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JSON--Java与AJAX(Jquery)

2015-11-20 22:58 579 查看
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>                                                

        如果字符串本身符合json格式,可以使用如下方法,将json字符串转换为json对象

        String str = "{'check': '1'}"; 

        JSONObject resultJSON = JSONObject.fromObject(str);

       

        获得json对象的内容,各种get方法

        String check = resultJSON.getString("check");


                                                                                                                                                                                           

* @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': 'kelly@seankelly.biz'},{'type': 'home', 'pref': 1, 'value': 'kelly@seankelly.tv'}]");

   //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": "kelly@seankelly.biz"

   },

      {

    "type": "home",

    "pref": 1,

    "value": "kelly@seankelly.tv"

   }

  ]

}

/**                                                         

* 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": "kelly@seankelly.biz"

   },

      {

    "type": "home",

    "pref": 1,

    "value": "kelly@seankelly.tv"

   }

  ]

}

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。

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

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
 另外,请特别关注如下资料,介绍的非常详细:
http://jiangzhengjun.iteye.com/category/78136 
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