Adding a PropertyEditor to NervousText

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: NervousText07TextPropertyEditor.java: 

    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;
      }
    }
Defining this class is the only real work you need to do. NervousText07 NervousText07BeanInfo, are also required, but these can effectively be copied and modified with a global search and replace.

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");
to 
     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. Next override the getTags method. This method simply returns a list of strings that the property editor will display when a programmer tries to edit the text property of NervousText07 in a builder tool. 

      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);
to the getPropertyDescriptors in NervousText07BeanInfo. The full definition of the class should now look like this: 
    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());
        }
      }
    }
That's it. Now you're ready to compile.

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
Be sure to subsitute your BDK installation directory for BDK_HOME in the above commands. 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

NervousText07TextPropert yEditor.java




Questions?
30-Jan-98
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