关于Spring属性编辑器详解

   最近刚在研究Spring的编辑器，发现很有意思，刚好galaxystar起了一个这样贴，我想对PropertyEditor作一个详细的整理会对大家有益，特定启了这个新帖。
   
    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：
 

private void registerDefaultEditors()
    {
        // Simple editors, without parameterization capabilities.
        // The JDK does not contain a default editor for any of these target types.
        this.defaultEditors.put(byte[].class, new ByteArrayPropertyEditor());
        this.defaultEditors.put(Class.class, new ClassEditor());
        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(String[].class, new StringArrayPropertyEditor());
        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 instances of character and boolean editors.
        // Can be overridden by registering custom instances of those as custom editors.
        PropertyEditor characterEditor = new CharacterEditor(false);
        PropertyEditor booleanEditor = new CustomBooleanEditor(false);

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

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

        // The JDK does not contain default editors for number wrapper types!
        // Override JDK primitive number editors with our own CustomNumberEditor.
        PropertyEditor byteEditor = new CustomNumberEditor(Byte.class, false);
        PropertyEditor shortEditor = new CustomNumberEditor(Short.class, false);
        PropertyEditor integerEditor = new CustomNumberEditor(Integer.class, false);
        PropertyEditor longEditor = new CustomNumberEditor(Long.class, false);
        PropertyEditor floatEditor = new CustomNumberEditor(Float.class, false);
        PropertyEditor doubleEditor = new CustomNumberEditor(Double.class, false);

        this.defaultEditors.put(byte.class, byteEditor);
        this.defaultEditors.put(Byte.class, byteEditor);

        this.defaultEditors.put(short.class, shortEditor);
        this.defaultEditors.put(Short.class, shortEditor);

        this.defaultEditors.put(int.class, integerEditor);
        this.defaultEditors.put(Integer.class, integerEditor);

        this.defaultEditors.put(long.class, longEditor);
        this.defaultEditors.put(Long.class, longEditor);

        this.defaultEditors.put(float.class, floatEditor);
        this.defaultEditors.put(Float.class, floatEditor);

        this.defaultEditors.put(double.class, doubleEditor);
        this.defaultEditors.put(Double.class, doubleEditor);

        this.defaultEditors.put(BigDecimal.class,
                                new CustomNumberEditor(BigDecimal.class, false));
        this.defaultEditors.put(BigInteger.class,
                                new CustomNumberEditor(BigInteger.class, false));
    }

   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。

  下面给出一个小例子，例子先作一个简单描述：
  1)Person 需要进行属性注入的Bean，有两个属性 一个是name,一个是address Address是一个类
  2)Address Person的属性类型，本身有3个属性。
  3)AddressPropertyEditor Address类型对应的属性编辑器。
 
  开工：
  1.Person.java

package com.stamen.propedit;

import org.apache.commons.lang.builder.ToStringBuilder;


public class Person {
	private String name;

	private Address address;


	public Address getAddress() {
		return address;
	}

	public void setAddress(Address address) {
		this.address = address;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
    public String toString() {
    	return ToStringBuilder.reflectionToString(this);
    }
 } 

  2.Address.java

package com.stamen.propedit;
import org.apache.commons.lang.builder.ToStringBuilder;
public class Address {
	private String street;

	private String doorNum;

	private String postCode;

	public String getDoorNum() {
		return doorNum;
	}

	public void setDoorNum(String doorNum) {
		this.doorNum = doorNum;
	}

	public String getPostCode() {
		return postCode;
	}

	public void setPostCode(String postCode) {
		this.postCode = postCode;
	}

	public String getStreet() {
		return street;
	}

	public void setStreet(String street) {
		this.street = street;
	}
	
    public String toString() {
    	return ToStringBuilder.reflectionToString(this);
    }

}
 

 
AddressPropertyEditor.java

package com.stamen.propedit;

import java.beans.PropertyEditorSupport;
import java.util.Date;

import org.springframework.util.StringUtils;
public class AddressPropertyEditor extends PropertyEditorSupport{
	//支持的格式为 streeValue,doorNumValue,postCode
	public void setAsText(String text)
	{
		System.out.println("使用自己的编辑器。");
		if (text == null || !StringUtils.hasText(text)) {
			throw new IllegalArgumentException("老大，不能为空啊！");
		}
		else
		{
			String[] strArr = StringUtils.tokenizeToStringArray(text,",");
			Address add = new Address();
			add.setStreet(strArr[0]);
			add.setDoorNum(strArr[1]);
			add.setPostCode(strArr[2]);
			setValue(add);
		}
	}
	
    public String getAsText()
    {
    	Address add = (Address)getValue();
    	return ""+add;
    }
}
 

打开Spring配置文件，添上这两个配置项：

   <bean id="customEditorConfigurer"  class="org.springframework.beans.factory.config.CustomEditorConfigurer">
   <property name="customEditors">
     <map>
       <entry key="com.stamen.propedit.Address"> <!-- 属性类型 -->
         <bean class="com.stamen.propedit.AddressPropertyEditor"/> <!--对应Address的编辑器 -->
       </entry>
     </map>
   </property>
 </bean>

  <bean id="person" class="com.stamen.propedit.Person">
     <property name="name" value="Tom"/>
     <property name="address" value="朝阳区,Soho 1601,010101"/>
  </bean>

  
  收工，刷牙，上床，睡觉。