Question

我已经能够使用import org.json.JSONObject从servlet发出一个json对象; 请参阅下面的代码

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
                response.setContentType("application/json");
                response.setHeader("Cache-Control", "nocache");
                response.setCharacterEncoding("utf-8");
                PrintWriter out = response.getWriter();

                JSONObject json = new JSONObject();

                // put a "person" 
                JSONObject person = new JSONObject();
                try {
                    person.put("age", "24");
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                try {
                    person.put("gender", "M");
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                try {
                    person.put("ID", "10082");
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                try {
                    json.put("person", person);
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

                // finally output the json string       
                out.print(json.toString());
}

这给了我一个json响应，如：

{"person":{"age":"24","gender":"M","ID":"10082"}}

但是，我想得到一个包含3个json对象的数组。我怎么能得到它？

[
    {
        "age": "21",
        "gender": "M",
        "ID": "10092"
    },
    {
        "age": "25",
        "gender": "M",
        "ID": "10091"
    },
    {
        "age": "24",
        "gender": "M",
        "ID": "10095"
    }
]

Answer 1

您必须为每个用户创建不同的JSON对象，然后将所有这些对象放入JSON数组中。最后将数组添加到主JSON对象。您可以从以下代码中获得想法（我假设您的数据位于某些ArrayList中，例如All_Users。）：

JSONObject main_JSON_Object =new JSONObject();
JSONArray main_JSON_Array=new JSONArray();

    for(int i= 0;i<All_Users.size();i++)
                 {
                     JSONObject user_Object=new JSONObject();

                                try
                                {

                                user_Object.put("person", All_Users.get(i));
                                }
                                catch(NullPointerException ex)
                                {

                                }

                                 main_JSON_Array.put(user_Object);
                       }

                 main_JSON_Object.put("userarray", main_JSON_Array);

Answer 2

使用JSONArray和JSONObject

创建JSON对象

JSONObject objJSON =new JSONObject();

创建一个JSON数组

JSONArray arrJSON =new JSONArray();

Loop Over包含数据的集合，假设来自DB的RESULSET

    while(resultset.next()){

                // put a "person" 
                JSONObject person = new JSONObject();
                try {
                    person.put("age", "24");
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                try {
                    person.put("gender", "M");
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                try {
                    person.put("ID", "10082");
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                try {
                    arrJSON .add(person);
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

     }

    objJSON.put("person",arrJSON  );

如果您在使用objJSON.put("person",arrJSON );时遇到任何异常，请尝试使用此objJSON.put("person",(Object)arrJSON );。

你会得到一个像你这样的结构。

{"person" : [{"age":"24","gender":"M","ID":"10082"},{"age":"25","gender":"F","ID":"10083"},{"age":"26","gender":"O","ID":"10084"}]

使用地图和列表

LinkedList listOfPerson = new LinkedList();

while(resultset.next()){

            // put a "person" 
            Map person = new HashMap();
            try {
                person.put("age", "24");
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                person.put("gender", "M");
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                person.put("ID", "10082");
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                listOfPerson.add(person);
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

 }

objJSON.put("person",listOfPerson);

从servlet发出一个json数组

2 个答案: