
(DT3010, HT11)
Java Database Connectivity (JDBC)
Federico Pecora
School of Science and Technology
Örebro University
[email protected]
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Outline
1
Java and DBMSs: background
2
Java Database Connectivity (JDBC)
JDBC: connecting and querying
JDBC: updating
3
Applets and JDBC
Security issues
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java and DBMSs: background
Outline
1
Java and DBMSs: background
2
Java Database Connectivity (JDBC)
JDBC: connecting and querying
JDBC: updating
3
Applets and JDBC
Security issues
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java and DBMSs: background
Java and DBMS
The Java Database Connectivity (JDBC) API allows
database-independent connectivity between the Java
programming language and a wide range of DBMSs
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java and DBMSs: background
Relational databases
Database: collection of data managed by a Database
Management System (DBMS)
Relational database: one or more tables, each with with zero or
more rows and one or more columns
Each table has a name
Each column has a name
The contents of a table a RDB represent a relation
A query in a RDB is a relation also
queries are expressed via SQL (Structured Query Language)
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java and DBMSs: background
Relational databases
Number
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Name
Olle
Peter
Holga
Lotta
Phone
260088
282677
260088
174590
A simple query
select number, name from person where number < 4
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java and DBMSs: background
Relational databases
Number
1
2
3
4
Name
Olle
Peter
Holga
Lotta
Number
1
2
3
Phone
260088
282677
260088
174590
Name
Olle
Peter
Holga
Federico Pecora – Java for Interfaces and Networks – Lecture 6
6 / 16
Java for Interfaces and Networks
Java and DBMSs: background
Relational databases
Number
1
2
3
4
Name
Olle
Peter
Holga
Lotta
Phone
260088
282677
260088
174590
Creating a table
create table Person
(number integer,
name varchar(6),
phone varchar(6),
primary key (number));
Federico Pecora – Java for Interfaces and Networks – Lecture 6
6 / 16
Java for Interfaces and Networks
Java and DBMSs: background
Relational databases
Number
1
2
3
4
Name
Olle
Peter
Holga
Lotta
Phone
260088
282677
260088
174590
Adding rows
insert into person values (7, ’Klas’, ’260088’);
Federico Pecora – Java for Interfaces and Networks – Lecture 6
6 / 16
Java for Interfaces and Networks
Java and DBMSs: background
Relational databases
Number
1
2
3
4
Name
Olle
Peter
Holga
Lotta
Phone
260088
282677
260088
174590
Updating rows
update person set phone = ’20270’ where number = 7;
Federico Pecora – Java for Interfaces and Networks – Lecture 6
6 / 16
Java for Interfaces and Networks
Java and DBMSs: background
Relational databases
Number
1
2
3
4
Name
Olle
Peter
Holga
Lotta
Phone
260088
282677
260088
174590
Another query...
select * from person where phone in
(select phone from
(select distinct phone,
count(*) as n from person group by phone) as p
where n > 1);
Federico Pecora – Java for Interfaces and Networks – Lecture 6
6 / 16
Java for Interfaces and Networks
Java and DBMSs: background
Relational databases
Number
1
2
3
4
Name
Olle
Peter
Holga
Lotta
Phone
260088
282677
260088
174590
Number
1
3
Name
Olle
Holga
Phone
260088
260088
Federico Pecora – Java for Interfaces and Networks – Lecture 6
6 / 16
Java for Interfaces and Networks
Java Database Connectivity (JDBC)
Outline
1
Java and DBMSs: background
2
Java Database Connectivity (JDBC)
JDBC: connecting and querying
JDBC: updating
3
Applets and JDBC
Security issues
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC
JDBC: standard API for accessing relational databases
send SQL statements in a vendor-independent way
standardised way to establish a connection to a database
standardised way of sending queries
standardised way of committing transactions
allows for vendor specific SQL syntax (try to avoid that!)
JDBC is part of JDK since version 1.4
DBMS vendors distribute their own JDBC driver
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC drivers
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
Useful links on JDBC
Using JDBC with MySQL, Getting started
http://www.developer.com/java/data/print.php/3417381
Get Started with Mimer JDBC
http://developer.mimer.com/howto/howto_17.htm
Getting started with the JDBC API
http://java.sun.com/j2se/1.5.0/docs/guide/jdbc/
getstart/GettingStartedTOC.fm.html
The Java Tutorial. Trail: JDBC Database Access
http://java.sun.com/docs/books/tutorial/jdbc
JDBC 2.0 Fundamentals
http:
//java.sun.com/developer/onlineTraining/Database
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: connecting and querying
JDBC: connecting to a DBMS
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PersonTest.java
import java.sql.*;
public class PersonTest {
public static void main(String args[]) {
try {
Class.forName("com.mimer.jdbc.Driver");
String url =
"jdbc:mimer://<user>:<pass>@<hostName>/<dbName>";
Connection con = DriverManager.getConnection(url);
Statement stmt = con.createStatement();
String sql = "select number, name from person
where number < 4";
ResultSet rs = stmt.executeQuery(sql);
while (rs.next()) {
int number = rs.getInt(1);
String name = rs.getString(2);
System.out.println("Person " + number +
"’s name is " + name + ".");
}
//continues...
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: connecting and querying
JDBC: connecting to a DBMS
PersonTest.java (cont.)
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rs.close();
stmt.close();
con.close();
}
catch (SQLException e) {
while (e != null) {
System.out.println("SQLException:");
System.out.println(" SQLState: " + e.getSQLState());
System.out.println(" Message: " + e.getMessage());
System.out.println(" ErrorCode: " + e.getErrorCode());
e = e.getNextException();
}
} catch (Exception e) {
System.out.println("Another exception:");
e.printStackTrace();
}
} //main
} //class PersonTest
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: connecting and querying
JDBC: connecting to a DBMS
Normal execution. . .
linux>
linux>
Person
Person
Person
linux>
[make sure com.mimer.jdbc.Driver is in your classpath]
java PersonTest
1’s name is Olle
2’s name is Peter
3’s name is Holga
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: connecting and querying
JDBC: connecting to a DBMS
Wrong password. . .
linux> java PersonTest
SQLException:
SQLState: 08004
Message: Login failure
ErrorCode: -14006
linux>
Federico Pecora – Java for Interfaces and Networks – Lecture 6
11 / 16
Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: connecting and querying
JDBC: connecting to a DBMS
Wrong SQL query. . .
linux> java PersonTest
SQLException:
SQLState: 42000
Message: NUMMER is not a column of an inserted table,
updated table or any table identified in a FROM clause
ErrorCode: -12202
linux>
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: updating
JDBC: interactive DBMS interface
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NewPersonTest.java
public class NewPersonTest {
public static String readUserInput() throws MyReadException {
BufferedReader reader
= new BufferedReader(new InputStreamReader(System.in));
String numberString;
int number; String name; String phone;
try {
System.out.println("Enter a new person.");
System.out.print(" number: ");
numberString = reader.readLine();
number = Integer.parseInt(numberString);
System.out.print(" name: ");
name = reader.readLine();
System.out.print(" phone: ");
phone = reader.readLine();
}
//continues...
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: updating
JDBC: interactive DBMS interface
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NewPersonTest.java (cont.)
catch (IOException e) {
throw new MyReadException("Could not read form input!");
} catch (NumberFormatException e) {
throw new MyReadException("Not a number!");
}
return new String("insert into person values (" +
number + ", ’" + name + "’, ’" + phone + "’)");
} //readUserInput
//continues...
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: updating
JDBC: interactive DBMS interface
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NewPersonTest.java (cont.)
public static void main(String args[]) {
try {
Class.forName("com.mysql.jdbc.Driver");
String url =
"jdbc:mysql://<hostname>/<dbName>";
Connection con =
DriverManager.getConnection(url, <user>, <pass>);
Statement stmt = con.createStatement();
String sql = readUserInput();
System.out.println("SQL command: " + sql);
int rowCount = stmt.executeUpdate(sql);
System.out.println(rowCount + " row(s) updated.");
stmt.close();
con.close();
}
//continues...
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: updating
JDBC: interactive DBMS interface
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NewPersonTest.java (cont.)
catch (SQLException e) {
while (e != null) {
System.out.println("SQLException:");
System.out.println(" SQLState: " + e.getSQLState());
System.out.println(" Message: " + e.getMessage());
System.out.println(" ErrorCode: " + e.getErrorCode());
e = e.getNextException();
}
} catch (ClassNotFoundException e) {
System.out.println("SQLException:");
e.printStackTrace();
} catch (MyReadException e) {
System.out.println("A MyReadException has occured!");
e.printStackTrace();
}
System.exit(0);
} //main
} //class NewPersonTest
Federico Pecora – Java for Interfaces and Networks – Lecture 6
12 / 16
Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: updating
JDBC: interactive DBMS interface
Normal execution. . .
linux> [make sure com.mysql.jdbc.Driver is in your classpath]
linux> java NewPersonTest
Enter a new person.
number: 7
name: Klas
phone: 260088
SQL command: insert into person values (7, ’Klas’, ’260088’)
1 row(s) updated.
linux>
Federico Pecora – Java for Interfaces and Networks – Lecture 6
12 / 16
Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: updating
JDBC: interactive DBMS interface
Duplicate keys. . .
linux> java NewPersonTest
Enter a new person.
number: 1
name: Hanna
phone: 767610
SQL command: insert into person values (1, ’Hanna’, ’767610’)
SQLException:
SQLState: 23000
Message: Duplicate entry ’1’ for key 1
ErrorCode: 1062
linux>
Federico Pecora – Java for Interfaces and Networks – Lecture 6
12 / 16
Java for Interfaces and Networks
Java Database Connectivity (JDBC)
JDBC: updating
JDBC: interactive DBMS interface
Use of MyReadException. . .
linux> java NewPersonTest
Enter a new person.
number: SeventySeven
A MyReadException has occured!
MyReadException: Not a number!
at NewPersonTest.readUserInput(NewPersonTest.java:21)
at NewPersonTest.main(NewPersonTest.java:35)
linux>
Federico Pecora – Java for Interfaces and Networks – Lecture 6
12 / 16
Java for Interfaces and Networks
Applets and JDBC
Outline
1
Java and DBMSs: background
2
Java Database Connectivity (JDBC)
JDBC: connecting and querying
JDBC: updating
3
Applets and JDBC
Security issues
Federico Pecora – Java for Interfaces and Networks – Lecture 6
13 / 16
Java for Interfaces and Networks
Applets and JDBC
JDBC and Applets: simple Swing interface
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MySQLApplet.java
public class MySQLApplet extends JApplet
implements ActionListener {
public void actionPerformed (ActionEvent event) {
try {
Class.forName("com.mysql.jdbc.Driver");
String url =
"jdbc:mysql://<host>/<dbName>";
Connection con =
DriverManager.getConnection(url, <user>, <pass>);
Statement stmt = con.createStatement();
String sql =
"select number, name from person where number < 4";
ResultSet rs = stmt.executeQuery(sql);
text.setText("Persons:\n");
//continues...
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Java for Interfaces and Networks
Applets and JDBC
JDBC and Applets: simple Swing interface
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MySQLApplet.java (cont.)
while (rs.next()) {
int number = rs.getInt(1);
String name = rs.getString(2);
text.append("Person " + number + "’s name is " +
name + ".\n");
}
rs.close();
stmt.close();
con.close();
}
//continues...
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Applets and JDBC
JDBC and Applets: simple Swing interface
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MySQLApplet.java (cont.)
catch (SQLException se) {
while (se != null) {
text.setText("SQLException:\n");
text.append(" SQLState: " + se.getSQLState() + "\n");
text.append(" Message: " + se.getMessage() + "\n");
text.append(" ErrorCode: " + se.getErrorCode() + "\n");
se = se.getNextException();
}
} catch (Exception exc) {
text.setText("Other Exception:\n");
text.append(exc.toString() + "\n");
}
} //actionPerformed
//continues...
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Applets and JDBC
JDBC and Applets: simple Swing interface
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MySQLApplet.java (cont.)
private JTextArea text;
public void init() {
Container cp = getContentPane();
cp.setLayout(new FlowLayout());
cp.add(new JLabel("An applet that gets persons"));
text = new JTextArea("Output field", 6, 30);
cp.add(new JScrollPane(text));
JButton runButton = new JButton("Get persons");
runButton.addActionListener(this);
cp.add(runButton);
} //init
} //class MySQLApplet
Federico Pecora – Java for Interfaces and Networks – Lecture 6
14 / 16
Java for Interfaces and Networks
Applets and JDBC
JDBC and Applets: simple Swing interface
Federico Pecora – Java for Interfaces and Networks – Lecture 6
14 / 16
Java for Interfaces and Networks
Applets and JDBC
JDBC and Applets: simple Swing interface
Federico Pecora – Java for Interfaces and Networks – Lecture 6
14 / 16
Java for Interfaces and Networks
Applets and JDBC
Security issues
JDBC and Applets: security
Applets are restricted in what they can access
SQLException:
SQLState: 08001
Message: Could not establish connection to server XXXX on
host YYYY using port 1360,
java.security.AccessControlException: access
denied (java.net.SocketPermission YYYY resolve)
ErrorCode: -22017
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Applets and JDBC
Security issues
JDBC and Applets: security
JVM runs applets under a different security regime than
applications
applications are trusted by default (it is assumed that the user
starts them)
applets are untrusted because they are started by browsers
(user cannot be expected to know what an applet does)
Cannot access any internet site other than the one they were
obtained from
Cannot access Java Native Interface (JNI)
Cannot access filesystem (except “inside” their .jar)
These limitations can be overcome with digital certificates
http://java.sun.com/javase/6/docs/technotes/
guides/security/index.html
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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Java for Interfaces and Networks
Applets and JDBC
Security issues
Java Database Connectivity (JDBC)
Thank you!
Federico Pecora – Java for Interfaces and Networks – Lecture 6
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