Android笔记---使用HttpClient发送POST和GET请求

2022-12-14 07:36:43

在Android上发送 HTTP 请求的方式一般有两种, HttpURLConnection 和 HttpClient，关于HttpURLConnection的使用方法能够參考HTTP之利用HttpURLConnection訪问网页，这里仅仅介绍HttpClient发送POST与GET请求的使用方法。

HttpClient 是 Apache 提供的 HTTP 网络訪问接口, 使用须要注意下面几点：

首先看下发送GET请求:

1.声明一下网络权限，改动AndroidManifest.xml中的代码:

<uses-permission android:name="android.permission.INTERNET" />

2.HttpClient 是一个接口,因此无法创建它的实例, 通常情况下都会创建一个 DefaultHttpClient 的实例

HttpClient httpClient = new DefaultHttpClient();

3.创建一个 HttpGet 对象,并传入目标的网络地址, 然后调用 HttpClient 的 execute()方法就可以：

HttpGet httpGet = new HttpGet("http://www.baidu.com");

httpClient.execute(httpGet);

4.执行execute()方法之后会返回一个HttpResponse对象, server所返回的全部信息就会包括在这里面, 因此我们能够实例化一个HttpResponse对象来接收execute()方法返回的结果：

HttpResponse response = httpClient.execute(httpGet);

5.推断server返回的状态码,假设等于 200就说明请求和响应都成功了：

if(httpResponse.getStatusLine().getStatusCode() == 200) {

    // 请求和响应都成功了

}

6.在上面的if推断里面调用getEntity()方法获取到一个HttpEntity实例,然后再用EntityUtils.toString()这个静态方法将 HttpEntity 转换成字符串就可以获取:

if(httpResponse.getStatusLine().getStatusCode() == 200) {

    HttpEntity entity = response.getEntity();

    String content = EntityUtils.toString(entity);

}

下面以一个样例获取一个ip的归属地和运营商(结合了解析JSON。Handler异步更新机制。HttpClient发送GET请求)。这里直接给出MianActivity中的代码例如以下:

package com.example.androidstudyhttpclient;

import java.io.IOException;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.HttpStatus;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.HttpClient;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.util.EntityUtils;

import org.json.JSONException;

import org.json.JSONObject;

import com.example.androidstudypostget.R;

import android.app.Activity;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

public class MainActivity extends Activity implements OnClickListener{

    protected static final int SHOW_RESPONSE = 0;

    private TextView textview;

    private Button button1;

    private Button button2;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        textview = (TextView) findViewById(R.id.tv);

        button1 = (Button) findViewById(R.id.bt1);

        button2 = (Button) findViewById(R.id.bt2);

        button1.setOnClickListener(this);

        button2.setOnClickListener(this);

    }

    public Handler handler = new Handler(){

        public void handleMessage(Message msg){

            switch(msg.what){

            case SHOW_RESPONSE:

                String response = (String) msg.obj;

                try {

                    JSONObject jsobject1 = new JSONObject(response);

                    String data = jsobject1.getString("data");

                    JSONObject jsobject2 = new JSONObject(data);

                    String region = jsobject2.getString("region");

                    String isp = jsobject2.getString("isp");

                    textview.setText("归属地:"+region+" 运营商:"+isp);

                } catch (JSONException e) {

                    e.printStackTrace();

                }

            }

        }

    };

    public void sendget(){

        new Thread(new Runnable() {

            @Override

            public void run() {

                final String url = "http://ip.taobao.com/service/getIpInfo.php?

ip=220.181.57.217";

                HttpClient getClient = new DefaultHttpClient();

                HttpGet httpGet = new HttpGet(url);

                HttpResponse response;

                try {

                    response = getClient.execute(httpGet);

                    if(response.getStatusLine().getStatusCode() ==200){

                        HttpEntity entity = response.getEntity();

                        String content = EntityUtils.toString(entity);

                        Message message = new Message();

                        message.what = SHOW_RESPONSE;

                        message.obj = content;

                        handler.sendMessage(message);

                    }

                } catch (ClientProtocolException e) {

                    e.printStackTrace();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        }).start();

    }

    @Override

    public void onClick(View v) {

        switch(v.getId()){

        case R.id.bt1:

            sendget();

            break;

        case R.id.bt2:

            break;

        default:

            break;

        }

    }

}

执行后点击httpGet按钮截图例如以下:

Android笔记---使用HttpClient发送POST和GET请求

接下来看下发送POST请求:

1.声明一下网络权限，改动AndroidManifest.xml中的代码:

<uses-permission android:name="android.permission.INTERNET" />

2.HttpClient 是一个接口,因此无法创建它的实例, 通常情况下都会创建一个 DefaultHttpClient 的实例

HttpClient httpClient = new DefaultHttpClient();

3.创建一个HttpPost 对象, 并传入目标的网络地址(比方Servlet用于接收POST请求的地址)

final String url = "xxx";

HttpPost httpPost = new HttpPost(url);

4.通过一个NameValuePair集合来存放待提交的參数, 并将这个參数集合传入到一个UrlEncodedFormEntity中, 然后调用 HttpPost的setEntity()方法将构建好的 UrlEncodedFormEntity传入:

List<NameValuePair> params = new ArrayList<NameValuePair>();

params.add(new BasicNameValuePair("username", "admin"));

params.add(new BasicNameValuePair("password", "123456"));

UrlEncodedFormEntity entity = new UrlEncodedFormEntity(params, "utf-8");

httpPost.setEntity(entity);

5.调用 HttpClient 的 execute()方法,并将 HttpPost 对 象传入：

httpClient.execute(httpPost);

6.执行execute()方法之后会返回一个HttpResponse对象, server所返回的全部信息就会包括在这里面, 因此我们能够实例化一个HttpResponse对象来接收execute()方法返回的结果：

HttpResponse response = httpClient.execute(httpGet);

7.推断server返回的状态码,假设等于200就说明请求和响应都成功了：

if(httpResponse.getStatusLine().getStatusCode() == 200) {

    // 请求和响应都成功了

}

8.在上面的if推断里面调用getEntity()方法获取到一个HttpEntity实例,然后再用EntityUtils.toString()这个静态方法将 HttpEntity 转换成字符串就可以获取:

if(httpResponse.getStatusLine().getStatusCode() == 200) {

    HttpEntity entity = response.getEntity();

    String content = EntityUtils.toString(entity);

}

下面给出提供HttpClient发送POST数据到serverMainActivity代码:

package com.example.androidstudyhttpclient;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.util.ArrayList;

import java.util.List;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.HttpStatus;

import org.apache.http.NameValuePair;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.HttpClient;

import org.apache.http.client.entity.UrlEncodedFormEntity;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.client.methods.HttpPost;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.message.BasicNameValuePair;

import org.apache.http.util.EntityUtils;

import org.json.JSONException;

import org.json.JSONObject;

import com.example.androidstudypostget.R;

import android.app.Activity;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.util.Log;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.TextView;

public class MainActivity extends Activity implements OnClickListener{

    protected static final int SHOW_RESPONSE = 0;

    protected static final int SHOW_RESPONSE2 = 1;

    private TextView textview;

    private Button button1;

    private Button button2;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        textview = (TextView) findViewById(R.id.tv);

        button1 = (Button) findViewById(R.id.bt1);

        button2 = (Button) findViewById(R.id.bt2);

        button1.setOnClickListener(this);

        button2.setOnClickListener(this);

    }

    public Handler handler = new Handler(){

        public void handleMessage(Message msg){

            switch(msg.what){

            case SHOW_RESPONSE2:

                String response2 = (String) msg.obj;

                textview.setText(response2);

            }

        }

    };

    public void sendpost(){

        new Thread(new Runnable() {

            public void run() {

                final String url = "http://192.168.51.103:8080/ServletDemo/servlet/HttpClientPostDemo";

                HttpClient postClient = new DefaultHttpClient();

                HttpPost httpPost = new HttpPost(url);

                List<NameValuePair> params = new ArrayList<NameValuePair>();

                params.add(new BasicNameValuePair("name", "geek"));

                params.add(new BasicNameValuePair("city", "shanghai"));

                UrlEncodedFormEntity entity;

                HttpResponse response;

                try {

                    entity = new UrlEncodedFormEntity(params, "utf-8");

                    httpPost.setEntity(entity);

                    response = postClient.execute(httpPost);

                    if(response.getStatusLine().getStatusCode()==200){

                        HttpEntity entity2 = response.getEntity();

                        String content = EntityUtils.toString(entity2);

                        Message message = new Message();

                        message.what = SHOW_RESPONSE2;

                        message.obj = content;

                        handler.sendMessage(message);

                    }

                } catch (UnsupportedEncodingException e) {

                    e.printStackTrace();

                } catch (ClientProtocolException e) {

                    e.printStackTrace();

                } catch (IOException e) {

                    e.printStackTrace();

                }

            }

        }).start();

    }

    @Override

    public void onClick(View v) {

        switch(v.getId()){

        case R.id.bt1:

            sendget();

            break;

        case R.id.bt2:

            sendpost();

            break;

        default:

            break;

        }

    }

}

Servlet代码例如以下:

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class HttpClientPostDemo extends HttpServlet {

    public HttpClientPostDemo() {

        super();

    }

    public void destroy() {

        super.destroy();

    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doPost(request,response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html");

        String name = request.getParameter("name");

        String city = request.getParameter("city");

        PrintWriter out = response.getWriter();

        out.write("Name is:"+name+"  City is"+city);

        out.flush();

        out.close();

    }

    public void init() throws ServletException {

    }

}

执行后点击httpPost按钮截图例如以下:

Android笔记---使用HttpClient发送POST和GET请求

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