一、HttpClient介绍
HttpClient是用来模拟HTTP请求的，其实实质就是把HTTP请求模拟后发给Web服务器；
Android已经集成了HttpClient，因此可以直接使用；
注：此处HttpClient代码不只可以适用于Android，也可适用于一般的Java程序；
HTTP GET核心代码：
(1)DefaultHttpClient client = new DefaultHttpClient();
(2)HttpGet get = new HttpGet(String url);//此处的URL为http://..../path?arg1=value&....argn=value
(3)HttpResponse response = client.execute(get); //模拟请求
(4)int code = response.getStatusLine().getStatusCode();//返回响应码
(5)InputStream in = response.getEntity().getContent();//服务器返回的数据
HTTP POST核心代码：
(1)DefaultHttpClient client = new DefaultHttpClient();
(2)BasicNameValuePair pair = new BasicNameValuePair(String name,String value);//创建一个请求头的字段，比如content-type,text/plain
(3)UrlEncodedFormEntity entity = new UrlEncodedFormEntity(List<NameValuePair> list,String encoding);//对自定义请求头进行URL编码
(4)HttpPost post = new HttpPost(String url);//此处的URL为http://..../path
(5)post.setEntity(entity);
(6)HttpResponse response = client.execute(post);
(7)int code = response.getStatusLine().getStatusCode();
(8)InputStream in = response.getEntity().getContent();//服务器返回的数据
二、服务器端代码
服务器端代码和通过URLConnection发出请求的代码不变：
package org.xiazdong.servlet;import java.io.IOException;import java.io.OutputStream;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("/Servlet1")public class Servlet1 extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String nameParameter = request.getParameter("name"); String ageParameter = request.getParameter("age"); String name = new String(nameParameter.getBytes("ISO-8859-1"),"UTF-8"); String age = new String(ageParameter.getBytes("ISO-8859-1"),"UTF-8"); System.out.println("GET"); System.out.println("name="+name); System.out.println("age="+age); response.setCharacterEncoding("UTF-8"); OutputStream out = response.getOutputStream();//返回数据 out.write("GET请求成功!".getBytes("UTF-8")); out.close(); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); String name = request.getParameter("name"); String age = request.getParameter("age"); System.out.println("POST"); System.out.println("name="+name); System.out.println("age="+age); response.setCharacterEncoding("UTF-8"); OutputStream out = response.getOutputStream(); out.write("POST请求成功!".getBytes("UTF-8")); out.close(); }}三、Android客户端代码
效果如下：
在AndroidManifest.xml加入：
<uses-permission android:name="android.permission.INTERNET"/>
MainActivity.java
package org.xiazdong.network.httpclient;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.InputStream;import java.net.URLEncoder;import java.util.ArrayList;import java.util.List;import org.apache.http.HttpResponse;import org.apache.http.NameValuePair;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 android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;import android.widget.Toast;public class MainActivity extends Activity { private EditText name, age; private Button getbutton, postbutton; private OnClickListener listener = new OnClickListener() { @Override public void onClick(View v) { try{ if(postbutton==v){ /* * NameValuePair代表一个HEADER，List<NameValuePair>存储全部的头字段 * UrlEncodedFormEntity类似于URLEncoder语句进行URL编码 * HttpPost类似于HTTP的POST请求 * client.execute()类似于发出请求，并返回Response */ DefaultHttpClient client = new DefaultHttpClient(); List<NameValuePair> list = new ArrayList<NameValuePair>(); NameValuePair pair1 = new BasicNameValuePair("name", name.getText().toString()); NameValuePair pair2 = new BasicNameValuePair("age", age.getText().toString()); list.add(pair1); list.add(pair2); UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list,"UTF-8"); HttpPost post = new HttpPost("http://192.168.0.103:8080/Server/Servlet1"); post.setEntity(entity); HttpResponse response = client.execute(post); if(response.getStatusLine().getStatusCode()==200){ InputStream in = response.getEntity().getContent();//接收服务器的数据，并在Toast上显示 String str = readString(in); Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT).show(); } else Toast.makeText(MainActivity.this, "POST提交失败", Toast.LENGTH_SHORT).show(); } if(getbutton==v){ DefaultHttpClient client = new DefaultHttpClient(); StringBuilder buf = new StringBuilder("http://192.168.0.103:8080/Server/Servlet1"); buf.append("?"); buf.append("name="+URLEncoder.encode(name.getText().toString(),"UTF-8")+"&"); buf.append("age="+URLEncoder.encode(age.getText().toString(),"UTF-8")); HttpGet get = new HttpGet(buf.toString()); HttpResponse response = client.execute(get); if(response.getStatusLine().getStatusCode()==200){ InputStream in = response.getEntity().getContent(); String str = readString(in); Toast.makeText(MainActivity.this, str, Toast.LENGTH_SHORT).show(); } else Toast.makeText(MainActivity.this, "GET提交失败", Toast.LENGTH_SHORT).show(); } } catch(Exception e){} } }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); name = (EditText) this.findViewById(R.id.name); age = (EditText) this.findViewById(R.id.age); getbutton = (Button) this.findViewById(R.id.getbutton); postbutton = (Button) this.findViewById(R.id.postbutton); getbutton.setOnClickListener(listener); postbutton.setOnClickListener(listener); } protected String readString(InputStream in) throws Exception { byte[]data = new byte[1024]; int length = 0; ByteArrayOutputStream bout = new ByteArrayOutputStream(); while((length=in.read(data))!=-1){ bout.write(data,0,length); } return new String(bout.toByteArray(),"UTF-8"); }}