java.lang.ClassCastException: java.lang.NullPointerException incompatible with javax.el.ELException
如题，在was环境报的这个错，请问如何解决？
java.lang.ClassCastException: java.lang.NullPointerException incompatible with javax.el.ELException
org.apache.el.lang.ExpressionBuilder.prepare(ExpressionBuilder.java:140)
org.apache.el.lang.ExpressionBuilder.build(ExpressionBuilder.java:152)
org.apache.el.lang.ExpressionBuilder.createValueExpression(ExpressionBuilder.java:195)
org.apache.el.ExpressionFactoryImpl.createValueExpression(ExpressionFactoryImpl.java:68)
org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:773)
com.ibm._jsp._xxxxxx._jspService(_xxxxx.java:329)
.....