JSP数据库综合练习

2021-11-04 06:31:29

一.问题概述

        实现了数据库的增删改查和分页显示。

        分页显示:mysql



String cmd = "select * from t_user limit "+firstResult+","+pageSize;





mysql> SELECT * FROM table LIMIT 5,10; // 检索记录行 6-15 



--为了检索从某一个偏移量到记录集的结束所有的记录行，可以指定第二个参数为 -1： 



mysql> SELECT * FROM table LIMIT 95,-1; // 检索记录行 96-last. 



--如果只给定一个参数，它表示返回最大的记录行数目： 



mysql> SELECT * FROM table LIMIT 5; //检索前 5 个记录行 



--换句话说，LIMIT n 等价于 LIMIT 0,n。 
                  分页显示:sql server 




select top 10 * from table --这是选出前10条



select top 100 *from table where id not in(select Top 50 id from table)



--这是选出第51到100条,使用存储过程也好。



        文档结构如下：



            JSP数据库综合练习



二.代码实现 
    





<!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>



<form action="insert.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 colspan="2"><input type="submit" value="提交"/> </td>



	</tr>



</table>



	



</form>



</body>



</html>





<%@page import="java.sql.Statement"%>



<%@page import="java.sql.DriverManager"%>



<%@page import="java.sql.Connection"%>



<%@ page language="java" contentType="text/html; charset=UTF-8"



    pageEncoding="UTF-8"%>



<%



	String username = request.getParameter("username");



	String password = request.getParameter("password");



	



	String cmd = "insert into t_user (username,password) values('"+username+"','"+password+"')";



	int count = 0;



	try{



		Class.forName("com.mysql.jdbc.Driver");



		String url= "jdbc:mysql://127.0.0.1/db_user";



		String uid = "root";



		String pwd = "root";



		Connection conn = DriverManager.getConnection(url,uid,pwd);



		Statement st = conn.createStatement();



		count = st.executeUpdate(cmd);



		conn.close();



	}catch(Exception e){



		e.printStackTrace();



	}



	if(count>0) response.sendRedirect("list.jsp");



	else response.sendRedirect("error.jsp");



%>





<%@page import="java.sql.ResultSet"%>



<%@page import="java.sql.Statement"%>



<%@page import="java.sql.DriverManager"%>



<%@page import="java.sql.Connection"%>



<%@ 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>



	<a href="fill.html">添加新人员</a>



	<br />



	<table border="1">



		<tr>



			<td>ID</td>



			<td>username</td>



			<td>password</td>



			<td>操作</td>



		</tr>



		<%



	String pageNum = request.getParameter("pageNum");



	int rowCount = 0;//数据库表总纪录数



	int pageSize = 3;//每页显示纪录数，假设为3



	int pageCount =0;//共有多少页



	//pn做pageNum的中间变量使用的



	int pn = 1;



	if(null != pageNum && pageNum.length()>0)



		pn = Integer.parseInt(pageNum);



	



	



	try{



		Class.forName("com.mysql.jdbc.Driver");



		String url = "jdbc:mysql://127.0.0.1/db_user";



		String uid = "root";



		String pwd = "root";



		Connection conn = DriverManager.getConnection(url,uid,pwd);



		



		Statement st2 = conn.createStatement();



		String cmd2 = "select count(*) from t_user ";



		ResultSet rs2 = st2.executeQuery(cmd2);



		if(rs2.next()){



			rowCount = rs2.getInt(1);



		}



		rs2.close();



		



		pageCount = rowCount%pageSize ==0 ? (rowCount/pageSize) : (rowCount/pageSize+1);



		if(pn < 1 ) pn = 1;



		if(pn >pageCount) pn = pageCount;



		



		int firstResult = (pn-1)*pageSize;



		



		



		Statement st = conn.createStatement();



		/*MySql数据库有limit关键字，注意用法



		第一个参数是从0开始的，不是一



		SELECT * FROM table LIMIT 5,10; // 检索记录行 6-15 



		*/



		String cmd = "select * from t_user limit "+firstResult+","+pageSize;



		ResultSet rs = st.executeQuery(cmd);



		while(rs.next()){



			



%>



		<tr>



			<td><%=rs.getInt(1) %></td>



			<td><%=rs.getString(2) %></td>



			<td><%=rs.getString(3) %></td>



			<td>



				<a href="edit.jsp?id=<%=rs.getInt(1) %>">编辑</a> 



				<a href="delete.jsp?id=<%=rs.getInt(1) %>"> 删除</a>



			</td>



		</tr>



		<%			



		}



		conn.close();



		



	}catch(Exception e){



		e.printStackTrace();



	}



%>



		<tr>



			<td colspan="4">共有<%=rowCount %>条记录，每页显示<%=pageSize %>条记录，共显示<%=pageCount %>页，当前是第<%=pn %>页。



			</td>





		</tr>



		<tr>



			<td colspan="4"><a href="list.jsp?pageNum=1">第一页</a> 



				<a href="list.jsp?pageNum=<%=pn-1 %>">上一页</a> 



				<a href="list.jsp?pageNum=<%=pn+1 %>">下一页</a> 



				<a href="list.jsp?pageNum=<%=pageCount %>">最后页</a>



			</td>



		</tr>



	</table>



</body>



</html>





<%@page import="java.sql.ResultSet"%>



<%@ page language="java" contentType="text/html; charset=UTF-8"



    pageEncoding="UTF-8"%>



<%@page import="java.sql.Statement"%>



<%@page import="java.sql.DriverManager"%>



<%@page import="java.sql.Connection"%>    



<!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 id = request.getParameter("id");



String username = "";



String password = "";



try{



	Class.forName("com.mysql.jdbc.Driver");



	String url= "jdbc:mysql://127.0.0.1/db_user";



	String uid = "root";



	String pwd = "root";



	Connection conn = DriverManager.getConnection(url,uid,pwd);



	Statement st = conn.createStatement();



	String cmd = "select * from t_user where id="+id;



	ResultSet rs = st.executeQuery(cmd);



	if(rs.next()){



		username = rs.getString(2);



		password = rs.getString(3);



	}



	conn.close();



}catch(Exception e){



	e.printStackTrace();



}





%>





<form action="update.jsp" method="post">



<input type="hidden" name="id" value="<%=id %>"/>



<table>





	<tr>



		<td>用户名：</td>



		<td><input type="text" name="username" value="<%=username %>"></td>



	</tr>



	<tr>



		<td>密码：</td>



		<td><input type="text" name="password" value="<%=password %>"></td>



	</tr>



	<tr>



		<td colspan="2"><input type="submit" value="提交"/> </td>



	</tr>



</table>



	



</form>



</body>



</html>





<%@ page language="java" contentType="text/html; charset=UTF-8"



    pageEncoding="UTF-8"%>



<%@page import="java.sql.Statement"%>



<%@page import="java.sql.DriverManager"%>



<%@page import="java.sql.Connection"%>



<%



	int count = 0;



	String id = request.getParameter("id");



    if(null != id && id.length()>0){



	



		String cmd = "delete from t_user where id="+id;



		try{



			Class.forName("com.mysql.jdbc.Driver");



			String url= "jdbc:mysql://127.0.0.1/db_user";



			String uid = "root";



			String pwd = "root";



			Connection conn = DriverManager.getConnection(url,uid,pwd);



			Statement st = conn.createStatement();



			count = st.executeUpdate(cmd);



			conn.close();



		}catch(Exception e){



			e.printStackTrace();



		}



    }



	if(count>0) response.sendRedirect("list.jsp");



	else response.sendRedirect("error.jsp");



%>





<%@ page language="java" contentType="text/html; charset=UTF-8"



    pageEncoding="UTF-8"%>



<%@page import="java.sql.Statement"%>



<%@page import="java.sql.DriverManager"%>



<%@page import="java.sql.Connection"%>



<%



	int count = 0;



	String id = request.getParameter("id");



	String username = request.getParameter("username");



	String password = request.getParameter("password");



	if(null != id && id.length()>0){



	



		String cmd = "update t_user set username='"+username+"',password='"+password+"' where id="+id;



		try{



			Class.forName("com.mysql.jdbc.Driver");



			String url= "jdbc:mysql://127.0.0.1/db_user";



			String uid = "root";



			String pwd = "root";



			Connection conn = DriverManager.getConnection(url,uid,pwd);



			Statement st = conn.createStatement();



			count = st.executeUpdate(cmd);



			conn.close();



		}catch(Exception e){



			e.printStackTrace();



		}



	}



	if(count>0) response.sendRedirect("list.jsp");



	else response.sendRedirect("error.jsp");



%>





<?xml version="1.0" encoding="UTF-8"?>



<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">



  <display-name>db</display-name>



  <welcome-file-list>



    <welcome-file>index.html</welcome-file>



    <welcome-file>index.htm</welcome-file>



    <welcome-file>index.jsp</welcome-file>



    <welcome-file>default.html</welcome-file>



    <welcome-file>default.htm</welcome-file>



    <welcome-file>default.jsp</welcome-file>



  </welcome-file-list>



</web-app>
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