Spring属性编辑器

所谓的PropertyEditor，顾名思义，就是属性编辑器。由于Bean属性通过配置文档以字符串了方式为属性赋值，所以必须有一个“东东”负责将这个字符串转换为属性的直接对象，如属性的类型为int，那么编辑器要做的工作就是int i = Integer.parseInt(“1“);
   Spring为一般的属性类型提供了默认的编辑器，BeanWrapperImpl是Spring框架中重要的类，它负责对注入的Bean进行包装化的管理，常见属性类型对应的编辑器即在该类中通过以下代码定义：
 

Java代码

registerDefaultEditors

protected void registerDefaultEditors() {
		this.defaultEditors = new HashMap(32);

		// Simple editors, without parameterization capabilities.
		// The JDK does not contain a default editor for any of these target types.
		this.defaultEditors.put(Class.class, new ClassEditor());
		this.defaultEditors.put(Class[].class, new ClassArrayEditor());
		this.defaultEditors.put(File.class, new FileEditor());
		this.defaultEditors.put(InputStream.class, new InputStreamEditor());
		this.defaultEditors.put(Locale.class, new LocaleEditor());
		this.defaultEditors.put(Properties.class, new PropertiesEditor());
		this.defaultEditors.put(Resource[].class, new ResourceArrayPropertyEditor());
		this.defaultEditors.put(URL.class, new URLEditor());

		// Default instances of collection editors.
		// Can be overridden by registering custom instances of those as custom editors.
		this.defaultEditors.put(Collection.class, new CustomCollectionEditor(Collection.class));
		this.defaultEditors.put(Set.class, new CustomCollectionEditor(Set.class));
		this.defaultEditors.put(SortedSet.class, new CustomCollectionEditor(SortedSet.class));
		this.defaultEditors.put(List.class, new CustomCollectionEditor(List.class));

		// Default editors for primitive arrays.
		this.defaultEditors.put(byte[].class, new ByteArrayPropertyEditor());
		this.defaultEditors.put(char[].class, new CharArrayPropertyEditor());

		// The JDK does not contain a default editor for char!
		this.defaultEditors.put(char.class, new CharacterEditor(false));
		this.defaultEditors.put(Character.class, new CharacterEditor(true));

		// Spring's CustomBooleanEditor accepts more flag values than the JDK's default editor.
		this.defaultEditors.put(boolean.class, new CustomBooleanEditor(false));
		this.defaultEditors.put(Boolean.class, new CustomBooleanEditor(true));

		// The JDK does not contain default editors for number wrapper types!
		// Override JDK primitive number editors with our own CustomNumberEditor.
		this.defaultEditors.put(byte.class, new CustomNumberEditor(Byte.class, false));
		this.defaultEditors.put(Byte.class, new CustomNumberEditor(Byte.class, true));
		this.defaultEditors.put(short.class, new CustomNumberEditor(Short.class, false));
		this.defaultEditors.put(Short.class, new CustomNumberEditor(Short.class, true));
		this.defaultEditors.put(int.class, new CustomNumberEditor(Integer.class, false));
		this.defaultEditors.put(Integer.class, new CustomNumberEditor(Integer.class, true));
		this.defaultEditors.put(long.class, new CustomNumberEditor(Long.class, false));
		this.defaultEditors.put(Long.class, new CustomNumberEditor(Long.class, true));
		this.defaultEditors.put(float.class, new CustomNumberEditor(Float.class, false));
		this.defaultEditors.put(Float.class, new CustomNumberEditor(Float.class, true));
		this.defaultEditors.put(double.class, new CustomNumberEditor(Double.class, false));
		this.defaultEditors.put(Double.class, new CustomNumberEditor(Double.class, true));
		this.defaultEditors.put(BigDecimal.class, new CustomNumberEditor(BigDecimal.class, true));
		this.defaultEditors.put(BigInteger.class, new CustomNumberEditor(BigInteger.class, true));
	}

   但是，并非Bean的属性都是这些常见的类型，如果你的Bean需要注入一个自定义类型的属性，而又想享受IoC的好处，那么就只得自己开干，提供一个自定义的PropertyEditor了。
   下面，分几个步骤来说明，定义一个自定义PropertyEditor的过程。
  1)首先，碰到的问题即是，要如何编辑自己的PropertyEditor,其实需要了解一点java.beans包的知识，在该包中，有一个java.beans.PropertyEditor的接口，它定义了一套接口方法（12个），即通过这些方法如何将一个String变成内部的一个对象，这两个方法是比较重要的：
    a)setValue(Object value) 直接设置一个对象，一般不直接用该方法设置属性对象
     b)setAsText(String text) 通过一个字符串来构造对象，一般在此方法中解析字符串，将构造一个
     类对象，调用setValue(Object)来完成属性对象设置操作。
 
  2)实现所有的接口方法是麻烦的，java.beans.PropertyEditorSupport 适时登场，一般情况下，我们通过扩展这个方便类即可。

  3)编写完后，就是在Spring配置文件中注册该属性类型编辑器的问题，Spring提供了专门的注册工具类
   org.springframework.beans.factory.config.CustomEditorConfigurer，它负责将属性类型和
   属性编辑器关联起来。到时BeanFactory注入Bean的属性时，即会在注册表中查找属性类型对应的编辑器。

小例子：

UtilDatePropertyEditor .java

package com.bjsxt.spring;

import java.beans.PropertyEditorSupport;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * java.util.Date属性编辑器 
 * @author Administrator
 *
 */
public class UtilDatePropertyEditor extends PropertyEditorSupport {

	private String format="yyyy-MM-dd";
	
	@Override
	public void setAsText(String text) throws IllegalArgumentException {
		System.out.println("UtilDatePropertyEditor.saveAsText() -- text=" + text);
		
		SimpleDateFormat sdf = new SimpleDateFormat(format);
		try {
			Date d = sdf.parse(text);
			this.setValue(d);
		} catch (ParseException e) {
			e.printStackTrace();
		}
	}

	public void setFormat(String format) {
		this.format = format;
	}

}

定义属性编辑器applicationContext-editor.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"
	     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	     xmlns:aop="http://www.springframework.org/schema/aop"
	     xmlns:tx="http://www.springframework.org/schema/tx"
	     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
           http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
           http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd">
     <!-- 定义属性编辑器 -->      
	<bean id="customEditorConfigurer" class="org.springframework.beans.factory.config.CustomEditorConfigurer">
		<property name="customEditors">
			<map>
				<entry key="java.util.Date">
					<bean class="com.bjsxt.spring.UtilDatePropertyEditor">
						<property name="format" value="yyyy-MM-dd"/>
					</bean>
				</entry>
			</map>
		</property>
	</bean>	
	
	<!-- 
	<bean id="utilDatePropertyEditor" class="com.bjsxt.spring.UtilDatePropertyEditor"></bean>
	 -->
</beans>