CS 696 Emerging Technologies: Distributed Objects

1. References
2. Introspection
   1. Design Patterns
      1. Properties
      2. Events
      3. Capital Letters in Name Patterns
   2. Analyzing A Bean
   3. BeanInfo Interface
      1. getIcon
      2. java.beans.FeatureDescriptor
      3. getBeanDescriptor
      4. PropertyDescriptor
      5. getPropertyDescriptors
   4. Property Editors

Doc 33, Bean Introspection & Customization Slide # 2

   public < PropertyType> get< PropertyName>();
   public void set< PropertyName>(< PropertyType> a);

   public Wombat getFoo();
   public void setFoo(Wombat w);

   public boolean is< PropertyName>();

   public boolean getFoo();
   public void setFoo(boolean w);
   public boolean isFoo()

Doc 33, Bean Introspection & Customization Slide # 3

   public < PropertyElement> get< PropertyName>(int index);
   public void set< PropertyName>(int index, < PropertyElement> b);
   public < PropertyElement>[] get< PropertyName>();
   public void set< PropertyName>( < PropertyElement>[] b);

   public Bah[] getFoo();
   public void setFoo(Bah a[]);
   public Bah getFoo(int a);
   public void setFoo(int a, Bah b);

   public void add< EventListenerType>(< EventListenerType> a)
   public void remove< EventListenerType>(< EventListenerType> a)

   public void addFredListener(FredListener t);
   public void removeFredListener(FredListener t);

   public void addJackListener(JackListener t)
      throws java.util.TooManyListenersException;
   public void removeJackListener(JackListener t);

Doc 33, Bean Introspection & Customization Slide # 4

normally the first character is converted to lower case

if the first two characters of the name are both upper case then do not change the first letter

Doc 33, Bean Introspection & Customization Slide # 5

The builder tools can use the BeanInfo class

Applications using your bean do not need the BeanInfo class

Users can not extract the bean from the application and use it in a builder tool

This allows you sell beans to developers without giving it way to users of their applications

Doc 33, Bean Introspection & Customization Slide # 6

Returns an image to be used to represent the bean in toolboxes, toolbars, etc.

Returns overall information about the bean, such as its displayName,

Returns a list of methods supported by the bean with a description of each method

Returns a list of properties supported by the bean with a description of each property

Returns a list of events fired by the bean with a description of each event

This method allows a BeanInfo object to return an arbitrary collection of other BeanInfo objects that provide additional information on the current bean

A bean may have a "default" event that is the event that will mostly commonly be used by human's when using the bean

A bean may have a "default" property that is the property that will mostly commonly be initially chosen for update by human's who are customizing the bean

Doc 33, Bean Introspection & Customization Slide # 7

package beanExamples;
import java.beans.*;

public class SDSUReporterBeanInfo extends SimpleBeanInfo
   {
   public java.awt.Image getIcon( int kind )
      {
      if ((kind == ICON_MONO_16x16 ) || 
         (kind == ICON_COLOR_16x16  ))
         return loadImage( "sample.gif");
      else
         return null;
      }
   }

ICON_MONO_16x16
ICON_COLOR_16x16
ICON_MONO_32x32
ICON_COLOR_32x32

resourceName - A pathname relative to the directory holding the class file of the current class. For example, "wombat.gif".

Doc 33, Bean Introspection & Customization Slide # 8

The name displayed in builder tool for this item

The programmatic name of the property/method/event

You can associate a short descriptive string with a feature

Supports name/value pairs with this feature

Distinguishes between features for expert users from those for normal users

Identifies features that are intended only for tool use, and which should not be exposed to humans

Doc 33, Bean Introspection & Customization Slide # 9

package beanExamples;
import java.beans.*;

public class SDSUReporterBeanInfo extends SimpleBeanInfo
   {
   public java.awt.Image getIcon( int kind )
      {
      if ((kind == ICON_MONO_16x16 ) || 
         (kind == ICON_COLOR_16x16  ))
         return loadImage( "sample.gif");
      else
         return null;
      }
   
   public BeanDescriptor getBeanDescriptor()
      {
      BeanDescriptor myInfo = 
         new BeanDescriptor( SDSUReporter.class );
      myInfo.setDisplayName( "Hot Stuff");
      return myInfo;
      }
   }

Doc 33, Bean Introspection & Customization Slide # 10

public PropertyDescriptor(String propertyName, 
      Class beanClass) throws IntrospectionException

public PropertyDescriptor(String propertyName, 
      Class beanClass, String getterName, 
      String setterName) throws IntrospectionException

public PropertyDescriptor(String propertyName, Method getter, 
      Method setter) throws IntrospectionException

The programmatic name of the property

The method used for reading the property value. Set null if the property is write-only

The method used for writing the property value. Set null if the property is read-only

The Class object for the target bean

Doc 33, Bean Introspection & Customization Slide # 11

package beanExamples;
import java.beans.*;

public class SDSUReporterBeanInfo extends SimpleBeanInfo {
   public java.awt.Image getIcon( int kind ) {
      if ((kind == ICON_MONO_16x16 ) || 
         (kind == ICON_COLOR_16x16  ))
         return loadImage( "sample.gif");
      else
         return null;
   }
   
   public BeanDescriptor getBeanDescriptor() {
      BeanDescriptor myInfo = 
         new BeanDescriptor( SDSUReporter.class );
      myInfo.setDisplayName( "Hot Stuff");
      return myInfo;
   }
      
   public PropertyDescriptor[] getPropertyDescriptors() {
      try {
         PropertyDescriptor nameProperty = 
            new PropertyDescriptor( "name", SDSUReporter.class );
         nameProperty.setDisplayName( "Reporter's Name");
         nameProperty.setShortDescription(
            "This is the name of your reporter");       
         
         PropertyDescriptor[] allProperties = { nameProperty };
         return allProperties;
      }
      catch ( IntrospectionException error ) {
         return super.getPropertyDescriptors(); // use default if there is an error
      }
   }
}

Doc 33, Bean Introspection & Customization Slide # 12

Use the getAsText() method to convert a property to a string and display it

Use the getTags() method to display a dropdown menu of the allowed values

Use the paintValue() method to display the value using a graphical format

You need to use isPaintable to specify that a graphical format is supported

Doc 33, Bean Introspection & Customization Slide # 13

User types value into a simple text field

Using the methods getCustomEditor() and supportsCustomEditor() you can have the BeanBox use a custom editing window that you supply

Doc 33, Bean Introspection & Customization Slide # 14

Set the property value by parsing a given String.

A PropertyEditor may choose to make available a full custom Component that edits its property value.

This method is intended for use when generating Java code to set the value of the property.

If the property value must be one of a set of known tagged values, then this method should return an array of the tags.

Set (or change) the object that is to be edited.

Paint a representation of the value into a given area of screen real estate.

Doc 33, Bean Introspection & Customization Slide # 15

package beanExamples;
import java.beans.*;

public class School
   {
   public static final int SDSU = 1;
   public static final int USD = 2;
   public static final int UCSD = 3;
   
   private int aSchool;
   
   public School( int id ){aSchool = id;}
   
   public int getType(){   return aSchool;}

   public String getName()
      {
      switch ( aSchool )
         {
         case 1:
            return "SDSU";
         case 2:
            return "USD";
         case 3:
            return "UCSD";
         default:
            return "Not Known";
         }
         
      }
   }

Doc 33, Bean Introspection & Customization Slide # 16

package beanExamples;
import java.beans.*;

public class SchoolEditor extends PropertyEditorSupport {
   
   public String[] getTags() {
      return new String[] { "SDSU", "USD", "UCSD" };
   }
   
   public void setAsText( String input ) {
      if ( input.equals( "SDSU" ) )
         setValue( new School( School.SDSU ));
      else if ( input.equals( "USD" ) )
         setValue( new School( School.USD ));
      else if  ( input.equals( "UCSD" ) )
         setValue( new School( School.UCSD ));
      else 
         throw new IllegalArgumentException( input );
   }
   
   public String getJavaInitializationString() {
      School value =  (School) getValue();
      int type = value.getType();
      
      switch ( type ) {
         default:
         case 1: return "new School( School.SDSU )";
         case  2: return "new School( School.USD )";
         case 3: return "new School( School.UCSD )";
      }
   }
}

visitors since 05-May-98