Add Shutdown Icon to Desktop

Today, I added a shutdown icon to my Dad's Windows XP desktop, to make it easier for him to turn off the computer. This is how you can do it:

• Right-click on the desktop and choose New > Shortcut.
• Type shutdown.exe -s -t 00 in the location box and press Next.
• Type Turn off computer as the name of the shortcut and then press Finish.
• Right-click the new icon that has appeared on the desktop and select Properties.
• Click the Change Icon... button on the Shortcut tab.
• Type %SystemRoot%\system32\SHELL32.dll in the location box and pick the Shutdown icon, which looks like a red square containing a circle with a vertical line.

Now, you can shutdown your computer by simply clicking the "Turn off computer" icon on your desktop, instead of going via the Start menu.

Adding a JProgressBar to a JTable Cell

Create a cell TableCellRenderer which uses a JProgressBar as follows:

import java.awt.Component;

import javax.swing.JProgressBar;
import javax.swing.JTable;
import javax.swing.table.TableCellRenderer;

public class ProgressCellRenderer extends JProgressBar
                        implements TableCellRenderer {

  /**
   * Creates a JProgressBar with the range 0,100.
   */
  public ProgressCellRenderer(){
    super(0, 100);
    setValue(0);
    setString("0%");
    setStringPainted(true);
  }

  public Component getTableCellRendererComponent(
                                    JTable table,
                                    Object value,
                                    boolean isSelected,
                                    boolean hasFocus,
                                    int row,
                                    int column) {

    //value is a percentage e.g. 95%
    final String sValue = value.toString();
    int index = sValue.indexOf('%');
    if (index != -1) {
      int p = 0;
      try{
        p = Integer.parseInt(sValue.substring(0, index));
      }
      catch(NumberFormatException e){
      }
      setValue(p);
      setString(sValue);
    }
    return this;
  }
}

Apply the cell renderer to a specific column in the table:

JTable myTable = new JTable();
TableColumn myCol = myTable.getColumnModel().getColumn(1);
myCol.setCellRenderer(new ProgressCellRenderer());

Now whenever you update a value in that column, the JProgressBar will get updated accordingly.

Using Hermes to Browse WebLogic Topics/Queues

Hermes is a useful tool which allows you to browse JMS topics and queues. I use WebLogic as my JMS provider and it was not trivial trying to connect to my topic using Hermes, so I thought I'd post instructions to help others trying to do the same.

Here are the steps you need to take, in order to browse WebLogic queues and topics using Hermes:

1. Install HermesJMS

• Download Hermes from here.
• It comes as an installer jar file which you can run using the command: java -jar hermes-installer-1.13.jar.
• Once installed, start it using hermes.bat.

2. Add WebLogic Provider
You need to add the weblogic jar to the classpath as follows:

• On the menubar go to Actions > New > New session... to open the Preferences dialog.
• Click on the Providers tab.
• Right-click to Add Group and call it "weblogic92", for example.
• Right-click on Library to Add JAR(s) and select your weblogic jar file from the file chooser dialog.
• Select Don't Scan when prompted to scan the jar file.
• Click Apply and close the dialog.

3. Create WebLogic Session

• On the menubar go to Actions > New > New session... to open the Preferences dialog.
• Click on the Sessions tab.
• Type a name for the session. For example, "myweblogic".
• In the Plug In list select BEA WebLogic.
• Under Connection Factory class, pick hermes.JNDITopicConnectionFactory.
• Select weblogic92 (defined in step 2) from the Loader dropdown.
• Add property: initialContextFactory with a value of weblogic.jndi.WLInitialContextFactory.
• Add property: providerURL with a value of your URL e.g. t3://myhost:2120.
• Add property: binding with a value of the name of your connection factory e.g. myConnectionFactory.
• Add any other properties you may have e.g. securityCredentials etc.
• Remove all Destinations by right-clicking and selecting Remove.
• Press OK.

4. Discover Topics/Queues

• On the left navigation tree, go into jms > sessions > myweblogic.
• Right-click "myweblogic" (the new session created in step 3), and click Discover. You will see a list of queues and topics appear.
• Click on any one of them to browse.

Generics and Class.forName

This post shows how you can create objects of a specified class, using a class name and the supertype of the class you are trying to create.

public final class BeanCreator {

  /**
   * Suppress constructor.
   */
  private BeanCreator(){
  }

  /**
   * Creates an object of the class name and supertype.
   * @param <T>
   * @param className
   * @param superType
   * @return
   * @throws ClassNotFoundException
   */
  public static <T> T create(final String className,
             final Class<T> superType) throws Exception {
    final Class< ? extends T> clazz =
         Class.forName(className).asSubclass(superType);
    return create(clazz);
  }

  /**
   * Creates an object of the specified class using
   * its public or private no-arg constructor.
   *
   * @param <T>
   * @param classToCreate
   * @return
   */
  public static <T> T create(final Class<T> classToCreate)
                                      throws Exception {
        final Constructor<T> constructor =
                   classToCreate.getDeclaredConstructor();
        if (constructor == null) {
         throw new Exception("Could not create a new "+
         "instance of the dest object: " + classToCreate
         + ".  Could not find a no-arg constructor.");
        }

        // If private, make it accessible
        if (!constructor.isAccessible()) {
            constructor.setAccessible(true);
        }
        return constructor.newInstance();
  }
}