如何解析JSON字符串并填充包含Map的对象？

Question

I have for example this JSON string:

{"name":"Nataraj", "job":"Programmer","property":["chair":"my","table":"brothers","cabinet":"mothers"]}

and, i want to get this data to class as:

public class A{
  String name;
  String job;
  //Map<String, String> property; (Maybe: <String, Object>?)
}

How do I get the data to this map? The main problem I have with "property". I used JSONObject and ObjectMapper, but on the property i have problem. Of course, every variable in class A has getter and setter. Any help for me?

Answer 1

First of all your JSON has to be modified a bit. The property is not an Array rather an Object containing key-value pairs. It should be like this:

{"name":"Nataraj", "job":"Programmer","property":
{"chair":"my","table":"brothers","cabinet":"mothers"}}

As I mentioned in the comment to original post, you may use org.json:json library or Jackson or Gson library to parse any JSON string and populate your objects.

Here is the executable program that parses your JSON using basic org.json:json library and populates the data structure you expect:

import org.json.JSONObject;

import java.util.HashMap;
import java.util.Map;

public class ParseJsonIntoMap {
    public static void main(String[] args) {
        String data="{\"name\":\"Nataraj\", \"job\":\"Programmer\",\"property\":{\"chair\":\"my\",\"table\":\"brothers\",\"cabinet\":\"mothers\"}}";
        JSONObject parsedData = new JSONObject(data);
        A a = new A();
        a.setName(parsedData.getString("name"));
        a.setJob(parsedData.getString("job"));
        JSONObject propertyMap = parsedData.getJSONObject("property");
        for (String key : propertyMap.keySet()) {
            a.getProperty().put(key, propertyMap.getString(key));
        }
        System.out.println("Output: "+a);
    }

    public static class A{
        String name;
        String job;
        Map<String, String> property = new HashMap<>();

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getJob() {
            return job;
        }

        public void setJob(String job) {
            this.job = job;
        }

        public Map<String, String> getProperty() {
            return property;
        }

        public void setProperty(Map<String, String> property) {
            this.property = property;
        }

        @Override
        public String toString() {
            return "A{" +
                    "name='" + name + '\'' +
                    ", job='" + job + '\'' +
                    ", property=" + property +
                    '}';
        }
    }
}

You should add Maven (or equivalent Gradle or other) dependency to:

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20180813</version>
</dependency>

Answer 2

The following works just fine with Gson 2.8.5 :

A instance = new Gson().fromJson(data, A.class)

The full class for you to try :

import java.util.Map;
import com.google.gson.Gson;

public class Main {

    public static void main(String[] args) {
        String data="{\"name\":\"Nataraj\", \"job\":\"Programmer\",\"property\":{\"chair\":\"my\",\"table\":\"brothers\",\"cabinet\":\"mothers\"}}";
        System.out.println(new Gson().fromJson(data, A.class));
    }

    static class A{
        String name;
        String job;
        Map<String, String> property;

        @Override
        public String toString() { // just there for the System.out.println in main
            return String.format("name: %s, job: %s, property: %s", name, job, property);
        }
    }
}

Most other JSON parsing libraries provide similar functionality.