JSP+Servlet+JavaBean模式 -- 简易登录注册模型

深碍√TFBOYSˉ_ 2022-05-26 22:35 102阅读 0赞

模式分析:

![20180407195105982][]

对于Jsp来说：

Model层：实现系统的业务逻辑，即javaBean部分

View层：负责与用户交互，即在界面上展示数据对象给用户，即html，jsp

Control层：Model与View之间沟通的桥梁，它可以分派用户的请求并选择恰当的视图以用于显示，同时它也可以解释用户的输入并将它们映射为模型层可执行的操作，当然就是Servlet的职责了。

Model层代码:

User.Java

package JavaBean;
    
    public class User {
        private String UserName;//User表用户名
        private String Password;//User表用户密码
    
        public void setPassword(String password) {
            Password = password;
        }
    
        public void setUserName(String userName) {
    
            UserName = userName;
        }
    
        public String getUserName() {
    
            return UserName;
        }
    
        public String getPassword() {
    
            return Password;
        }
    }

UserSQL.Java

package JavaBean;
    
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    
    public class UserSQL {
        public static final String DRIVER = "com.mysql.jdbc.Driver";
        //数据库驱动(需将下载好后的jar包放入../web/WEB-INF/lib文件中)
        public static final String DBURL = "jdbc:mysql://127.0.0.1/DataBaseName?useUnicode=true&characterEncoding=UTF-8&useSSL=false";
        public static final String DBUser = "username";
        public static final String DBPassword = "password";
        private Connection conn = null;
        //用于数据库连接
        private PreparedStatement pStat = null;
        //用于执行SQL语句
        private ResultSet resultSet = null;
        //用于获取SQL语句的执行结果
    
        public UserSQL(){//对数据库所需操作初始化
            try {
                Class.forName(DRIVER);
                //加载JDBC驱动程序
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            }
        }
    
        public Connection getConn(){
            try{
                return DriverManager.getConnection(DBURL, DBUser, DBPassword);
                //连接数据库,并将该连接返回
            }catch (Exception e){
                e.printStackTrace();
                return null;
            }
        }
    
        public void close(){
            try {
                if(resultSet != null)
                    resultSet.close();
                if(pStat != null)
                    pStat.close();
                if(conn != null)
                    conn.close();
                //关闭数据库的连接
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    
        public boolean isUserNameExists(String username){
            conn = getConn();
            //获取数据库的连接
            if(conn != null){
                try {
                    pStat = conn.prepareStatement("select * from User where User=?");
                    pStat.setString(1, username);
                    //执行SQL语句
                    resultSet = pStat.executeQuery();
                    //获取SQL语句执行结果
                    if(resultSet.next())
                        return true;
                        //如果结果集中有元素,则说明该UserName存在
                    return false;
                }catch (Exception e) {
                    e.printStackTrace();
                    return false;
                }finally {
                    close();
                }
            }
            return false;
        }
    
        public boolean findUser(String username, String password){
            conn = getConn();
            //获取数据库的连接
            if(conn != null){
                try {
                    pStat = conn.prepareStatement("select * from User where User=? and Password=?");
                    pStat.setString(1, username);
                    pStat.setString(2, password);
                    //执行SQL语句
                    resultSet = pStat.executeQuery();
                    //获取SQL语句执行结果
                    if(resultSet.next())
                        return true;
                        //如果结果集中有元素,则说明该UserName存在
                    return false;
                }catch (Exception e) {
                    e.printStackTrace();
                    return false;
                }finally {
                    close();
                }
            }
            return false;
        }
    
        public boolean addUser(User user){
            conn = getConn();
            //获取数据库的连接
            if(conn != null){
                try {
                    pStat = conn.prepareStatement("insert into User values(?, ?)");
                    pStat.setString(1, user.getUserName());
                    pStat.setString(2, user.getPassword());
                    //执行SQL语句
                    int cnt = pStat.executeUpdate();
                    //将更新结果commit
                    if(cnt > 0)
                        return true;
                        //成功commit,返回true
                    return false;
                }catch (Exception e) {
                    e.printStackTrace();
                    return false;
                }finally {
                    close();
                }
            }
            return false;
        }
    }

Controler层代码:

package Servlet;
    
    import JavaBean.UserSQL;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet("/login")//此行代码后,可不用在web.xml中手动部署
    public class Login extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            String username = req.getParameter("username");
            //获取表单中name=username的值
            String password = req.getParameter("password");
            //获取表单中name=password的值
            UserSQL userSQL = new UserSQL();
            //创建userSQL对象
            boolean flag = userSQL.findUser(username, password);
            //判断对应的用户名和密码是否正确
            if(flag){
                req.getSession().setAttribute("username", username);
                resp.sendRedirect("JSP/Welcome.jsp");
                //若正确,则设置相应session,并跳转到欢迎界面
            }else{
                req.getSession().setAttribute("err", "用户名或密码错误");
                resp.sendRedirect("JSP/Login.jsp");
                //若不正确,则设置相应错误信息,并返回登录界面
            }
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            doGet(req, resp);
        }
    }

package Servlet;
    
    import JavaBean.User;
    import JavaBean.UserSQL;
    import com.sun.deploy.net.HttpResponse;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet("/register")//此行代码后,可不用在web.xml中手动部署
    public class Register extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            String username = req.getParameter("username");
            //获取表单中name=username的值
            String password = req.getParameter("password");
            //获取表单中name=password的值
            User user = new User();
            //创建User对象
            user.setPassword(password);
            user.setUserName(username);
            //设置User对象属性
            UserSQL userSQL = new UserSQL();
            //创建userSQL对象
            if(userSQL.isUserNameExists(username)){//判断数据库中用户名是否存在
                req.getSession().setAttribute("err", "用户名已存在");
                resp.sendRedirect("JSP/Register.jsp");
                //若该用户已存在,设置相应错误信息,并返回Register页面
            }
            else {
                boolean flag = userSQL.addUser(user);
                //数据库中该用户不存在;在数据库中添加该用户,判断是否成功添加
                if (flag) {
                    req.getSession().setAttribute("username", username);
                    resp.sendRedirect("JSP/Welcome.jsp");
                    //若成功添加,设置相应session,并跳转到欢迎页面
                } else {
                    req.getSession().setAttribute("err", "注册失败,请重试");
                    resp.sendRedirect("JSP/Register.jsp");
                    //若添加失败,设置相应错误信息,并返回注册界面
                }
            }
        }
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            doGet(req, resp);
        }
    }

`View层代码`

`Register.jsp`

<%--
      Created by IntelliJ IDEA.
      User: vina
      Date: 18-4-7
      Time: 下午3:57
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>register</title>
    </head>
    <body>
        <%
            String errMsg = (String)session.getAttribute("err");
            if(errMsg != null){
                out.println("<div style=\"color:red;\">" + errMsg + "</div>");
                session.removeAttribute("err");
            }
        %>
        <form action="/register">
            用户名:<input type="text" name="username">
            密码:<input type="password" name="password">
            <br>
            <input type="submit" value="注册">
            <input type="reset" value="重填">
        </form>
    </body>
    </html>

<%--
      Created by IntelliJ IDEA.
      User: vina
      Date: 18-4-7
      Time: 下午3:57
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>Login</title>
    </head>
    <body>
        <%
            String errMsg = (String)session.getAttribute("err");
            if(errMsg != null){
                out.println("<div style=\"color:red;\">" + errMsg + "</div>");
                session.removeAttribute("err");
            }
        %>
        <form action="/login">
            用户名:<input type="text" name="username">
            密码:<input type="password" name="password">
            <br>
            <input type="submit" value="登录">
            <input type="reset" value="重填">
        </form>
        <a href="Register.jsp">注册</a>
    </body>
    </html>

Welcome.jsp

<%--
      Created by IntelliJ IDEA.
      User: vina
      Date: 18-4-7
      Time: 下午3:57
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <html>
    <head>
        <title>welcome</title>
    </head>
    <body>
        <%
            String username = (String)session.getAttribute("username");
            if(username != null && !username.isEmpty())
                out.print("你已登录,欢迎");
            else {
                out.print("你还没有登录,3秒后自动跳往登录页面");
                response.setHeader("refresh", "3;url=Login.jsp");
            }
        %>
    </body>
    </html>

以上就是本简易登录模型的全部代码.

记录在此,加深自己这几天对JSP,Servlet,JavaBean和JDBC学习的理解.希望也能帮助到你.共勉!

[20180407195105982]: /images/20220527/b25793cfaf5e4cc482a663ad091602f4.png