Java Tutorial/Development/JavaBeans

Bean has a single property called property.

   <source lang="java">

import java.io.Serializable; public class BasicBean implements Serializable {

 boolean property;
 public BasicBean() {
 }
 public boolean getProperty() {
   return property;
 }
 public boolean isProperty() {
   return property;
 }
 public void setProperty(boolean newValue) {
   property = newValue;
 }

}</source>

Constructs a method name from element"s bean name for a given prefix

   <source lang="java">

/*

* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
* 
* Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
* 
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common Development
* and Distribution License("CDDL") (collectively, the "License").  You
* may not use this file except in compliance with the License. You can obtain
* a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
* or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
* language governing permissions and limitations under the License.
* 
* When distributing the software, include this License Header Notice in each
* file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
* Sun designates this particular file as subject to the "Classpath" exception
* as provided by Sun in the GPL Version 2 section of the License file that
* accompanied this code.  If applicable, add the following below the License
* Header, with the fields enclosed by brackets [] replaced by your own
* identifying information: "Portions Copyrighted [year]
* [name of copyright owner]"
* 
* Contributor(s):
* 
* If you wish your version of this file to be governed by only the CDDL or
* only the GPL Version 2, indicate your decision by adding "[Contributor]
* elects to include this software in this distribution under the [CDDL or GPL
* Version 2] license."  If you don"t indicate a single choice of license, a
* recipient has the option to distribute your version of this file under
* either the CDDL, the GPL Version 2 or to extend the choice of license to
* its licensees as provided above.  However, if you add GPL Version 2 code
* and therefore, elected the GPL Version 2 license, then the option applies
* only if the new code is made subject to such option by the copyright
* holder.
*/

/**

*   
* @author  Rajeshwar Patil
* @version %I%, %G%
*/

public class Utils {

 /** 
  * Constructs a method name from  element"s bean
  * name for a given prefix.(schema2beans convention)
  *
  * @param elementName the given element name
  * @param prefix the given prefix
  * @return a method name formed from the given name and the prefix
  */
 public String methodNameFromBeanName(String elementName,
         String prefix){
     if((null == elementName) || (null == prefix) ||
             (prefix.length() <= 0 )){
         return elementName;
     }
     String methodName = upperCaseFirstLetter(elementName);
     return methodName = prefix + methodName;
 }
 /**
  * Converts the first letter of the given string to Uppercase.
  * 
  * @param string the input string
  * @return the string with the Uppercase first letter
  */
  public String upperCaseFirstLetter(String string)
  {
      if(string == null || string.length() <= 0){
          return string;
      }
      return string.substring(0, 1).toUpperCase() + string.substring(1);
  }

}</source>

Convert a bean to XML persistence

   <source lang="java">

import java.beans.XMLEncoder; import java.io.BufferedOutputStream; import java.io.FileOutputStream; public class Main {

 public static void main(String[] args) throws Exception {
   Item bean = new Item();
   bean.setId(new Long(1));
   bean.setItemName("a");
   bean.setItemColour("Red");
   bean.setItemQuantities(new Integer(100));
   XMLEncoder encoder = new XMLEncoder(new BufferedOutputStream(new FileOutputStream("Bean.xml")));
   encoder.writeObject(bean);
   encoder.close();
 }

} class Item {

 private Long id;
 private String itemName;
 private String itemColour;
 private Integer itemQuantities;
 public Long getId() {
   return id;
 }
 public void setId(Long id) {
   this.id = id;
 }
 public String getItemName() {
   return itemName;
 }
 public void setItemName(String itemName) {
   this.itemName = itemName;
 }
 public String getItemColour() {
   return itemColour;
 }
 public void setItemColour(String itemColour) {
   this.itemColour = itemColour;
 }
 public Integer getItemQuantities() {
   return itemQuantities;
 }
 public void setItemQuantities(Integer itemQuantities) {
   this.itemQuantities = itemQuantities;
 }

}</source>

Convert an XML persistence to bean

   <source lang="java">

import java.beans.XMLDecoder; import java.io.BufferedInputStream; import java.io.FileInputStream; import java.io.Serializable; public class Main {

 public static void main(String[] argv) throws Exception {
   XMLDecoder decoder = new XMLDecoder(new BufferedInputStream(new FileInputStream("Bean.xml")));
   Bean bean = (Bean) decoder.readObject();
   decoder.close();
   System.out.println("ID = " + bean.getId());
 }

} class Bean implements Serializable {

 private Long id;
 public Long getId() {
   return id;
 }
 public void setId(Long id) {
   this.id = id;
 }

} Here is our Bean.xml persistence file: <?xml version="1.0" encoding="UTF-8"?> <java version="1.6.0_02" class="java.beans.XMLDecoder">

<object class="org.username.example.bean.BeanToXML"> 
 <void property="id"> 
  <long>1</long> 
 </void> 
</object> 

</java></source>

Create an instance a Bean

   <source lang="java">

import java.beans.Beans; import java.io.Serializable; public class Main implements Serializable {

 private Long id;
 private String name;
 public Main() {
 }
 public static void main(String[] args) throws Exception {
   Main bean = (Main) Beans.instantiate(ClassLoader.getSystemClassLoader(),
       "Main");
   System.out.println("The Bean = " + bean);
 }
 public Long getId() {
   return id;
 }
 public void setId(Long id) {
   this.id = id;
 }
 public String getName() {
   return name;
 }
 public void setName(String name) {
   this.name = name;
 }
 @Override
 public String toString() {
   return "[id=" + id + "; name=" + name + "]";
 }

}</source>

Deserializing a Bean from XML

   <source lang="java">

import java.beans.XMLDecoder; import java.io.BufferedInputStream; import java.io.FileInputStream; public class Main {

 public static void main(String[] argv) throws Exception {
   XMLDecoder decoder = new XMLDecoder(new BufferedInputStream(
       new FileInputStream("infilename.xml")));

   MyClass o = (MyClass) decoder.readObject();
   decoder.close();
   int prop = o.getProp(); // 1
   int[] props = o.getProps(); // [1, 2, 3]
 }

} class MyClass {

 // The prop property
 int i;
 public int getProp() {
   return i;
 }
 public void setProp(int i) {
   this.i = i;
 }
 // The props property
 int[] iarray = new int[0];
 public int[] getProps() {
   return iarray;
 }
 public void setProps(int[] iarray) {
   this.iarray = iarray;
 }

} /*

   <?xml version="1.0" encoding="UTF-8"?>
   <java version="1.4.0" class="java.beans.XMLDecoder">
       <object class="MyClass">
           <void property="prop">
               <int>1</int>
           </void>
           <void property="props">
               <array class="int" length="3">
                   <void index="0">
                       <int>1</int>
                   </void>
                   <void index="1">
                       <int>2</int>
                   </void>
                   <void index="2">
                       <int>3</int>
                   </void>
               </array>
           </void>
       </object>
   </java>

• /</source>

Determine bean"s property type

   <source lang="java">

import org.apache.rumons.beanutils.PropertyUtils; public class Main {

 public static void main(String[] args) throws Exception {
   Recording recording = new Recording();
   recording.setTitle("Magical Mystery Tour");
   Class type = PropertyUtils.getPropertyType(recording, "title");
   System.out.println("type = " + type.getName());
   String value = (String) PropertyUtils.getProperty(recording, "title");
   System.out.println("value = " + value);
 }

}</source>

Displaying the Current Directory in the Title of a JFileChooser Dialog

   <source lang="java">

import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.io.File; import javax.swing.JFileChooser; public class Main {

 public static void main(String[] argv) {
   final JFileChooser chooser = new JFileChooser();
   File curDir = chooser.getCurrentDirectory();
   chooser.setDialogTitle("" + curDir.getAbsolutePath());
   chooser.addPropertyChangeListener(new PropertyChangeListener() {
     public void propertyChange(PropertyChangeEvent evt) {
       if (JFileChooser.DIRECTORY_CHANGED_PROPERTY.equals(evt.getPropertyName())) {
         File curDir = chooser.getCurrentDirectory();
         chooser.setDialogTitle("" + curDir.getAbsolutePath());
       }
     }
   });
 }

}</source>

extends SimpleBeanInfo

   <source lang="java">

/**

* FontSelectorBeanBeanInfo.java  1.00 97/08/09 Merlin Hughes
*
* Copyright (c) 1997 Merlin Hughes, All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this software
* for commercial and non-commercial purposes and without fee is
* hereby granted provided that this copyright notice appears in
* all copies.
*
* http://prominence.ru/                         ego@merlin.org
*/

import java.awt.Image; import java.beans.SimpleBeanInfo; public class FontSelectorBeanBeanInfo extends SimpleBeanInfo {

 public Image getIcon(int iconKind) {
   if (iconKind == ICON_COLOR_16x16) {
     return loadImage("FontSelectorBeanIconColor16.gif");
   } else {
     return null;
   }
 }

}</source>

Get a list of selected files

   <source lang="java">

import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.io.File; import javax.swing.JFileChooser; public class Main {

 public static void main(String[] argv) throws Exception {
   JFileChooser chooser = new JFileChooser();
   chooser.addPropertyChangeListener(new PropertyChangeListener() {
     public void propertyChange(PropertyChangeEvent evt) {
       if (JFileChooser.SELECTED_FILES_CHANGED_PROPERTY.equals(evt.getPropertyName())) {
         JFileChooser chooser = (JFileChooser) evt.getSource();
         File[] oldFiles = (File[]) evt.getOldValue();
         File[] newFiles = (File[]) evt.getNewValue();
         // Get list of selected files
         File[] files = chooser.getSelectedFiles();
       }    
     }
   });
 }

}</source>

Get and set an Object type property

   <source lang="java">

import java.beans.Expression; import java.beans.Statement; public class Main {

 public static void main(String[] argv) throws Exception {
   Object o = new MyBean();
   // Get the value of prop1
   Expression expr = new Expression(o, "getProp1", new Object[0]);
   expr.execute();
   String s = (String) expr.getValue();
   // Set the value of prop1
   Statement stmt = new Statement(o, "setProp1", new Object[] { "new string" });
   stmt.execute();
 }

} class MyBean {

 String prop1;
 public String getProp1() {
   return prop1;
 }
 public void setProp1(String s) {
   prop1 = s;
 }
 int prop2;
 public int getProp2() {
   return prop2;
 }
 public void setProp2(int i) {
   prop2 = i;
 }
 byte[] prop3;
 public byte[] getProp3() {
   return prop3;
 }
 public void setProp3(byte[] bytes) {
   prop3 = bytes;
 }

}</source>

Get and set properties on a bean

   <source lang="java">

/*

* The contents of this file are subject to the Sapient Public License
* Version 1.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
* http://carbon.sf.net/License.html.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
* the specific language governing rights and limitations under the License.
*
* The Original Code is The Carbon Component Framework.
*
* The Initial Developer of the Original Code is Sapient Corporation
*
* Copyright (C) 2003 Sapient Corporation. All Rights Reserved.
*/

import java.beans.BeanInfo; import java.beans.IntrospectionException; import java.beans.Introspector; import java.beans.PropertyDescriptor; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.StringTokenizer;

/**

* This class implements the ability to get and set properties on a
* bean.  This included the concept of embedded properties that may
* be referenced like Bean.property.property.property.
*
* Copyright 2002 Sapient
* @since carbon 1.0
* @author Greg Hinkle, January 2002
* @version $Revision: 1.11 $ ($Author: dvoet $)
*/

public final class BeanUtil {

   /**
    * String used to separate multiple properties inside of embedded
    * beans.
    */
   private static final String PROPERTY_SEPARATOR = ".";
   /**
    * An empty class array used for null parameter method reflection
    */
   private static Class[] NO_PARAMETERS_ARRAY = new Class[] {
   };
   /**
    * an empty object array used for null parameter method reflection
    */
   private static Object[] NO_ARGUMENTS_ARRAY = new Object[] {
   };
   /**
    * The constructor is private so that new cannot be used.
    */
   private BeanUtil() {
   }
   /**
    * Retreives a property descriptor object for a given property.
    * 
    * Uses the classes in java.beans to get back
    * a descriptor for a property.  Read-only and write-only
    * properties will have a slower return time.
    * 
    *
    * @param propertyName The programmatic name of the property
    * @param beanClass The Class object for the target bean.
    *                  For example sun.beans.OurButton.class.
    * @return a PropertyDescriptor for a property that follows the
    *         standard Java naming conventions.
    * @throws PropertyNotFoundException indicates that the property
    *         could not be found on the bean class.
    */
   private static final PropertyDescriptor getPropertyDescriptor(
       String propertyName,
       Class beanClass) {
       PropertyDescriptor resultPropertyDescriptor = null;

       char[] pNameArray = propertyName.toCharArray();
       pNameArray[0] = Character.toLowerCase(pNameArray[0]);
       propertyName = new String(pNameArray);
       try {
           resultPropertyDescriptor =
               new PropertyDescriptor(propertyName, beanClass);
       } catch (IntrospectionException e1) {
           // Read-only and write-only properties will throw this
           // exception.  The properties must be looked up using
           // brute force.
           // This will get the list of all properties and iterate
           // through looking for one that matches the property
           // name passed into the method.
           try {
               BeanInfo beanInfo = Introspector.getBeanInfo(beanClass);
               PropertyDescriptor[] propertyDescriptors =
                   beanInfo.getPropertyDescriptors();
               for (int i = 0; i < propertyDescriptors.length; i++) {
                   if (propertyDescriptors[i]
                       .getName()
                       .equals(propertyName)) {
                       // If the names match, this this describes the
                       // property being searched for.  Break out of
                       // the iteration.
                       resultPropertyDescriptor = propertyDescriptors[i];
                       break;
                   }
               }
           } catch (IntrospectionException e2) {
               e2.printStackTrace();
           }
       }
       // If no property descriptor was found, then this bean does not
       // have a property matching the name passed in.
       if (resultPropertyDescriptor == null) {
           System.out.println("resultPropertyDescriptor == null");
       }
       return resultPropertyDescriptor;
   }
   /**
    * Gets the specified attribute from the specified object.  For example,
    * getObjectAttribute(o, "address.line1") will return
    * the result of calling o.getAddress().getLine1().
    *
    * The attribute specified may contain as many levels as you like. If at
    * any time a null reference is acquired by calling one of the successive
    * getter methods, then the return value from this method is also null.
    *
    * When reading from a boolean property the underlying bean introspector
    * first looks for an is<Property> read method, not finding one it will
    * still look for a get<Property> read method.  Not finding either, the
    * property is considered write-only.
    *
    * @param bean the bean to set the property on
    * @param propertyNames the name of the propertie(s) to retrieve.  If this is
    *        null or the empty string, then bean will be returned.
    * @return the object value of the bean attribute
    *
    * @throws PropertyNotFoundException indicates the the given property
    *         could not be found on the bean
    * @throws NoSuchMethodException Not thrown
    * @throws InvocationTargetException if a specified getter method throws an
    *   exception.
    * @throws IllegalAccessException if a getter method is
    *   not public or property is write-only.
    */
   public static Object getObjectAttribute(Object bean, String propertyNames)
       throws
           NoSuchMethodException,
           InvocationTargetException,
           IllegalAccessException {

       Object result = bean;
       StringTokenizer propertyTokenizer =
           new StringTokenizer(propertyNames, PROPERTY_SEPARATOR);
       // Run through the tokens, calling get methods and
       // replacing result with the new object each time.
       // If the result equals null, then simply return null.
       while (propertyTokenizer.hasMoreElements() && result != null) {
           Class resultClass = result.getClass();
           String currentPropertyName = propertyTokenizer.nextToken();
           PropertyDescriptor propertyDescriptor =
               getPropertyDescriptor(currentPropertyName, resultClass);
           Method readMethod = propertyDescriptor.getReadMethod();
           if (readMethod == null) {
               throw new IllegalAccessException(
                   "User is attempting to "
                       + "read from a property that has no read method.  "
                       + " This is likely a write-only bean property.  Caused "
                       + "by property ["
                       + currentPropertyName
                       + "] on class ["
                       + resultClass
                       + "]");
           }
           result = readMethod.invoke(result, NO_ARGUMENTS_ARRAY);
       }
       return result;
   }
   /**
    * Sets the specified attribute on the specified object.  For example,
    * getObjectAttribute(o, "address.line1", value) will call
    * o.getAddress().setLine1(value).
    *
    * The attribute specified may contain as many levels as you like. If at
    * any time a null reference is acquired by calling one of the successive
    * getter methods, then a NullPointerException is thrown.
    *
    * @param bean the bean to call the getters on
    * @param propertyNames the name of the attribute(s) to set.  If this is
    *        null or the empty string, then an exception is thrown.
    * @param value the value of the object to set on the bean property
    *
    * @throws PropertyNotFoundException indicates the the given property
    *         could not be found on the bean
    * @throws IllegalArgumentException if the supplied parameter is not of
    *   a valid type
    * @throws NoSuchMethodException never
    * @throws IllegalAccessException if a getter or setter method is
    *   not public or property is read-only.
    * @throws InvocationTargetException if a specified getter method throws an
    *   exception.
    */
   public static void setObjectAttribute(
       Object bean,
       String propertyNames,
       Object value)
       throws
           IllegalAccessException,
           IllegalArgumentException,
           InvocationTargetException,
           NoSuchMethodException {

       Object result = bean;
       String propertyName = propertyNames;
       // Check if this has some embedded properties.  If it does, use the
       // getObjectAttribute to get the proper object to call this on.
       int indexOfLastPropertySeparator =
           propertyName.lastIndexOf(PROPERTY_SEPARATOR);
       if (indexOfLastPropertySeparator >= 0) {
           String embeddedProperties =
               propertyName.substring(0, indexOfLastPropertySeparator);
           // Grab the final property name after the last property separator
           propertyName =
               propertyName.substring(
                   indexOfLastPropertySeparator + PROPERTY_SEPARATOR.length());
           result = getObjectAttribute(result, embeddedProperties);
       }
       Class resultClass = result.getClass();
       PropertyDescriptor propertyDescriptor =
           getPropertyDescriptor(propertyName, resultClass);
       Method writeMethod = propertyDescriptor.getWriteMethod();
       if (writeMethod == null) {
           throw new IllegalAccessException(
               "User is attempting to write "
                   + "to a property that has no write method.  This is likely "
                   + "a read-only bean property.  Caused by property ["
                   + propertyName
                   + "] on class ["
                   + resultClass
                   + "]");
       }
       writeMethod.invoke(result, new Object[] { value });
   }

}</source>

Get and set the value of a property in a bean using Expression and Statement

   <source lang="java">

import java.beans.Expression; import java.beans.Statement; public class Main {

 public static void main(String[] argv) throws Exception {
   Object o = new MyBean();
   // Get the value of prop1
   Expression expr = new Expression(o, "getProp1", new Object[0]);
   expr.execute();
   String s = (String) expr.getValue();
   // Set the value of prop1
   Statement stmt = new Statement(o, "setProp1", new Object[] { "new string" });
   stmt.execute();
 }

} class MyBean {

 String prop1;
 public String getProp1() {
   return prop1;
 }
 public void setProp1(String s) {
   prop1 = s;
 }
 int prop2;
 public int getProp2() {
   return prop2;
 }
 public void setProp2(int i) {
   prop2 = i;
 }
 byte[] prop3;
 public byte[] getProp3() {
   return prop3;
 }
 public void setProp3(byte[] bytes) {
   prop3 = bytes;
 }

}</source>

gets and sets an array type property

   <source lang="java">

import java.beans.Expression; import java.beans.Statement; public class Main {

 public static void main(String[] argv) throws Exception {
   Object o = new MyBean();
   Expression expr = new Expression(o, "getProp3", new Object[0]);
   expr.execute();
   byte[] bytes = (byte[]) expr.getValue();
   Statement stmt = new Statement(o, "setProp3", new Object[] { new byte[] {
       0x12, 0x23 } });
   stmt.execute();
 }

} class MyBean {

 String prop1;
 public String getProp1() {
   return prop1;
 }
 public void setProp1(String s) {
   prop1 = s;
 }
 int prop2;
 public int getProp2() {
   return prop2;
 }
 public void setProp2(int i) {
   prop2 = i;
 }
 byte[] prop3;
 public byte[] getProp3() {
   return prop3;
 }
 public void setProp3(byte[] bytes) {
   prop3 = bytes;
 }

}</source>

gets and sets a primitive type property

   <source lang="java">

import java.beans.Expression; import java.beans.Statement; public class Main {

 public static void main(String[] argv) throws Exception {
   Object o = new MyBean();
   // Get the value of prop2
   Expression expr = new Expression(o, "getProp2", new Object[0]);
   expr.execute();
   int i = ((Integer) expr.getValue()).intValue();
   // Set the value of prop2
   Statement stmt = new Statement(o, "setProp2", new Object[] { new Integer(123) });
   stmt.execute();
 }

} class MyBean {

 String prop1;
 public String getProp1() {
   return prop1;
 }
 public void setProp1(String s) {
   prop1 = s;
 }
 int prop2;
 public int getProp2() {
   return prop2;
 }
 public void setProp2(int i) {
   prop2 = i;
 }
 byte[] prop3;
 public byte[] getProp3() {
   return prop3;
 }
 public void setProp3(byte[] bytes) {
   prop3 = bytes;
 }

}</source>

Getting and Setting a Property of a Bean

   <source lang="java">

import java.beans.Expression; import java.beans.Statement; public class Main {

 public static void main(String[] argv) throws Exception {
   Object o = new MyBean();
   // Get the value of prop1
   Expression expr = new Expression(o, "getProp1", new Object[0]);
   expr.execute();
   String s = (String) expr.getValue();
   // Set the value of prop1
   Statement stmt = new Statement(o, "setProp1", new Object[] { "new string" });
   stmt.execute();
 }

} class MyBean {

 String prop1;
 public String getProp1() {
   return prop1;
 }
 public void setProp1(String s) {
   prop1 = s;
 }
 int prop2;
 public int getProp2() {
   return prop2;
 }
 public void setProp2(int i) {
   prop2 = i;
 }
 byte[] prop3;
 public byte[] getProp3() {
   return prop3;
 }
 public void setProp3(byte[] bytes) {
   prop3 = bytes;
 }

}</source>

Implementing a Bound Property

   <source lang="java">

import java.beans.PropertyChangeListener; import java.beans.PropertyChangeSupport; public class MyBean {

 PropertyChangeSupport pceListeners = new PropertyChangeSupport(this);
 int myProperty;
 public int getMyProperty() {
   return myProperty;
 }
 public void setMyProperty(int newValue) {
   int oldValue = myProperty;
   myProperty = newValue;
   pceListeners.firePropertyChange("myProperty", new Integer(oldValue),
       new Integer(newValue));
 }
 public synchronized void addPropertyChangeListener(
     PropertyChangeListener listener) {
   pceListeners.addPropertyChangeListener(listener);
 }
 public synchronized void removePropertyChangeListener(
     PropertyChangeListener listener) {
   pceListeners.removePropertyChangeListener(listener);
 }

}</source>

Implementing a Constrained Property: fires a PropertyChangeEvent whenever its value is about to be changed.

   <source lang="java">

import java.beans.PropertyVetoException; import java.beans.VetoableChangeListener; import java.beans.VetoableChangeSupport; public class MyBean {

 VetoableChangeSupport vceListeners = new VetoableChangeSupport(this);
 int myProperty;
 public int getMyProperty() {
   return myProperty;
 }
 public void setMyProperty(int newValue) throws PropertyVetoException {
   try {
     vceListeners.fireVetoableChange("myProperty", new Integer(myProperty),
         new Integer(newValue));
     myProperty = newValue;
   } catch (PropertyVetoException e) {
     throw e;
   }
 }
 public synchronized void addVetoableChangeListener(
     VetoableChangeListener listener) {
   vceListeners.addVetoableChangeListener(listener);
 }
 public synchronized void removeVetoableChangeListener(
     VetoableChangeListener listener) {
   vceListeners.removeVetoableChangeListener(listener);
 }

}</source>

Instantiating a Bean

   <source lang="java">

import java.beans.Beans; import java.beans.PropertyVetoException; import java.beans.VetoableChangeListener; import java.beans.VetoableChangeSupport; public class Main {

 public static void main(String[] argv) throws Exception {
   MyBean bean = (MyBean) Beans.instantiate(
       ClassLoader.getSystemClassLoader(), "MyBean");
 }

} class MyBean {

 VetoableChangeSupport vceListeners = new VetoableChangeSupport(this);
 int myProperty;
 public int getMyProperty() {
   return myProperty;
 }
 public void setMyProperty(int newValue) throws PropertyVetoException {
   try {
     vceListeners.fireVetoableChange("myProperty", new Integer(myProperty),
         new Integer(newValue));
     myProperty = newValue;
   } catch (PropertyVetoException e) {
     throw e;
   }
 }
 public synchronized void addVetoableChangeListener(
     VetoableChangeListener listener) {
   vceListeners.addVetoableChangeListener(listener);
 }
 public synchronized void removeVetoableChangeListener(
     VetoableChangeListener listener) {
   vceListeners.removeVetoableChangeListener(listener);
 }

}</source>

Is JavaBean Compliant Setter

   <source lang="java">

import java.lang.reflect.Method; public class Utils {

 public static boolean isJavaBeanCompliantSetter (Method method)
 {
     if (method == null)
         return false;
     
     if (method.getReturnType() != Void.TYPE)
         return false;
     
     if (!method.getName().startsWith("set"))
         return false;
     
     if (method.getParameterTypes().length != 1)
         return false;
     
     return true;
 }

}</source>

Listen for a constrained property change

   <source lang="java">

import java.beans.PropertyChangeEvent; import java.beans.PropertyVetoException; import java.beans.VetoableChangeListener; import java.beans.VetoableChangeSupport;

public class Main {

   private double interest;

   private VetoableChangeSupport vcs = new VetoableChangeSupport(this);

   public Main() {
       vcs.addVetoableChangeListener(new VetoChangeListener());
   }

   public double getInterest() {
       return interest;
   }

   public void setInterest(double interest) {
       try {
           vcs.fireVetoableChange("interest", new Double(this.interest), new Double(interest));
            this.interest = interest;
       } catch (PropertyVetoException e) {
           e.printStackTrace();
       }
   }

   public static void main(String[] args) {
       Main bean = new Main();
       bean.setInterest(10.99);
       bean.setInterest(15.99);
       
       bean.setInterest(20.99);
   }

}

class VetoChangeListener implements VetoableChangeListener {

   public void vetoableChange(PropertyChangeEvent evt) throws PropertyVetoException {
       String eventName = evt.getPropertyName();
       if (eventName.equalsIgnoreCase("interest")) {
           double interest = ((Double) evt.getNewValue()).doubleValue();
           if (interest > 20.00) {
               throw new PropertyVetoException("Interest must be below 20.00", evt);                
           }
           System.out.println("Interest applied = " + interest);
       }
   }

}</source>

Listen for bean"s property change event

   <source lang="java">

import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.beans.PropertyChangeSupport; import java.io.Serializable; public class Main {

 public static void main(String[] argv) throws Exception {
   MyBean bean = new MyBean();
   bean.setName("A");
   bean.setName("B");
   bean.setName("C");
 }

} class MyBean implements PropertyChangeListener, Serializable {

 private Long id;
 private String name;
 private PropertyChangeSupport pcs = new PropertyChangeSupport(this);
 public MyBean() {
   pcs.addPropertyChangeListener(this);
 }
 public void propertyChange(PropertyChangeEvent evt) {
   System.out.println("Name      = " + evt.getPropertyName());
   System.out.println("Old Value = " + evt.getOldValue());
   System.out.println("New Value = " + evt.getNewValue());
 }
 public Long getId() {
   return id;
 }
 public void setId(Long id) {
   this.id = id;
 }
 public String getName() {
   return name;
 }
 public void setName(String name) {
   String oldValue = this.name;
   this.name = name;
   pcs.firePropertyChange("name", oldValue, name);
 }

}</source>

Listening for a Property Change Event: A property change event is fired when a bound property is changed.

   <source lang="java">

import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.beans.PropertyChangeSupport; public class Main {

 public static void main(String[] argv) throws Exception {
   MyBean bean = new MyBean();
   bean.addPropertyChangeListener(new MyPropertyChangeListener());
 }

} class MyPropertyChangeListener implements PropertyChangeListener {

 public void propertyChange(PropertyChangeEvent evt) {
   Object oldValue = evt.getOldValue();
   Object newValue = evt.getNewValue();
 }

} class MyBean {

 PropertyChangeSupport pceListeners = new PropertyChangeSupport(this);
 int myProperty;
 public int getMyProperty() {
   return myProperty;
 }
 public void setMyProperty(int newValue) {
   int oldValue = myProperty;
   myProperty = newValue;
   pceListeners.firePropertyChange("myProperty", new Integer(oldValue),
       new Integer(newValue));
 }
 public synchronized void addPropertyChangeListener(
     PropertyChangeListener listener) {
   pceListeners.addPropertyChangeListener(listener);
 }
 public synchronized void removePropertyChangeListener(
     PropertyChangeListener listener) {
   pceListeners.removePropertyChangeListener(listener);
 }

}</source>

Listening for a Vetoable Property Change Event

   <source lang="java">

// A vetoable property change event is fired when a constrained property is changed. // A listener can veto the change by throwing PropertyVetoException and preventing the change. import java.beans.PropertyChangeEvent; import java.beans.PropertyVetoException; import java.beans.VetoableChangeListener; import java.beans.VetoableChangeSupport; public class Main {

 public static void main(String[] argv) throws Exception {
   MyBean bean = new MyBean();
   bean.addVetoableChangeListener(new MyVetoableChangeListener());
 }

} class MyVetoableChangeListener implements VetoableChangeListener {

 public void vetoableChange(PropertyChangeEvent evt)
     throws PropertyVetoException {
   Object oldValue = evt.getOldValue();
   Object newValue = evt.getNewValue();
   boolean veto = false;
   if (veto) {
     throw new PropertyVetoException("the reason for the veto", evt);
   }
 }

} class MyBean {

 VetoableChangeSupport vceListeners = new VetoableChangeSupport(this);
 int myProperty;
 public int getMyProperty() {
   return myProperty;
 }
 public void setMyProperty(int newValue) throws PropertyVetoException {
   try {
     vceListeners.fireVetoableChange("myProperty", new Integer(myProperty),
         new Integer(newValue));
     myProperty = newValue;
   } catch (PropertyVetoException e) {
     throw e;
   }
 }
 public synchronized void addVetoableChangeListener(
     VetoableChangeListener listener) {
   vceListeners.addVetoableChangeListener(listener);
 }
 public synchronized void removeVetoableChangeListener(
     VetoableChangeListener listener) {
   vceListeners.removeVetoableChangeListener(listener);
 }

}</source>

Listening for Changes to the Current Directory in a JFileChooser Dialog

   <source lang="java">

import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.io.File; import javax.swing.JFileChooser; public class Main {

 public static void main(String[] argv) throws Exception {
   final JFileChooser chooser = new JFileChooser();
   chooser.addPropertyChangeListener(new PropertyChangeListener() {
     public void propertyChange(PropertyChangeEvent evt) {
       if (JFileChooser.DIRECTORY_CHANGED_PROPERTY.equals(evt.getPropertyName())) {
         JFileChooser chooser = (JFileChooser) evt.getSource();
         File oldDir = (File) evt.getOldValue();
         File newDir = (File) evt.getNewValue();
         File curDir = chooser.getCurrentDirectory();
       }
     }
   });
 }

}</source>

Listening for Changes to the Selected File in a JFileChooser Dialog

   <source lang="java">

import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.io.File; import javax.swing.JFileChooser; public class Main {

 public static void main(String[] argv) throws Exception {
   JFileChooser chooser = new JFileChooser();
   chooser.addPropertyChangeListener(new PropertyChangeListener() {
     public void propertyChange(PropertyChangeEvent evt) {
       if (JFileChooser.SELECTED_FILE_CHANGED_PROPERTY.equals(evt.getPropertyName())) {
         JFileChooser chooser = (JFileChooser) evt.getSource();
         File oldFile = (File) evt.getOldValue();
         File newFile = (File) evt.getNewValue();
         
         File curFile = chooser.getSelectedFile();
       }       
     }
   });
 }

}</source>

Listing the Property Names of a Bean

   <source lang="java">

import java.beans.BeanInfo; import java.beans.Introspector; import java.beans.PropertyDescriptor; public class Main {

 public static void main(String[] argv) throws Exception {
   BeanInfo bi = Introspector.getBeanInfo(MyBean.class);
   PropertyDescriptor[] pds = bi.getPropertyDescriptors();
   for (int i = 0; i < pds.length; i++) {
     String propName = pds[i].getDisplayName();
     System.out.println(propName);
   }
 }

} class MyBean {

 public String getProp1() {
   return null;
 }
 public void setProp1(String s) {
 }
 public int getProp2() {
   return 0;
 }
 public void setProp2(int i) {
 }
 public byte[] getPROP3() {
   return null;
 }
 public void setPROP3(byte[] bytes) {
 }

}</source>

List property names of a Bean

   <source lang="java">

import java.beans.BeanInfo; import java.beans.Introspector; import java.beans.PropertyDescriptor; import java.io.Serializable; public class Main {

 public static void main(String[] argv) throws Exception {
   BeanInfo beanInfo = Introspector.getBeanInfo(Fruit.class);
   PropertyDescriptor[] pds = beanInfo.getPropertyDescriptors();
   for (PropertyDescriptor pd : pds) {
     String propertyName = pd.getName();
     System.out.println("propertyName = " + propertyName);
   }
 }

} class Fruit implements Serializable {

 private Long id;
 private String name;
 private double price;
 public Fruit() {
 }
 public Long getId() {
   return id;
 }
 public void setId(Long id) {
   this.id = id;
 }
 public String getName() {
   return name;
 }
 public void setName(String name) {
   this.name = name;
 }
 public double getPrice() {
   return price;
 }
 public void setPrice(double price) {
   this.price = price;
 }

}</source>

Prevent bean"s property being serialized to XML

   <source lang="java">

import java.beans.BeanInfo; import java.beans.Introspector; import java.beans.PropertyDescriptor; import java.beans.XMLEncoder; import java.io.BufferedOutputStream; import java.io.FileOutputStream; public class Main {

 public static void main(String[] argv) throws Exception {
   BeanInfo bi = Introspector.getBeanInfo(BeanToXmlTransient.class);
   PropertyDescriptor[] pds = bi.getPropertyDescriptors();
   for (int i = 0; i < pds.length; i++) {
     PropertyDescriptor propertyDescriptor = pds[i];
     if (propertyDescriptor.getName().equals("itemQuantities")) {
       propertyDescriptor.setValue("transient", Boolean.TRUE);
     }
   }
   BeanToXmlTransient bean = new BeanToXmlTransient();
   bean.setId(new Long(1));
   bean.setItemName("Item");
   bean.setItemColour("Red");
   bean.setItemQuantities(new Integer(100));
   XMLEncoder encoder = new XMLEncoder(new BufferedOutputStream(new FileOutputStream(
       "BeanTransient.xml")));
   encoder.writeObject(bean);
   encoder.close();
 }

} class BeanToXmlTransient {

 private Long id;
 private String itemName;
 private String itemColour;
 private Integer itemQuantities;
 public Long getId() {
   return id;
 }
 public void setId(Long id) {
   this.id = id;
 }
 public String getItemName() {
   return itemName;
 }
 public void setItemName(String itemName) {
   this.itemName = itemName;
 }
 public String getItemColour() {
   return itemColour;
 }
 public void setItemColour(String itemColour) {
   this.itemColour = itemColour;
 }
 public Integer getItemQuantities() {
   return itemQuantities;
 }
 public void setItemQuantities(Integer itemQuantities) {
   this.itemQuantities = itemQuantities;
 }

}</source>

Preventing a Bean Property from Being Serialized to XML

   <source lang="java">

import java.beans.BeanInfo; import java.beans.IntrospectionException; import java.beans.Introspector; import java.beans.PropertyDescriptor; import java.beans.XMLEncoder; import java.io.BufferedOutputStream; import java.io.FileOutputStream; public class Main {

 public static void main(String[] argv) throws Exception {
   MyClass o = new MyClass();
   o.setProp(1);
   o.setProps(new int[] { 1, 2, 3 });
   XMLEncoder encoder = new XMLEncoder(new BufferedOutputStream(
       new FileOutputStream("outfilename.xml")));
   encoder.writeObject(o);
   encoder.close();
 }

} class MyClass {

 int i;
 public int getProp() {
   return i;
 }
 public void setProp(int i) {
   this.i = i;
 }
 int[] iarray = new int[0];
 public int[] getProps() {
   return iarray;
 }
 public void setProps(int[] iarray) {
   this.iarray = iarray;
 }
 static {
   try {
     BeanInfo info = Introspector.getBeanInfo(MyClass.class);
     PropertyDescriptor[] propertyDescriptors = info.getPropertyDescriptors();
     for (int i = 0; i < propertyDescriptors.length; ++i) {
       PropertyDescriptor pd = propertyDescriptors[i];
       if (pd.getName().equals("props")) {
         pd.setValue("transient", Boolean.TRUE);
       }
     }
   } catch (IntrospectionException e) {
   }
 }

}</source>

Process bean properties getter by applying the JavaBean naming conventions.

   <source lang="java">

// $Id: ReflectionHelper.java 16271 2009-04-07 20:20:12Z hardy.ferentschik $ /*

• JBoss, Home of Professional Open Source
• Copyright 2008, Red Hat Middleware LLC, and individual contributors
• by the @authors tag. See the copyright.txt in the distribution for a
• full listing of individual contributors.
• Licensed under the Apache License, Version 2.0 (the "License");
• you may not use this file except in compliance with the License.
• You may obtain a copy of the License at
• http://www.apache.org/licenses/LICENSE-2.0
• Unless required by applicable law or agreed to in writing, software
• distributed under the License is distributed on an "AS IS" BASIS,
• WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
• See the License for the specific language governing permissions and
• limitations under the License.
• /

import java.beans.Introspector; import java.lang.annotation.Annotation; import java.lang.reflect.AccessibleObject; import java.lang.reflect.Field; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Member; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; import java.lang.reflect.WildcardType; import java.util.ArrayList; import java.util.Arrays; import java.util.Iterator; import java.util.List; import java.util.Map;

/**

* Some reflection utility methods.
*
* @author Hardy Ferentschik
*/

public class ReflectionHelper {

 /**
  * Process bean properties getter by applying the JavaBean naming conventions.
  *
  * @param member the member for which to get the property name.
  *
  * @return The bean method name with the "is" or "get" prefix stripped off, null
  *         the method name id not according to the JavaBeans standard.
  */
 public static String getPropertyName(Member member) {
   String name = null;
   if ( member instanceof Field ) {
     name = member.getName();
   }
   if ( member instanceof Method ) {
     String methodName = member.getName();
     if ( methodName.startsWith( "is" ) ) {
       name = Introspector.decapitalize( methodName.substring( 2 ) );
     }
     else if ( methodName.startsWith( "get" ) ) {
       name = Introspector.decapitalize( methodName.substring( 3 ) );
     }
   }
   return name;
 }

}</source>

Read bean"s property value

   <source lang="java">

import java.lang.reflect.InvocationTargetException; import org.apache.rumons.beanutils.PropertyUtils; public class Main {

 public static void main(String[] args) {
   MyClass track = new MyClass();
   track.setTitle("this is a test");
   String title = (String) PropertyUtils.getSimpleProperty(track, "title");
   System.out.println("Title = " + title);
 }

} class MyClass {

 private Integer id;
 private String title;
 public Integer getId() {
   return id;
 }
 public void setId(Integer id) {
   this.id = id;
 }
 public String getTitle() {
   return title;
 }
 public void setTitle(String title) {
   this.title = title;
 }

}</source>

Returns attribute"s setter method. If the method not found then NoSuchMethodException will be thrown.

   <source lang="java">

import java.lang.reflect.Method; import java.util.HashSet; import java.util.List; import java.util.Set; /*

* JBoss, Home of Professional Open Source
* Copyright 2005, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/

public class Main {

 /**
  * Returns attribute"s setter method. If the method not found then
  * NoSuchMethodException will be thrown.
  * 
  * @param cls
  *          the class the attribute belongs to
  * @param attr
  *          the attribute"s name
  * @param type
  *          the attribute"s type
  * @return attribute"s setter method
  * @throws NoSuchMethodException
  *           if the setter was not found
  */
 public final static Method getAttributeSetter(Class cls, String attr, Class type)
     throws NoSuchMethodException {
   StringBuffer buf = new StringBuffer(attr.length() + 3);
   buf.append("set");
   if (Character.isLowerCase(attr.charAt(0))) {
     buf.append(Character.toUpperCase(attr.charAt(0))).append(attr.substring(1));
   } else {
     buf.append(attr);
   }
   return cls.getMethod(buf.toString(), new Class[] { type });
 }

}</source>

Serializing a Bean to XML: XMLEncoder only persists the value of public properties.

   <source lang="java">

import java.beans.XMLEncoder; import java.io.BufferedOutputStream; import java.io.FileOutputStream; public class Main {

 public static void main(String[] argv) throws Exception {
   MyClass o = new MyClass();
   o.setProp(1);
   o.setProps(new int[] { 1, 2, 3 });
   XMLEncoder encoder = new XMLEncoder(new BufferedOutputStream(
       new FileOutputStream("outfilename.xml")));
   encoder.writeObject(o);
   encoder.close();
 }

} class MyClass {

 // The prop property
 int i;
 public int getProp() {
   return i;
 }
 public void setProp(int i) {
   this.i = i;
 }
 // The props property
 int[] iarray = new int[0];
 public int[] getProps() {
   return iarray;
 }
 public void setProps(int[] iarray) {
   this.iarray = iarray;
 }

}</source>

Serializing an Immutable Bean Property to XML

   <source lang="java">

import java.beans.DefaultPersistenceDelegate; import java.beans.XMLEncoder; import java.io.BufferedOutputStream; import java.io.FileOutputStream; public class Main {

 public static void main(String[] argv) throws Exception {
   MyClass o = new MyClass(123);
   XMLEncoder encoder = new XMLEncoder(new BufferedOutputStream(
       new FileOutputStream("outfilename.xml")));
   String[] propertyNames = new String[] { "prop" };
   encoder.setPersistenceDelegate(MyClass.class,
       new DefaultPersistenceDelegate(propertyNames));
   encoder.writeObject(o);
   encoder.close();
 }

} class MyClass {

 int prop;
 public MyClass(int prop) {
   this.prop = prop;
 }
 public int getProp() {
   return prop;
 }

}</source>

Setting an Accessory Component in a JFileChooser Dialog

   <source lang="java">

import java.awt.Dimension; import java.awt.Graphics; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.io.File; import javax.swing.JComponent; import javax.swing.JFileChooser; public class Main {

 public static void main(String[] argv) {
   JFileChooser chooser = new JFileChooser();
   chooser.setAccessory(new MyAccessory(chooser));
   chooser.showOpenDialog(null);
 }

} class MyAccessory extends JComponent implements PropertyChangeListener {

 public MyAccessory(JFileChooser chooser) {
   chooser.addPropertyChangeListener(this);
   setPreferredSize(new Dimension(50, 50));
 }
 public void propertyChange(PropertyChangeEvent evt) {
   if (JFileChooser.SELECTED_FILE_CHANGED_PROPERTY.equals(evt.getPropertyName())) {
     JFileChooser chooser = (JFileChooser) evt.getSource();
     // Get the new selected file
     File newFile = (File) evt.getNewValue();
     repaint();
   }
 }
 public void paint(Graphics g) {
   // Paint a preview of the selected file
 }

}</source>