Json & Gson

Json是一种数据格式，便于数据传输、存储、交换（不同的语言有不同的规定，android 2.3中引入了Json的解析类），有如下两种形式：

·对象{ key:value,key:value,......}

·数组[a,b,c,d......]

Java中主要使用JSONObject代表一个JSON对象， 完成json字符串和Java对象之间的相互转换，JSONArray代表一个JSON数组，完成json字符串和Java集合之间的相互转换

Gson是一种组件库，可以把Java对象数据转换成Json数据格式,也可以把Json数据格式转换成Java对象(要加入Gson包，方可使用)

Json中文官网对于Json的解释：http://www.json.org.cn/

Gson的介绍：

1. 用到的主要的方法

   String toJson(Object obj/...)

  Object  fromJson(String str/...)

2. 例子如下：

public class TextGson{

<span style="white-space:pre"></span>class Student {int id;String name;String birthday;int age;List<String> listStr = new ArrayList<String>();HashMap<String, String> map = new HashMap<String, String>();public Student() {}public Student(int id, String name, String birthday, int age) {setId(id);setName(name);setBirthday(birthday);setAge(age);listStr.add("1");listStr.add("2");map.put("map1", "map1str");map.put("map2", "map2str");}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getBirthday() {return birthday;}public void setBirthday(String birthday) {this.birthday = birthday;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}@Overridepublic String toString() {// TODO Auto-generated method stubreturn "Student id:" + getId() + " name:" + getName()+ " birthday:" + getBirthday() + " age:" + getAge();// return super.toString();}}

}

//Gson

<span style="white-space:pre"></span>TestGson tg = new TestGson();Gson gson = new Gson();Student s1 = tg.new Student(0, "小猫", new Date().toString(), 24);Student s2 = tg.new Student(1, "小狗", new Date().toString(), 25);Student s3 = tg.new Student(2, "阿狸", new Date().toString(), 123);String jsonStr = gson.toJson(s1);System.out.println("s4:" + jsonStr);List<Student> list = new ArrayList<Student>();list.add(s3);list.add(s2);String jsonStrlist = gson.toJson(list);System.out.println("list:" + jsonStrlist);System.out.println("s1object:" + gson.fromJson(jsonStr, Student.class));System.out.println("listobject:"+ gson.fromJson(jsonStrlist, new TypeToken<List<Student>>() {}.getType()));

</pre><span style="white-space:pre"></span>//JSONObject <span style="color:#ff0000">在android中使用的</span><p></p><p><span style="white-space:pre"><span style="white-space:pre"></span></span><span style="background-color:rgb(240,240,240); white-space:pre">try {</span><span style="white-space:pre"><span style="white-space:pre"></span></span></p><pre name="code" class="java">JSONObject jsonObject = new JSONObject(jsonStr);int id = (Integer) jsonObject.get("id");String name = jsonObject.getString("name");JSONArray lstr = jsonObject.getJSONArray("listStr");int i = lstr.getInt(0);System.out.println(" id:" + id + " name:" + name + " i:" + i+ " lstr:" + lstr.toString() + " jsonobject:" + jsonObject);} catch (JSONException e) {// TODO Auto-generated catch blocke.printStackTrace();}