Java Beans Tutorial, Pt. 4: Adding a PropertyEditor to NervousText

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[Tutorial Contents]

In this section, you're going to add a PropertyEditor class associated with your NervousText Bean. The name of the class will be NervousText07TextPropertyEditor. Here's the full text for the source file:

#ifdef COMMENT
 NervousText07TextPropertyEditor.java:
#endif

package sun.beanbox.beans;
import java.beans.*;

public class NervousText07TextPropertyEditor
  extends PropertyEditorSupport {
  public String[] getTags() {
    String values[] = {
      "Nervous Text",
      "Anxious Text",
      "Funny Text",
      "Wobbly Text"};
    return values;
  }
}

Step 1. Create NervousText07 and NervousText07BeanInfo classes

Copy the NervousText06.java and NervousText06BeanInfo.java source files to NervousText07.java and NervousText07BeanInfo.java respectively.

Do a global search and replace in both files changing NervousText06 to NervousText07 and rename the classes. Compared to adding the BeanInfo in the previous section, adding the Property editor will be easy. Actually, two minor changes are required for NervousText07BeanInfo.java. For consistency, you'll want to change the name of the Bean in the property descriptor to distinguish it from NervousText06BeanInfo.java. Change:

     bd.setDisplayName("Uneasy Text");

     bd.setDisplayName("Uneasy Text 07");

The second change causes the property editor you're about to create to be attached to instances of the BeanInfo class associated with your Bean. You'll see how that's done at the end of the section after you've created NervousText07TextPropertyEditor.

Step 2. Create NervousText07TextPropertyEditor

Start by creating a file called: NervousText07TextPropertyEditor.java.

Implement the class skeleton:

package sun.beanbox.beans;
import java.beans.*;

public class NervousText07TextPropertyEditor
  extends PropertyEditorSupport {
  ....
  }
}

Note that NervousText07TextPropertyEditor.java extends the PropertyEditorSupport class that implements the PropertyEditor interface.

  public String[] getTags() {
    String values[] = {
      "Nervous Text",
      "Anxious Text",
      "Funny Text",
      "Wobbly Text"};
    return values;
  }

Step 3. Set the PropertyEditor in the text Property's PropertyDescriptor

Now it's time for that second change to NervousText07BeanInfo mentioned earlier. Add the line:

   textPD.setPropertyEditorClass(
     NervousText07TextPropertyEditor.class);

  public class NervousText07BeanInfo 
      extends SimpleBeanInfo {
    private final static Class beanClass =
        NervousText07.class;
    public BeanDescriptor getBeanDescriptor() {
      System.err.println(
        "ENTER---> " + 
        "NervousText07BeanInfo.getBeanDescriptor");
      BeanDescriptor bd = new BeanDescriptor(beanClass);
      bd.setDisplayName("Uneasy Text 07");
      System.err.println(
        "EXIT----> " + 
        "NervousText07BeanInfo.getBeanDescriptor");
      return bd;
    }
    public PropertyDescriptor[] getPropertyDescriptors() {
      try {
        PropertyDescriptor textPD =
          new PropertyDescriptor("text", beanClass);
        PropertyDescriptor rv[] = {textPD};
        textPD.setPropertyEditorClass(
          NervousText07TextPropertyEditor.class);
        return rv;
      } catch (IntrospectionException e) {
        throw new Error(e.toString());
      }
    }
  }

Step 5. Compile the programs

The routine is pretty much the same as in the previous section:

    javac -d . NervousText07.java
    javac -d . NervousText07BeanInfo.java
    javac -d . NervousText07TextPropertyEditor.java

Step 6. Build and install the JAR

The manifest should look like this:

Manifest-Version: 1.0

Name: sun/beanbox/beans/NervousText07.class
Java-Bean: True

Name: sun/beanbox/beans/NervousText07BeanInfo.class

Name: 
  sun/beanbox/beans/NervousText07TextPropertyEditor.class

As before, there are three classes in the JAR, but only one is a Bean.

The manifest can be created with the following set of commands. See the makefile in the example-1.1 directory.

  echo "Manifest-Version: 1.0" > 
manifest.tmp
  echo "" >>
manifest.tmp
  echo "Name: 
    sun/beanbox/beans/NervousText07.class" >>
manifest.tmp
  echo "Java-Bean: True" >>
manifest.tmp
  echo "" >>
manifest.tmp
  echo "Name: 
    sun/beanbox/beans/NervousText07BeanInfo.class" >>
manifest.tmp
  echo "" >>
manifest.tmp
  echo "Name: 
    sun/beanbox/beans/
    NervousText07TextPropertyEditor.class" >>
 
manifest.tmp
  jar cfm NervousText07.jar manifest.tmp \
    sun/beanbox/beans/NervousText07.class \
    sun/beanbox/beans/NervousText07BeanInfo.class \
    sun/beanbox/beans/
    NervousText07TextPropertyEditor.class
  cp -p NervousText07.jar BDK_HOME/beans/jars

A makefile will make the manifest for you if you don't want to do it by hand. It will also build the JAR file and copy it to the right location provided that you have set the target directories at the top of the file.

Step 7. Test the Bean in the BeanBox

Now when you see the property editor associated with the NervousText08 Bean, instead of a editable text field you'll get a drop-down choice choice box containing the array of strings in the getTags method of NervousText07TextPropertyEditor.

For the final versions of the examples in this section, see:

NervousText07.java

NervousText07BeanInfo.java

NervousText07TextPropertyEditor.java