BeanMap這個Map類用于把一個javaBean轉換為Map,在其中存儲了javaBean的各個屬性的setXXX方法和getXXX方法，屬性的類型。
復制代碼 public class BeanMap extends AbstractMap implements Cloneable? { private transient Object bean;//javaBean對象
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();//成員變量類型集
public static final Object[] NULL_ARGUMENTS = {};//空參數集，用于通過reflection調用getXXX方法 public static HashMap defaultTransformers = new HashMap();//把基本類型映射為transformer類型，后者用于將字符串轉換為合適的基本型的包裝類 //默認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) {//若底層bean不存在，則返回一個復制的空BeanMap, return newMap; } Object newBean = null; ? ? ? ? ? ? Class beanClass = null; try { beanClass = bean.getClass();//底層bean的Class newBean = beanClass.newInstance();//實例化一個新的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 { //復制所有可讀寫的屬性 Iterator readableKeys = readMethods.keySet().iterator(); while(readableKeys.hasNext()) { Object key = readableKeys.next();//屬性名稱 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();//重新實例化,一切都回到默認狀態 } catch (Exception e) { throw new UnsupportedOperationException( "Could not create new instance of class: " + beanClass ); } }
public Object get(Object name) {//獲取指定名稱屬性的值 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 {//設置指定名稱的屬性的值 if ( bean != null ) { Object oldValue = get( name );//原來的值 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 );//轉換參數 method.invoke( bean, arguments );//設置新值 Object newValue = get( name );//獲取新設置的值? firePropertyChange( name, oldValue, newValue );//fire屬性值改變事件 } 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) {//獲取指定名稱屬性的getXXX方法 return (Method) readMethods.get(name); }
public Method getWriteMethod(String name) {//獲取指定名稱屬性的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();//屬性名稱 Method readMethod = propertyDescriptor.getReadMethod();//getXXX方法 Method writeMethod = propertyDescriptor.getWriteMethod();//setXXX方法 Class aType = propertyDescriptor.getPropertyType();//屬性類型 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 );//保存屬性類型 } } } } catch ( IntrospectionException e ) { logWarn( ?e ); } }
protected static class MyMapEntry extends AbstractMapEntry? {//BeanMap使用的Map entry ? ? ? ? private BeanMap owner;//所屬的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方法的參數類型 if ( types != null && types.length > 0 )? { Class paramType = types[0]; if ( ! paramType.isAssignableFrom( value.getClass() ) )? { value = convertType( paramType, value );//把新參數轉換為setXXX方法的參數類型 } } } 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 {//嘗試用帶一個參數的構造函數進行轉換 Constructor constructor = newType.getConstructor( types ); ? ? ? ? Object[] arguments = { value }; return constructor.newInstance( arguments ); } catch ( NoSuchMethodException e ) { // try using the transformers Transformer transformer = getTypeTransformer( newType );//獲取可用的transformer if ( transformer != null ) { return transformer.transform( value );//轉換類型 } return value; } }
protected Transformer getTypeTransformer( Class aType ) { return (Transformer) defaultTransformers.get( aType ); }
} 復制代碼

本文轉自Phinecos(洞庭散人)博客園博客，原文鏈接：http://www.cnblogs.com/phinecos/archive/2008/12/20/1358910.html，如需轉載請自行聯系原作者

總結

以上是生活随笔為你收集整理的Commons Collections学习笔记（四）的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。