Heck's Blog

首先我们看下什么是属性编辑器，到底它有什么作用呢？
* 自定义属性编辑器，spring配置文件中的字符串转换成相应的对象进行注入
spring已经有内置的属性编辑器，我们可以根据需求自己定义属性编辑器

* 如何定义属性编辑器？
  * 继承PropertyEditorSupport类，覆写setAsText()方法（注意要将处理完成的对象通过PropertyEditorSupport的setValue设置回去）
*向IoC容器中注册自定义的属性编辑器(两种方式：1 在配置文件中注册 2 在程序中注册)
接下来我们就看看一个关于日期的属性编辑器的部署过程：
首先定义一个测试类：

比如：
有一个类里面有一个Date属性
package tk.hecks.property;

import java.util.Date;

public class User {
  private String username;
  private Date birthday;
  public String getUsername() {
    return username;
  }
  public void setUsername(String username) {
    this.username = username;
  }
  public Date getBirthday() {
    return birthday;
  }
  public void setBirthday(Date birthday) {
    this.birthday = birthday;
  }

}


然后继承PropertyEditorSupport,实现自定义的属性编辑器，UtilDatePropertyEditor.java 如下，必须继承java.beans.PropertyEditorSupport类，覆写setAsText()方法，再将处理完的对象setValue回去。

package tk.hecks.property;  
import java.beans.PropertyEditorSupport;  
import java.util.Date;  
import java.text.ParseException;  
import java.text.SimpleDateFormat;  
public class UtilDatePropertyEditor extends PropertyEditorSupport{  

private String format;  
public UtilDatePropertyEditor(String format) {  
  this.format=format;  
}  

public void setAsText(String text) throws IllegalArgumentException {  
  SimpleDateFormat sdf=new SimpleDateFormat(format);  
  try {  
   Date date=sdf.parse(text);  
   this.setValue(date);  
  } catch (ParseException e) {  
   System.out.println(e.getMessage()+"日期的格式不对");  
  }  
}  

public void setFormat(String format) {  
  this.format = format;  
}  
  
}  


接着我们首先定义配置文件：(采用配置方式)
applicationContext.xml配置文件如下：
<?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.xsd  
">  
<!--将user中的Date赋值2014-03-28，spring会认为2014-03-28是String，无法转换成Date，会报错！-->
<bean id="user" class="tk.hecks.property.User">  
    <property name="username" value="heck"/>  
    <property name="birthday" value="2014-03-28"/>  
</bean>  

<!-- 所以自定义的属性编辑器 -->  
<bean id="customEditorConfigurer" class="org.springframework.beans.factory.config.CustomEditorConfigurer">  
        <property name="customEditors">  
            <map>  
                <entry key="java.util.Date">  
                    <bean class="com.property.UtilDatePropertyEditor">  
                          <!--干脆把format也注入，灵活处理格式-->
                        <property name="format" value="yyyy-MM-dd"/>  
                    </bean>  
                </entry>  
            </map>  
        </property>  
    </bean>  
</beans>  

这样就可以完成正确解析了，注意customEditors是Spring的类CustomEditorConfigurer提供的属性，是一个Map,里面存放的都是自定义的编辑器（customEditors），比如这里存放的是UtilDatePropertyEditor日期编辑器，看CustomEditorConfigurer源码就知道了。

接下来我们测试一下：
import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import junit.framework.TestCase;

public class InjectionTest extends TestCase {
  
  private BeanFactory factory;
  
  @Override
  protected void setUp() throws Exception {
    factory = new ClassPathXmlApplicationContext("applicationContext.xml");  
  }

  public void testInjection1() {
    User user= (User)factory.getBean("user");
    System.out.println("name:"+user.getUsername()+"\nbirthday:"+user.getBirthday());
  }
  
}

或者用main方法来测试

package tk.hecks.property;  
  
import org.springframework.beans.factory.config.ConfigurableBeanFactory;  
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;  
import org.springframework.beans.factory.config.CustomEditorConfigurer;  
import org.springframework.beans.factory.xml.XmlBeanFactory;  
import org.springframework.context.ApplicationContext;  
import org.springframework.context.support.ClassPathXmlApplicationContext;  
import org.springframework.core.io.ClassPathResource;  
  
public class TestPropertyEditor {  
    public static void main(String[] args) {  
//      ApplicationContext ac=new ClassPathXmlApplicationContext("applicationContext-*.xml");  
//      User user=(User)ac.getBean("user");  
//      System.out.println("name:"+user.getUsername()+"\nbirthday:"+user.getBirthday());  
        //它等价于  
        ConfigurableBeanFactory beanFactory=new XmlBeanFactory(new ClassPathResource("applicationContext-beans.xml"));  
        CustomEditorConfigurer configurer=(CustomEditorConfigurer)beanFactory.getBean("customEditorConfigurer");  
        configurer.postProcessBeanFactory((ConfigurableListableBeanFactory) beanFactory);  
        User user=(User)beanFactory.getBean("user");  
        System.out.println("name:"+user.getUsername()+"\nbirthday:"+user.getBirthday());  
          
    }  
  
}

输出结果：
name:heck  
birthday:Fri Mar 28 00:00:00 CDT 2014  

接下来我们在程序中注册自定义的属性编辑器：
package tk.hecks.property;  
  
import org.springframework.beans.PropertyEditorRegistrar;  
import org.springframework.beans.PropertyEditorRegistry;  
import org.springframework.beans.factory.config.ConfigurableBeanFactory;  
import org.springframework.beans.factory.xml.XmlBeanFactory;  
import org.springframework.core.io.ClassPathResource;  
  
public class TestPropertyEditorResgister {  
    public static void main(String[] args) {  
        ConfigurableBeanFactory beanFactory=new XmlBeanFactory(new ClassPathResource("applicationContext.xml"));  
        beanFactory.addPropertyEditorRegistrar(new PropertyEditorRegistrar() {  
            public void registerCustomEditors(PropertyEditorRegistry registry) {  
                registry.registerCustomEditor(java.util.Date.class, new UtilDatePropertyEditor("yyyy-MM-dd"));  
                  
            }  
        });  
        User user=(User)beanFactory.getBean("user");  
        System.out.println("name:"+user.getUsername()+"\nbirthday:"+user.getBirthday());  
          
    }  
  
}  

来源：Heck's Blog
地址：https://www.heckjj.com/post/420/
转载时须以链接形式注明作者和原始出处及本声明，否则将追究法律责任，谢谢配合！