model1纯JSP（实现分页）

Login.jsp  ----LoginCL.jsp-----跳转

Login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录界面</title>
</head>
<body>
<form action="LoginCl.jsp" method="post">
<table >
                <tr><td>用户名</td><td><input type="text" name="username"/></td></tr>
                <tr><td>密    码</td><td><input type="text" name="password"/></td></tr>
                <tr><td><input type="submit" value="登录" /></td><td><input type="reset" value="清空"/></td></tr>
            </table>
</form>
</body>
</html>
View Code

LoginCL.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"
    import="java.sql.*"
    %>
    
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String name=request.getParameter("username");
String password=request.getParameter("password");

Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;

    Class.forName("com.mysql.jdbc.Driver");
    conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/user", "root", "123456");

    String sql = "select* from user where username=? and password=?";
    ps = conn.prepareStatement(sql);
    ps.setString(1, name);
    ps.setString(2, password);
   out.println(sql);
    // 结果
    rs = ps.executeQuery();
    if (rs.next()) {
        out.println(rs.getString(1) + " " + rs.getString(2));
    } else {
       out.println("登陆失败");
    }
%>
</body>
</html>
View Code

 改进版:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"
    import="java.sql.*"
    %>
    
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String name=request.getParameter("username");
String password=request.getParameter("password");

Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try{
    Class.forName("com.mysql.jdbc.Driver");
    conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/user", "root", "123456");

    String sql = "select* from user where username=? and password=?";
    ps = conn.prepareStatement(sql);
    ps.setString(1, name);
    ps.setString(2, password);
    // 结果
    rs = ps.executeQuery();
    if (rs.next()) {
        if(rs.getString(2).equals(name)&&rs.getString(5).equals(password)){
            out.print("登陆成功");
        }else{
            out.print("账号或者密码错误");
        } 
    } else {
       out.println("登陆失败,重新登陆");
    }}catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            rs.close();
            ps.close();
            conn.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }}
%>
</body>
</html>
View Code

 标准版：

LoginCL.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"
    import="java.sql.*"
    %>
    
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String name=request.getParameter("username");
String password=request.getParameter("password");

Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try{
    Class.forName("com.mysql.jdbc.Driver");
    conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/user", "root", "123456");

    String sql = "select password from user where username=? ";
    ps = conn.prepareStatement(sql);
    ps.setString(1, name);
    // 结果
    rs = ps.executeQuery();
    if (rs.next()) {
        if(rs.getString(1).equals(password))
            {out.print("登陆成功");
            response.sendRedirect("Main.jsp?user="+name);
            }else{
                out.print("密码错误");
                response.sendRedirect("Login.jsp?error=1");    
            }
    } else {
        response.sendRedirect("Login.jsp?error=2");    
       out.println("账号错误 ,重新登陆");
    }}catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            rs.close();
            ps.close();
            conn.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }}
%>
</body>
</html>
View Code

Login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录界面</title>
</head>
<body>
<form action="LoginCl.jsp" method="post">
<table >
                <tr><td>用户名</td><td><input type="text" name="username"/></td></tr>
                <tr><td>密    码</td><td><input type="text" name="password"/></td></tr>
                <tr><td><input type="submit" value="登录" /></td><td><input type="reset" value="清空"/></td></tr>
            </table>
</form>
</body>
</html>
View Code

Main.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
欢迎来到新的页面！
</body>
</html>
View Code

实现分页版：

Login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登录界面</title>
</head>
<body>
<form action="LoginCl.jsp" method="post">
<table >
                <tr><td>用户名</td><td><input type="text" name="username"/></td></tr>
                <tr><td>密    码</td><td><input type="text" name="password"/></td></tr>
                <tr><td><input type="submit" value="登录" /></td><td><input type="reset" value="清空"/></td></tr>
            </table>
</form>
</body>
</html>
View Code

LoginCl.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"
    import="java.sql.*"
    %>
    
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String name=request.getParameter("username");
String password=request.getParameter("password");
out.print(name+"  "+password);
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try{
    Class.forName("com.mysql.jdbc.Driver");
    conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/user", "root", "123456");

    String sql = "select password from user where username=? ";
    ps = conn.prepareStatement(sql);
    ps.setString(1, name);
    // 结果
    rs = ps.executeQuery();
    if (rs.next()) {
        if(rs.getString(1).equals(password))
            {out.print("登陆成功");
            response.sendRedirect("http://localhost:8080/practice/Welcom.jsp?pageNow=1");
            }else{
                out.print("密码错误");
                response.sendRedirect("Login.jsp?error=1");    
            }
    } else {
        response.sendRedirect("Login.jsp?error=2");    
       out.println("账号错误 ,重新登陆");
    }}catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            rs.close();
            ps.close();
            conn.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }}
%>
</body>
</html>
View Code

Welcom.jsp(分页)

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"
    import="java.sql.*"
    %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
欢迎来到新的页面！ <a href="Login.jsp">返回主页面</a>
   <hr/>
<%
//定义分页可以用到的变量
int pageSize=3;
int pageNow=1;
int rowCount=0;
int pageCount=0;
String page1=request.getParameter("pageNow");
if(page!=null){
    pageNow=Integer.parseInt(page1);
}
String name=request.getParameter("user");
//查询得到
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try{
    Class.forName("com.mysql.jdbc.Driver");
    conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/user", "root", "123456");

    String sql = "select count(*) from user";
    ps = conn.prepareStatement(sql);
    // 结果
    rs = ps.executeQuery();
    if (rs.next()) {//next不要忘了
        rowCount=rs.getInt(1);
        out.print(rowCount);
    }     
    ps.close();
    rs.close();
    //计算PageCount
    if(rowCount%pageSize==0){
        pageCount=rowCount/pageSize;
    }else {
        pageCount=rowCount/pageSize+1;
    }
    out.print("pageCount="+pageCount);
    //查询出需要显示的页面
    if(rowCount>=pageNow*pageSize){
        sql="select *from user limit "+(pageNow-1)*pageSize+","+pageSize;        
    }
    else{
        sql="select *from user limit "+(pageNow-1)*pageSize+","+(rowCount-(pageNow-1)*pageSize);
    }
    out.print(sql);
            ps = conn.prepareStatement(sql);
    // 结果
    rs = ps.executeQuery();  
   %>
   <table border="1px" >
  <tr><td>用户ID</td><td>用户名</td><td>邮箱</td><td>等级</td><td>密码</td></tr>
   <%
   while(rs.next()){
      %>
      <tr><td><%=rs.getInt(1)%></td><td><%=rs.getString(2)%></td><td><%=rs.getString(3)%></td><td><%=rs.getInt(4)%></td><td><%=rs.getString(5)%></td></tr>
      <%  
   }
   %>
   </table>
   <%
   if(pageNow!=1){
   out.print("<a href='Welcom.jsp?pageNow="+(pageNow-1)+"'>上一页</a>");}
   //显示超链接
   for(int i=1;i<=pageCount;i++){
       out.print("<a href='Welcom.jsp?pageNow="+i+"'>["+i+"]</a>");
   }
   if(pageNow!=pageCount){
   out.print("<a href='Welcom.jsp?pageNow="+(pageNow+1)+"'>下一页</a>");}
    }catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            rs.close();
            ps.close();
            conn.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        }
%>
<hr/>
</body>
</html>
View Code

 缺点分析;

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原文地址：https://www.cnblogs.com/helloworld2019/p/11052328.html