BeanMap这个Map类用于把一个javaBean转换为Map,在其中存储了javaBean的各个属性的setXXX方法和getXXX方法，属性的类型。
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public class BeanMap extends AbstractMap implements Cloneable
{
private transient Object bean;//javaBean对象
private transient HashMap readMethods = new HashMap();//getXXX方法集
private transient HashMap writeMethods = new HashMap();//setXXX方法集
private transient HashMap types = new HashMap();//成员变量类型集
public static final Object[] NULL_ARGUMENTS = {};//空参数集，用于通过reflection调用getXXX方法
public static HashMap defaultTransformers = new HashMap();//把基本类型映射为transformer类型，后者用于将字符串转换为合适的基本型的包装类
//默认transformer
static
{
defaultTransformers.put( Boolean.TYPE, new Transformer()
{
public Object transform( Object input )
{
return Boolean.valueOf( input.toString() );
}
}
);
defaultTransformers.put( Character.TYPE, new Transformer()
{
public Object transform( Object input )
{
return new Character( input.toString().charAt( 0 ) );
}
}
);
defaultTransformers.put( Byte.TYPE, new Transformer()
{
public Object transform( Object input )
{
return Byte.valueOf( input.toString() );
}
}
);
defaultTransformers.put( Short.TYPE, new Transformer()
{
public Object transform( Object input )
{
return Short.valueOf( input.toString() );
}
}
);
defaultTransformers.put(
Integer.TYPE,
new Transformer() {
public Object transform( Object input ) {
return Integer.valueOf( input.toString() );
}
}
);
defaultTransformers.put( Long.TYPE, new Transformer()
{
public Object transform( Object input ) {
return Long.valueOf( input.toString() );
}
}
);
defaultTransformers.put( Float.TYPE, new Transformer()
{
public Object transform( Object input ) {
return Float.valueOf( input.toString() );
}
}
);
defaultTransformers.put( Double.TYPE, new Transformer()
{
public Object transform( Object input ) {
return Double.valueOf( input.toString() );
}
}
);
}
public BeanMap(Object bean) {
this.bean = bean;
initialise();
}
public Object clone() throws CloneNotSupportedException {
BeanMap newMap = (BeanMap)super.clone();
if(bean == null) {//若底层bean不存在，则返回一个复制的空BeanMap,
return newMap;
}
Object newBean = null;
Class beanClass = null;
try {
beanClass = bean.getClass();//底层bean的Class
newBean = beanClass.newInstance();//实例化一个新的bean
} catch (Exception e) {
// unable to instantiate
throw new CloneNotSupportedException
("Unable to instantiate the underlying bean \"" +
beanClass.getName() + "\": " + e);
}
try {
newMap.setBean(newBean);
} catch (Exception exception) {
throw new CloneNotSupportedException
("Unable to set bean in the cloned bean map: " +
exception);
}
try {
//复制所有可读写的属性
Iterator readableKeys = readMethods.keySet().iterator();
while(readableKeys.hasNext()) {
Object key = readableKeys.next();//属性名称
if(getWriteMethod(key) != null) {
newMap.put(key, get(key));//放入到新BeanMap中
}
}
} catch (Exception exception) {
throw new CloneNotSupportedException
("Unable to copy bean values to cloned bean map: " +
exception);
}
return newMap;
}
public void clear() {
if(bean == null) return;
Class beanClass = null;
try {
beanClass = bean.getClass();
bean = beanClass.newInstance();//重新实例化,一切都回到默认状态
}
catch (Exception e) {
throw new UnsupportedOperationException( "Could not create new instance of class: " + beanClass );
}
}
public Object get(Object name) {//获取指定名称属性的值
if ( bean != null ) {
Method method = getReadMethod( name );
if ( method != null ) {
try {
return method.invoke( bean, NULL_ARGUMENTS );
}
catch ( IllegalAccessException e ) {
logWarn( e );
}
catch ( IllegalArgumentException e ) {
logWarn( e );
}
catch ( InvocationTargetException e ) {
logWarn( e );
}
catch ( NullPointerException e ) {
logWarn( e );
}
}
}
return null;
}
public Object put(Object name, Object value) throws IllegalArgumentException, ClassCastException
{//设置指定名称的属性的值
if ( bean != null ) {
Object oldValue = get( name );//原来的值
Method method = getWriteMethod( name );
if ( method == null ) {
throw new IllegalArgumentException( "The bean of type: "+ bean.getClass().getName() + " has no property called: " + name );
}
try {
Object[] arguments = createWriteMethodArguments( method, value );//转换参数
method.invoke( bean, arguments );//设置新值
Object newValue = get( name );//获取新设置的值
firePropertyChange( name, oldValue, newValue );//fire属性值改变事件
}
catch ( InvocationTargetException e ) {
logInfo( e );
throw new IllegalArgumentException( e.getMessage() );
}
catch ( IllegalAccessException e ) {
logInfo( e );
throw new IllegalArgumentException( e.getMessage() );
}
return oldValue;
}
return null;
}
public Method getReadMethod(String name) {//获取指定名称属性的getXXX方法
return (Method) readMethods.get(name);
}
public Method getWriteMethod(String name) {//获取指定名称属性的setXXX方法
return (Method) writeMethods.get(name);
}
private void initialise()
{
if(getBean() == null) return;
Class beanClass = getBean().getClass();//bean的Class
try
{
//BeanInfo beanInfo = Introspector.getBeanInfo( bean, null );
BeanInfo beanInfo = Introspector.getBeanInfo( beanClass );//bean的信息
PropertyDescriptor[] propertyDescriptors = beanInfo.getPropertyDescriptors();
if ( propertyDescriptors != null )
{
for ( int i = 0; i < propertyDescriptors.length; i++ )
{
PropertyDescriptor propertyDescriptor = propertyDescriptors[i];
if ( propertyDescriptor != null )
{
String name = propertyDescriptor.getName();//属性名称
Method readMethod = propertyDescriptor.getReadMethod();//getXXX方法
Method writeMethod = propertyDescriptor.getWriteMethod();//setXXX方法
Class aType = propertyDescriptor.getPropertyType();//属性类型
if ( readMethod != null ) {
readMethods.put( name, readMethod );//保存到getXXX集合
}
if ( writeMethod != null ) {
writeMethods.put( name, writeMethod );//保存到setXXX集合
}
types.put( name, aType );//保存属性类型
}
}
}
}
catch ( IntrospectionException e ) {
logWarn( e );
}
}
protected static class MyMapEntry extends AbstractMapEntry
{//BeanMap使用的Map entry
private BeanMap owner;//所属的Map
protected MyMapEntry( BeanMap owner, Object key, Object value ) {
super( key, value );
this.owner = owner;
}
public Object setValue(Object value) {
Object key = getKey();
Object oldValue = owner.get( key );
owner.put( key, value );
Object newValue = owner.get( key );
super.setValue( newValue );
return oldValue;
}
}
protected Object[] createWriteMethodArguments( Method method, Object value ) throws IllegalAccessException, ClassCastException
{
try
{
if ( value != null )
{
Class[] types = method.getParameterTypes();//setXXX方法的参数类型
if ( types != null && types.length > 0 )
{
Class paramType = types[0];
if ( ! paramType.isAssignableFrom( value.getClass() ) )
{
value = convertType( paramType, value );//把新参数转换为setXXX方法的参数类型
}
}
}
Object[] answer = { value };
return answer;
}
catch ( InvocationTargetException e ) {
logInfo( e );
throw new IllegalArgumentException( e.getMessage() );
}
catch ( InstantiationException e ) {
logInfo( e );
throw new IllegalArgumentException( e.getMessage() );
}
}
protected Object convertType( Class newType, Object value )
throws InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
// try call constructor
Class[] types = { value.getClass() };
try {//尝试用带一个参数的构造函数进行转换
Constructor constructor = newType.getConstructor( types );
Object[] arguments = { value };
return constructor.newInstance( arguments );
}
catch ( NoSuchMethodException e ) {
// try using the transformers
Transformer transformer = getTypeTransformer( newType );//获取可用的transformer
if ( transformer != null ) {
return transformer.transform( value );//转换类型
}
return value;
}
}
protected Transformer getTypeTransformer( Class aType ) {
return (Transformer) defaultTransformers.get( aType );
}
}
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本文转自Phinecos(洞庭散人)博客园博客，原文链接：http://www.cnblogs.com/phinecos/archive/2008/12/20/1358910.html，如需转载请自行联系原作者
