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com.bea.wlevs.ede.api
Interface FaultHandler

public interface FaultHandler

Service for providing custom fault handlers.

When processing events in the context of Java code, such as it is the case for custom adapters event beans, and general beans, a developer can always make use of Java's exception handling mechanism (i.e. try-catch) to treat event processing errors. However, there are cases when it is not possible to do so. For example, this is the case if the error occurs within a processor's query (e.g. CQL), or if the error occurs in a channel's background thread. Fault handlers allow a developer to provide Java code for handling these situations where normally the developer cannot use Java's try-catch for handling errors that occur during the event processing flow.

The fault handler service must be registered in the OSGi service registry using the following service properties: application.identity, stage.identity. These properties identify where the handler is attached. For example, use the following declarative code to associate a fault handler to a processor called 'proc' in the EPN of an application called 'helloworld':

   <osgi:service interface="com.bea.wlevs.ede.api.FaultHandler">
    <osgi:service-properties>
      <entry key="application.identity" value="helloworld"/>
      <entry key="stage.identity" value="proc"/>
    </osgi:service-properties>
    <bean class="mypackage.MyFaultHandler"/>
  </osgi:service>
 

See Also:

EventProcessingException

Field Summary

static java.lang.String	APP_ID Use this mandatory service property to specify target application.
static java.lang.String	STAGE_ID Use this mandatory service property to specify target stage.

Method Summary
void	handleFault(java.lang.Throwable fault, java.lang.String[] catchers) This method is called-back informing handler of a fault that happened while processing an event, or a batch of events, allowing client to provide custom handling of faults.

Field Detail

APP_ID

public static final java.lang.String APP_ID

Use this mandatory service property to specify target application.

STAGE_ID

public static final java.lang.String STAGE_ID

Use this mandatory service property to specify target stage.

Method Detail

handleFault

public void handleFault(java.lang.Throwable fault,
                        java.lang.String[] catchers)
                 throws java.lang.Throwable

This method is called-back informing handler of a fault that happened while processing an event, or a batch of events, allowing client to provide custom handling of faults.

Handler may consume fault, or re-throw fault, or throw a new exception. If fault is not consumed, then upstream event sources (catchers) would receive it.

The parameter catchers specifies potential upstream event sources that receives the fault in case it is not handled. In case of a concurrent channel or a heart-beat CQL thread, there are no upstream sources and so this is an empty array.

If no fault handlers exist for a particular stage (node) in the EPN, then a default one is used. If a custom fault handler is provided, then the default one is NOT used. Most default fault handlers just re-throw fault. However, the default behavior for a CQL processor fault handler is to stop a running CQL query where fault was emitted.

In the specific case of an EventChannel, a custom fault handler only catches faults that happen downstream to it. For example, an exception raised by an output event bean. EventProcessingException raised due to the EventChannel being full can only be caught by an upstream node in the EPN.

Fault may be an EventProcessingException, or even a JVM Error.

Parameters:

fault - EventProcessingException or JVM error

catchers - Name of upstream event sources that potentially may receive fault if not handled.

Throws:

java.lang.Throwable - re-throw or not handled fault