Jsp+Servlet+Tomcat+Mysql+JDBC+MVC模式简单实用范例

这里用到的软件分别如下：

Tomcat：apache-tomcat-6.0.29.zip

Mysql：mysql-essential-5.1.50-win32.msi

JDBC：mysql-connector-java-5.1.13-bin.jar

Myeclipse：myeclipse-8.6.0-win32.exe

这里要做的配置如下：

mysql默认安装，建立root账户，密码root

mysql-connector-java-5.1.13-bin.jar放到Web应用的WEB-INF/lib/目录下或者是tomcat的lib/目录下

这里要制作的效果如下：

登录页面：

注销页面：

这里用到的关键代码如下：

SQL:

create database test;

use test;

CREATE TABLE  test.user (
  pid varchar(45) default NULL,
  username varchar(45) NOT NULL,
  password varchar(45) NOT NULL
)  DEFAULT CHARSET=GB2312;

INSERT user(pid, username, password) VALUES('1', 'root', 'root');
INSERT user(pid, username, password) VALUES('2', 'admin', 'admin');

首页（视图）：

 1   <body>
 2     <%if (null != session.getAttribute("username")) { %>
 3         欢迎您回来：<%=session.getAttribute("username") %>
 4         <a href="servlet/ServletLogout">注销</a><br/>
 5         <br/>
 6     <%} else {%>
 7         <form action="servlet/ServletLogin" method="POST">
 8             <input type="text" name="username"/><br/>
 9             <input type="password" name="password"/><br/>
10             <input type="submit" value="登录"/>
11         </form>
12     <%} %>
13         在线会员人数：<%=application.getAttribute("onlineMember") %><br/>
14         当前在线人数：<%=application.getAttribute("onlineNumber") %><br/>
15         历史访问人数：<%=application.getAttribute("totalNumber") %><br/>
16   </body>

 1     public void doGet(HttpServletRequest request, HttpServletResponse response)
 2             throws ServletException, IOException {
 3 
 4         HttpSession session = request.getSession();
 5         ServletContext application = this.getServletContext();
 6         
 7         if (null == session.getAttribute("username")) {
 8             try {
 9                 // 获得表单数据
10                  String username = request.getParameter("username");
11                 String password = request.getParameter("password");
12                 
13                 // 建立数据库连接
14                  Connection conn = DBUtil.getConnection();
15                 
16                 // 定义查询语句
17                  String sql = "select * from user where `username`=? and `password`=?";
18                 PreparedStatement pstmt = conn.prepareStatement(sql);
19                 pstmt.setString(1, username);
20                 pstmt.setString(2, password);
21                 
22                 // 查询获得结果集
23                  ResultSet rs = pstmt.executeQuery();
24                 if (rs.next()) {
25                     session.setAttribute("username", rs.getString("username"));
26                     //session.setAttribute("password", rs.getString("password"));
27                      int olMember = ((Integer) application.getAttribute("onlineMember")).intValue();
28                     application.setAttribute("onlineMember", olMember + 1);
29                 }
30                 
31                 // 关闭结果集，查询语句，数据库连接
32                  rs.close();
33                 pstmt.close();
34                 conn.close();
35             } catch (InstantiationException e) {
36                 // TODO Auto-generated catch block
37                  e.printStackTrace();
38             } catch (IllegalAccessException e) {
39                 // TODO Auto-generated catch block
40                  e.printStackTrace();
41             } catch (ClassNotFoundException e) {
42                 // TODO Auto-generated catch block
43                  e.printStackTrace();
44             } catch (SQLException e) {
45                 // TODO Auto-generated catch block
46                  e.printStackTrace();
47             }
48         }
49            
50            // 返回上一个页面
51             response.sendRedirect(request.getHeader("Referer"));
52     }

注销（控制器）：

 1     public void doGet(HttpServletRequest request, HttpServletResponse response)
 2             throws ServletException, IOException {
 3 
 4         HttpSession session = request.getSession();
 5         ServletContext application = this.getServletContext();
 6         
 7         // 如果此用户没有登录过
 8          if (null != session.getAttribute("username")) {
 9                int olMember = ((Integer)application.getAttribute("onlineMember")).intValue();
10                application.setAttribute("onlineMember", olMember - 1);
11                //session.invalidate();
12                 session.removeAttribute("username");
13            }
14            
15            // 返回上一个页面
16             response.sendRedirect(request.getHeader("Referer"));
17     }

数据库（模型）：

 1 public class DBUtil {
 2     private static String username = "root";
 3     private static String password = "root";
 4     private static String driver = "com.mysql.jdbc.Driver";
 5     private static String url = "jdbc:mysql://localhost:3306/test";
 6     
 7     // 得到数据库连接
 8      public static Connection getConnection() throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException {
 9         Class.forName(driver).newInstance();
10         return DriverManager.getConnection(url, username, password);
11     }
12     
13 }

Web配置页面：

 1 <?xml version="1.0" encoding="UTF-8"?>
 2  <web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
 5     <listener>
 6         <listener-class>listener.WebListener</listener-class>
 7     </listener>
 8     <servlet>
 9         <servlet-name>ServletWebInitializer</servlet-name>
10         <servlet-class>servlet.ServletWebInitializer</servlet-class>
11         <load-on-startup>1</load-on-startup>
12     </servlet>
13     <servlet>
14         <servlet-name>ServletLogin</servlet-name>
15         <servlet-class>servlet.ServletLogin</servlet-class>
16     </servlet>
17     <servlet>
18         <servlet-name>ServletLogout</servlet-name>
19         <servlet-class>servlet.ServletLogout</servlet-class>
20     </servlet>
21 
22     <servlet-mapping>
23         <servlet-name>ServletWebInitializer</servlet-name>
24         <url-pattern>/servlet/ServletWebInitializer</url-pattern>
25     </servlet-mapping>
26     <servlet-mapping>
27         <servlet-name>ServletLogin</servlet-name>
28         <url-pattern>/servlet/ServletLogin</url-pattern>
29     </servlet-mapping>
30     <servlet-mapping>
31         <servlet-name>ServletLogout</servlet-name>
32         <url-pattern>/servlet/ServletLogout</url-pattern>
33     </servlet-mapping>
34     <welcome-file-list>
35         <welcome-file>index.jsp</welcome-file>
36     </welcome-file-list>
37  </web-app>

Web初始化：

1     public void init() throws ServletException {
2         // Put your code here
3          ServletContext app = this.getServletContext();
4         app.setAttribute("onlineMember", new Integer(0)); // 在线会员人数
5         app.setAttribute("onlineNumber", new Integer(0)); // 当前在线人数
6         app.setAttribute("totalNumber", new Integer(0)); // 历史访问人数
7     }

Web监听器：

 1 public class WebListener implements HttpSessionListener {
 2 
 3     public WebListener() {
 4         // TODO Auto-generated constructor stub
 5     }
 6 
 7     public void sessionCreated(HttpSessionEvent se) {
 8         // TODO Auto-generated method stub
 9         
10         ServletContext app = se.getSession().getServletContext();
11         int olCount = ((Integer)app.getAttribute("onlineNumber")).intValue();
12         app.setAttribute("onlineNumber", olCount + 1);
13         
14         int ttlCount = ((Integer)app.getAttribute("totalNumber")).intValue();
15         app.setAttribute("totalNumber", ttlCount + 1);
16     }
17 
18     public void sessionDestroyed(HttpSessionEvent se) {
19         // TODO Auto-generated method stub
20         ServletContext app = se.getSession().getServletContext();
21         int olCount = ((Integer)app.getAttribute("onlineNumber")).intValue();
22         app.setAttribute("onlineNumber", olCount - 1);
23     }
24 
25 }

总结如下：

1. 如果要在Web应用中初始化一些值，那么可以采用在web.xml加入1个或者多个特殊的servlet，并设置对应的servlet配置：

<servlet>
  <servlet-name>ServletWebInitializer</servlet-name>
  <servlet-class>servlet.ServletWebInitializer</servlet-class>
  <load-on-startup>x</load-on-startup>（x>=1，顺序越小启动优先级越高)
</servlet>

将要初始化的内容写在这些特殊的servlet的init()方法内：

public void init() throws ServletException

2. 如果在一个新会话的开始，或者一个会话的结束时要进行某些计算，比如统计在线人数，那么可以在web.xml加入1个或者多个监听器：

<listener>
<listener-class>listener.WebListener</listener-class>
</listener>

对应的计算放在sessionCreated和sessionDestroyed里面：

public class WebListener implements HttpSessionListener

public void sessionCreated(HttpSessionEvent se)

public void sessionDestroyed(HttpSessionEvent se)

3. mysql数据库采用jdbc连接的步骤如下：

 1 public class DBUtil {
 2     private static String username = "root";
 3     private static String password = "root";
 4     private static String driver = "com.mysql.jdbc.Driver";
 5     private static String url = "jdbc:mysql://localhost:3306/test";
 6     
 7     // 得到数据库连接
 8     public static Connection getConnection() throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException {
 9         Class.forName(driver).newInstance();
10         return DriverManager.getConnection(url, username, password);
11     }
12     
13 }

    // 建立数据库连接
    Connection conn = DBUtil.getConnection();

    // 定义查询语句
    String sql = "select * from user where `username`=? and `password`=?";
    PreparedStatement pstmt = conn.prepareStatement(sql);
    // 查询获得结果集
    ResultSet rs = pstmt.executeQuery();

    // 关闭结果集，查询语句，数据库连接
    rs.close();
    pstmt.close();
    conn.close();

4. jsp页面除了少量的if语句，基本上都是输出语句，将数据计算放到对应的JavaBean或者控制器内部完成。

完整程序下载页面：http://u.115.com/file/f8930734df

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原文地址：https://www.cnblogs.com/nysanier/p/2022705.html

Jsp+Servlet+Tomcat+Mysql+JDBC+MVC模式 简单实用范例

Jsp+Servlet+Tomcat+Mysql+JDBC+MVC模式简单实用范例