json学习（一）--将一个对象或集合转换成符合json数据格式的字符串

json主要用于传送数据，主要格式如下：{“name“:"value"}

有如下xml文件

<section>

 <title>Book-Singing Event</title>

 <signing>

  <author title="Mr" name="Vikram Seth"/>

  <book title="A Suitable Boy" price="$22.95"/>

 </signing>

 <signing>

  <author title="Dr" name="Oliver Sacks"/>

  <book title="The Island of the Color-Blind" price="$1295"/>

 </signing>

</section>
将其转换成javascript中的json数据如下：

<script type="text/javascript">

 function check()

 {

  var info = {"section":{

      "title":"Book-Singing Event",

      "singing":[{

       "author":{"title":"Mr","name":"Vikram Seth"},

       "book":{"title":"A Suitable Boy","price":"$22.95"}

      },{

       "author":{"title":"Dr","name":"Oliver Stacks"},

       "book":{"title":"The Island of Color-Blind", "price":"$12.95"}

      }]

   }};

  alert(info.section.title);

  alert(info.section.singing[0].book.title);

 }

</script>
     将会弹出提示框：Book-Singin Event和A Suitable Boy

 

json in java 源码下载地址：https://github.com/douglascrockford/JSON-java点击图标ZIP

下载完成后，将源码复制到org.json包下

编写一个类使用JSONObject类和JSONArray类

package com.json.study;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

public class Test {

 public static void main(String[] args) throws JSONException {

  //假设这个字符串从客户端传来

  String jsonContext = "{'hello':'world','abc':'xyz'}";

  //抛异常，json数据的格式可能不正确

  JSONObject jsonObject = new JSONObject(jsonContext);

  String str1 = jsonObject.getString("hello");

  String str2 = jsonObject.getString("abc");

  

  System.out.println(str1);

  System.out.println(str2);

  

  System.out.println("---------------------------");

  

  jsonContext = "[{'hello':333,'abc':false, 'xyz':'test'},{'hello':555,'abc':true,'xyz':'test'}]";

  JSONArray jsonArray = new JSONArray(jsonContext);

  System.out.println(jsonArray.length());

  for(int i = 0; i < jsonArray.length(); i++)

  {

   JSONObject jsonObject2 = jsonArray.getJSONObject(i);

   int value1 = jsonObject2.getInt("hello");

   boolean value2 = jsonObject2.getBoolean("abc");

   String value3 = jsonObject2.getString("xyz");

   System.out.println(value1+"   "+value2+"   "+value3);  

  }

 }

}

 执行结果：

world

xyz

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

2

333   false   test

555   true   test

 

 

将一个对象（bean）转换成可以符合json数据格式的字符串，需要gson.jar包，下载地址：http://code.google.com/p/google-gson/

    Person类：

ackage com.json.study;

import java.util.List;

public class Person {

 private String username;

 private String password;

 private int age;

 private String address;

 private List list;

 public Person() {

  super();

 }

 

 public String getUsername() {

  return username;

 }

 public void setUsername(String username) {

  this.username = username;

 }

 public String getPassword() {

  return password;

 }

 public void setPassword(String password) {

  this.password = password;

 }

 public int getAge() {

  return age;

 }

 public void setAge(int age) {

  this.age = age;

 }

 public String getAddress() {

  return address;

 }

 public void setAddress(String address) {

  this.address = address;

 }

 public List<String> getList() {

  return list;

 }

 public void setList(List<String> list) {

  this.list = list;

 }

 

}

转换方式如下：

package com.json.study;

import java.util.ArrayList;

import java.util.List;

import com.google.gson.Gson;

public class Test2 {

 public static void main(String[] args) {

  Person person = new Person();

  person.setUsername("zhangsan");

  person.setPassword("123456");

  person.setAddress("beijing");

  person.setAge(30);

  

  List list = new ArrayList();

  list.add(new String("abc"));

  list.add(false);

  

  person.setList(list);

  Gson gson = new Gson();

  //将一个对象转换成符合json格式的字符串

  String result = gson.toJson(person);

  System.out.println(result);

  

  

 }

}

结果：

{"username":"zhangsan","password":"123456","age":30,"address":"beijing","list":["abc",false]}