爲什麼要寫這篇博客呢？因爲我覺得使用這種http請求框架 進行客戶端與服務器的通信十分簡單，而且它很有用。舉個例子，客戶端訪問服務器的數據庫的時候，那些SQL語句相關的代碼不應該寫在android客戶端，而是SQL代碼放在後臺，客戶端只負責發送請求參數給服務器，然後服務器將接收到的請求參數之後，再對數據庫進行操作。
1
準備3個jar包httpcore-4.4.3.jar，android-async-http-1.4.8.jar，httpclient-4.3.6.jar
鏈接：https://pan.baidu.com/s/1CK1NPfHBtppF-lxR-RcUmQ
密碼：f16a
2
android客戶端代碼：
MainActivity
package com.example.xeonrnc.req_resp;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import com.loopj.android.http.AsyncHttpClient;
import com.loopj.android.http.AsyncHttpResponseHandler;
import com.loopj.android.http.RequestParams;
import org.apache.http.Header;
public class MainActivity extends AppCompatActivity {
//這是服務端名爲req_resp的servlet的url
//這個servlet發佈到tomcat運行的
String url="http://192.168.43.173:8080/request_parameter/servlet/req_resp";
@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button btn=(Button)findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
send_request();
}
});
}
public void send_request(){
AsyncHttpClient client=new AsyncHttpClient();
RequestParams params=new RequestParams();
//向設置請求參數
params.put("username","張三");
params.put("password","123456");
params.put("age","666");
client.post(this, url, params, new AsyncHttpResponseHandler() {
@Override
public void onSuccess(int i, Header[] headers, byte[] bytes) {
//在servlet裏面調用response.getWriter()方法，寫入的字符串都會傳到下面的response的變量裏面去
//通過new String(bytes)可以獲取服務器響應的內容
String response=new String(bytes);
//根據逗號的分隔，將服務器返回的每一條信息存到數組裏面
String result[]=response.split(",");
System.out.println("下面是服務器響應返回的數據：");
for(int j=0;j<result.length;j++){
System.out.println(result[j]);
}
}
@Override
public void onFailure(int i, Header[] headers, byte[] bytes, Throwable throwable) {
}
});
}
}
activity.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="@+id/btn"
android:text="向服務器發送請求"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
</android.support.constraint.ConstraintLayout>
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.xeonrnc.req_resp">
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme"
android:usesCleartextTraffic="true">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<uses-library android:name="org.apache.http.legacy" android:required="false" />
</application>
</manifest>
3
新建web項目，這裏java EE版本爲：
項目名爲：request_parameter
servelt 爲 req_resp
服務端 servlet 代碼
package request_parameter;
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;
@WebServlet("/req_resp")
public class req_resp extends HttpServlet {
private static final long serialVersionUID = 1L;
public req_resp() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
System.out.println("下面是客戶端請求的內容：");
System.out.println("用戶名是："+request.getParameter("username"));
System.out.println("密碼是："+request.getParameter("password"));
System.out.println("年齡是："+request.getParameter("age"));
//服務器響應信息給android客戶端，當然響應的內容是可以自定義的，這裏用逗號隔開是爲了在android客戶端可以根據逗號來切割字符串，區分每個請求對應的響應
response.getWriter().println(request.getParameter("username")+","+request.getParameter("password")+","+request.getParameter("age"));
doGet(request, response);
}
}
web.xml 文件
設置servlet映射
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
<display-name>request_parameter</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>req_resp</servlet-name>
<servlet-class>request_parameter.req_resp</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>req_resp</servlet-name>
<url-pattern>/servlet/req_resp</url-pattern>
</servlet-mapping>
</web-app>
4
運行效果展示：
在android客戶端點擊”向服務器發送請求“的按鈕以後：
這是服務端控制檯打印的信息：
這是android客戶端控制檯的打印的信息：
