json数据与Gson工具类的使用

JS中使用JSON
JSON对象 --> JSON字符串：JSON.stringify(对象)
JSON字符串 --> JSON对象：JSON.parse(JSON字符串)

<script type="text/javascript">
    var json={"name":"chen","age":18,"date":new Date(),"school":null,"hobby":[1,2,3],"gender":true};
    document.write(typeof json+"<br>");//object
    document.write(json+"<br>");//[object Object]
    document.write(json.name+"<br>");//chen
    document.write(json.hobby[0]+"<br>");//1
    document.write("JSON转化成string<br>");
    var jsonStr=JSON.stringify(json);
    document.write(typeof jsonStr+"<br>");//string
    document.write(jsonStr+"<br>");//{"name":"chen","age":18,"date":"2017-08-17T13:15:32.981Z","school":null,"hobby":[1,2,3],"gender":true}
    //document.write(jsonStr.name+"<br>");//undefined出错
    //document.write(jsonStr.hobby[0]+"<br>");//undefined出错
    document.write("string转化成JSON<br>");
    var jsonObj=JSON.parse(jsonStr);
    document.write(typeof jsonObj+"<br>");//object
    document.write(jsonObj+"<br>");//[object Object]
    document.write(jsonObj.name+"<br>");//chen
    document.write(jsonObj.hobby[0]+"<br>");//1
</script>

JAVA中使用JSON

目前Java中用的比较多的JSON解析工具：

• json-lib --> 使用麻烦，解析性能最差
• Jackson --> 使用较麻烦，解析性能最好
• Gson --> 使用简单，解析性能中等
  • Gson是谷歌出的一款JSON解析工具，使用简单，且性能较好。

GSON工具类的使用

// 将普通对象转换为JSON字符串！
Student stu = new Student("尘", 18);
System.out.println(stu);//com.test.Student@15db9742-----内存地址
Gson gson = new Gson();
String json = gson.toJson(stu);
System.out.println(json);//{"name":"尘","age":18}
Student fromJson1 = gson.fromJson(json, Student.class);
System.out.println(fromJson1);//com.test.Student@25f38edc-----内存地址

// 把Map转换成JSON字符串
 Map<String,String> map2 = new HashMap<String,String>();
 map2.put("hobby","篮球");
 map2.put("gender", "男");
 String json2 = gson.toJson(map2);
 System.out.println(json2);//{"gender":"男","hobby":"篮球"}
 Map<String,String> fromJson2 = gson.fromJson(json2, Map.class);
 System.out.println(fromJson2);//{gender=男, hobby=篮球}

// 将List转换为JSON字符串
List<Student> list = new ArrayList<Student>();
list.add(new Student("Tom", 7));
list.add(new Student("Jerry", 5));
String json3 = gson.toJson(list);
System.out.println(json3);//[{"name":"Tom","age":7},{"name":"Jerry","age":5}]
List<Map<String, Object>> fromJson3 = gson.fromJson(json3, List.class);
for (Map map3 : fromJson3) {
    System.out.println(map3.get("name"));
    //Tom
    //Jerry
}

 付gson-2.2.4.jar下载地址（百度云） 密码：9ngh