Servlet入门

 1 package com.alphajuns.context;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.ServletContext;
 6 import javax.servlet.ServletException;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 
11 /**
12  * Servlet implementation class ContextServlet
13  */
14 public class ContextServlet extends HttpServlet {
15     private static final long serialVersionUID = 1L;
16        
17     public ContextServlet() {
18         super();
19     }
20 
21     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
22         // 获取ServletContext对象
23         ServletContext servletContext = getServletContext();
24         // 获取初始化参数
25         String initParameter = servletContext.getInitParameter("driver");
26         System.out.println(initParameter);
27         // 1、获得a.txt的绝对路径
28         String realPath_a = servletContext.getRealPath("a.txt");
29         System.out.println(realPath_a);
30         // 2、获得b.txt的绝对路径
31         String realPath_b = servletContext.getRealPath("WEB-INF/b.txt");
32         System.out.println(realPath_b);
33         // 3、获得c.txt的绝对路径
34         String realPath_c = servletContext.getRealPath("WEB-INF/classes/c.txt");
35         System.out.println(realPath_c);
36         
37         // 获取在src下的资源可以通过类加载器的方式
38         String path = ContextServlet.class.getClassLoader().getResource("c.txt").getPath();
39         System.out.println(path);
40     }
41 
42     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
43         // TODO Auto-generated method stub
44         doGet(request, response);
45     }
46 
47 }

 1 package com.alphajuns.login;
 2 
 3 import java.io.IOException;
 4 import java.sql.SQLException;
 5 
 6 import javax.servlet.ServletContext;
 7 import javax.servlet.ServletException;
 8 import javax.servlet.http.HttpServlet;
 9 import javax.servlet.http.HttpServletRequest;
10 import javax.servlet.http.HttpServletResponse;
11 
12 import org.apache.commons.dbutils.QueryRunner;
13 import org.apache.commons.dbutils.handlers.BeanHandler;
14 
15 import com.alphajuns.domain.User;
16 import com.alphajuns.utils.DataSourceUtils;
17 
18 public class LoginServlet extends HttpServlet {
19     
20     @Override
21     public void init() throws ServletException {
22         int count = 0;
23         this.getServletContext().setAttribute("count", count);
24     }
25 
26     public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
27         // 获得用户名和密码
28         String username = request.getParameter("username");
29         String password = request.getParameter("password");
30         
31         // 从数据库获取用户名和密码
32         // 获取数据库执行对象
33         QueryRunner qr = new QueryRunner(DataSourceUtils.getDataSource());
34         String sql = "select * from user where username=? and password=?";
35         // 对查询结果进行封装
36         User user = null;
37         try {
38             user = qr.query(sql, new BeanHandler<User>(User.class), username, password);
39         } catch (SQLException e) {
40             e.printStackTrace();
41         }
42         
43         // 根据查询结果判断登录状态
44         if (user != null) {
45             // 从ServletContext中取出count进行计算++
46             ServletContext servletContext = this.getServletContext();
47             Integer count = (Integer) servletContext.getAttribute("count");
48             count++;
49             response.getWriter().write(user.toString() + "login successful" + count);
50             // 把登录次数存入ServletContext
51             servletContext.setAttribute("count", count);
52         } else {
53             response.getWriter().write("your username or password is wrong");
54         }
55     }
56 
57     public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
58         doGet(request, response);
59     }
60 }