java - 加载程序约束违规

Question

我在一个项目中遇到了两次相同的 .jar(对我来说是 el-api.jar v2.1)的问题，因此，当我尝试使用 Tomcat 6 运行我的项目时出现以下错误堆栈。

WARNING: Unexpected error forwarding to login page
javax.servlet.ServletException: java.lang.LinkageError: loader constraint violation: when resolving interface method "javax.servlet.jsp.JspApplicationContext.getExpressionFactory()Ljavax/el/ExpressionFactory;" the class loader (instance of org/apache/jasper/servlet/JasperLoader) of the current class, org/apache/jsp/login_jsp, and the class loader (instance of org/apache/catalina/loader/StandardClassLoader) for resolved class, javax/servlet/jsp/JspApplicationContext, have different Class objects for the type javax/el/ExpressionFactory used in the signature

 at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.LinkageError: loader constraint violation: when resolving interface method "javax.servlet.jsp.JspApplicationContext.getExpressionFactory()Ljavax/el/ExpressionFactory;" the class loader (instance of org/apache/jasper/servlet/JasperLoader) of the current class, org/apache/jsp/login_jsp, and the class loader (instance of org/apache/catalina/loader/StandardClassLoader) for resolved class, javax/servlet/jsp/JspApplicationContext, have different Class objects for the type javax/el/ExpressionFactory used in the signature

我找到了 http://blog.springsource.com/2008/10/20/understanding-the-osgi-uses-directive/

但这没有用，因为解决方案影响了我项目的太多部分。

我无法对 Tomcat 进行任何更改，并且该项目将被许多其他用户使用。

当前的解决方法是每次我们进行构建并使用 Tomcat6 时手动删除 el-api.jar。然后我们需要把 .jar 放回去，因为这是其他东西的要求。

我使用 Maven 2 和 Maven 3 构建。 (顺便说一句，有人知道在 Jruby 上使用 Maven3 吗？)

谁能帮我解决这个问题？

Answer 1

I encountered the problem of having the same .jar (for my case, el-api.jar v2.1)twice for one project, hence, the following error stack when I try to run my project using Tomcat 6.

如果是，则将 el-api.jar 工件标记为 provided。

The current work around is to manuelly delete the el-api.jar every time we do a build AND uses Tomcat6. Then we need to put the .jar back as that is requested for other stuff.

处理此问题的更好方法是在配置文件中声明依赖项并将其标记为 provided(例如在“tomcat6”配置文件中)或不根据需要。