老师帮看下我的代码，好像有个bug，当输入超过指定长度时会显示插入正常，但是数据库没有信心
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<title>添加数据</title>
<link rel="stylesheet" type="text/css" href="css/addcourse.css">
<script type="text/javascript" src="js/jQuery.js"></script>
<script type="text/javascript" src="js/addcourse.js"></script>
</head>
<body>
<div class="div1">
<div class="div2">
<p class="p1">${requestScope.error}</p>
<p class="p2">课程添加</p>
<form action="${pageContext.request.contextPath}/addsourse" method="post">
<ul>
<li><span>课程名称：</span><input type="text" name="name"></li>
<li><span>所属方向：</span><input type="text" name="category"></li>
<li><span>课程描述：</span><input type="text" name="desc"></li>
<li><input type="submit" name="submit" value="添加"></li>
<li><input type="button" name="search" onclick="window.location.href='${pageContext.request.contextPath}/search'" value="查询所有课程信息"></li>
</ul>
</form>
</div>
</div>
</body>
</html>
package com.liujia.connectionjdbcutils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class ConnectionUtil {
private static final ComboPooledDataSource cpl=new ComboPooledDataSource();
public static Connection getConnection() throws ClassNotFoundException, SQLException {
Connection cnn=cpl.getConnection();
return cnn;
}
public static void releas(Connection cnn,Statement pst) {
if(cnn!=null) {
try {
cnn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(pst!=null) {
try {
pst.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public static void releas(Connection cnn,Statement pst,ResultSet rs) {
if(cnn!=null) {
try {
cnn.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(pst!=null) {
try {
pst.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(rs!=null) {
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
package com.liujia.course;
public class Course {
private int cid;
private String cname;
private String ccategory;
private String cdesc;
private String ctime;
public Course() {
}
public Course(int cid, String cname, String ccategory, String cdesc, String ctime) {
super();
this.cid = cid;
this.cname = cname;
this.ccategory = ccategory;
this.cdesc = cdesc;
this.ctime = ctime;
}
public int getCid() {
return cid;
}
public void setCid(int cid) {
this.cid = cid;
}
public String getCname() {
return cname;
}
public void setCname(String cname) {
this.cname = cname;
}
public String getCcategory() {
return ccategory;
}
public void setCcategory(String ccategory) {
this.ccategory = ccategory;
}
public String getCdesc() {
return cdesc;
}
public void setCdesc(String cdesc) {
this.cdesc = cdesc;
}
public String getCtime() {
return ctime;
}
public void setCtime(String ctime) {
this.ctime = ctime;
}
@Override
public String toString() {
return "[cid=" + cid + ", cname=" + cname + ", ccategory=" + ccategory + ", cdesc=" + cdesc + ", ctime="
+ ctime + "]";
}
}
package com.liujia.service;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import com.liujia.connectionjdbcutils.ConnectionUtil;
import com.liujia.course.Course;
public class Service {
public static boolean Insert(String name,String category,String desc) {
boolean flag=true;
Connection cnn=null;
PreparedStatement pst=null;
try {
cnn=ConnectionUtil.getConnection();
String sql="INSERT INTO course VALUES(null,?,?,?,now())";
pst=cnn.prepareStatement(sql);
pst.setString(1, name);
pst.setString(2, category);
pst.setString(3, desc);
int num=pst.executeUpdate();
System.out.println(num);
if(num>0) {
System.out.println("能正常插入数据库");
flag=true;
}else {
System.out.println("无法插入数据库");
flag=false;
}
}catch(Exception e) {
e.printStackTrace();
}finally {
ConnectionUtil.releas(cnn, pst);
}
return flag;
}
public static List getNews() {
List clist=new ArrayList();
Course course=new Course();
Connection cnn=null;
PreparedStatement pst=null;
ResultSet rs=null;
try {
cnn=ConnectionUtil.getConnection();
String sql="SELECT*FROM course";
pst=cnn.prepareStatement(sql);
rs=pst.executeQuery();
while(rs.next()) {
int id=rs.getInt("id");
String name=rs.getString("name");
String category=rs.getString("category");
String desp=rs.getString("desp");
String ctime=rs.getString("createTime");
clist.add(new Course(id,name,category,desp, ctime));
}
}catch(Exception e) {
e.printStackTrace();
}finally {
ConnectionUtil.releas(cnn, pst,rs);
}
return clist;
}
}
package com.liujia.servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.liujia.service.Service;
/**
* Servlet implementation class addServlet
*/
@WebServlet("/addsourse")
public class addServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public addServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
String name=request.getParameter("name");
String category=request.getParameter("category");
String desc=request.getParameter("desc");
boolean f=Service.Insert(name, category, desc);
if(f) {
System.out.println("插入数据成功");
request.setAttribute("error","数据插入成功！");
request.getRequestDispatcher("/search").forward(request, response);
}else {
System.out.println("插入数据失败");
request.getSession().setAttribute("error","插入失败略略略！");
// response.sendRedirect("/addcourse.jsp");
request.getRequestDispatcher("addcourse.jsp").forward(request, response);
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
package com.liujia.servlet;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.liujia.service.Service;
/**
* Servlet implementation class searchServlet
*/
@WebServlet("/search")
public class searchServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
List cl=Service.getNews();
request.getServletContext().setAttribute("cl", cl);
request.getRequestDispatcher("/showcourse.jsp").forward(request, response);
// response.sendRedirect("/JdbcWebProject/showcourse.jsp");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
.div1{
width:50%;
margin: 0 auto;
text-align: center;
}
.div2{
width:400px;
height: auto;
margin: 0 auto;
text-align: center;
background-color: #DCDCDC;
position: relative;
}
.div2 p{
padding-top: 10px;
}
.div2 .p1{
color: red;
font-size: 30px;
}
.div2 .p2{
font-size: 20px;
font-weight: bold;
}
.div2 li{
margin-top: 10px;
padding-bottom: 10px;
list-style: none;
}
.div2 span{
margin-right: 10px;
}
div{
margin: 0 auto;
text-align: center;
}
.div1 .div2 p{
color: red;
font-size: 30px;
margin-top: 10%;
top: 15px;
position: relative;
}
.div1 .div2{
width: 30%;
height: auto;
background-color: #C0C0C0;
}
.div1 .div2 table{
width: 100%;
background-color: #F5F5F5;
}
.div1 .div2 table tr{
border: 1px solid black;
}
.div1 input{
margin-top:20px;
height:30px;
}
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html>
<html>
<head>
<title>展示数据</title>
<link rel="stylesheet" type="text/css" href="css/show.css">
</head>
<body>
<div class="div1">
<div class="div2">
<p>${requestScope.error}</p>
<table>
<tr>
<td>课程ID</td>
<td>课程名称</td>
<td>所属方向</td>
<td>课程描述</td>
<td>创建时间</td>
</tr>
<c:forEach items="${applicationScope.cl}" var="c" varStatus="idx">
<tr>
<td>${c.cid}</td>
<td>${c.cname}</td>
<td>${c.ccategory}</td>
<td>${c.cdesc}</td>
<td>${c.ctime}</td>
</tr>
</c:forEach>
</table>
</div>
<input type="button" name="search" onclick="window.location.href='${pageContext.request.contextPath}/addcourse.jsp'" value="返回继续添加">
</div>
</body>
</html>
正在回答
同学你好，测试代码，当输入超过指定长度时，程序是会报错的，比如：
报错位置：
报错信息：
这并不是一个bug，而是在当传入的数据超过字段长度限制，数据库就会报错。
在实际开发中，这里的数据长度一般在项目设计的时候，针对字段内容就要考虑到，然后在前端页面或者后台接收数据时就可以加上验证内容。
如果我的回答解决了你的疑惑，请采纳！祝学习愉快！
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