Java. Lang. linkageerror: loader Constraint Violation: when resolving interface... Troubleshooting

Severe: servlet. Service () for servlet JSP threw exception
Java. Lang. linkageerror: loader Constraint Violation: when resolving Interface Method

"Javax. servlet. jsp. jspapplicationcontext. getexpressionfactory () ljavax/El/expressionfactory;" The Class Loader (instance

Org/Apache/Jasper/servlet/jasperloader) of the current class, org/Apache/JSP/index_jsp, and the class loader (instance

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 org. Apache. jsp. index_jsp. _ jspinit (index_jsp.java: 24)
 At org. Apache. Jasper. runtime. httpjspbase. INIT (httpjspbase. Java: 52)
 At org. Apache. Jasper. servlet. jspservletwrapper. getservlet (jspservletwrapper. Java: 164)
 At org. Apache. Jasper. servlet. jspservletwrapper. Service (jspservletwrapper. Java: 338)
 At org. Apache. Jasper. servlet. jspservlet. servicejspfile (jspservlet. Java: 313)
 At org. Apache. Jasper. servlet. jspservlet. Service (jspservlet. Java: 260)
 At javax. servlet. http. httpservlet. Service (httpservlet. Java: 717)
 At org. Apache. Catalina. Core. applicationfilterchain. internaldofilter (applicationfilterchain. Java: 290)
 At org. Apache. Catalina. Core. applicationfilterchain. dofilter (applicationfilterchain. Java: 206)
 At org. Apache. Catalina. Core. standardwrappervalve. Invoke (standardwrappervalve. Java: 233)
 At org. Apache. Catalina. Core. standardcontextvalve. Invoke (standardcontextvalve. Java: 191)
 At org. Apache. Catalina. Core. standardhostvalve. Invoke (standardhostvalve. Java: 127)
 At org. Apache. Catalina. Valves. errorreportvalve. Invoke (errorreportvalve. Java: 102)
 At org. Apache. Catalina. Core. standardenginevalve. Invoke (standardenginevalve. Java: 109)
 At org. Apache. Catalina. connector. coyoteadapter. Service (coyoteadapter. Java: 298)
 At org. Apache. Coyote. http11.http11processor. Process (http11processor. Java: 859)
 At org. Apache. Coyote. http11.http11protocol $ http11connectionhandler. Process (http11protocol. Java: 588)
 At org.apache.tomcat.util.net. jioendpoint $ worker. Run (jioendpoint. Java: 489)
 At java. Lang. thread. Run (thread. Java: 619)

Cause:

This error occurs when jbpm4 is under Tomcat 6!

The reason is that the three jar packages (juel. jar, WEB-INF, juel-engine.jar) in the juel-impl.jar \ Lib in the project conflicts with the jar package (el-api.jar) in the Lib under tomcat6

Solution:

Method 1: replace tomcat5.5 with no problem

Method 2: copy the three packages juel. jar, juel-engine.jar and juel-impl.jar to the Lib under tomcat6 and delete the original el-api.jar,

Remember to delete juel. jar, WEB-INF, juel-engine.jar from juel-impl.jar \ Lib. Otherwise, conflict is still required.