无法为JSP编译类：无法解析为类型 [英] Unable to compile class for JSP: cannot be resolved to a type
问题描述
我正在开发一个动态网络项目。项目在本地服务器上运行良好但不在线上运行。在实时服务器上，它在我使用任何java对象的行抛出异常：
I am developing a Dynamic web project. Project is running well on local server but not on live. On live server it throws exception at the line I have used any java object:
org.apache.jasper.JasperException：无法为JSP编译类：
org.apache.jasper.JasperException: Unable to compile class for JSP:
An error occurred at line: 7 in the jsp file: /groups.jsp
CollectionAppService cannot be resolved to a type
4: <%
5: String json = "[]";
6: try {
7: CollectionAppService collectionAppService = new CollectionAppService();
8: json = collectionAppService.getGroupsJson();
9: } catch (Exception e) {
10: e.printStackTrace();
项目在本地服务器上运行，但在最大类文件的错误日志中也有错误：
Project run on local server but also have errors in error log for max class files:
错误：
Thu Sep 20 01:16:11 GMT+05:30 2012
File not found: /Users/sukhpal/Data/Workspaces/J2EE Workspace/CollectionApp/build/classes/com/mut/service/common/Constants.class.
请帮助。（在我的实时服务器上启用Tomcat）。
Please help.(Tomcat is enabled on my live server).
以下是实时服务器的链接
http://mutmanager.com/ webservice / groups.jsp
Following is link of live server http://mutmanager.com/webservice/groups.jsp
推荐答案
您好像忘记导入 CollectionAppService 在您的JSP中：
It looks like you forgot to import your CollectionAppService in your JSP:
<%@ page import="your.package.CollectionAppService" %>
但是，存在一个主要问题，你不应该在JSP中加入Java代码。相反，您应该将代码移动到类并从Servlet或类似代码调用它。
But, there is a major problem, you should not put Java code in your JSP. Instead, you should move your code to a class and invoke it from a Servlet or similar.
主要文章：
- How to avoid Java Code in JSP-Files?
不要忘记学习是好的，但也要以正确的方式学习。
Do not forget that learning is good, but also learning in the right way.
再次阅读你的问题后，我看到这个Stacktrace行：
After read your question again, I see this Stacktrace line:
找不到文件：/ Users / sukhpal / Data / Workspaces / J2EE Workspace / CollectionApp / build / classes / com / mut / service / common / Constants.class
File not found: /Users/sukhpal/Data/Workspaces/J2EE Workspace/CollectionApp/build/classes/com/mut/service/common/Constants.class
我想你的问题是常量类（以及你的 CollectionApp ）也在项目B中。你是使用来自包含这些类的另一个项目的绝对路径引用，也许你没有上传它。
I guess that your problem is Constant class (and your CollectionApp as well) is inside a project B. You're using absolute path references from another project that contains these classes and maybe you're not uploading it.
想象一下这种情况：你有一个web项目（项目A）和你有一些 已经在另一个项目（项目B）中完成繁重工作的类，您可以在大多数项目中重复使用这些项目。在开发环境中，您有从项目A到项目B的引用，但之后只将项目A上载到生产环境。这样，当项目A想要从项目B调用一个类时，它将永远不会找到它，并抛出异常。
Imagine this situation: You have a web project (project A) and you have some classes that already do a heavy and fancy job in another project (project B) that you reuse on most projects you work on. In your development environment, you have a reference from project A to project B, but then you only upload project A to your production environment. In this way, when project A wants to call a class from project B, it will never find it, and the exception is thrown.
最佳解决方案：
- 从项目B创建一个jar。
- 在项目A中，删除对项目B的所有引用。
- 将jar添加到项目A并在Build Path中设置。
- 将项目A上传到生产。
- Create a jar from project B.
- In project A, remove all the references to project B.
- Add the jar into project A and set it in the Build Path.
- Upload your project A to production.
这篇关于无法为JSP编译类：无法解析为类型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
