{
  "firstName":"John",
  "lastName":"Doe"
}

{
  "employees":[
    {"firstName":"John","lastName":"Doe"},
    {"firstName":"Anna","lastName":"Smith"},
    {"firstName":"Peter","lastName":"Jones"}
  ]
}

<dependency>
  <groupId>com.google.code.gson</groupId>
  <artifactId>gson</artifactId>
  <version>2.2.4</version>
</dependency>

{
  "cat":"it",
  "languages":[
    {"id":1,"ide":"Eclipse","name":"Java"},
    {"id":2,"ide":"Xcode","name":"Swift"},
    {"id":3,"ide":"Visual Studio","name":"C#"}
  ],
  "pop":true
}

public void readJSON() throws Exception{

  // 创建json解析器
  JsonParser parser = new JsonParser(); 
  // 使用解析器解析json数据，返回值是JsonElement，强制转化为其子类JsonObject类型
  JsonObject object = (JsonObject) parser.parse(new FileReader("test.json"));

  // 使用JsonObject的get(String memeberName)方法返回JsonElement，再使用JsonElement的getAsXXX方法得到真实类型
  System.out.println("cat = " + object.get("cat").getAsString());

  // 遍历JSON数组
  JsonArray languages = object.getAsJsonArray("languages");
  for (JsonElement jsonElement : languages) {
    JsonObject language = jsonElement.getAsJsonObject();
    System.out.println("id = " + language.get("id").getAsInt() + ",ide = " + language.get("ide").getAsString() + ",name = " + language.get("name").getAsString());
  }

  System.out.println("pop = " + object.get("pop").getAsString());
}

public void createJSON() throws IOException{

  JsonObject object = new JsonObject(); // 创建一个json对象
  object.addProperty("cat", "it");    // 为json对象添加属性  

  JsonArray languages = new JsonArray(); // 创建json数组
  JsonObject language = new JsonObject();
  language.addProperty("id", 1);
  language.addProperty("ide", "Eclipse");
  language.addProperty("name", "java");
  languages.add(language);        // 将json对象添加到数组 

  language = new JsonObject();
  language.addProperty("id", 2);
  language.addProperty("ide", "XCode");
  language.addProperty("name", "Swift");
  languages.add(language);

  language = new JsonObject();
  language.addProperty("id", 3);
  language.addProperty("ide", "Visual Studio");
  language.addProperty("name", "C#");
  languages.add(language);

  object.add("languages", languages);  // 将数组添加到json对象  
  object.addProperty("pop", true);

  String jsonStr = object.toString();  // 将json对象转化成json字符串
  PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter("data.json")));
  pw.print(jsonStr);
  pw.flush();
  pw.close();
}

//construct json and output it  
public String jsonTest() throws JSONException{ 
  JSONObject json=new JSONObject(); 
  JSONArray jsonMembers = new JSONArray(); 
  JSONObject member1 = new JSONObject(); 
  member1.put("loginname", "zhangfan"); 
  member1.put("password", "userpass"); 
  member1.put("email","10371443@qq.com"); 
  member1.put("sign_date", "2007-06-12"); 
  jsonMembers.put(member1); 
 
  JSONObject member2 = new JSONObject(); 
  member2.put("loginname", "zf"); 
  member2.put("password", "userpass"); 
  member2.put("email","8223939@qq.com"); 
  member2.put("sign_date", "2008-07-16"); 
  jsonMembers.put(member2); 
  json.put("users", jsonMembers); 
 
  return json.toString(); 
} 

//construct json from String and resolve it. 
public String jsonTest2() throws JSONException{ 
  String jsonString="{"users":[{"loginname":"zhangfan","password":"userpass","email":"10371443@qq.com"},{"loginname":"zf","password":"userpass","email":"822393@qq.com"}]}"; 
  JSONObject json= new JSONObject(jsonString); 
  JSONArray jsonArray=json.getJSONArray("users"); 
  String loginNames="loginname list:"; 
  for(int i=0;i<jsonArray.length();i++){ 
    JSONObject user=(JSONObject) jsonArray.get(i); 
    String userName=(String) user.get("loginname"); 
    if(i==jsonArray.length()-1){ 
      loginNames+=userName; 
    }else{ 
      loginNames+=userName+","; 
    } 
  } 
  return loginNames; 
}