Spring攻略學習筆記 --在Spring中注冊屬性編輯器

一、知識點

       屬性編輯器是JavaBeans API的一項功能，用於屬性值與文本值相互轉換。每個屬性編輯器僅用於某一類屬性。

       Spring IoC容器支持使用屬性編輯器來簡化Bean配置。例如，使用java.net.URL類型的屬性編輯器，可以指定用於URL類型屬性的URL字符串。Spring會自動地將這個URL字符串轉換成一個URL對象，注入到你的屬性中。Spring自帶多種用於轉換常見類型Bean屬性的屬性編輯器。

        需要在Spring IoC容器中注冊屬性編輯器，然後才能使用。CustomEditorConfigurer是作為Bean工廠後處理器來實現的，用於在任何Bean實例化之前注冊你的自定義屬性編輯器。

二、代碼示例   

[java]
package com.codeproject.jackie.springrecipesnote.springadvancedioc; 
 
import java.util.Date; 
 
/**
 * 產品銷售排名
 * @author jackie
 * 
 */ 
public class ProductRanking { 
    private Product bestSeller; 
 
    private Date fromDate; 
 
    private Date toDate; 
 
    /**
     * @return the bestSeller
     */ 
    public Product getBestSeller() { 
        return bestSeller; 
    } 
 
    /**
     * @param bestSeller
     *            the bestSeller to set
     */ 
    public void setBestSeller(Product bestSeller) { 
        this.bestSeller = bestSeller; 
    } 
 
    /**
     * @return the fromDate
     */ 
    public Date getFromDate() { 
        return fromDate; 
    } 
 
    /**
     * @param fromDate
     *            the fromDate to set
     */ 
    public void setFromDate(Date fromDate) { 
        this.fromDate = fromDate; 
    } 
 
    /**
     * @return the toDate
     */ 
    public Date getToDate() { 
        return toDate; 
    } 
 
    /**
     * @param toDate
     *            the toDate to set
     */ 
    public void setToDate(Date toDate) { 
        this.toDate = toDate; 
    } 
} 

package com.codeproject.jackie.springrecipesnote.springadvancedioc;

import java.util.Date;

/**
 * 產品銷售排名
 * @author jackie
 *
 */
public class ProductRanking {
 private Product bestSeller;

 private Date fromDate;

 private Date toDate;

 /**
  * @return the bestSeller
  */
 public Product getBestSeller() {
  return bestSeller;
 }

 /**
  * @param bestSeller
  *            the bestSeller to set
  */
 public void setBestSeller(Product bestSeller) {
  this.bestSeller = bestSeller;
 }

 /**
  * @return the fromDate
  */
 public Date getFromDate() {
  return fromDate;
 }

 /**
  * @param fromDate
  *            the fromDate to set
  */
 public void setFromDate(Date fromDate) {
  this.fromDate = fromDate;
 }

 /**
  * @return the toDate
  */
 public Date getToDate() {
  return toDate;
 }

 /**
  * @param toDate
  *            the toDate to set
  */
 public void setToDate(Date toDate) {
  this.toDate = toDate;
 }
}         以下是Java程序轉換特定模式的日期字符串。
[java]
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd"); 
productRanking.setFromDate(dateFormat.parse("2007-09-01")); 
productRanking.setToDate(dateFormat.parse("2007-09-30")); 

DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
productRanking.setFromDate(dateFormat.parse("2007-09-01"));
productRanking.setToDate(dateFormat.parse("2007-09-30"));       Spring中等價Bean配置如下：  [java] view plaincopyprint?<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">     
    <bean id="dateFormat" class="java.text.SimpleDateFormat"> 
        <constructor-arg value="yyyy-MM-dd" /> 
    </bean> 
     
    <bean id="productRanking" class="com.codeproject.jackie.springrecipesnote.springadvancedioc.ProductRanking"> 
    <property name="bestSeller"> 
        <bean class="com.codeproject.jackie.springrecipesnote.springadvancedioc.Disc"> 
        <property name="name" value="CD-RW" /> 
        <property name="price" value="1.5" /> 
        </bean> 
    </property> 
    <property name="fromDate"> 
        <bean factory-bean="dateFormat" factory-method="parse"> 
        <constructor-arg value="2007-09-01"></constructor-arg> 
        </bean> 
    </property> 
    <property name="toDate"> 
        <bean factory-bean="dateFormat" factory-method="parse"> 
        <constructor-arg value="2007-09-30"></constructor-arg> 
        </bean> 
    </property> 
     </bean> 
</beans> 

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">   
    <bean id="dateFormat" class="java.text.SimpleDateFormat">
     <constructor-arg value="yyyy-MM-dd" />
    </bean>
   
    <bean id="productRanking" class="com.codeproject.jackie.springrecipesnote.springadvancedioc.ProductRanking">
 <property name="bestSeller">
     <bean class="com.codeproject.jackie.springrecipesnote.springadvancedioc.Disc">
  <property name="name" value="CD-RW" />
  <property name="price" value="1.5" />
     </bean>
 </property>
 <property name="fromDate">
     <bean factory-bean="dateFormat" factory-method="parse">
  <constructor-arg value="2007-09-01"></constructor-arg>
     </bean>
 </property>
 <property name="toDate">
     <bean factory-bean="dateFormat" factory-method="parse">
  <constructor-arg value="2007-09-30"></constructor-arg>
     </bean>
 </property>
     </bean>
</beans>         前述配置對於設置日期屬性太復雜了。Spring IoC容器能夠使用屬性編輯器為你的屬性轉換文本值。Spring自帶的CustomDateEditor類用於將日期字符串轉換為java.util.Date屬性。首先在Bean配置文件中聲明實例。
[java]
<bean id="dateEditor" class="org.springframework.beans.propertyeditors.CustomDateEditor"> 
    <constructor-arg> 
        <bean class="java.text.SimpleDateFormat"> 
            <constructor-arg value="yyyy-MM-dd"></constructor-arg> 
        </bean> 
    </constructor-arg> 
    <!-- 表示該編輯器是否允許空值 --> 
    <constructor-arg value="true" /> 
</bean> 

<bean id="dateEditor" class="org.springframework.beans.propertyeditors.CustomDateEditor">
    <constructor-arg>
     <bean class="java.text.SimpleDateFormat">
         <constructor-arg value="yyyy-MM-dd"></constructor-arg>
     </bean>
    </constructor-arg>
    <!-- 表示該編輯器是否允許空值 -->
    <constructor-arg value="true" />
</bean>      然後在CustomEditorConfigurer實例中注冊這個屬性編輯器，這樣Spring可以轉換類型為java.util.Date屬性。
[html] view plaincopyprint?<bean id="dateEditor" class="org.springframework.beans.propertyeditors.CustomDateEditor"> 
    <constructor-arg> 
        <bean class="java.text.SimpleDateFormat"> 
            <constructor-arg value="yyyy-MM-dd"></constructor-arg> 
        </bean> 
    </constructor-arg> 
    <constructor-arg value="true" /> 
</bean> 
     
<bean class="org.springframework.beans.factory.config.CustomEditorConfigurer"> 
    <property name="customEditors"> 
        <map> 
           <entry key="java.util.Date"> 
              <ref local="dateEditor"/> 
           </entry> 
        </map> 
    </property> 
</bean> 
     
<bean id="productRanking" class="com.codeproject.jackie.springrecipesnote.springadvancedioc.ProductRanking"> 
    <property name="bestSeller"> 
       <bean class="com.codeproject.jackie.springrecipesnote.springadvancedioc.Disc"> 
      <property name="name" value="CD-RW" /> 
      <property name="price" value="1.5" /> 
       </bean> 
    </property> 
    <property name="fromDate" value="2007-09-01" /> 
    <property name="toDate" value="2007-09-30" />      
</bean> 

<bean id="dateEditor" class="org.springframework.beans.propertyeditors.CustomDateEditor">
    <constructor-arg>
     <bean class="java.text.SimpleDateFormat">
         <constructor-arg value="yyyy-MM-dd"></constructor-arg>
     </bean>
    </constructor-arg>
    <constructor-arg value="true" />
</bean>
   
<bean class="org.springframework.beans.factory.config.CustomEditorConfigurer">
    <property name="customEditors">
     <map>
        <entry key="java.util.Date">
           <ref local="dateEditor"/>
        </entry>
     </map>
    </property>
</bean>
   
<bean id="productRanking" class="com.codeproject.jackie.springrecipesnote.springadvancedioc.ProductRanking">
    <property name="bestSeller">
       <bean class="com.codeproject.jackie.springrecipesnote.springadvancedioc.Disc">
   <property name="name" value="CD-RW" />
   <property name="price" value="1.5" />
       </bean>
    </property>
    <property name="fromDate" value="2007-09-01" />
    <property name="toDate" value="2007-09-30" />  
</bean>  測試類PropertyEditorTest
[java] view plaincopyprint?package com.codeproject.jackie.springrecipesnote.springadvancedioc; 
 
import org.junit.Test; 
import org.springframework.context.ApplicationContext; 
import org.springframework.context.support.ClassPathXmlApplicationContext; 
 
/**
 * @author jackie
 *
 */ 
public class PropertyEditorTest { 
    @Test 
    public void testPropertyEditor(){ 
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); 
        ProductRanking productRanking = (ProductRanking) context.getBean("productRanking"); 
        System.out.println("Product ranking from " + productRanking.getFromDate() + " to " + productRanking.getToDate()); 
    } 
} 

package com.codeproject.jackie.springrecipesnote.springadvancedioc;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @author jackie
 *
 */
public class PropertyEditorTest {
 @Test
 public void testPropertyEditor(){
  ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
  ProductRanking productRanking = (ProductRanking) context.getBean("productRanking");
  System.out.println("Product ranking from " + productRanking.getFromDate() + " to " + productRanking.getToDate());
 }
}    除了CustomDateEditor之外, Spring自帶多個轉換常見數據類型的屬性編輯器，例如CustomNumberEditor, ClassEditor, FileEditor, LocaleEditor,StringArrayPropertyEditor以及URLEditor. 其中, ClassEditor, FileEditor, LocaleEditor以及URLEditor由Spring預先注冊，不需要再次注冊。關於這些編輯器使用的更多信息，可以參考org.springframework.beans.propertyeditors包中這些類的Javadoc。