关于Spring属性编辑器详解

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Spring Bean JDK 配置管理 Apache

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：

Java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

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

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

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：

Java代码

<bean id= "customEditorConfigurer" class = "org.springframework.beans.factory.config.CustomEditorConfigurer" >
<property name= "customEditors" >
<map>
<entry key= "com.stamen.propedit.Address" >
<bean class = "com.stamen.propedit.AddressPropertyEditor" />
</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>