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>