Very Computer

Hi,

I'm a Java (JDK 1.3) primer and trying to create an applet that
can connect to my database and make some queries. I was trying
to convert an example from Ivor Horton's Java2 book. It was a
normal application and I customised it according to my database.
But I couldn't convert it to an applet.

So I tried a simpler applet and put the SQL connection into it,
it compiled but when it worked I received the following error
messages from the console:

--------------------------------------------------------------
C:\jdk1.3\bin>appletviewer applet.html

Exception occurred during event dispatching:

java.security.AccessControlException: access denied
(java.lang.RuntimePermission
accessClassInPackage.sun.jdbc.odbc)
at java.security.AccessControlContext.checkPermission
(AccessControlConte
xt.java:272)
at java.security.AccessController.checkPermission
(AccessController.java:
399)
at java.lang.SecurityManager.checkPermission
(SecurityManager.java:545)
at java.lang.SecurityManager.checkPackageAccess
(SecurityManager.java:150
1)
at sun.applet.AppletSecurity.checkPackageAccess
(AppletSecurity.java:169)
---------------------------------------------------------------

I'm a little bit confused because the similar code works OK as a
Java application but I have this trouble when it is in an
applet.

What must I do so that my applet can connect to my database?

Please bear in mind that I'm a primer and didn't use that
policytool, etc. :-)

Thanks in advance.

The sample code:
----------------------------------------------------------
/*
* Swing Version
*/

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.sql.*; // For JDBC classes

public class TextDemo extends JApplet implements ActionListener
{
JTextField textField;
JTextArea textArea;
String newline = "\n";

//Hack to avoid annoying error message (1.1).
public TextDemo() {
getRootPane().putClientProperty
("defeatSystemEventQueueCheck",
Boolean.TRUE);

Quote:}

public void init() {
textField = new JTextField(20);
textField.addActionListener(this);

textArea = new JTextArea(5, 20);
textArea.setEditable(false);
JScrollPane scrollPane = new JScrollPane(textArea,

JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,

JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

//Add Components to the Applet.
GridBagLayout gridBag = new GridBagLayout();
Container contentPane = getContentPane();
contentPane.setLayout(gridBag);
GridBagConstraints c = new GridBagConstraints();
c.gridwidth = GridBagConstraints.REMAINDER;

c.fill = GridBagConstraints.HORIZONTAL;
gridBag.setConstraints(textField, c);
contentPane.add(textField);

c.fill = GridBagConstraints.BOTH;
c.weightx = 1.0;
c.weighty = 1.0;
gridBag.setConstraints(scrollPane, c);
contentPane.add(scrollPane);

Quote:}

public void actionPerformed(ActionEvent evt) {
String text = textField.getText();

// try
// {
// Load the driver class
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

// Define the data source for the driver
String sourceURL = "jdbc:odbc:LocalSQLServer";

// Create a connection through the DriverManager
Connection databaseConnection =
DriverManager.getConnection(sourceURL);

Statement statement = databaseConnection.createStatement ();

/*ResultSet authorNames = statement.executeQuery("SELECT Name
FROM Film");*/

// Output the resultset data
/*while(authorNames.next())
System.out.println(authorNames.getString("Name"));*/
// }

/*catch(ClassNotFoundException cnfe)
{
System.err.println(cnfe);

Quote:}

catch(SQLException sqle)
{
System.err.println(sqle);

Quote:}*/

textArea.append(text + newline);
textField.selectAll();

Quote:}
}

Try policytool.exe form jdk/bin directory to set up appletviewer policy.

Quote:> Hi,

> I'm a Java (JDK 1.3) primer and trying to create an applet that
> can connect to my database and make some queries. I was trying
> to convert an example from Ivor Horton's Java2 book. It was a
> normal application and I customised it according to my database.
> But I couldn't convert it to an applet.

> So I tried a simpler applet and put the SQL connection into it,
> it compiled but when it worked I received the following error
> messages from the console:

> --------------------------------------------------------------
> C:\jdk1.3\bin>appletviewer applet.html

> Exception occurred during event dispatching:

> java.security.AccessControlException: access denied
> (java.lang.RuntimePermission
> accessClassInPackage.sun.jdbc.odbc)
> at java.security.AccessControlContext.checkPermission
> (AccessControlConte
> xt.java:272)
> at java.security.AccessController.checkPermission
> (AccessController.java:
> 399)
> at java.lang.SecurityManager.checkPermission
> (SecurityManager.java:545)
> at java.lang.SecurityManager.checkPackageAccess
> (SecurityManager.java:150
> 1)
> at sun.applet.AppletSecurity.checkPackageAccess
> (AppletSecurity.java:169)
> ---------------------------------------------------------------

> I'm a little bit confused because the similar code works OK as a
> Java application but I have this trouble when it is in an
> applet.

> What must I do so that my applet can connect to my database?

> Please bear in mind that I'm a primer and didn't use that
> policytool, etc. :-)

> Thanks in advance.

> The sample code:
> ----------------------------------------------------------
> /*
> * Swing Version
> */

> import java.awt.*;
> import java.awt.event.*;
> import javax.swing.*;
> import java.sql.*; // For JDBC classes

> public class TextDemo extends JApplet implements ActionListener
> {
> JTextField textField;
> JTextArea textArea;
> String newline = "\n";

> //Hack to avoid annoying error message (1.1).
> public TextDemo() {
> getRootPane().putClientProperty
> ("defeatSystemEventQueueCheck",
> Boolean.TRUE);
> }

> public void init() {
> textField = new JTextField(20);
> textField.addActionListener(this);

> textArea = new JTextArea(5, 20);
> textArea.setEditable(false);
> JScrollPane scrollPane = new JScrollPane(textArea,

> JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,

> JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);

> //Add Components to the Applet.
> GridBagLayout gridBag = new GridBagLayout();
> Container contentPane = getContentPane();
> contentPane.setLayout(gridBag);
> GridBagConstraints c = new GridBagConstraints();
> c.gridwidth = GridBagConstraints.REMAINDER;

> c.fill = GridBagConstraints.HORIZONTAL;
> gridBag.setConstraints(textField, c);
> contentPane.add(textField);

> c.fill = GridBagConstraints.BOTH;
> c.weightx = 1.0;
> c.weighty = 1.0;
> gridBag.setConstraints(scrollPane, c);
> contentPane.add(scrollPane);
> }

> public void actionPerformed(ActionEvent evt) {
> String text = textField.getText();

> // try
> // {
> // Load the driver class
> Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

> // Define the data source for the driver
> String sourceURL = "jdbc:odbc:LocalSQLServer";

> // Create a connection through the DriverManager
> Connection databaseConnection =
> DriverManager.getConnection(sourceURL);

> Statement statement = databaseConnection.createStatement ();

> /*ResultSet authorNames = statement.executeQuery("SELECT Name
> FROM Film");*/

> // Output the resultset data
> /*while(authorNames.next())
> System.out.println(authorNames.getString("Name"));*/
> // }

> /*catch(ClassNotFoundException cnfe)
> {
> System.err.println(cnfe);
> }
> catch(SQLException sqle)
> {
> System.err.println(sqle);
> }*/

> textArea.append(text + newline);
> textField.selectAll();
> }

> }

Hi,

I think unsigned applets are not allowed to make database connections,
whereas signed applets and applications are viewed as secure enough to
do so. See the JDBC FAQ on http://www.javasoft.com/products/jdbc/ for
details.

Regards,
Stefan