JSON--Java与AJAX(Jquery)

一、JSON 是什么？
JSON 的全称是JavaScript Object Notation，是一种轻量级的数据交换格式。

JSON 与XML 具有相同的特性，例如易于人编写和阅读，易于机器生成和解析。但是JSON 比
XML 数据传输的有效性要高出很多。JSON 完全独立与编程语言，使用文本格式保存。
JSON 数据有两种结构：
• Name-Value 对构成的集合，类似于Java 中的Map。
• Value 的有序列表，类似于Java 中的Array。
一个JSON 格式的数据示例：
{
"Name": "Apple",
"Expiry": "2007/10/11 13:54",
"Price": 3.99,
"Sizes": [
"Small",
"Medium",
"Large"
]
}
更多关于JSON 数据格式的说明参看JSON 官方网站：http://www.json.org（中文
内容参看：http://www.json.org/json-zh.html）

二、通过java来创建JSON对象

1.引入jar包

我这里使用的是json-lib-2.3-jdk15.jar，下载地址：http://sourceforge.net/projects/json-lib/files/

Json-lib requires (at least) the following dependencies in your classpath:

jakarta commons-lang 2.4
jakarta commons-beanutils 1.7.0
jakarta commons-collections 3.2
jakarta commons-logging 1.1.1
ezmorph 1.0.6
2.重要的对象及方法

1）JSONObject：JSON对象{}。

2）JSONArray：JSON数组对象，[{},{}]。

3）fromObject(object)：将对象转换为JSON对象。

4）JSONObject.accumulate(key,value)：向JSONObject中增加JSON数据，可以重复。

5）element(key,value)：向JSON对象中增加JSON数据，如果重复后一个会替换前一个。

6）toString(i,i)：将JSON对象转换为字符串，如果包含参数，是将其美化后输出。

以下是一个servlet输出JSON的例子：

package com.netqin.function.demo.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import net.sf.json.JSONArray;
import net.sf.json.JSONException;
import net.sf.json.JSONObject;

import com.netqin.function.demo.model.People;
import com.netqin.function.demo.model.Phone;

public class JsonServlet extends HttpServlet{
private static final String CONTENT_TYPE = "text/plain; charset=UTF-8";

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse response)
   throws ServletException, IOException {
  // TODO Auto-generated method stub
  this.StringToJson(req, response);
//  this.MapToJson(req, response);
//  this.BeanToJson(req, response);
//  this.ListToJson(req, response);
}

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  // TODO Auto-generated method stub
  doGet(req, resp);
}

/**                                                         
* 描述 : <输出>. <br>
*<p>                                                
                                                                                                                                                                                                      
* @param response
* @param content
* @throws IOException                                                                                         
*/
private void print(HttpServletResponse response,String content) throws IOException{
  response.setContentType(CONTENT_TYPE);
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        PrintWriter write = response.getWriter();
        write.print(content);
        write.close();
}


--------------------------------------------------------------------------------



/**                                                         
* 描述 : <将字符串或数组转换为JSON>. <br>
*<p>                                                
                                                                                                                                                                                                      
* @param req
* @param response
* @throws ServletException
* @throws IOException                                                                                         
*/
// @SuppressWarnings("unused")
private void StringToJson(HttpServletRequest req, HttpServletResponse response)throws ServletException, IOException{
  JSONObject resultJSON = new JSONObject();   
        try {   
        
            resultJSON.accumulate("name", "Violet")   
                      .accumulate("occupation", "developer")   
                      .accumulate("age", new Integer(22))
                      .accumulate("array", new int[] { 1, 2, 3 })
                      .accumulate("muliArray","[{'type': '你好', 'value': '[e-mail]'},{'type': 'home', 'pref': 1, 'value': '[e-mail]'}]");
   //System.out.println(resultJSON.toString(1,1));
  } catch (JSONException e) {
   e.printStackTrace();
  }
  this.print(response, resultJSON.toString(1,1));
 
}

输出结果：

{
  "name": "Violet",
  "occupation": "developer",
  "age": 22,
  "array":   [
   1,
   2,
   3
  ],
  "muliArray":   [
      {
    "type": "你好",
    "value": "[e-mail]"
   },
      {
    "type": "home",
    "pref": 1,
    "value": "[e-mail]"
   }
  ]
}
--------------------------------------------------------------------------------



/**                                                         
* 描述 : <将Map转换为JSON>. <br>
*<p>                                                
                                                                                                                                                                                                      
* @param req
* @param response
* @throws ServletException
* @throws IOException                                                                                         
*/
@SuppressWarnings("unchecked")
private void MapToJson(HttpServletRequest req, HttpServletResponse response)throws ServletException, IOException{
  JSONObject resultJSON = null;   
  Map map = new HashMap(15);
        try {   
         map.put("name", "hanqf");
         map.put("age", 28);
         map.put("phone", "{home:135,busi:139}");
         resultJSON = JSONObject.fromObject(map);
   //System.out.println(resultJSON.toString());
  } catch (JSONException e) {
   e.printStackTrace();
  }
  this.print(response, resultJSON.toString(1,1));
}


输出结果：

{
  "phone": "{home:135,busi:139}",
  "age": 28,
  "name": "hanqf"
}
--------------------------------------------------------------------------------



/**                                                         
* 描述 : <JavaBean转换为JSON>. <br>
*<p>                                                
                                                                                                                                                                                                      
* @param req
* @param response
* @throws ServletException
* @throws IOException                                                                                         
*/
private void BeanToJson(HttpServletRequest req, HttpServletResponse response)throws ServletException, IOException{
  JSONObject resultJSON = null;  
  People people = new People();
  Phone phone = new Phone("135","138");
        try {   
         people.setPhone(phone);
         resultJSON = JSONObject.fromObject(people);
   //System.out.println(resultJSON.toString());
  } catch (JSONException e) {
   e.printStackTrace();
  }
  this.print(response, resultJSON.toString(1,1));
}

public class People{
String name;
int age;
Phone phone = new Phone();

setter and getter

…………………………

}

public class Phone{
String home;
String busi;

setter and getter

…………………………

}

输出结果：

{
  "age": 0,
  "name": "",
  "phone":   {
   "busi": "138",
   "home": "135"
  }
}
--------------------------------------------------------------------------------



/**                                                         
* 描述 : <List转换为JSON>. <br>
*<p>                                                
                                                                                                                                                                                                      
* @param req
* @param response
* @throws ServletException
* @throws IOException                                                                                         
*/
private void ListToJson(HttpServletRequest req, HttpServletResponse response)throws ServletException, IOException{
  JSONArray jsonArray = null;  
  People people = null;
  Phone phone = null;
  List<People> list = new ArrayList<People>();
        try {   
         for(int i =0;i<3;i++){
          people = new People();
          phone = new Phone("135"+i,"138"+i);
          people.setAge(i);
          people.setPhone(phone);
          list.add(people);
         }
         jsonArray = JSONArray.fromObject(list);

   //System.out.println(jsonArray.toString());
  } catch (JSONException e) {
   e.printStackTrace();
  }
  this.print(response, jsonArray.toString(1,1));
}
}
输出结果：

[
    {
   "age": 0,
   "name": "",
   "phone":    {
    "busi": "1380",
    "home": "1350"
   }
  },
    {
   "age": 1,
   "name": "",
   "phone":    {
    "busi": "1381",
    "home": "1351"
   }
  },
    {
   "age": 2,
   "name": "",
   "phone":    {
    "busi": "1382",
    "home": "1352"
   }
  }
]
--------------------------------------------------------------------------------

三、Ajax调用

以<将字符串或数组转换为JSON>. 为例，

{
  "name": "Violet",
  "occupation": "developer",
  "age": 22,
  "array":   [
   1,
   2,
   3
  ],
  "muliArray":   [
      {
    "type": "你好",
    "value": "[e-mail]"
   },
      {
    "type": "home",
    "pref": 1,
    "value": "[e-mail]"
   }
  ]
}

jsp中主要的代码如下：

<script type="text/javascript" src="jquery-1.2.6.pack.js"></script>

<script type="text/javascript">
jQuery(function($){


  $("#onebut").click(function(){

    $.getJSON("http://localhost:8080/points/json.do",function(data){


      $("#one").html("");
      $("#one").append(data.name);
      $("#one").append("##");
      $("#one").append(data.age);
      $("#one").append("##");
      $("#one").append(data.array[0]);
      //$("#one").append("##");
      //$("#one").append(data.muliArray[0].type);
  
      $.each(data.muliArray,function(i,item){
          $("#one").append("##");
          $("#one").append(item.type);
   
      });


   });


});


});
</script>

<button id="onebut">onebut</button>
<div id="one"></div>

点击"onebut”按钮后，页面上显示如下：

Violet##22##1##你好##home


--------------------------------------------------------------------------------

四、JSON进阶

1.再来看几个重要的对象和方法

1）JSON：JSON对象的顶级接口，JSONObject,JSONArray都实现了该接口

2）JSONSerializer：JSON串行化对象

3）JSONSerializer.toJSON(object)：将对象串行化为JSON

4）JSONSerializer.toJava(json)：将JSON转换为对象

5）MorphDynaBean：JSONSerializer.toJava(json)后的值默认为MorphDynaBean

6）XMLSerializer：JSON转换为xml对象

7）xMLSerializer.write(json)：将JSON对象转换为xml

8）xMLSerializer.read(xml)：将xml转换为JSON对象

2.实例

1）json转map

   JSONObject resultJSON = JSONObject.fromObject(map);

   Map mapp = (Map)JSONObject.toBean(resultJSON, Map.class);
   System.out.println(mapp.get("name"));


--------------------------------------------------------------------------------

2）json转JavaBean

   JSONObject resultJSON =JSONObject.fromObject(people);

   People pp = (People)JSONObject.toBean(resultJSON, People.class);
   System.out.println(pp.getPhone().getBusi());


--------------------------------------------------------------------------------

3）json转list

  JSONObject resultJSON = JSONConvert.generate(list);
   
  Map mapp = (Map)JSONObject.toBean(resultJSON, Map.class);
  List<MorphDynaBean> list2 = (List<MorphDynaBean>)mapp.get("root");
  for(MorphDynaBean pp : list2){
   System.out.println(((MorphDynaBean)pp.get("phone")).get("busi"));
  }

说明：

为什么没有使用JSONArray.toArray(jsonArray)或JSONArray.toCollection(jsonArray)呢？

笔者在使用过程中发现其在转换时不能对people.phone对象赋值，也就是说不能嵌套赋值，所以才改用map加MorphDynaBean的方式，也许是笔者没有搞明白，希望高手指点。

这里提供一个JSONConvert工具类，方便bean对象、map和list转换为JSONObject ，如下：

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import net.sf.json.JSONObject;

public class JSONConvert {

public static JSONObject generate(List list) {

        Map<String, Object> map = new HashMap<String, Object>();
        map.put("totalProperty", list.size());
        map.put("root", list);
        return JSONObject.fromObject(map);
    }

    public static JSONObject javabean2json(Object object) {
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("success", true);
        map.put("data", object);
        return JSONObject.fromObject(map);
    }

    public static JSONObject objectcollect2json(List list, String total) {
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("totalProperty", total);
        map.put("root", list);
        return JSONObject.fromObject(map);
    }

}


--------------------------------------------------------------------------------

4）json转xml

需要引入该包：xom-1.1.jar，下载地址：http://repo1.maven.org/maven2/xom/xom/1.1/

  XMLSerializer xmlSe = new XMLSerializer();

  System.out.println("json=="+resultJSON.toString(1, 1));
  String xml = xmlSe.write(resultJSON);
  System.out.println("xml=="+xml);

输出结果：

json==

{
  "age": 0,
  "name": "",
  "phone":   {
   "busi": "139",
   "home": "135"
  }
}
xml==

<?xml version="1.0" encoding="UTF-8"?>
<o>

<age type="number">0</age>

<name type="string"/>

<phone class="object">

<busi type="string">139</busi>

<home type="string">135</home>

</phone>

</o>


--------------------------------------------------------------------------------

5）json的特殊字符处理

由于json的格式要求，“：”“{}”，“[]”，“\”等等都是json的特定字符，

所以如果在name或value中出现了这些字符就会造成json解析异常，

比如：

resultJSON.accumulate("phone", "{home:135,busi:139}");

在页面上的显示结果如下：

{
   "phone":   {
   "home": "135",
   "busi": 139
  }

}

如果json修改成如下形式:

resultJSON.accumulate("phone", "{home:135:11{[,busi:139}");

在页面上的显示结果如下：

{
   "phone": "{home:135:11{[,busi:139}",
}

此时，json会将"{home:135:11{[,busi:139}"都作为phone的值，而不会再向下解析

所以，在遇到这样的问题时只要将value用引号括起来就行了，如下：

resultJSON.accumulate("phone", "{home:'135:11{[',busi:139}");

输出结果如下：

{
   "phone":   {
   "home": "135:11{[",
   "busi": 139
  }

}

这样就可以正常解析了，所以，在创建json时，最好将name和value都用引号扩上。


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提供几个JSON的参考资料：

http://www.diybl.com/course/3_program/java/javashl/2007123/89756.html

http://developer.51cto.com/art/201001/176686.htm

http://www.iteye.com/topic/78243


http://www.iteye.com/topic/71343

另外，请特别关注如下资料，介绍的非常详细：

http://jiangzhengjun.iteye.com/category/78136