如何在Android应用中实现服务端网页的POST请求？

服务端网页Android Post请求详解

一、创建Web服务

1. 环境准备

开发工具：Eclipse和MyEclipse（用于编写Android客户端和服务端代码）。

服务器：Tomcat服务器，用于部署Servlet。

2. 创建Servlet

2.1 创建LoginAction类

package com.android.Login;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.sf.json.JSONSerializer;
public class LoginAction extends HttpServlet {
    private static final long serialVersionUID = 1L;
    private LoginService service;
    @Override
    public void init() throws ServletException {
        super.init();
        service = new LoginDao(); // 初始化登录服务
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        request.setCharacterEncoding("utf-8");
        PrintWriter writer = response.getWriter();
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        List<Object> params = new ArrayList<Object>();
        params.add(username);
        params.add(password);
        boolean flag = service.isUserExitLogin(params); // 调用服务判断用户是否存在
        if (flag) {
            ResultMessage message = new ResultMessage(1, "登陆成功"); // 封装结果信息
            Map<String, Object> map = new HashMap<String, Object>();
            map.put("result", message);
            String jsonString = JSONSerializer.toJSON(map).toString(); // 结果封装成JSON并传给客户端
            writer.println(jsonString);
        } else {
            writer.println("登录失败");
        }
        writer.flush();
        writer.close();
    }
}

2.2 配置web.xml

<servlet>
    <servlet-name>LoginAction</servlet-name>
    <servlet-class>com.android.Login.LoginAction</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>LoginAction</servlet-name>
    <url-pattern>/loginaction</url-pattern>
</servlet-mapping>

二、Android客户端发送POST请求

1. 创建Activity布局文件activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    tools:context=".MainActivity">
    <EditText android:id="@+id/etUsername" android:layout_width="wrap_content" android:layout_height="wrap_content" />
    <EditText android:id="@+id/etPassword" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/etUsername"/>
    <Button android:id="@+id/butPost" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/etPassword" android:text="提交"/>
</RelativeLayout>

2. 编写MainActivity类

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.UrlEncodedFormEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends Activity {
    private EditText mEtUsername;
    private EditText mEtPassword;
    private Button mButPost;
    private String LOGIN_URL = "http://10.0.2.2:8080/webtest/loginaction"; // 注意模拟器中的IP地址是10.0.2.2
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mEtUsername = findViewById(R.id.etUsername);
        mEtPassword = findViewById(R.id.etPassword);
        mButPost = findViewById(R.id.butPost);
        mButPost.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                submitPost();
            }
        });
    }
    private void submitPost() {
        String username = mEtUsername.getText().toString();
        String password = mEtPassword.getText().toString();
        HttpPost httpPost = new HttpPost(LOGIN_URL);
        List<BasicNameValuePair> params = new ArrayList<BasicNameValuePair>();
        params.add(new BasicNameValuePair("username", username));
        params.add(new BasicNameValuePair("password", password));
        try {
            httpPost.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpResponse httpResponse = httpClient.execute(httpPost);
            if (httpResponse.getStatusLine().getStatusCode() == 200) {
                String result = EntityUtils.toString(httpResponse.getEntity());
                Toast.makeText(MainActivity.this, "登录结果：" + result, Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(MainActivity.this, "请求失败", Toast.LENGTH_SHORT).show();
            }
        } catch (Exception e) {
            e.printStackTrace();
            Toast.makeText(MainActivity.this, "发生异常", Toast.LENGTH_SHORT).show();
        }
    }
}

三、相关问题与解答

1. 为什么使用HttpPost而不是HttpGet？

答：HttpPost将数据放在请求体中进行传输，适合传输大量数据或敏感数据，而HttpGet将参数放在URL后面，不适合传输敏感数据且有长度限制，HttpPost更适合表单提交等操作。

2. 如何在Android中使用Handler更新UI？

答：在子线程中通过Handler发送消息到主线程，然后在主线程的handleMessage方法中更新UI，创建一个继承自Handler的内部类，并在其中实现handleMessage方法来处理从子线程发送的消息。

以上内容就是解答有关“服务端网页androidpost”的详细内容了，我相信这篇文章可以为您解决一些疑惑，有任何问题欢迎留言反馈，谢谢阅读。