无法使用: “Bean 无法解析为类型”

发布于 2024-12-18 23:27:36 字数 1576 浏览 3 评论 0原文

我只是在玩JSP。我只是想测试一些东西，但我不能。每次如果我使用，我都会收到错误。即使我只有这个，我也会收到一个错误：

<%@ 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>

没有它运行正常。使用我收到如下错误：

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。

有什么想法吗？

PS：我不得不将端口8xxx更改为9xxx，因为oracle DB使用标准8xxx。但这可能不是问题的原因。

原文

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>

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>

I am using Eclipse, Tomcat 7.0.23 and Java 1.7.0_01.

Any ideas?

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.

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高速公鹿 2024-12-25 23:27:36

您需要将类放入包中，以便能够在其他类中使用它们。默认包中的类对于包中的类是不可见的（就像 JSP 最终的结果）。

因此，为 Users 类提供一个 package，如下所示：

package com.example;

public class Users {
    // ...
}

重新编译并将其放入 /WEB-INF/classes/com/example/Users.class。

然后您可以按如下方式引用它：

<jsp:useBean id="myBean" class="com.example.Users" />

与具体问题无关，使用复数作为实体的类名通常是一种味道。该类的单个实例真的代表多个用户吗？例如，为什么您没有 List ？或者它实际上代表单个用户？然后应将其命名为 User。

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).

So, give the Users class a package like so:

package com.example;

public class Users {
    // ...
}

Recompile and put it in /WEB-INF/classes/com/example/Users.class.

Then you can reference it as follows:

<jsp:useBean id="myBean" class="com.example.Users" />

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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