json转对象 gson 应用

使用Gson将Java对象转换为Json

Gson是Google的一个开源项目，可以将Java对象转换成JSON，也可能将JSON转换成Java对象。

Gson里最重要的对象有2个Gson 和GsonBuilder。

Gson有2个最基本的方法
1) toJson() – 转换java 对象到JSON
2) fromJson() – 转换JSON到java对象

注意使用Gson时记得添加第三方类库gson-1.6.jar

    

main.xml布局文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<Button android:id="@+id/btn01"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="开始解析01"/>
<Button android:id="@+id/btn02"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="开始解析02"/>
<Button android:id="@+id/btn03"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="开始解析03"/>
<Button android:id="@+id/btn04"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="JavaToJson"/>
<Button android:id="@+id/btn05"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="把对象的属性转换成json的名字"/>
</LinearLayout>

实体类User

package com.ljq.json;

import com.google.gson.annotations.SerializedName;

public class User {
//将java对象的属性转换成指定的json名字
@SerializedName("username")
private String name;
private int age;

public User() {
super();
}

public User(String name, int age) {
super();
this.name = name;
this.age = age;
}

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;
}
}

工具类JsonUtils

package com.ljq.json;

import java.io.StringReader;
import java.lang.reflect.Type;
import java.util.Iterator;
import java.util.LinkedList;


import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;

public class JsonUtils {
public void parseJson01(String jsonData){
try {
//解析json对象首先要生产一个JsonReader对象
JsonReader reader=new JsonReader(new StringReader(jsonData));
reader.beginArray();
while(reader.hasNext()){
reader.beginObject();
while(reader.hasNext()){
String tagName=reader.nextName();
if("name".equals(tagName)){
System.out.println("name--->"+reader.nextString());
}else if("age".equals(tagName)){
System.out.println("age--->"+reader.nextInt());
}
}
reader.endObject();
}
reader.endArray();
} catch (Exception e) {
e.printStackTrace();
}
}

public void parseJson02(String jsonData){
Gson gson=new Gson();
User user=gson.fromJson(jsonData, User.class);
System.out.println("name--->" + user.getName());
System.out.println("age---->" + user.getAge());
}

public void parseJson03(String jsonData){
Type listType = new TypeToken<LinkedList<User>>(){}.getType();
Gson gson=new Gson();
LinkedList<User> users=gson.fromJson(jsonData, listType);
for(User user:users){
System.out.println("name--->" + user.getName());
System.out.println("age---->" + user.getAge());
}
System.out.println("==================");
for (Iterator iterator = users.iterator(); iterator.hasNext();) {
User user = (User) iterator.next();
System.out.println("name--->" + user.getName());
System.out.println("age---->" + user.getAge());
}
}
}

JsonActivity

package com.ljq.json;

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

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class JsonActivity extends Activity {
private Button btn01=null;
private Button btn02=null;
private Button btn03=null;
private Button btn04=null;
private Button btn05=null;
private String jsonData01 = "[{\"name\":\"Michael\",\"age\":20},{\"name\":\"Mike\",\"age\":21}]";
private String jsonData02 = "{\"name\":\"Michael\",\"age\":20}";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

btn01=(Button)findViewById(R.id.btn01);
btn02=(Button)findViewById(R.id.btn02);
btn03=(Button)findViewById(R.id.btn03);
btn04=(Button)findViewById(R.id.btn04);
btn05=(Button)findViewById(R.id.btn05);
btn01.setOnClickListener(listener);
btn02.setOnClickListener(listener);
btn03.setOnClickListener(listener);
btn04.setOnClickListener(listener);
btn05.setOnClickListener(listener);
}

View.OnClickListener listener=new View.OnClickListener(){
public void onClick(View v) {
JsonUtils jsonUtils=new JsonUtils();
switch (v.getId()) {
case R.id.btn01:
jsonUtils.parseJson01(jsonData01);
break;
case R.id.btn02:
jsonUtils.parseJson02(jsonData02);
break;
case R.id.btn03:
jsonUtils.parseJson03(jsonData01);
break;
case R.id.btn04:
//把java对象转换成json
User user01=new User("linjiqin", 24);
Gson gson=new Gson();
String obj=gson.toJson(user01);
System.out.println(obj);//输出{"name":"linjiqin", "age":24}
break;
case R.id.btn05:
//将java对象的属性转换成指定的json名字
User user02=new User("lintepeng", 22);
Gson gson2=new GsonBuilder().setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE).create();
String obj2=gson2.toJson(user02);
System.out.println(obj2);//输出{"username":"lintepeng","Age":22}
break;
}
}
};
}

运行结果