GSON執行個體詳解

GSON是Google提供的用來在Java對象和JSON資料之間進行映射的Java類庫，GSON可以很容易的将一個java對象轉換成json文本，也可以很容易的将json文本轉換為java對象，兩種轉換方式分别對應的方法是：toJson()和fromJson()。
           

一：toJson()詳解（将一個java對象轉換成json文本）

1,生成生成數組類型的json文本，效果圖：

（點選按鈕 toJsonArray）

代碼:

首先建立一個類：GsonInfo;

public class GsonInfo {

    private String name;
    private int age;
    private String gender;

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "GsonInfo{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", gender='" + gender + '\'' +
                '}';
    }

    public GsonInfo(String name, int age, String gender) {
        this.name = name;
        this.age = age;
        this.gender = gender;
    }

}
           

layout布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <Button
            android:id="@+id/btn_tojson"
            android:layout_width="1dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="toJsonArray"/>
        <Button
            android:id="@+id/btn_fromjson"
            android:layout_width="1dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="fromJsonArray"/>
    </LinearLayout>
    <TextView
        android:id="@+id/branch1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/branch2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <Button
            android:id="@+id/btn_tojson2"
            android:layout_width="1dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="toJsonMix"/>
        <Button
            android:id="@+id/btn_fromjson2"
            android:layout_width="1dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="fromJsonMix"/>
    </LinearLayout>
    <TextView
        android:id="@+id/branch3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/branch4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/branch5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>
           

MainActivity代碼：

import android.annotation.TargetApi;
import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import com.google.gson.Gson;

import org.json.JSONObject;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class MainActivity extends Activity implements View.OnClickListener{

    private TextView tv_branch1;
    private TextView tv_branch2;
    private TextView tv_branch3;
    private TextView tv_branch4;
    private TextView tv_branch5;

    private Gson gson = new Gson();//初始化Gson

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

        findViewById(R.id.btn_tojson).setOnClickListener(this);
        findViewById(R.id.btn_tojson2).setOnClickListener(this);
        tv_branch1 = (TextView) findViewById(R.id.branch1);
        tv_branch2 = (TextView) findViewById(R.id.branch2);
        tv_branch3 = (TextView) findViewById(R.id.branch3);
        tv_branch4 = (TextView) findViewById(R.id.branch4);
        tv_branch5 = (TextView) findViewById(R.id.branch5);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.btn_tojson:
                toJson();//生成數組類型的json文本
                break;
        }
    }

    /**
     * 格式類似于：
     * [{
     "name": "小琛",
     "gender": "男",
     "age": "21"
     },
     {
     "name": "中琛",
     "gender": "未知",
     "age": "22"
     },
     {
     "name": "大琛",
     "gender": "男",
     "age": "23"
     }]
     */
    private StringtoJson(){
        List<GsonInfo> list = new ArrayList<GsonInfo>();
        GsonInfo info1 = new GsonInfo("小琛",,"男");
        list.add(info1);
        GsonInfo info2 = new GsonInfo("中琛",,"未知");
        list.add(info2);
        GsonInfo info3 = new GsonInfo("大琛",,"男");
        list.add(info3);
        tv_branch1.setText(gson.toJson(list));
        return gson.toJson(list);
    }
}
           

2,一個對象嵌套一個對象的json文本,效果圖：

(點選按鈕 toJsonMix)

代碼：

除了 GsonInfo類，還要建立一個類：GsonInfo2:

public class GsonInfo2 {
    private String boyFriend;
    private String grilFriend;

    public GsonInfo2() {
        super();
    }

    public GsonInfo2(String boyFriend, String grilFriend) {
        super();
        this.boyFriend = boyFriend;
        this.grilFriend = grilFriend;
    }

    public String getBoyFriend() {
        return boyFriend;
    }

    public void setBoyFriend(String boyFriend) {
        this.boyFriend = boyFriend;
    }

    public String getGrilFriend() {
        return grilFriend;
    }

    public void setGrilFriend(String grilFriend) {
        this.grilFriend = grilFriend;
    }

    @Override
    public String toString() {
        return "GsonInfo2{" +
                "boyFriend='" + boyFriend + '\'' +
                ", grilFriend='" + grilFriend + '\'' +
                '}';
    }
}
           

布局不用修改，MainActivity:

import android.annotation.TargetApi;
import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import com.google.gson.Gson;

import org.json.JSONObject;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

public class MainActivity extends Activity implements View.OnClickListener{

    private TextView tv_branch1;
    private TextView tv_branch2;
    private TextView tv_branch3;
    private TextView tv_branch4;
    private TextView tv_branch5;

    private Gson gson = new Gson();//初始化Gson

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

        findViewById(R.id.btn_tojson).setOnClickListener(this);
        findViewById(R.id.btn_fromjson).setOnClickListener(this);
        findViewById(R.id.btn_tojson2).setOnClickListener(this);
        findViewById(R.id.btn_fromjson2).setOnClickListener(this);
        tv_branch1 = (TextView) findViewById(R.id.branch1);
        tv_branch2 = (TextView) findViewById(R.id.branch2);
        tv_branch3 = (TextView) findViewById(R.id.branch3);
        tv_branch4 = (TextView) findViewById(R.id.branch4);
        tv_branch5 = (TextView) findViewById(R.id.branch5);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.btn_tojson2:
                toJson2();//一個對象嵌套一個對象的json文本
                break;
        }
    }


    /**
     * 格式類似于：
     * {
     "friend": {
     "grilFriend": "小花",
     "bogFriend": "小美"
     },
     "name": "小明",
     "gender": "男",
     "age": 11
     }
     */
    private void toJson2(){
        GsonInfo info = new GsonInfo("小明",,"男");
        GsonInfo2 info2 = new GsonInfo2("小美","小花");
        String infoStr = gson.toJson(info);
        String info2Str = gson.toJson(info2);

        tv_branch3.setText(infoStr);
        tv_branch4.setText(info2Str);

        JSONObject object = null;
        try {
            JSONObject infoObject = new JSONObject(info2Str);
            object = new JSONObject(infoStr);
            object.put("friend",infoObject);//鍵值對
        }catch (Exception e){
            e.printStackTrace();
        }
        tv_branch5.setText(object.toString());

    }
}
           

二：fromJson()詳解(将json文本轉換為java對象)

private void fromJson() {
        //獲得toJson()中的JSON的字元串
        String fromData = toJson();
        Type type = new TypeToken<GsonInfo>() {
        }.getType();
        GsonInfo gsonInfo = new GsonInfo();
        gsonInfo = gson.fromJson(fromData, type);
        tv_branch2.setText(gsonInfo.toString());
    }