今天想把一个用使用了HttpClient的自动签到小程序移植到Android上,还好Android的SDK自带了HttpClient的包。翻Android的文档时发现官方还提供了一个实现了HttpClient接口的AndroidHttpClient,上网搜了下没发现关于AndroidHttpClient的文章。当然也可以继续使用DefaultHttpClient,但用为Android定制的AndroidHttpClient自然更好。 
下面是2个测试用的HttpServlet: 
 
public class LogIn extends HttpServlet { 
/** 
* Processes requests for both HTTP 
* <code>GET</code> and 
* <code>POST</code> methods. 
* 
* @param request servlet request 
* @param response servlet response 
* @throws ServletException if a servlet-specific error occurs 
* @throws IOException if an I/O error occurs 
*/ 
protected void processRequest(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException { 
response.setContentType("text/html;charset=UTF-8"); 
request.setCharacterEncoding("utf-8"); 
PrintWriter out = response.getWriter(); 
HttpSession session=request.getSession(); 
String info=request.getParameter("info"); 
session.setAttribute("info", info); 
try { 
/* TODO output your page here. You may use following sample code. */ 
out.println("OK"); 
} finally { 
out.close(); 
} 
} 
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code."> 
/** 
* Handles the HTTP 
* <code>GET</code> method. 
* 
* @param request servlet request 
* @param response servlet response 
* @throws ServletException if a servlet-specific error occurs 
* @throws IOException if an I/O error occurs 
*/ 
@Override 
protected void doGet(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException { 
processRequest(request, response); 
} 
/** 
* Handles the HTTP 
* <code>POST</code> method. 
* 
* @param request servlet request 
* @param response servlet response 
* @throws ServletException if a servlet-specific error occurs 
* @throws IOException if an I/O error occurs 
*/ 
@Override 
protected void doPost(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException { 
processRequest(request, response); 
} 
/** 
* Returns a short description of the servlet. 
* 
* @return a String containing servlet description 
*/ 
@Override 
public String getServletInfo() { 
return "Short description"; 
}// </editor-fold> 
} 
  
public class Info extends HttpServlet { 
/** 
* Processes requests for both HTTP 
* <code>GET</code> and 
* <code>POST</code> methods. 
* 
* @param request servlet request 
* @param response servlet response 
* @throws ServletException if a servlet-specific error occurs 
* @throws IOException if an I/O error occurs 
*/ 
protected void processRequest(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException { 
response.setContentType("text/html;charset=UTF-8"); 
PrintWriter out = response.getWriter(); 
HttpSession session=request.getSession(); 
String info=(String)session.getAttribute("info"); 
try { 
/* TODO output your page here. You may use following sample code. */ 
if(info==null) 
out.print("null"); 
else 
out.print(info); 
} finally { 
out.close(); 
} 
} 
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code."> 
/** 
* Handles the HTTP 
* <code>GET</code> method. 
* 
* @param request servlet request 
* @param response servlet response 
* @throws ServletException if a servlet-specific error occurs 
* @throws IOException if an I/O error occurs 
*/ 
@Override 
protected void doGet(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException { 
processRequest(request, response); 
} 
/** 
* Handles the HTTP 
* <code>POST</code> method. 
* 
* @param request servlet request 
* @param response servlet response 
* @throws ServletException if a servlet-specific error occurs 
* @throws IOException if an I/O error occurs 
*/ 
@Override 
protected void doPost(HttpServletRequest request, HttpServletResponse response) 
throws ServletException, IOException { 
processRequest(request, response); 
} 
/** 
* Returns a short description of the servlet. 
* 
* @return a String containing servlet description 
*/ 
@Override 
public String getServletInfo() { 
return "Short description"; 
}// </editor-fold> 
} 
 主要代码在processRequest里,其他可以不用看。 
访问LogIn时传一个name为info的值,这时浏览器会得到一个用于定位服务端session的cookie。然后访问Info,如果有cookie的话服务端能找到刚才你传的值并返回给你,没带cookie的话就不能找到。 
Android端代码: 
 
public class MainActivity extends Activity { 
private AndroidHttpClient mHttpclient=AndroidHttpClient.newInstance(""); 
@Override 
public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.activity_main); 
findViewById(R.id.button1).setOnClickListener(new OnClickListener() { 
@Override 
public void onClick(View v) { 
// TODO Auto-generated method stub 
new Thread(rTest).start(); 
} 
}); 
} 
private String toString(InputStream is) throws IOException{ 
String ret=""; 
InputStreamReader isr=new InputStreamReader(is); 
BufferedReader br=new BufferedReader(isr); 
String tmp=br.readLine(); 
while(tmp!=null){ 
ret+=tmp; 
tmp=br.readLine(); 
} 
br.close(); 
return ret; 
} 
private Runnable rTest=new Runnable() { 
@Override 
public void run() { 
// TODO Auto-generated method stub 
try { 
BasicHttpContext context=new BasicHttpContext(); 
context.setAttribute(ClientContext.COOKIE_STORE,new BasicCookieStore()); 
HttpPost httppost = new HttpPost("http://10.226.233.48:8080/WebApplication1/LogIn"); 
List <NameValuePair> nvps = new ArrayList <NameValuePair>(); 
nvps.add(new BasicNameValuePair("info", "你好 世界!!")); 
httppost.setEntity(new UrlEncodedFormEntity(nvps,"utf-8")); 
HttpResponse response=mHttpclient.execute(httppost,context); 
HttpEntity entity = response.getEntity(); 
Log.i("kagami", MainActivity.this.toString(entity.getContent())); 
entity.consumeContent(); 
HttpGet httpget2 = new HttpGet("http://10.226.233.48:8080/WebApplication1/Info"); 
HttpResponse response2=mHttpclient.execute(httpget2,context); 
HttpEntity entity2 = response2.getEntity(); 
Log.i("kagami", MainActivity.this.toString(entity2.getContent())); 
entity2.consumeContent(); 
} catch (IOException e) { 
// TODO Auto-generated catch block 
e.printStackTrace(); 
} 
} 
}; 
} 
  AndroidHttpClient和DefaultHttpClient的区别
 AndroidHttpClient和DefaultHttpClient的区别: 
AndroidHttpClient不能在主线程中execute,会抛出异常。AndroidHttpClient通过静态方法newInstance获得实例,参数是代理,不用代理的话填“”。DefaultHttpClient默认是启用Cookie的,AndroidHttpClient默认不启用Cookie,要使用的话每次execute时要加一个HttpContext参数,并且添加CookieStore。用完后别忘了close不然不能创建新实例。