java.lang.LinkageError：javax.servlet.jsp

Question

当我尝试在Tomcat 7上运行webapp时，出现以下异常：

exception

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/index_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

org.apache.jasper.servlet.JspServlet.service(JspServlet.java:343)

javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

root cause

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/index_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

org.apache.jsp.index_jsp._jspInit(index_jsp.java:31)

org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:49)

org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:180)

org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:369)

org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)

org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)

javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

似乎两个.jar库之间存在冲突，但我不知道它们是哪个。我该如何解决它们？

Answer 1

当你包括在不同的服务器品牌/版服务器专用库，会发生/WEB-INF/lib你的web应用，如jsp-api.jar，el-api.jar，servlet-api.jar，等你需要删除它们。该/WEB-INF/lib不应包含任何特定于服务器的库。它们属于特定的服务器本身（Tomcat已将其放在其/lib文件夹中）。顺便说一句，这是每当初学者在IDE项目中的JSP / Servlet API上遇到编译错误时，都会犯的错误。应该以不同的方式解决此问题，即通过将服务器集成到IDE中并将服务器作为“目标运行时”添加到项目中。

Answer 2

我被这个错误困扰了很长时间，这个线程节省了我很多时间。在解决此问题之前，我做了一些研究。是的，我们需要jsp-api.jar, el-api.jar, servlet-api.jar从/WEB-INF/lib文件夹中删除类似的库。但是如何？就我而言，我使用Apache Ivy作为依赖项管理器，并使用Spring MVC。它将下载所有依赖项以及上述库。在运行时，这些与Tomcat库提供的API冲突。一种简单的解决方案是从依赖项中排除这些jar或创建配置，并将这些库仅包括在编译时配置中。快速为我工作的是排除这些库。&nbsp; &nbsp; <dependency org="org.springframework" name="spring-webmvc"&nbsp; &nbsp; &nbsp; &nbsp; rev="4.0.4.RELEASE">&nbsp; &nbsp; &nbsp; &nbsp; <exclude org="javax.servlet" name="javax.servlet-api" />&nbsp; &nbsp; &nbsp; &nbsp; <exclude org="javax.servlet.jsp" name="jsp-api" />&nbsp; &nbsp; &nbsp; &nbsp; <exclude org="javax.el" name="javax.el-api" />&nbsp; &nbsp; </dependency>