不能使用< jsp:useBean> ;:"Bean无法解析为类型" [英] Can't use <jsp:useBean>: "Bean cannot be resolved to a type"
问题描述
我只是在玩JSP.我只是想测试一些<jsp:useBean>东西，但不能.每次使用<jsp:useBean>时，都会出现错误.即使我只有这个，也会出现错误:
I'm just playing around with JSP. I just wanted to test some <jsp:useBean> stuff, but I can't. Every time if I'm using <jsp:useBean>, I get an error. Even if I just have this, I get an error:
<%@ 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>Test</title>
</head>
<body>
<jsp:useBean id="mybean" class="Users" scope="session" >
<jsp:setProperty name="mybean" property="name" value="Hello world" />
</jsp:useBean>
</body>
</html>
没有<jsp:useBean>，它运行正常.出现<jsp:useBean>时，出现类似以下错误:
Without the <jsp:useBean> it runs fine. With the <jsp:useBean> I get an error like:
Servlet.service() for servlet [jsp] in context with path [/JSPTest] threw exception [Unable to compile class for JSP:
An error occurred at line: 10 in the jsp file: /index.jsp
Users cannot be resolved to a type
7: <title>Insert title here</title>
8: </head>
9: <body>
10: <jsp:useBean id="mybean" class="Users" scope="session" >
11: <jsp:setProperty name="mybean" property="name" value="Hello world" />
12: </jsp:useBean>
13: </body>
我正在使用Eclipse，Tomcat 7.0.23和Java 1.7.0_01.
I am using Eclipse, Tomcat 7.0.23 and Java 1.7.0_01.
有什么想法吗?
PS:我必须将端口8xxx更改为9xxx，因为oracle DB使用的是标准8xxx.但这可能不是问题的原因.
PS: I had to change the port 8xxx to 9xxx because the oracle DB is using the standard 8xxx. But that's likely not the cause of the problem.
推荐答案
您需要将类放入包中，以便能够在其他类中使用它们.缺省包中的类对于单独存在于包中的类是不可见的(就像JSP最终会出现的那样).
You need to put classes in a package in order to be able to use them in another classes. Classes in the default package are invisible to classes which are by itself in a package (like as the JSP would end up).
因此，像这样为Users类提供package:
So, give the Users class a package like so:
package com.example;
public class Users {
// ...
}
重新编译并将其放入/WEB-INF/classes/com/example/Users.class.
然后您可以按以下方式引用它:
Then you can reference it as follows:
<jsp:useBean id="myBean" class="com.example.Users" />
无关与具体问题无关，将复数作为实体的类名称通常是一种气味.该类的单个实例是否真的代表多个用户?例如，为什么没有List<User>?还是实际上代表一个用户?然后应将其命名为User.
Unrelated to the concrete problem, having a plural as class name of an entity is usually a smell. Does a single instance of that class really represent multiple users? Why would you not have a List<User> for example? Or does it actually represent a single user? It should then be named User instead.
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