1、下面测试截图，基本过程就是：点击按钮向服务器端发送请求，后台收到请求后给出返回的数据，前台只需要显示服务端数据就可以了。例子很简单能但引发很多思考。

2、客户端(Android)关键代码

MainActivity.java：

 1 package thonlon.example.cn.sendgetdemo; 2  3 import android.inputmethodservice.KeyboardView; 4 import android.support.v7.app.AppCompatActivity; 5 import android.os.Bundle; 6 import android.view.View; 7 import android.widget.Button; 8 import android.widget.ScrollView; 9 import android.widget.TextView;10 11 import java.io.IOException;12 13 import okhttp3.Call;14 import okhttp3.Callback;15 import okhttp3.OkHttpClient;16 import okhttp3.Request;17 import okhttp3.Response;18 19 public class MainActivity extends AppCompatActivity {20 21     private TextView tv;22     private String mBaseUrl = "//192.168.43.218:8080/OkHttpGetServer/";23     @Override24     protected void onCreate(Bundle savedInstanceState) {25         super.onCreate(savedInstanceState);26         setContentView(R.layout.activity_main);27     }28 29     public void doGet(View view) {30         //拿到okHttpClient对象31         OkHttpClient okHttpClient = new OkHttpClient();32         //构造Request33         Request request = new Request.Builder().get()34                 .url(mBaseUrl+"login?username=Thanlon&password=123").build();35 //        将Request封装成Call36 //        执行Call37         okHttpClient.newCall(request).enqueue(new Callback() {38             @Override39             public void onFailure(Call call, IOException e) {40                 e.printStackTrace();41             }42 43             @Override44             public void onResponse(Call call, Response response) throws IOException {45                 String res = response.body().string();46                 showResultInfo(res);47             }48         });49     }50 51     private void showResultInfo(final String resultInfo) {52         tv = (TextView) findViewById(R.id.tv);53         runOnUiThread(new Runnable() {54             @Override55             public void run() {56                 tv.setText(resultInfo);57             }58         });59     }60 }

 activity_main.xml：(布局也发了，做个参考)

<?xml version="1.0" encoding="utf-8"?><android.support.constraint.ConstraintLayout xmlns:android="//schemas.android.com/apk/res/android"

    xmlns:app="//schemas.android.com/apk/res-auto"

    xmlns:tools="//schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context="thonlon.example.cn.sendgetdemo.MainActivity">

    <Button

        android:id="@+id/btn_send"

        android:layout_width="0dp"

        android:layout_height="wrap_content"

        android:onClick="doGet"

        android:text="向服务器端发送请求（这里以Get请求作为示例)"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintLeft_toLeftOf="parent"

        app:layout_constraintRight_toRightOf="parent"

        app:layout_constraintTop_toTopOf="parent"

        app:layout_constraintVertical_bias="0.0" />

    <TextView

        android:id="@+id/tv"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintLeft_toLeftOf="parent"

        app:layout_constraintRight_toRightOf="parent"

        app:layout_constraintTop_toTopOf="parent"

        app:layout_constraintHorizontal_bias="0.0"

        app:layout_constraintVertical_bias="0.097" />

</android.support.constraint.ConstraintLayout>

3、服务器端主要代码

UserLoginAction.java：（Servlet自然也可以，这里借助了strut2框架）

 1 package com.okhttp; 2  3 import java.io.IOException; 4 import java.io.PrintWriter; 5  6 import javax.security.auth.message.callback.PrivateKeyCallback.Request; 7 import javax.servlet.http.HttpServletResponse; 8  9 import org.apache.struts2.ServletActionContext;10 11 import com.opensymphony.xwork2.ActionSupport;12 13 public class UserLoginAction extends ActionSupport {14 15     private String username;16     private String password;17 18     public String login() throws IOException {19 //        System.out.println(username+ "," + password);20         HttpServletResponse response = ServletActionContext.getResponse();21         response.setCharacterEncoding("utf-8");  //防止服务端发送到到客户端的数据出现中文乱码22         PrintWriter pw = response.getWriter();23         pw.write("下面是服务器端返回的数据:\n\n");24         pw.write("您提交的用户名是："+username);25         pw.flush();26         return null;27     }28 29     public String getUsername() {30         return username;31     }32 33     public void setUsername(String username) {34         this.username = username;35     }36 37     public String getPassword() {38         return password;39     }40 41     public void setPassword(String password) {42         this.password = password;43     }44 }

 struts.xml：

 1 <?xml version="1.0" encoding="UTF-8" ?> 2 <!DOCTYPE struts PUBLIC 3     "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" 4     "//struts.apache.org/dtds/struts-2.0.dtd"> 5 <struts> 6     <package name="default" namespace="/" extends="struts-default"> 7         <action name="login" class="com.okhttp.UserLoginAction" method="login"> 8         </action> 9     </package>10 </struts>

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