jsp学习笔记3——用户登录系统（mv模式）

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（一）纯jsp开发框图

（二）mv模式框图

（三）技术关键点

以上代码如下：

（1）实现1号线和2号线

// 分页功能,思考——为什么不是返回ResultSet结果集public ArrayList<UserBean> getUsersByPage(int pageNow) {ArrayList<UserBean> al = new ArrayList<UserBean>();try {ConnDB cd = new ConnDB();ct = cd.getConn();sm = ct.createStatement();rs = sm.executeQuery("select * from users limit " + (pageNow - 1)* pageSize + "," + pageSize);// 把结果集封装到ArrayList中while (rs.next()) {// 将rs中的每一条记录封装到UserBean ub,实现一号线UserBean ub = new UserBean();ub.setUserId(rs.getInt(1));ub.setUsername(rs.getString(2));ub.setPasswd(rs.getString(3));ub.setEmail(rs.getString(4));ub.setGrade(rs.getInt(5));al.add(ub);// 实现第二根线,将ub放入到ArrayList中}} catch (Exception e) {e.printStackTrace();} finally {this.closeResource();}return al;}

（2）实现3号线

（四）具体代码

1.模型层

UserBean.java

//这是一个javabean，对应users表，代表数据//其一个实例（对象），对应users表中的一条记录package com.model1;public class UserBean {private int userId;private String username;private String passwd;private String email;private int grade;public int getUserId() {return userId;}public void setUserId(int userId) {this.userId = userId;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPasswd() {return passwd;}public void setPasswd(String passwd) {this.passwd = passwd;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}public int getGrade() {return grade;}public void setGrade(int grade) {this.grade = grade;}}

UserBeanCl.java

//这是一个处理类，有些人把它叫做bo，//主要是封装对users表的各种操作//主要是增、删、改package com.model1;import java.sql.*;import java.util.*;public class UserBeanCl {private Statement sm = null;private ResultSet rs = null;private Connection ct = null;private int pageSize = 3;private int rowCount = 0;private int pageCount = 0;// 验证用户是否合法public boolean checkUser(String u, String p) {boolean b = false;try {ConnDB cd = new ConnDB();ct = cd.getConn();sm = ct.createStatement();rs = sm.executeQuery("select passwd from users where username='"+ u + "'");if (rs.next()) {if (rs.getString(1).equals(p)) {b = true;}}} catch (Exception e) {e.printStackTrace();} finally {this.closeResource();}return b;}// 关闭资源public void closeResource() {// 关闭打开的各种资源try {if (rs != null) {rs.close();rs = null;}if (sm != null) {sm.close();sm = null;}if (ct != null) {ct.close();ct = null;}} catch (SQLException e) {e.printStackTrace();}}// 分页功能,思考——为什么不是返回ResultSet结果集public ArrayList<UserBean> getUsersByPage(int pageNow) {ArrayList<UserBean> al = new ArrayList<UserBean>();try {ConnDB cd = new ConnDB();ct = cd.getConn();sm = ct.createStatement();rs = sm.executeQuery("select * from users limit " + (pageNow - 1)* pageSize + "," + pageSize);// 把结果集封装到ArrayList中while (rs.next()) {// 将rs中的每一条记录封装到UserBean ub,实现一号线UserBean ub = new UserBean();ub.setUserId(rs.getInt(1));ub.setUsername(rs.getString(2));ub.setPasswd(rs.getString(3));ub.setEmail(rs.getString(4));ub.setGrade(rs.getInt(5));al.add(ub);// 实现第二根线,将ub放入到ArrayList中}} catch (Exception e) {e.printStackTrace();} finally {this.closeResource();}return al;}// 返回分页总页数public int getPageCount() {try {// 得到连接ct = new ConnDB().getConn();sm = ct.createStatement();rs = sm.executeQuery("select count(*) from users");// 计算pageCountif (rowCount % pageSize == 0) {pageCount = rowCount / pageSize;} else {pageCount = rowCount / pageSize + 1;}} catch (Exception e) {e.printStackTrace();} finally {this.closeResource();}return pageCount;}}

ConnDB.java //连接数据库

//得到数据库的连接package com.model1;import java.sql.*;public class ConnDB {private Connection ct=null;public Connection getConn(){try{ //1.加载驱动Class.forName("com.mysql.jdbc.Driver");// 加载驱动// 2.得到连接ct = DriverManager.getConnection("jdbc:mysql://localhost:3306/spdb", "root", "root");}catch(Exception e){e.printStackTrace();}return ct;}}

2.视图层

<%@page contentType="text/html;charset=UTF-8" %><html> <head> </head> <body bgcolor="pink"> <center> 用户登录 <br> <hr> <form action="loginCl.jsp" method="post"> 用户名:<input type="text" name="username" ><br> 密码:<input type="password" name="passwd"><br> <input type="submit" value="登录"> <input type="reset" value="重置"> </form> </center> </body></html>

LoginCl.jsp

<%@page contentType="text/html;charset=UTF-8" import="java.sql.*,java.util.*,com.model1.*"%><html> <head> </head> <body> <% //接受用户名和密码，完成对用户的验证 String u=request.getParameter("username"); String p=request.getParameter("passwd"); //到数据库中验证,交给UserBeanCl.java的方法处理 UserBeanCl ubc=new UserBeanCl(); if(ubc.checkUser(u,p)){ response.sendRedirect("wel.jsp"); }else{ response.sendRedirect("login.jsp"); } %> </body></html>

Wel.jsp

<%@page contentType="text/html;charset=UTF-8" import="java.sql.*,java.util.*,com.model1.*"%><html> <body> 登录成功！ <br> <%= request.getParameter("user")%><br> <a href="login.jsp" mce_href="login.jsp">返回重新登录</a> <hr> <center> <h1>用户信息列表</h1><br> <% //=================分页功能================ //1.定义四个分页会用到的变量 int pageNow=1;//默认显示第一页 //接收用户希望显示的页数(pageNow) String s_pageNow=request.getParameter("pageNow"); if(s_pageNow!=null){ //确实接收到pageNow pageNow=Integer.parseInt(s_pageNow); } //调用UserBeanCl()的方法（创建一个UserBean的实例，然后调用它的某个方法），完成分页显示 UserBeanCl ubc=new UserBeanCl(); ArrayList al=ubc.getUsersByPage(pageNow); //5.显示 %> <table border="1"> <tr><td>用户id</td><td>用户名</td><td>密码</td><td>邮件地址</td><td>用户级别</td></tr> <% for(int i=0;i<al.size();i++){//从al中取出UserBean UserBean ub=(UserBean)al.get(i); %> <tr><td><%=ub.getUserId()%></td><td><%=ub.getUsername()%></td><td><%=ub.getPasswd()%></td><td><%=ub.getEmail()%></td><td><%=ub.getGrade()%></td></tr> <% } %> </table> <% //6.显示超链接 int pageCount=ubc.getPageCount(); if(pageNow!=1){ out.print("<a href="wel.jsp?pageNow=1" mce_href="wel.jsp?pageNow=1">首页</a>"); out.print("<a href="wel.jsp?pageNow=" mce_href="wel.jsp?pageNow=""+(pageNow-1)+">上一页</a>"); } for(int i=pageNow;i<=pageNow+3;i++){ out.print("<a href="wel.jsp?pageNow=" mce_href="wel.jsp?pageNow=""+i+">["+i+"]</a>"); } if(pageNow!=pageCount){ out.print("<a href="wel.jsp?pageNow=" mce_href="wel.jsp?pageNow=""+(pageNow+1)+">下一页</a>"); out.print("<a href="wel.jsp?pageNow=" mce_href="wel.jsp?pageNow=""+pageCount+">尾页</a>"); } //=================分页功能================ %> </center> </body></html>