JDBC用户登录

DbUtil 连接数据库

public class DbUtil {

	private String dbUrl="jdbc:mysql://localhost:3306/db_jsp";
	private String dbUserName="root";
	private String dbPassword="123456";
	private String jdbcName="com.mysql.jdbc.Driver";
	
	public Connection getCon()throws Exception{
		Class.forName(jdbcName);
		Connection con=DriverManager.getConnection(dbUrl, dbUserName, dbPassword);
		return con;
	}
	
	public void closeCon(Connection con)throws Exception{
		if(con!=null){
			con.close();
		}
	}
	
	public static void main(String[] args) {
		DbUtil dbUtil=new DbUtil();
		try {
			dbUtil.getCon();
			System.out.println("连接成功");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

dao操作数据库

public class UserDao {

	public User login(Connection con,User user)throws Exception{
		User resultUser=null;
		String sql="select * from t_user where userName=? and password=?";
		PreparedStatement pstmt=con.prepareStatement(sql);
		pstmt.setString(1, user.getUserName());
		pstmt.setString(2, user.getPassword());
		ResultSet rs=pstmt.executeQuery();
		if(rs.next()){
			resultUser=new User();
			resultUser.setUserName(rs.getString("userName"));
			resultUser.setPassword(rs.getString("password"));
		}
		return resultUser;
	}
			
}

servlet获取前台的用户名与密码

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String userName=request.getParameter("userName");
		String password=request.getParameter("password");
		
		Connection con=null;
		try {
			User user=new User(userName,password);
			con=dbUtil.getCon();
			User currentUser=userDao.login(con, user);
			if(currentUser==null){
				request.setAttribute("error", "用户名或密码错误");
				request.setAttribute("userName", userName);
				request.setAttribute("password", password);
				request.getRequestDispatcher("login.jsp").forward(request, response);
			}else{
				HttpSession session=request.getSession();
				session.setAttribute("currentUser", currentUser);
				response.sendRedirect("main.jsp");
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

user实体封装

public class User {

	private int id;
	private String userName;
	private String password;
	
	
	
	public User() {
		super();
		// TODO Auto-generated constructor stub
	}
	
	
	public User(String userName, String password) {
		super();
		this.userName = userName;
		this.password = password;
	}

el表达式获取request作用域中设置的值

<body>
<form action="login" method="post">
<table>
	<tr>
		<th colspan="2">用户登录</th>
	</tr>
	<tr>
		<td>用户名：</td>
		<td><input type="text" id="userName" name="userName" value="${userName }"/></td>
	</tr>
	<tr>
		<td>密码：</td>
		<td><input type="password" id="password" name="password" value="${password }"/></td>
	</tr>
	<tr>
		<td><input type="submit" value="登录"/></td>
		<td><font color="red">${error }</font></td>
	</tr>
</table>
</form>
</body>

main.jsp

<body>
主页！当前登录用户：${currentUser.userName } &nbsp;&nbsp;<a href="logout">注销</a>
</body>

退出登录

  <a href="logout">注销</a>
  
  <servlet>
  	<servlet-name>logoutServlet</servlet-name>
  	<servlet-class>com.web.LogoutServlet</servlet-class>
  </servlet>
  
  <servlet-mapping>
  	<servlet-name>logoutServlet</servlet-name>
  	<url-pattern>/logout</url-pattern>
  </servlet-mapping>

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		request.getSession().invalidate();
		response.sendRedirect("login.jsp");
	}

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