4-8编程删除和查找的问题
删除功能和查找功能一点击就会出现500，感觉是判断key值的if语句问题，但是不知道具体为什么，请老师看一下。
DBUtil.java
package com.imooc.db;
import java.util.HashMap;
import java.util.Map;
import com.imooc.bean.Emp;
import com.imooc.bean.User;
public class DBUtil {
public static Map<String,Emp> map=new HashMap<String,Emp>();
public static Map<String,User> users=new HashMap<String,User>();
static {
users.put("admin", new User("admin","123","管理员"));
map.put("101",new Emp("101","开学","请同学们于9月1日前来报道！"));
map.put("102",new Emp("102","选课","开始选课啦~"));
map.put("103",new Emp("103","竞选班委","将于近期竞选班干部~"));
map.put("104",new Emp("104","评选奖学金","评选奖学金啦~"));
}
public static boolean in(User user) {
boolean flag =false;
for(String key:users.keySet()) {
User temp = users.get(key);
if (user.getAccount().equals(temp.getAccount()) && user.getPassword().equals(temp.getPassword())) {
flag = true;
break;
}
}
return flag;
}
public static boolean search(String num) {
boolean flag=false;
for(String key:map.keySet()) {
Emp temp=map.get(key);
if(num.equals(temp.getNum())){
flag=true;
}else {
flag=false;
}
}
return flag;
}
}User.java
package com.imooc.bean;
public class User {
private String account;
private String password;
private String name;
public User() {
super();
}
public User(String account, String password, String name) {
super();
this.account = account;
this.password = password;
this.name = name;
}
public String getAccount() {
return account;
}
public void setAccount(String account) {
this.account = account;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "User [account=" + account + ", password=" + password + ", name=" + name + "]";
}
}Emp.java
package com.imooc.bean;
public class Emp {
private String num;
private String title;
private String text;
public Emp() {
super();
}
public Emp(String num, String title, String text) {
super();
this.num = num;
this.title = title;
this.text = text;
}
public String getNum() {
return num;
}
public void setNum(String num) {
this.num = num;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
@Override
public String toString() {
return "Emp [num=" + num + ", title=" + title + ", text=" + text + "]";
}
}logon.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>登录系统</title> </head> <body> <h3 align=center>登录页面</h3> <hr> <form action="control.jsp"> <table align=center> <tr> <td> 用户名： </td> <td> <input type="text" name="account"> </td> </tr> <tr> <td> 密 码： </td> <td> <input type="password" name="password" /> </td> </tr> <tr> <td> <input type="submit" value="登录" /> </td> </tr> </table> </form> </body> </html>
control.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" import="com.imooc.db.*,com.imooc.bean.*,java.util.*"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String account=request.getParameter("account");
String password=request.getParameter("password");
User user=new User(account,password,null);
boolean flag=DBUtil.in(user);
if(flag){
pageContext.forward("announcement.jsp");
}else{
%>
<div align="center">
<h3>登录失败</h3>
<input type="button" value="back" onclick="location.href='logon.jsp'"/>
</div>
<%
}
%>
</body>
</html>announcements.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" import="com.imooc.db.*,com.imooc.bean.*,java.util.*"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>公告</title>
</head>
<body>
<h3>公告列表为</h3>
<hr>
<form action="search.jsp">
<table align="center" border="1">
<tr>
<td>公告编号:</td>
<td><input type="text" placeholder="请输入要查询的编号" name="num"></td>
<td><input type="submit" value="查 询"></td>
<tr>
</table>
</form>
<hr>
<table align="center" border="1">
<tr>
<td>编号</td>
<td>名称</td>
<td>内容</td>
<td>删除</td>
<td>修改</td>
<tr>
<%
for (Emp e : DBUtil.map.values()) {
%>
<tr>
<td><%=e.getNum()%></td>
<td><%=e.getTitle()%></td>
<td><%=e.getText()%></td>
<td><a href="delete.jsp?num=<%=e.getNum()%>">删除</a></td>
<td><a href="update.jsp?num=<%=e.getNum() %>">修改</a></td>
</tr>
<%
}
%>
</table>
</body>
</html>search.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" import="com.imooc.db.*,com.imooc.bean.*,java.util.*"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>查找</title>
</head>
<body>
<%
String num=request.getParameter("num");
boolean flag=DBUtil.search(num);
if(flag){
Emp e=DBUtil.map.get(num);
%>
<table align="center" border="1">
<tr>
<td>编号</td>
<td>名称</td>
<td>内容</td>
<tr>
<tr>
<td><%=e.getNum() %></td>
<td><%=e.getTitle() %></td>
<td><%=e.getText() %></td>
</tr>
</table>
<div align="center">
<input type="button" value="back" onclick="location.href='announcement.jsp'"/>
</div>
<%
}else{
%>
<h3 align="center">未找到该公告</h3>
<div align="center">
<input type="button" value="back" onclick="location.href='announcement.jsp'"/>
</div>
<%
}
%>
</body>
</html>点击查询按钮出现的问题，自己认为是DBUtil.java里的search函数出了问题，要么就是search.jsp引用函数时出了问题，但不知道具体出在哪里，请老师看一下
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4回答
chrismorgen
2018-10-17 18:34:11
走了一遍所有的流程，只有在删除时，key的值你写成了字符形式，其他都是没有问题的，需要将"key"改为key。
显示效果如下，并且数据内容也是被删除的。
如上所属，你的代码是没有问题的，同学用的是eclipse的内置浏览器吗？如果是，建议使用火狐浏览器或者chrome浏览器，因为eclipse自带的浏览器有bug，推荐你以后测试的时候都使用chrome或者火狐即可，祝学习愉快~
江湖骗子997
2018-10-17 18:10:23
删除时出现500页面，这是错误提示。
An error occurred at line: [12] in the jsp file: [/delete.jsp]
The method search(Emp) in the type DBUtil is not applicable for the arguments (String)
9: <body>
10: <%
11: String key = request.getParameter("num");
12: if (DBUtil.search(key)) {
13: DBUtil.map.remove(key);
14: %>
15: <h3 align ="center">鍒犻櫎鍏憡缂栧彿涓�:<%="key"%></h3>查找也是
An error occurred at line: [12] in the jsp file: [/search.jsp]
The method search(Emp) in the type DBUtil is not applicable for the arguments (String)
9: <body>
10: <%
11: String num=request.getParameter("num");
12: boolean flag=DBUtil.search(num);
13: if(flag){
14: Emp e=DBUtil.map.get(num);
15: %>
chrismorgen
2018-10-17 17:47:51
你好同学，应该将search方法的中的else语句去掉，因为在for循环的if语句中，如果num的值不匹配，就会执行else语句，此时flag的值就一直为false了。
修订之后的效果如下，如果我的建议解决了你的问题，请采纳，祝学习愉快~
江湖骗子997
2018-10-17 12:45:22
delete.jsp
delete.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" import="com.imooc.db.*,com.imooc.bean.*,java.util.*"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String key = request.getParameter("num");
if (DBUtil.search(key)) {
DBUtil.map.remove(key);
%>
<h3 align ="center">删除公告编号为:<%="key"%></h3>
<%
}
%>
<form action="announcement.jsp">
<div align="center">
<input type="button" value="back" onclick="location.href='announcement.jsp'"/>
</div>
</form>
</body>
</html>update.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" import="com.imooc.db.*,com.imooc.bean.*,java.util.*"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
String key = request.getParameter("num");
Emp e =DBUtil.map.get(key);
%>
<h3 align="center">修改公告信息</h3>
<form align="center" action="update_do.jsp">
<table>
<tr>
<td>编号:</td>
<td><input type="text" name="num" value = <%=e.getNum() %>></td>
</tr>
<tr>
<td>标题:</td>
<td><input type="text" name="title"value =<%=e.getTitle() %>></td>
</tr>
<tr>
<td>内容:</td>
<td><input type="text" name="text" value = <%=e.getText() %>></td>
</tr>
<tr>
<td><input type="submit" value="确认修改" href="announcement.jsp"></td>
</tr>
</table>
</form>
</body>
</html>update_do.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8" import="com.imooc.db.*,com.imooc.bean.*,java.util.*"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
Map<String,Emp> map = DBUtil.map;
Emp emp = map.get(request.getParameter("num"));
emp.setTitle(request.getParameter("title"));
emp.setText(request.getParameter("text"));
%>
<div align="center">
<input type="button" value="back" onclick="location.href='announcement.jsp'"/>
</div>
</body>
</html>完整代码这是，请老师指出问题。
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