Android中利用httpclient进行网络通信的方法(以用户登录为例说明)

http://www.android100.org/html/201406/09/22915.html

1.服务器端

      服务器端和android没有太大关系，对J2EE比较熟悉的话写起来应该很容易，这里就不一一贴出代码。

首先在本地创建一个数据库表，其中包含了一个userinfo表用来存储用户信息。

需要实现的代码如下：

DBUtils：创建数据库连接对象

User实体类：用来存放用户信息

UserDao：用来对处理User相关的数据操作

UserService：调用UserDao来处理事务

UserServlet：处理用户请求，并返回

当客户端访问该servlet时，获得客户端传入的数据，处理数据，并将结果写到response中返回给客户端。

UserServlet中doPost方法如下：

[java] <span style="font-size:16px;">1   public void doPost(HttpServletRequest request, HttpServletResponse response)   
2               throws ServletException, IOException {   
3           UserService us = UserService.getInstance();   
4           String username = request.getParameter("username"); //获得从客户端传入的用户名和密码    
5           String password = request.getParameter("password");   
6           //System.out.println("username:"+username);    
7           //System.out.println("password:"+password);    
8           //response.setContentType("text/html");    
9           PrintWriter out = response.getWriter();   
10          if(us.login(username, password))   
11          {   
12              //用户登录成功！    
13              out.println("success");   
14          }   
15          else    //用户登录失败    
16              out.println("failed");         
17          out.flush();   
18          out.close();   
19      }  </span> 
<span style="font-size:16px;">1 public void doPost(HttpServletRequest request, HttpServletResponse response) 
2             throws ServletException, IOException { 
3         UserService us = UserService.getInstance(); 
4         String username = request.getParameter("username"); //获得从客户端传入的用户名和密码 
5         String password = request.getParameter("password"); 
6         //System.out.println("username:"+username); 
7         //System.out.println("password:"+password); 
8         //response.setContentType("text/html"); 
9         PrintWriter out = response.getWriter(); 
10         if(us.login(username, password)) 
11         { 
12             //用户登录成功！ 
13             out.println("success"); 
14         } 
15         else    //用户登录失败 
16             out.println("failed");       
17         out.flush(); 
18         out.close(); 
19     }  </span>

2.客户端，首先创建一个登录Activity。如图所示：

 

当用户点击登录按钮后，创建一个http请求，发送到服务器端。获得服务器返回的结果后，再进行判断并执行相关操作。

httpclient相当于一个浏览器，通过它，可以很方便的发出GET,POST请求。

该Activity的具体代码如下：

[java] <span style="font-size:16px;">20  public class GossipActivity extends Activity {   
21      /** Called when the activity is first created. */   
22         
23      pivate EditText usernameEdit;   
24      private EditText passwordEdit;   
25      private Button loginButton;   
26         
27      @Override   
28      public void onCreate(Bundle savedInstanceState) {   
29          super.onCreate(savedInstanceState);   
30          setContentView(R.layout.main);   
31                 
32          usernameEdit = (EditText)findViewById(R.id.usernameEdit);   
33          passwordEdit = (EditText)findViewById(R.id.pwdEdit);   
34          loginButton = (Button)findViewById(R.id.loginButton);   
35             
36          loginButton.setOnClickListener(loginListener);   
37      }   
38         
39      //登陆监听器    
40      OnClickListener loginListener = new OnClickListener(){   
41     
42          @Override   
43          public void onClick(View v) {   
44              System.out.println("Login Button clicked!");   
45               String httpUrl = "http://10.0.2.2:8089/Gossip/LoginServlet";    
46               System.out.println(httpUrl);   
47               HttpPost request = new HttpPost(httpUrl);     
48               HttpClient httpClient = new DefaultHttpClient();     
49               //传递参数    
50               List<NameValuePair> params = new ArrayList<NameValuePair>();     
51               params.add(new BasicNameValuePair("username",usernameEdit.getText().toString()));    
52               params.add(new BasicNameValuePair("password",passwordEdit.getText().toString()));                                  
53               HttpResponse response;   
54                  try {   
55                      HttpEntity entity = new UrlEncodedFormEntity(params, "UTF-8");     
56                      request.setEntity(entity);     
57                      response = httpClient.execute(request);   
58                     
59                   //如果返回状态为200，获得返回的结果    
60                   if(response.getStatusLine().getStatusCode()==HttpStatus.SC_OK){     
61                       String str = EntityUtils.toString(response.getEntity());     
62                       System.out.println("response:"+str);   
63                       if(str.trim().equals("success")){   
64                           //用户登录成功    
65                           System.out.println("登录成功！");   
66                           Intent intent = new Intent(GossipActivity.this,GossiplistActivity.class);   
67                           startActivity(intent);   
68                       }   
69                       else{   
70                           //用户登录失败    
71                           System.out.println("登录失败！");   
72                       }   
73                   }else{     
74                       System.out.println("连接失败！");   
75                   }     
76                  } catch (ClientProtocolException e) {   
77                      // TODO Auto-generated catch block    
78                      e.printStackTrace();   
79                  } catch (IOException e) {   
80                      // TODO Auto-generated catch block    
81                      e.printStackTrace();   
82                  }     
83       
84          }};   
85  }  </span> 
<span style="font-size:16px;">20 public class GossipActivity extends Activity { 
21     /** Called when the activity is first created. */ 
22      
23     private EditText usernameEdit; 
24     private EditText passwordEdit; 
25     private Button loginButton; 
26      
27     @Override 
28     public void onCreate(Bundle savedInstanceState) { 
29         super.onCreate(savedInstanceState); 
30         setContentView(R.layout.main); 
31              
32         usernameEdit = (EditText)findViewById(R.id.usernameEdit); 
33         passwordEdit = (EditText)findViewById(R.id.pwdEdit); 
34         loginButton = (Button)findViewById(R.id.loginButton); 
35          
36         loginButton.setOnClickListener(loginListener); 
37     } 
38      
39     //登陆监听器 
40     OnClickListener loginListener = new OnClickListener(){ 
41  
42         @Override 
43         public void onClick(View v) { 
44             System.out.println("Login Button clicked!"); 
45              String httpUrl = "http://10.0.2.2:8089/Gossip/LoginServlet";  
46              System.out.println(httpUrl); 
47              HttpPost request = new HttpPost(httpUrl);   
48              HttpClient httpClient = new DefaultHttpClient();   
49              //传递参数 
50              List<NameValuePair> params = new ArrayList<NameValuePair>();   
51              params.add(new BasicNameValuePair("username",usernameEdit.getText().toString()));  
52              params.add(new BasicNameValuePair("password",passwordEdit.getText().toString()));                                
53              HttpResponse response; 
54                 try { 
55                     HttpEntity entity = new UrlEncodedFormEntity(params, "UTF-8");   
56                     request.setEntity(entity);   
57                     response = httpClient.execute(request); 
58                  
59                  //如果返回状态为200，获得返回的结果 
60                  if(response.getStatusLine().getStatusCode()==HttpStatus.SC_OK){   
61                      String str = EntityUtils.toString(response.getEntity());   
62                      System.out.println("response:"+str); 
63                      if(str.trim().equals("success")){ 
64                          //用户登录成功 
65                          System.out.println("登录成功！"); 
66                          Intent intent = new Intent(GossipActivity.this,GossiplistActivity.class); 
67                          startActivity(intent); 
68                      } 
69                      else{ 
70                          //用户登录失败 
71                          System.out.println("登录失败！"); 
72                      } 
73                  }else{   
74                      System.out.println("连接失败！"); 
75                  }   
76                 } catch (ClientProtocolException e) { 
77                     // TODO Auto-generated catch block 
78                     e.printStackTrace(); 
79                 } catch (IOException e) { 
80                     // TODO Auto-generated catch block 
81                     e.printStackTrace(); 
82                 }   
83    
84         }}; 
85 }  </span>

在数据库中添加一行：用户名为123，密码为456。登录后调转到另一Activity并在控制台中打印调试信息，结果如下：

 

3 在向本机发送HTTP请求时，有一点必须注意，就是在android 虚拟机中，127.0.0.1为android 虚拟机的IP地址，

如果要访问本机，IP地址应该改为10.0.2.2。否则肯定会导致访问不成功！

作者：余蒙