JSP + JDBC 技术对数据库进行增删改查操作

遇到了很多问题：

1.字符编码问题

error：Unknown initial character set index '255' received from server. Initial client character set can be forced via the 'characterEncoding' property.
解决：String url = "jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8";

主要是由于每个jsp文件的编码方式不同，数据库传过来的参数jsp页面无法识别，导致500错误；

2.数据库操作不对应

怪我数据库每学扎实，insert数据的时候忘记了table后面的参数：insert table（sno,sname） value(?,?)；

3.没有进行关联

这个困扰了我很久，驱动也放到了lib文件夹下面，就是一直报错；
解决：右击项目——> build path ——> add jars ——>找到目前项目对应的驱动包的位置即可；

3 问题图片

4.java web项目中如何引入css/js代码

//文件的开始需要写这一段，以便写入绝对路径，相对路径容易访问失败
<%
	String path = request.getContextPath();
	String basePath = request.getScheme() + "://" + request.getServerName() + ":" 
	+ request.getServerPort() +path + "/";
%>

然后head里面加入link即可，我的文档结构： sy3项目名称/css文件名/query.css

<head>
	<link rel = "stylesheet" type = "text/css" href = "/sy3/css/query.css">
</head>

疑问：

① 一个eclipse可以下载多个tomcat么？

答：可以，打开server窗口，需要用哪个tomcat就启动哪个，然后把项目部署到tomcat上，打开网址输入相应的端口号即可。

② 同时下载了mysql与sql server会冲突吗？

答：不会，两个数据库的驱动不一样，把对应的驱动放到lib文件下面，并写入完整的驱动代码即可。

③ 驱动应该怎么下载？版本不对应会影响么？

答：一般没什么影响，我mysql是8.0版本的，驱动是5.0.8版本，可以正常启动。

基本步骤：

① 打开eclipse，新建项目Java web

② 部署驱动到lib文件夹，并与当前的项目关联

③ 写代码

④ 打开server窗口，将项目部署到tomcat中，启动tomcat

⑤ 在浏览器窗户输入ip地址：http://localhost:8080/sy3/mysqlquery.jsp

附：源码

1.mysqlquery.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@page import="java.sql.*"%>
<%
	String path = request.getContextPath();
	String basePath = request.getScheme() + "://" + request.getServerName() + ":" 
	+ request.getServerPort() +path + "/";
%>
<html>
<head>
	<link rel = "stylesheet" type = "text/css" href = "/sy3/css/query.css">
</head>
<body>
<div class = "dv1" align = "center">
	<span class="title">MYSQL数据库连接</span>
</div>
<%!   
  public static final String DBDRIVER="com.mysql.jdbc.Driver";
  
  public static final String DBURL="jdbc:mysql://localhost:3306/test?characterEncoding=utf8";
  public static final String DBUSER="root";
  public static final String DBPASS="imshsyxxarsh";
%>
<% 
   Connection conn=null;
   PreparedStatement pstmt=null;
   ResultSet rs=null;

   Class.forName(DBDRIVER);		//
   conn=DriverManager.getConnection(DBURL,DBUSER,DBPASS);	//�������Ӷ���
   String sql="select * from xs";
   pstmt=conn.prepareStatement(sql);		//��ӡ�ɾ�����޸�
   rs=pstmt.executeQuery();
%>

<div class = "dv2" align = "center">
	<table class = "table">
	   <tr style = "background-color:#FF6666; height:60px; color:white;">
	      <td width = "33%">学号</td>
	      <td width = "33%">姓名</td>
	      <td>编辑</td>
	   </tr>
	<%
	   int num=1; 
	   while(rs.next()){
	   if(num%2!=0) {
	%>
	     <tr>
	        <td  style = "height:60px;">
	          <%=rs.getString("sno") %>
	        </td>
	        <td>
	          <%=rs.getString("sname") %>
	        </td>
	        <td>
	           <a class = "lik" href="mysqlupdate.jsp?sno=<%=rs.getString("sno")%>&&sname=<%=rs.getString("sname")%>">update</a>&nbsp;&nbsp;<a class = "lik" href="mysqldelete.jsp?sno=<%=rs.getString("sno")%>">delete</a>
	        </td>
	     </tr>
	<% 
	   }else {
	%>
		   <tr  style = "background-color:#FFCCCC; height:60px;"> 
	        <td>
	          <%=rs.getString("sno") %>
	        </td>
	        <td>
	          <%=rs.getString("sname") %>
	        </td>
	        <td>
	           <a class = "lik" href="mysqlupdate.jsp?sno=<%=rs.getString("sno")%>&&sname=<%=rs.getString("sname")%>">update</a>&nbsp;&nbsp;<a class = "lik" href="mysqldelete.jsp?sno=<%=rs.getString("sno")%>">delete</a>
	        </td>
	     </tr>
	 <% 
	   }
	   num++;
	  }
	%>   
	</table>
	<br><br>
	<div class = "lik2"><a class="title2" href="mysqlinsert.html">添加学生基本信息</a></div>
</div>
<%
     rs.close();
     pstmt.close();
     conn.close();
 %>
</body>
</html>

2. mysqldelete.jsp

<%@ page language="java" import="java.util.*,java.sql.*" pageEncoding="utf-8"%>
<html>
  <head>
  </head>
  <body>
<%
   String sno=request.getParameter("sno");
%>
<%!   
  public static final String DBDRIVER="com.mysql.jdbc.Driver";
  
  public static final String DBURL="jdbc:mysql://localhost:3306/test?characterEncoding=utf8";
  public static final String DBUSER="root";
  public static final String DBPASS="imshsyxxarsh";
%>
<% 
   Connection conn=null;
   PreparedStatement pstmt=null;
   ResultSet rs=null;

   Class.forName(DBDRIVER);
   conn=DriverManager.getConnection(DBURL,DBUSER,DBPASS);
   String sql="delete from xs where sno=?";
   pstmt=conn.prepareStatement(sql);
   pstmt.setString(1,sno);
   pstmt.executeUpdate();
%> 
<%
   pstmt.close();
   conn.close();
   response.sendRedirect("mysqlquery.jsp");
%>      
  </body>
</html>

3.mysqlinsert.jsp

<%@ page language="java" import="java.util.*,java.sql.*" pageEncoding="utf-8"%>
<body>
<%
   //request.setCharacterEncoding("utf-8");
   String sno=request.getParameter("usernum");
   String sname=request.getParameter("username");
   
   String sname1="章";
   System.out.println(sname1);

   sname=new String(sname.getBytes("ISO-8859-1"), "gb2312");
   System.out.println(sname);
   
%>
<%!   
  public static final String DBDRIVER="com.mysql.jdbc.Driver";
  
  public static final String DBURL="jdbc:mysql://localhost:3306/test?characterEncoding=utf-8";
  public static final String DBUSER="root";
  public static final String DBPASS="imshsyxxarsh";
%>
<% 
   Connection conn=null;
   PreparedStatement pstmt=null;
   ResultSet rs=null;

   Class.forName(DBDRIVER);
   conn=DriverManager.getConnection(DBURL,DBUSER,DBPASS);
   String sql="insert into xs(sno,sname) values(?,?)";
   pstmt=conn.prepareStatement(sql);
   pstmt.setString(1,sno);
   pstmt.setString(2,sname);
   pstmt.executeUpdate();
%> 
<%
   pstmt.close();
   conn.close();
   response.sendRedirect("mysqlquery.jsp");
%>   
  </body>

4.mysqlinsert.html

<head>
	<link href = "/sy3/css/query.css" rel = "stylesheet" type = "text/css">
</head>
<body>
<div class = "submit" align = "center">
    <form action="mysqlinsert.jsp" method="post">
    <table class = "table2">
    	<tr height = "60px;">
    		<td width = "150px" align = "right">学号 ：</td>
    		<td><input class = "put" type="text" name="usernum"></td>
    	</tr>
    	<tr height = "60px;">
    		<td  align = "right"> 姓名：</td>
    		<td><input class = "put" type="text" name="username"></td>
    	</tr>
    	<tr height = "60px;" align = "center">
    		<td colspan = "2"><input class = "sub" type="submit" value="提交 "></td>
    	</tr>
    </table>
    </form> 
</div>
</body>

5.mysqlupdate.jsp

<%@ page language = "java" pageEncoding = "utf-8" %>
<head>
	<link href = "/sy3/css/query.css" rel = "stylesheet" type = "text/css">
</head>
<body>
<% 
   
   String sname=request.getParameter("sname");
   //byte b[]=sname.getBytes("ISO-8859-1");
   //sname=new String(b);
   sname=new String(sname.getBytes("ISO-8859-1"),"gb2312");
%>  
<div class = "submit" align = "center">
    <form action="mysqlupdate1.jsp" method="post">
    <table class = "table2">
    	<tr height = "60px;">
    		<td width = "150px" align = "right">学号 ：</td>
    		<td><input class = "put" type="text" name="usernum" value="<%=request.getParameter("sno")%>"></td>
    	</tr>
    	<tr height = "60px;">
    		<td  align = "right"> 姓名：</td>
    		<td><input class = "put" type="text" name="username" value="<%=sname%>"></td>
    	</tr>
    	<tr height = "60px;" align = "center">
    		<td colspan = "2"><input class = "sub" type="submit" value="提交 "></td>
    	</tr>
    </table>
   </form>
</div>
  </body>
</html>

6.mysqlupdate1.jsp

<%@ page language="java" import="java.util.*,java.sql.*" pageEncoding="utf-8"%>

<html>
  <head>    
  </head>
  <body>
<%
   request.setCharacterEncoding("utf-8"); 
   String sno=request.getParameter("usernum");
   String sname=request.getParameter("username");
 
%>
<%!   
  public static final String DBDRIVER="com.mysql.jdbc.Driver";
  
  public static final String DBURL="jdbc:mysql://localhost:3306/test?characterEncoding=utf8";
  public static final String DBUSER="root";
  public static final String DBPASS="imshsyxxarsh";
%>
<% 
   Connection conn=null;
   PreparedStatement pstmt=null;
   ResultSet rs=null;

   Class.forName(DBDRIVER);
   conn=DriverManager.getConnection(DBURL,DBUSER,DBPASS);
   String sql="update xs set sname=? where sno=?";
   pstmt=conn.prepareStatement(sql);
   pstmt.setString(2,sno);
   pstmt.setString(1,sname);
   pstmt.executeUpdate();
%> 
<%
   pstmt.close();
   conn.close();
   response.sendRedirect("mysqlquery.jsp");
%>   <br>
  </body>
</html>

7.query.css

@charset "UTF-8";
body{
	color:#666666;
}
.title{
	display:block;
	width:400px;
	margin:auto;
	margin-top:80px;
	color:#666666;
	border:2px;
	font-size:40px;
	font-weight:bold;
}
a{
	text-decoration:none;
}
.lik{
	color:#993366;
}
.dv1{
	width:100%;
	height:120px;
	border:2px;
}
.dv2{
	width:100%;
}
.lik2{
	width:200px;
	height:35px;
	border-radius:14px;
	padding-top:5px;
	background-color:#FF6666;
}
.title2{
	font-size:20px;
	font-weight:blod;
	color:white;
	margin:auto;
}
.table{
	width:80%;
	border:1px solid #ffcece;
}
.submit{
	 background:#ffcece;
	 height:600px; 
	 padding-top:200px;
}
.put{
	width:300px;
	height: 40px;
}
.sub{
	border:none; 
	background:#FF6666; 
	width:70px; 
	height:30px; 
	color:white; 
	font-size:15px;
}
.table2{
	font-size:15px; 
	font-weight:bold; 
	align:center; 
	width:40%;
}

深深记得老师的话：你就不听我讲，这能学会啦？？？那魔性的声音，我相信，他不会看的，hhhh，我偏偏要学会，能咋地，丢了老脸又何妨？

告大家一个小秘密：我们东来老师，，，还喷香水，，，，hhhhhhh

JSP + JDBC 技术对数据库进行增删改查操作

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