[Java] import com.google.gson.*

build.gradle (Module: app)

android {
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {
    // com.google.gson
    implementation 'com.squareup.retrofit2:converter-gson:2.7.1'
}

 

 

 

 

 

 

Privacy.java

package com.jwsoft.javaproject;

public class Privacy {

    private int height;
    private int weight;

    public Privacy(int height, int weight) {
        this.height = height;
        this.weight = weight;
    }

}

 

 

 

 

 

 

 

User.java

package com.jwsoft.javaproject;

public class User {

    private String name;
    private int age;
    private String[] hobby;
    private Privacy privacy;

    public User(String name, int age, String[] hobby, Privacy privacy) {
        this.name = name;
        this.age = age;
        this.hobby = hobby;
        this.privacy = privacy;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

}

 

 

 

 

 

 

 

 

MainActivity.java

package com.jwsoft.javaproject;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonObject;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // user 1
        String jsonString = "{ 'name':'James Kim', 'age':30 }";

        Gson gson = new GsonBuilder().create(); // = new Gson()
        User user = gson.fromJson(jsonString, User.class);  // hobby, privacy 없으면 제외하고 삽입됨.
        Log.e("name", user.getName());
        Log.e("age", Integer.toString(user.getAge()));

        String jsonUser = gson.toJson(user);
        Log.e("jsonUser", jsonUser);


        // user 2
        String[] arr = {"music", "movie"};
        Privacy privacy = new Privacy(184, 84);
        User user2 = new User("Jason Park", 33, arr, privacy);

        String jsonUser2 = gson.toJson(user2);
        Log.e("jsonUser2", jsonUser2);

        user2 = gson.fromJson(jsonUser2, User.class);
        Log.e("name", user2.getName());
        Log.e("age", Integer.toString(user2.getAge()));

    }

}

실행 결과

 

 

 

 

 

 

 

---

MainActivity.java

package com.jwsoft.javaproject;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;

import com.google.gson.Gson;

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

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Gson gson = new Gson();
        Map<String, Object> userMap = new HashMap<>();
        userMap.put("name", "James Kim");
        userMap.put("age", 30);

        String[] arrHobby = {"music", "movie"};
        userMap.put("hobby", arrHobby);

        Privacy privacy = new Privacy(184, 84);
        userMap.put("privacy", privacy);

        String jsonUser = gson.toJson(userMap);
        Log.e("jsonUser", jsonUser);

        Map map = gson.fromJson(jsonUser, Map.class);
        Log.e("map", map.toString());

        User user = gson.fromJson(jsonUser, User.class);
        Log.e("name", user.getName());
        Log.e("age", Integer.toString(user.getAge()));

    }

}

실행 결과

 

 

 

 

 

 

 

---

MainActivity.java

package com.jwsoft.javaproject;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonArray;
import com.google.gson.JsonObject;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        JsonObject jsonObject =  new JsonObject();
        jsonObject.addProperty("name", "James Kim");
        jsonObject.addProperty("age", 30);

        JsonArray hobbyArray = new JsonArray();
        hobbyArray.add("music");
        hobbyArray.add("movie");
        jsonObject.add("hobby", hobbyArray);

        JsonObject privacy = new JsonObject();
        privacy.addProperty("height", 184);
        privacy.addProperty("weight", 84);
        jsonObject.add("privacy", privacy);

        Log.e("jsonObject", jsonObject.toString());

        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        String jsonUser = gson.toJson(jsonObject);
        Log.e("jsonUser", jsonUser);
    }

}

Gson gson = new Gson(); 에서

Gson gson = new GsonBuilder().setPrettyPrinting().create(); 로 수정

콘솔 출력 시 예쁘게 출력됨.

 

 

실행 결과