如何从 Json 字符串解析 Json 数组

Question

This is my input

String str ="{\n" +
            "    \"myKey\": [{\n" +
            "            \"myHhome\": \"home1\",\n" +
            "            \"myAddress\": \"add\",\n" +
            "            \"dateTimeStamp\": \"Wed, 20 Mar 2019 14:38:54 GMT\"\n" +
            "        }\n" +
            "    ],\n" +
            "    \"basedata\": {\n" +
            "        \"mydata\": {\n" +
            "            \"mytype\": \"m1\",\n" +
            "            \"mytype2\": \"m2\"\n" +
            "        }\n" +
            "    }\n" +
            "}\n";

I chekced the json and it is valid I want to use GSON to get the value of the myHhome ( in my case hom1)

 static class Myclass{


    public String generation = null;


  }



 final Gson GSON1 = new Gson();
  String result= GSON1.fromJson(str,Myclass.class);
      System.out.println(result);

but i got null

Answer 1

Don't understand what you trying to do.

As I understand MyClass should have getter and setter function Like

 public void setGeneration (String generation ) {
    this.generation = generation ;
}

public String getGeneration () {
    return generation ;
}

And call Gson

Gson gson = new GsonBuilder().create();
Myclass myclass= gson.fromJson(json, Myclass.class);

Answer 2

Your Json does not represents the class you are trying to deserialize it to.

{  
   "myKey":[  
      {  
         "myHhome":"home1",
         "myAddress":"add",
         "dateTimeStamp":"Wed, 20 Mar 2019 14:38:54 GMT"
      }
   ],
   "basedata":{  
      "mydata":{  
         "mytype":"m1",
         "mytype2":"m2"
      }
   }
}

Second, .fromJson is used to deserialization so the return must be the resultant Class.

Myclass myclass= GSON1.fromJson(json, Myclass.class);

For the Json you provided you need 2 more classes:

• MyKey

• MyData

  class Myclass { public List<MyKey> myKey = null; public Basedata basedata = null; // getters and setters } class Basedata { private MyData mydata; // getters and setters } class MyData { private String mytype; private String mytype2; // getters and setters } class MyKey { public String myHhome; public String myAddress; public String dateTimeStamp; // getters and setters }

I hope it helps you to understand how classes are represented though Json.

Answer 3

If you only want to get the value of a json object, consider using a different library such as org.json or Jackson .

Using org.json:

JSONObject json = new JSONObject("your JSON string here"); // Parse the JSON
JSONArray array = json.getJSONArray("myKey");              // Get the JSON array represented by the key "myKey"
JSONObject home = array.getJSONObject(0);                  // Get the element at index 0 as a JSONObject
String result = home.getString("myHhome");                 // Get the string represented by the key "myHhome"
System.out.println(result);