Retrofit2.0 GET 方式请求返回JAVA对象列表的JSON字符串

1.开发环境

客户端:Android Studio 3.0.1

服务端:Eclipse

2.客户端

(1)AS新建一个项目,然后要使用Retrofit2.0 添加依赖和权限

    //retrofit2 依赖库
    implementation 'com.squareup.retrofit2:retrofit:2.4.0'
    //Gson 数据解析器依赖库
    implementation 'com.squareup.retrofit2:converter-gson:2.4.0'


//网络权限
 

(2)写一个请求的接口

package com.example.nn.retrofitexample2;

import java.util.List;

import okhttp3.ResponseBody;
import retrofit2.Call;
import retrofit2.http.GET;
import retrofit2.http.Query;

/**
 * Created by nn on 2019/7/17.
 */

//完整的请求URL为:http://192.168.94.1:8080/retrofit/retrofitservice?retrofit=xx
public interface RetrofitRequest {
    @GET("retrofit/retrofitservice")
    //java对象列表
    Call> getData(@Query("retrofit") String retrofit);
}

(3)编写一个实体类

package com.example.nn.retrofitexample2;

/**
 * Created by nn on 2019/7/17.
 */

public class User {
    private String name;
    private String sex;

    public User(String name,String sex) {
        this.name = name;
        this.sex = sex;
    }

    public String getName() {
        return name;
    }

    public String getSex() {
        return sex;
    }
}

(4)编写MainActivity中的代码

package com.example.nn.retrofitexample2;

import android.os.*;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.io.IOException;
import java.util.List;

import okhttp3.ResponseBody;
import retrofit2.Call;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MainActivity extends AppCompatActivity {
    private TextView mshow;
    private Button mrequest;
    public static final String API_SERVICE = "http://192.168.94.1:8080/";
    private Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            Bundle data = msg.getData();
            String result = data.getString("result");
            mshow.setText(result);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //初始化控件
        init();

        mrequest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                new Thread(runnable).start(); //不能在UI线程中进行网络请求
            }
        });

    }

    private void init(){
        mshow = (TextView)findViewById(R.id.show);
        mrequest = (Button)findViewById(R.id.request);
    }

    //发送网络请求
    private String request() throws IOException {

        //创建Retrofit对象
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(API_SERVICE)
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        //创建网络接口实例
        RetrofitRequest retrofitRequest = retrofit.create(RetrofitRequest.class);

        //对发送请求进行封装
        Call> call = retrofitRequest.getData("REQUEST");

        //发送请求,获取请求的数据
        List list = call.execute().body();
        StringBuilder result = new StringBuilder();
        
        //遍历List
        for(User user:list){
            result.append("姓名:"+user.getName()+"  性别:"+user.getSex()+"\n");
        }

        return result.toString();
    }

    //网络请求线程
    Runnable runnable = new Runnable() {
        @Override
        public void run() {
            try {
                String result = request();
                Message msg = new Message();
                Bundle data = new Bundle();
                data.putString("result", result);
                msg.setData(data);
                handler.sendMessage(msg);
            } catch (IOException e) {
                Log.e("request_erro", e.toString());
            }
        }
    };
}

(5)activity_main.xml 的代码




    

    

3.服务端

(1)

打开eclipse建立一个动态的web项目,在src下面建立 一个  retrofit的包,在这个包里面建立一个servlet,名字为:retrofitservice

代码如下:

package com.example.service;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.example.entity.User;

import net.sf.json.JSONObject;

/**
 * Servlet implementation class retrofitservice
 */
@WebServlet("/retrofitservice")
public class retrofitservice extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public retrofitservice() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		request.setCharacterEncoding("utf-8");
		response.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");

		List list = new ArrayList();
		User user1 = new User("wenjian","man");
		User user2 = new User("liwu","man");
		User user3 = new User("张天","男");
		list.add(user1);
		list.add(user2);
		list.add(user3);
		
		//获得请求的数据
		String message = request.getParameter("retrofit");
	
		if (message.equals("REQUEST")) {
			//JAVA对象列表转为JSON对象数组,然后转为JSON字符串
			JSONArray jsonArray = JSONArray.fromObject(list);
			message = jsonArray.toString();
		}
		System.out.println(message);
		//返回数据
		response.getWriter().append(message);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

(2)

实体类的代码

package com.example.entity;

public class User {
	private String name;
	private String sex;

	public User() {

	}

	public User(String name, String sex) {
		this.name = name;
		this.sex = sex;
	}

	public String getName() {
		return name;
	}

	public String getSex() {
		return sex;
	}

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

	public void setSex(String sex) {
		this.sex = sex;
	}
}

4.JAVA对象和JSON的转换

JSON字符串与java对象的转换
        (1) 把java对象列表转换为json对象数组,并转为字符串
            JSONArray array = JSONArray.fromObject(list);
            String jsonstr = array.toString();
         
       (2) 把java对象转换成json对象,并转化为字符串
          JSONObject object = JSONObject.fromObject(user);
          Log4jInit.ysulogger.debug(object.toString());
         
       (3) 把JSON字符串转换为JAVA对象数组
          JSONArray json = JSONArray.fromObject(userStr);//userStr是json字符串
          List users= (List)JSONArray.toCollection(json,User.class);

        (4) 把JSON字符串转换为JAVA 对象
         JSONObject jsonobject = JSONObject.fromObject(jsonStr);
         User user= (User)JSONObject.toBean(object,User.class);

5.JSON所需的包

 

 

 

链接:https://pan.baidu.com/s/1Q8LNwn151VDkGPPGgWWgPw 
提取码:mv8w 
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6.项目结构

7.运行结果

Retrofit2.0 GET 方式请求返回JAVA对象列表的JSON字符串_第1张图片

 

 

 

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