原文http://www.yshjava.cn/post/546.html

将对象转换成字符串，是非常常用的功能，尤其在WEB应用中，使用JSON lib能够便捷地完成这项工作。JSON lib能够将Java对象转成json格式的字符串，也可以将Java对象转换成xml格式的文档，同样可以将json字符串转换成Java对象或是将xml字符串转换成Java对象。

无论出于何种原因，某些时候，我们需要对对象转为字符串的过程加以控制，最常见需求如数值格式化和日期格式化。JSON lib提供了JsonConfig对象，该对象能够深刻影响Java对象转成json字符串的行为。

增加忽略的属性

1. 第一种方式，实现JSONString接口的方法

@H_502_19@package cn.ysh.studio.test;

@H_502_19@import java.io.Serializable;

@H_502_19@import net.sf.json.JSONObject;
@H_502_19@import net.sf.json.JSONString;

/**
 * 
 * @author 杨胜寒
 * @date 2013-6-27
 *
 */
@H_502_19@public class User implements JSONString,Serializable{

   @H_502_19@private @H_502_19@static @H_502_19@final @H_502_19@long serialVersionUID = 1L;
   @H_502_19@private @H_502_19@long id;
   @H_502_19@private String name;
   @H_502_19@private String password;
   
   @H_502_19@public User(){}
   
   @H_502_19@public User(Long id,String name,String password){
      @H_502_19@this.id = id;
      @H_502_19@this.name = name;
      @H_502_19@this.password = password;
   }
   
   @H_502_19@public User(String name,String password){
      @H_502_19@this.name = name;
      @H_502_19@this.password = password;
   }
   
   @H_502_19@public @H_502_19@long getId() {
      @H_502_19@return id;
   }

   @H_502_19@public @H_502_19@void setId(@H_502_19@long id) {
      @H_502_19@this.id = id;
   }

   @H_502_19@public String getName() {
      @H_502_19@return name;
   }

   @H_502_19@public @H_502_19@void setName(String name) {
      @H_502_19@this.name = name;
   }

   @H_502_19@public String getPassword() {
      @H_502_19@return password;
   }

   @H_502_19@public @H_502_19@void setPassword(String password) {
      @H_502_19@this.password = password;
   }

   @Override
   @H_502_19@public String toJSONString() {
      //return "{\"id\":" + this.id + ",\"name\":\"" + this.name + "\",\"password\":\""+ this.password +"\"}";
      //忽略敏感字段password
      @H_502_19@return "{\"id\":" + @H_502_19@this.id + ",\"name\":\"" + @H_502_19@this.name + "\"}";
   }
   
   @H_502_19@public @H_502_19@static @H_502_19@void main(String[] args) {
      User user = @H_502_19@new User(12L,"JSON",68)">"json");
      System.out.println(JSONObject.fromObject(user).toString());
   }
}

2.第二种方式，通过jsonconfig实例，对包含和需要排除的属性进行方便的添加或删除

@H_502_19@package cn.ysh.studio.test;

@H_502_19@import java.io.Serializable;

@H_502_19@import net.sf.json.JSONObject;
@H_502_19@import net.sf.json.JSONString;
@H_502_19@import net.sf.json.JsonConfig;

class User {

   @H_502_19@private @H_502_19@long id;
   @H_502_19@private String name;
   @H_502_19@private String password;
   
   @H_502_19@public User(){}
   
   @H_502_19@public User(Long id,String password){
      @H_502_19@this.name = name;
      @H_502_19@this.password = password;
   }
   
   @H_502_19@public @H_502_19@long getId() {
      @H_502_19@return id;
   }

   @H_502_19@public @H_502_19@void setId(@H_502_19@long id) {
      @H_502_19@this.id = id;
   }

   @H_502_19@public String getName() {
      @H_502_19@return name;
   }

   @H_502_19@public @H_502_19@void setName(String name) {
      @H_502_19@this.name = name;
   }

   @H_502_19@public String getPassword() {
      @H_502_19@return password;
   }

   @H_502_19@public @H_502_19@void setPassword(String password) {
      @H_502_19@this.password = password;
   }

   @H_502_19@public @H_502_19@static @H_502_19@void main(String[] args) {
      JsonConfig config = @H_502_19@new JsonConfig();  
      config.setExcludes( @H_502_19@new String[]{"password"});
      User user = @H_502_19@new User("json");
      System.out.println(JSONObject.fromObject(user,config).toString());
   }
}

属性过滤器

使用propertyFilter可以允许同时对需要排除的属性和类进行控制，这种控制还可以是双向的，也可以应用到json字符串到java对象

JsonConfig config = @H_502_19@new JsonConfig();  
config.setJsonPropertyFilter(@H_502_19@new PropertyFilter() {
   
   @Override
   @H_502_19@public @H_502_19@boolean apply(Object source/* 属性的拥有者 */,String name /*属性名字*/,Object value/* 属性值 */) {
      @H_502_19@return source @H_502_19@instanceof User && "password".equalsIgnoreCase(name);
   }
});
User user = @H_502_19@new User("json");
System.out.println(JSONObject.fromObject(user,config).toString());

相对于上面的何种方式，如下的方式或许更为简便：

JsonConfig config = @H_502_19@new JsonConfig();
config.registerPropertyExclusions(User.@H_502_19@class,@H_502_19@new String[]{"password"});
User user = @H_502_19@new User("json");
System.@H_502_19@out.println(JSONObject.fromObject(user,config).toString());

自定义JsonBeanProcessor

JsonBeanProcessor和实现JsonString很类似，返回一个代表原来目标对象的合法JSONObject

JsonConfig config = @H_502_19@new JsonConfig();
config.registerJsonBeanProcessor(User.@H_502_19@class,@H_502_19@new JsonBeanProcessor() {

   @Override
   @H_502_19@public JSONObject processBean(Object bean,JsonConfig config) {
      User user = (User) bean;
      @H_502_19@return @H_502_19@new JSONObject().element("id",user.getId()).element("name",user.getName());
   }
});
User user = @H_502_19@new User( 自定义JsonValueProcessor 
 比如我们要控制JSON序列化过程中的Date对象的格式化，以及数值的格式化，JsonValueProcessor是最好的选择。
 
Map<String,Object> map = @H_502_19@new HashMap<String,Object>();
map.put("date",@H_502_19@new Date());
map.put("dates",Arrays.asList(@H_502_19@new Date()));
JsonConfig config = @H_502_19@new JsonConfig();
config.registerJsonValueProcessor(Date.class,@H_502_19@new JsonValueProcessor() {
   //自定义日期格式
   SimpleDateFormat simpleDateFormat = @H_502_19@new SimpleDateFormat("yyyy-MM-dd");

   @Override
   /**
    * 处理单个Date对象
    */
   @H_502_19@public Object processObjectValue(String propertyName,Object date,JsonConfig config) {
      @H_502_19@return simpleDateFormat.format(date);
   }

   @Override
   /**
    * 处理数组中的Date对象
    */
   @H_502_19@public Object processArrayValue(Object date,JsonConfig config) {
      @H_502_19@return simpleDateFormat.format(date);
   }
});
System.out.println(JSONObject.fromObject(map,254)"> 除了自定义日期格式外，还可以如法炮制，控制数值格式化、HTML内容转码等。