JBPM4.3 ScriptManager

在JBPM4.3允许配置变量搜索范围图下：

<process-engine-context>
<script-manager default-expression-language="juel"
                    default-script-language="juel"
                    read-contexts="execution,transaction,process-engine,spring" 
                    write-context="">
<script-language name="juel" factory="org.jbpm.pvm.internal.script.JuelScriptEngineFactory" />
<script-language name="bsh" factory="org.jbpm.pvm.internal.script.BshScriptEngineFactory" />
<script-language name="groovy" factory="org.jbpm.pvm.internal.script.GroovyScriptEngineFactory" />
</script-manager>
</process-engine-context>

“read-contexts="execution,transaction,process-engine,spring" 指定搜索范围，但实际上不起作用，实际的搜索范围是运行环境(Environment)中动态加入的Context,如[execution, transaction, process-engine, spring]，但不同的执行环境中会有不同，如果没有和Spring集成，自然不会有spring context,有时候execution也不会有,比如你在启动流程时设置流程的超时时间(注意：这里不是节点超时)使用变量表达式,虽然你在启动流程时把变量传入了，但由于初始化流程超时时还没有把ExcutionContext(传入的变量放在这里的)加入到Environment中，因此script-manager 会报异常如下：

javax.el.PropertyNotFoundException: Cannot find property d38b041b88b711dfab700016eca5d82f
	at de.odysseus.el.util.SimpleResolver.get(SimpleResolver.java:106)
	at de.odysseus.el.util.SimpleResolver.getValue(SimpleResolver.java:126)
	at de.odysseus.el.tree.impl.ast.AstIdentifier.eval(AstIdentifier.java:69)
	at de.odysseus.el.tree.impl.ast.AstEval.eval(AstEval.java:42)
	at de.odysseus.el.tree.impl.ast.AstNode.getValue(AstNode.java:29)
	at de.odysseus.el.TreeValueExpression.getValue(TreeValueExpression.java:120)
	at org.jbpm.pvm.internal.script.JuelScriptEngine.evalExpr(JuelScriptEngine.java:176)
	... 68 more