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] 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 } 
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 }

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] 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 } 
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 }

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