Java 如何在Mule ESB中访问流变量。。。？

这是我试图访问名为“question”的flowvariable的代码

但我得到了以下错误：

Message               : Failed to find entry point for component, the following resolvers tried but failed: [
CallableEntryPointResolver: Object "Main@2cad86ee" does not implement required interface "interface org.mule.api.lifecycle.Callable"
ReflectionEntryPointResolver: Could not find entry point on: "Main" with arguments: "{class [B}"
AnnotatedEntryPointResolver: Component: Main@2cad86ee doesn't have any annotated methods, skipping.
MethodHeaderPropertyEntryPointResolver: The required property "method" is not set on the event
]
Code                  : MULE_ERROR-321
--------------------------------------------------------------------------------
Exception stack is:
1. Failed to find entry point for component, the following resolvers tried but failed: [
CallableEntryPointResolver: Object "Main@2cad86ee" does not implement required interface "interface org.mule.api.lifecycle.Callable"
ReflectionEntryPointResolver: Could not find entry point on: "Main" with arguments: "{class [B}"
AnnotatedEntryPointResolver: Component: Main@2cad86ee doesn't have any annotated methods, skipping.
MethodHeaderPropertyEntryPointResolver: The required property "method" is not set on the event
] (org.mule.model.resolvers.EntryPointNotFoundException)
  org.mule.model.resolvers.DefaultEntryPointResolverSet:49 (http://www.mulesoft.org/docs/site/current3/apidocs/org/mule/model/resolvers/EntryPointNotFoundException.html)
--------------------------------------------------------------------------------
Root Exception stack trace:
org.mule.model.resolvers.EntryPointNotFoundException: Failed to find entry point for component, the following resolvers tried but failed: [
CallableEntryPointResolver: Object "Main@2cad86ee" does not implement required interface "interface org.mule.api.lifecycle.Callable"
ReflectionEntryPointResolver: Could not find entry point on: "Main" with arguments: "{class [B}"
AnnotatedEntryPointResolver: Component: Main@2cad86ee doesn't have any annotated methods, skipping.
MethodHeaderPropertyEntryPointResolver: The required property "method" is not set on the event
]
    at org.mule.model.resolvers.DefaultEntryPointResolverSet.invoke(DefaultEntryPointResolverSet.java:49)
    at org.mule.component.DefaultComponentLifecycleAdapter.invoke(DefaultComponentLifecycleAdapter.java:339)
    at org.mule.component.AbstractJavaComponent.invokeComponentInstance(AbstractJavaComponent.java:82)
    + 3 more (set debug level logging or '-Dmule.verbose.exceptions=true' for everything)
********************************************************************************

---

嗯，错误信息非常清楚：

对象“Main@2cad86ee未实现所需的接口“interface org.mule.api.lifecycle.Callable”

只要实现这个接口，生活就会很美好

Message               : Failed to find entry point for component, the following resolvers tried but failed: [
CallableEntryPointResolver: Object "Main@2cad86ee" does not implement required interface "interface org.mule.api.lifecycle.Callable"
ReflectionEntryPointResolver: Could not find entry point on: "Main" with arguments: "{class [B}"
AnnotatedEntryPointResolver: Component: Main@2cad86ee doesn't have any annotated methods, skipping.
MethodHeaderPropertyEntryPointResolver: The required property "method" is not set on the event
]
Code                  : MULE_ERROR-321
--------------------------------------------------------------------------------
Exception stack is:
1. Failed to find entry point for component, the following resolvers tried but failed: [
CallableEntryPointResolver: Object "Main@2cad86ee" does not implement required interface "interface org.mule.api.lifecycle.Callable"
ReflectionEntryPointResolver: Could not find entry point on: "Main" with arguments: "{class [B}"
AnnotatedEntryPointResolver: Component: Main@2cad86ee doesn't have any annotated methods, skipping.
MethodHeaderPropertyEntryPointResolver: The required property "method" is not set on the event
] (org.mule.model.resolvers.EntryPointNotFoundException)
  org.mule.model.resolvers.DefaultEntryPointResolverSet:49 (http://www.mulesoft.org/docs/site/current3/apidocs/org/mule/model/resolvers/EntryPointNotFoundException.html)
--------------------------------------------------------------------------------
Root Exception stack trace:
org.mule.model.resolvers.EntryPointNotFoundException: Failed to find entry point for component, the following resolvers tried but failed: [
CallableEntryPointResolver: Object "Main@2cad86ee" does not implement required interface "interface org.mule.api.lifecycle.Callable"
ReflectionEntryPointResolver: Could not find entry point on: "Main" with arguments: "{class [B}"
AnnotatedEntryPointResolver: Component: Main@2cad86ee doesn't have any annotated methods, skipping.
MethodHeaderPropertyEntryPointResolver: The required property "method" is not set on the event
]
    at org.mule.model.resolvers.DefaultEntryPointResolverSet.invoke(DefaultEntryPointResolverSet.java:49)
    at org.mule.component.DefaultComponentLifecycleAdapter.invoke(DefaultComponentLifecycleAdapter.java:339)
    at org.mule.component.AbstractJavaComponent.invokeComponentInstance(AbstractJavaComponent.java:82)
    + 3 more (set debug level logging or '-Dmule.verbose.exceptions=true' for everything)
********************************************************************************