Android笔记---使用HttpClient发送POST和GET请求

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:

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: