今天测试时遇到了第一个问题。。老火。一看发现网上有朋友早有解决方法了。下面我是我复制过来的!不好意思呀！嘿嘿
1、问题：org.hibernate.exception.ConstraintViolationException: could not delete: [org.jbpm.pvm.internal.model.ExecutionImpl#1]
连接Mysql5时，jBPM4运行到 End结点时的错误，把 hibernate.dialect 改为 org.hibernate.dialect.MySQLInnoDBDialect
2、问题：org.hibernate.HibernateException: instance not of expected entity type: org.jbpm.pvm.internal.type.variable.UnpersistableVariable is not a: org.jbpm.pvm.internal.type.Variable
In case you still got the problem. I also had this error due to the fact the Object I was adding as a variable was not Serializable.
Implementing java.io.Serializable should fix this error.
意思是压入上下文的对象要实现 Serializable接口
3、问题：Caused by: java.lang.ClassNotFoundException: de.odysseus.el.util.SimpleResolver
Requirements
JUEL requires Java 5 or later.
加入juel.jar
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I think I get same problem when trying to integrate JBPM4 into my app. And I find out why.
Because you're using Tomcat 6.0... The lib el-api.jar in %tomcat_home%/lib conflicts with juel.jar, which exists in %jbpm4_home%/lib.
juel: <http://juel.sourceforge.net/> You will find the 2 jars define the same api for javax/el/ExressionFactory.
The solution is that you use Tomcat 5.5 instead of Tomcat 6.0. Because tomcat 5.5 uses commons-el.jar (Tomcat5.5/common/lib)
Or you can still use Tomcat 6.0, but you must replace el-api.jar with juel.jar. And don't forget to remove juel.jar from your app lib(A duplicate import, if you don't remove).
Try it!
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总结：删掉tomcat6的el.jar，加入juel.jar,juel-impl.jar,juel-engine.jar
