javax.servlet.ServletException: java.lang.LinkageError: loader constraint violation:when resolving i...-优快云博客

本文详细解析了在部署JSP应用时遇到的LinkageError异常，指出错误源于WEB-INF/lib目录下包含的服务器特定库与Tomcat自带库冲突，如jsp-api.jar、el-api.jar等。文章提供了移除这些库的解决方案，并建议通过IDE集成服务器并设置Target runtime来避免此类问题。

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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)

That will happen when you include server-specific libraries of a different server make/version in the/WEB-INF/lib of your web application, such as jsp-api.jar, el-api.jar, servlet-api.jar, etc. You need to remove them all. The /WEB-INF/lib should not contain any server-specific libraries. They belongs in the specific server itself (Tomcat has them in its /lib folder already).

This is by the way a pretty common beginner's mistake whenever they encounter compilation errors on the JSP/Servlet API in their IDE project. This should have been solved differently, namely by integrating the server in the IDE and adding the server as "Target runtime" to the project.

一句话就是你不能在项目的lib目录中再包含服务器类提供过jar 比如jsp-api.jar, el-api.jar, servlet-api.jar, 等等