ISSUE java.lang.IllegalStateException: zip file closed

Question

I have created a jar file which throws the below error, Its a simple swing app which inserts a row whn i press a button, not sure where I am going wrong please advise.

private void jButton20ActionPerformed(java.awt.event.ActionEvent evt) {
    // TODO add your handling code here:

    setatmid(jTextField2.getText());
    setaa10(Integer.parseInt(jTextField3.getText()));
    setaa20(Integer.parseInt(jTextField4.getText()));
    setaa50(Integer.parseInt(jTextField5.getText()));
    setaa100(Integer.parseInt(jTextField6.getText()));

     try{
    System.err.println("Inserting values in Mysql database table!");
Connection con = null;
String url = "jdbc:mysql://localhost:3306/";
String db = "agents";
String driver = "com.mysql.jdbc.Driver";


  Class.forName(driver);
  con = DriverManager.getConnection(url+db,"root","");

    Statement st = con.createStatement();
    String qery="INSERT INTO schedule_data (`s_ID`, `schedule_date`, `atmID`, `notification`) VALUES ('"+System.currentTimeMillis()+"','2010-09-15','"+getatmid()+"','null')";
    st.executeUpdate(qery);
    System.err.println("1 row affected");
}catch(Exception e)
{
  e.printStackTrace();
}
}



java.lang.IllegalStateException: zip file closed
    at java.util.zip.ZipFile.ensureOpen(Unknown Source)
    at java.util.zip.ZipFile.getEntry(Unknown Source)
    at java.util.jar.JarFile.getEntry(Unknown Source)
    at java.util.jar.JarFile.getJarEntry(Unknown Source)
    at sun.misc.URLClassPath$JarLoader.getResource(Unknown Source)
    at sun.misc.URLClassPath.getResource(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at atmguis.atm.jButton20ActionPerformed(atm.java:588)
    at atmguis.atm.access$1600(atm.java:25)
    at atmguis.atm$17.actionPerformed(atm.java:226)
    at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
    at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
    at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
    at java.awt.Component.processMouseEvent(Unknown Source)
    at javax.swing.JComponent.processMouseEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
    at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

The method involved is being called from the Event Dispatch Thread. I'm sure this is a part of the problem. You are trying to access the JAR file containing the com.mysql.jdbc.Driver class from this thread. This is where the error is being thrown. I have to wonder if there is some sort of concurrency issue here. Here are a couple of general notes, things that should be addressed. Once you have addressed these issues, see if you are still having a problem.

1. You should not be doing a database query from inside the EDT. You should collect the information you need from the swing components and then use a Runnable object to execute the SQL query on a different thread. Do a search on SO for executing code on or off the EDT to find examples of how to do this. This will ensure that your UI doesn't lock up while you wait for your SQL results.

2. Opening and closing a database connection every time you need one is something better left to the SQL driver and its built-in connection pooling abilities. This method should be declared on some sort of controller object which already has a reference to the SQL connection. Then, when this method is called, you call your thread as in the last step, and that thread uses the reference to the SQL connection that it already has.

This will take the line that's throwing the exception and move it out of the EDT into some sort of setup phase, presumably where you will have better luck accessing the class file. Certainly it will be a much more controlled environment than within the EDT. If there continues to be a problem accessing it, it will be easier to debug in the more controlled environment.

As an added bonus, you will also be designing your application in much more robust way.