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：


代码
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


代码
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

代码
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

代码
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：


代码
<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>