1:jbpm4.3包冲突
错误如下:
严重: 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 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
    at org.apache.jsp.index_jsp._jspInit(index_jsp.java:
26)
    at org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:
52)
    at org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:
159)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:
329)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:
337)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:
266)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:
803)
    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:
175)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:
128)
    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:
286)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:
844)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:
583)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:
447)
    at java.lang.Thread.run(Unknown Source)

   这里面需要删除juel.jar ,juel-engine.jar,juel-impl.jar  三个 jar文件

————————————————————————————————————————————————

   但是在其他项目应用里面或许还需要这三个包,就只能把tomcat下面的el-api.jar删掉了
2:出现的错误如下:
严重: Servlet.service() for servlet LeaveServlet threw exception
java.lang.ClassNotFoundException: de.odysseus.el.util.SimpleResolver
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:
1360)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:
1206)
    at java.lang.ClassLoader.loadClassInternal(Unknown Source)
    at org.jbpm.pvm.internal.script.JuelScriptEngineFactory.getScriptEngine(JuelScriptEngineFactory.java:
185)
    at javax.script.ScriptEngineManager.getEngineByName(Unknown Source)
    at org.jbpm.pvm.internal.script.ScriptManager.evaluate(ScriptManager.java:
111)
    at org.jbpm.pvm.internal.script.ScriptManager.evaluateExpression(ScriptManager.java:
90)
    at org.jbpm.pvm.internal.model.ExecutionImpl.resolveAssignmentExpression(ExecutionImpl.java:
772)
    at org.jbpm.pvm.internal.model.ExecutionImpl.initializeAssignments(ExecutionImpl.java:
726)
    at org.jbpm.jpdl.internal.activity.TaskActivity.execute(TaskActivity.java:
95)
    at org.jbpm.jpdl.internal.activity.TaskActivity.execute(TaskActivity.java:
58)
    at org.jbpm.pvm.internal.model.op.ExecuteActivity.perform(ExecuteActivity.java:
60)
    at org.jbpm.pvm.internal.model.ExecutionImpl.performAtomicOperationSync(ExecutionImpl.java:
656)
    at org.jbpm.pvm.internal.model.ExecutionImpl.performAtomicOperation(ExecutionImpl.java:
616)
    at org.jbpm.pvm.internal.model.ExecutionImpl.start(ExecutionImpl.java:
217)
    at org.jbpm.pvm.internal.cmd.StartProcessInstanceInLatestCmd.execute(StartProcessInstanceInLatestCmd.java:
65)
    at org.jbpm.pvm.internal.cmd.StartProcessInstanceInLatestCmd.execute(StartProcessInstanceInLatestCmd.java:
38)
    at org.jbpm.pvm.internal.svc.DefaultCommandService.execute(DefaultCommandService.java:
42)
    at org.jbpm.pvm.internal.tx.StandardTransactionInterceptor.execute(StandardTransactionInterceptor.java:
54)
    at org.jbpm.pvm.internal.svc.EnvironmentInterceptor.executeInNewEnvironment(EnvironmentInterceptor.java:
53)
    at org.jbpm.pvm.internal.svc.EnvironmentInterceptor.execute(EnvironmentInterceptor.java:
40)
    at org.jbpm.pvm.internal.svc.RetryInterceptor.execute(RetryInterceptor.java:
55)
    at org.jbpm.pvm.internal.svc.SkipInterceptor.execute(SkipInterceptor.java:
43)
    at org.jbpm.pvm.internal.svc.ExecutionServiceImpl.startProcessInstanceByKey(ExecutionServiceImpl.java:
66)
    at cn.yu.qingjiaServlet.LeaveServlet.leave(LeaveServlet.java:
151)
    at cn.yu.qingjiaServlet.LeaveServlet.process(LeaveServlet.java:
80)
    at cn.yu.qingjiaServlet.LeaveServlet.doGet(LeaveServlet.java:
60)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:
690)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:
803)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:
290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:
206)
    at cn.yu.qingjiaServlet.SetCharaterEncodingFilter.doFilter(SetCharaterEncodingFilter.java:
26)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:
235)
    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:
175)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:
128)
    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:
286)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:
844)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:
583)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:
447)
    at java.lang.Thread.run(Unknown Source)

3:当删除掉el-api.jar的时候出现的错误如下:

java.lang.NoClassDefFoundError: javax/el/ExpressionFactory

解决jbpm4.3当中el-api.jar和三个包冲突的过程中,删除el-api.jar是出现的错误,把名为javaee.jar包(在myeclipse下有这个包)放到tomcat/lib里面就可以了