JSP数据库综合练习

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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