javaweb简单登陆例子

JSP+Servlet+JavaBean简单程序例子——用户名密码登陆，摘自《Tomcat&JavaWeb 技术手册》，亲测可用。

IDE环境：MyEclipse10

1、建立Web Project,命名为Login_test。创建userLogn表：

create table userLogin(

user_name varchar(10) not null,

user_pwd varchar(10) not null,

constraint user_pk primary key (user_name)

);

2、添加 JavaBean文件，创建新类UserLoginBean,java

package login;
import java.sql.*;

public class UserLoginBean {
    private Connection con;   //数据库连接
    private ResultSet rs;     //结果集
    private Statement stmt;
    private static final String DRIVER_NAME="com.mysql.jdbc.Driver";
    private static final String URL_STR="jdbc:mysql://localhost/test";
    //构造函数
    public UserLoginBean(){
        try{//加载驱动程序
            Class.forName(DRIVER_NAME);
            //获取数据库连接
            con=DriverManager.getConnection(URL_STR, "root", "jiangshan");    //自己的用户名和密码
        }
        catch(SQLException se){
            se.printStackTrace();
        }
        catch(ClassNotFoundException cnfe){
            cnfe.printStackTrace();
        }
    }

    //业务方法
    public boolean login(String userName,String password)
    {
        boolean b = false;
        try{
            stmt=con.createStatement();
            String sql="SELECT user_pwd FROM userLogin Where user_name='"+userName+"'";
            rs=stmt.executeQuery(sql);
            while(rs.next()){
                String pwd= rs.getString(1);
                if(pwd.equals(password)){
                    b=true;
                }
            }
        }catch(SQLException se){
            se.printStackTrace();
            b=false;
        }finally{
            this.close(con,rs,stmt);   //下面定义close方法
        }
        return b;
    }
    //close方法用于关闭相应资源
    public void close(Connection con,ResultSet rs,Statement stmt){
        try{
            if(con!=null){
                con.close();
            }
            if(rs!=null){
                rs.close();
            }
            if(stmt!=null){
                stmt.close();
            }
        }
        catch(SQLException se){
            se.printStackTrace();
        }
    }
}

3、添加Servlet类，命名UserLoginServlet.java

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import login.UserLoginBean;

public class UserLoginServlet extends HttpServlet{
    public void doGet(HttpServletRequest request,HttpServletResponse response)
            throws ServletException,IOException{
        this.doPost(request, response);
    }
    public void doPost(HttpServletRequest request,HttpServletResponse response)
            throws ServletException,IOException{
        PrintWriter out=response.getWriter();
        try{
            String userName=request.getParameter("userName").trim();
            String passWord=request.getParameter("passWord").trim();
            UserLoginBean ubl=new UserLoginBean();
            boolean b =ubl.login(userName, passWord);
            if(b){
                this.forward(request,response,"/loginOK.jsp");
            }
            else{
                this.forward(request,response,"/LoginFail.jsp");
            }
        }
        catch(Exception e){
            out.println("Login fail.<br>");
            out.println(e.toString());
        }
    }
    //
    private void forward(HttpServletRequest request,HttpServletResponse response,String url)
            throws ServletException,IOException{
        RequestDispatcher rd=request.getRequestDispatcher(url);
        rd.forward(request, response);
    }

}

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import login.UserLoginBean;

public class UserLoginServlet extends HttpServlet{
    public void doGet(HttpServletRequest request,HttpServletResponse response)
            throws ServletException,IOException{
        this.doPost(request, response);
    }
    public void doPost(HttpServletRequest request,HttpServletResponse response)
            throws ServletException,IOException{
        PrintWriter out=response.getWriter();
        try{
            String userName=request.getParameter("userName").trim();
            String passWord=request.getParameter("passWord").trim();
            UserLoginBean ubl=new UserLoginBean();
            boolean b =ubl.login(userName, passWord);
            if(b){
                this.forward(request,response,"/loginOK.jsp");
            }
            else{
                this.forward(request,response,"/LoginFail.jsp");
            }
        }
        catch(Exception e){
            out.println("Login fail.<br>");
            out.println(e.toString());
        }
    }
    //
    private void forward(HttpServletRequest request,HttpServletResponse response,String url)
            throws ServletException,IOException{
        RequestDispatcher rd=request.getRequestDispatcher(url);
        rd.forward(request, response);
    }

}

4、写登陆界面：创建index.jsp

<%@ page contentType="text/html; charset=GBK" %>

<html>
  <head>
    <title>User_Login</title>
  </head>

  <body><br><br>
  <font size="5" color="#FF0000">
  <b>Jsp+Servlet+JavaBean应用</b> </font><br><hr></hr><br><br>
  <form name="loginForm" method="post" action="UserLoginServlet">
  <table border="0" align="center" cellpadding="2" cellspacing="2" bgcolor="snow">
  <tr>
      <td>
      <div align ="center">用户名：</div>
      </td>
      <td><div align="center">
      <input type="text" name="userName" size=20 maxlength="10">
      </div></td></tr>
  <tr>
      <td>
      <div align="center">密&nbsp;&nbsp;码</div>
      </td>
      <td>
      <div align="center">
      <input type="password" name="passWord" size="20" maxlength="10">
      </div></td></tr>
  <tr width="100%">
      <td>
      <div align="center">
      <input type="submit" value="登陆">
      <input type="reset" value="重置">
      </div> </td></tr>
  </table></form>
  </body>
</html>

<%@ page contentType="text/html; charset=GBK" %>

<html>
  <head>
    <title>User_Login</title>
  </head>

  <body><br><br>
  <font size="5" color="#FF0000">
  <b>Jsp+Servlet+JavaBean应用</b> </font><br><hr></hr><br><br>
  <form name="loginForm" method="post" action="UserLoginServlet">
  <table border="0" align="center" cellpadding="2" cellspacing="2" bgcolor="snow">
  <tr>
      <td>
      <div align ="center">用户名：</div>
      </td>
      <td><div align="center">
      <input type="text" name="userName" size=20 maxlength="10">
      </div></td></tr>
  <tr>
      <td>
      <div align="center">密&nbsp;&nbsp;码</div>
      </td>
      <td>
      <div align="center">
      <input type="password" name="passWord" size="20" maxlength="10">
      </div></td></tr>
  <tr width="100%">
      <td>
      <div align="center">
      <input type="submit" value="登陆">
      <input type="reset" value="重置">
      </div> </td></tr>
  </table></form>
  </body>
</html>

5、登陆成功界面:LoginOK.jsp

<%@ page contentType="text/html; charset=GBK" %>

<html>
  <head>
    <title>User_LoginOK</title>
  </head>
  <body><br><br><br>
  <font size="5" color="#FF0000">
  <b>JSP+Servlet+JavaBean</b>
  </font><br><br><hr></hr><br><br>
  <center>
      <font color="red" size="4" >Login OK!</font>
  </center></body>
  </html>

<%@ page contentType="text/html; charset=GBK" %>

<html>
  <head>
    <title>User_LoginOK</title>
  </head>
  <body><br><br><br>
  <font size="5" color="#FF0000">
  <b>JSP+Servlet+JavaBean</b>
  </font><br><br><hr></hr><br><br>
  <center>
      <font color="red" size="4" >Login OK!</font>
  </center></body>
  </html>

6、登陆失败界面:LoginFail.jsp

%@ page contentType="text/html; charset=GBK" %>

<html>
  <head>
    <title>User_LoginOK</title>
  </head>
  <body><br><br><br>
  <font size="5" color="#FF0000">
  <b>JSP+Servlet+JavaBean</b>
  </font><br><br><hr></hr><br><br>
  <center>
      <font color="red" size="4" >Login Fail!</font>
  </center></body>
  </html>

<%@ page contentType="text/html; charset=GBK" %>

<html>
  <head>
    <title>User_LoginOK</title>
  </head>
  <body><br><br><br>
  <font size="5" color="#FF0000">
  <b>JSP+Servlet+JavaBean</b>
  </font><br><br><hr></hr><br><br>
  <center>
      <font color="red" size="4" >Login Fail!</font>
  </center></body>
  </html>

7、启动tomcat,将此项目部署至tomcat的webapps文件下，打开webapps下的项目里的WEB-INF文件夹，修改web.xml文件，在<web-app>和</web-app>之间添加如下代码：

<servlet>
      <servlet-name>UserLoginServlet</servlet-name>
      <servlet-class>UserLoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>UserLoginServlet</servlet-name>
        <url-pattern>/UserLoginServlet</url-pattern>
    </servlet-mapping>

也可以添加如下代码，将主页设置为index.jsp:
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>

8、打开浏览器，输入http://localhost:8080/Login_test/   即可进入登陆界面。