I am currently using Esper within a Storm topology and I am aware that there is a method callback called update() that is called when Esper produces a result.
I have been wondering what would happen if there is an error within the Esper engine itself.
Is there an error callback that I can override and catch the Exception?
Or is my best bet to simply wrap the sendEvent() call in a try-catch and then deal with the Exception accordingly?
After further reading I can see that Esper has the notion of Exception Handling:
http://esper.codehaus.org/esper-4.2.0/doc/reference/en/html/configuration.html#config-engine-exceptionhandling
This should satisfy my use case and catch any internal Esper exceptions.
Yes, Esper provides a way for Exception Handling.
You may register one or more exception handlers for the engine to invoke in the case it encounters an exception processing a continuously-executing statement
You can register ExceptionHandlerFactory like below.
Configuration config = new Configuration();
config.getEngineDefaults().getExceptionHandling().addClass(MyCEPEngineExceptionHandlerFactory.class);
You should give the full-qualified class name of each class that implements the com.espertech.esper.client.hook.ExceptionHandlerFactory interface in the engine defaults configuration.
For more details, please read the documentation.
.
Related
How does the exception strategy works in mulesoft when we have a flow having its own exception strategy calling another flow with its exception strategy. What will happen if an exception occurs in the called flow.
The called flow will throw the exception and the exception strategy of the called flow will be executed.
the calling flow wont throw an exception until its expecting something from the called flow and the called flow is not returning that.
Refer to this link Mule_Exception for further detailed information.
If the exception occurs in the called flow,The exception strategy of the called flow will get execute and control pass to calling flow to execute next message processor.
Regards,
Purnachandra
I have heard that it is possible to log (or do something else) Exceptions with Spring in my web-App, so I don't have to manually insert in every "catch(){}" block the Log-function.
Does anyone have experience with Spring-overall-logging? I just want to get informed when an error appears
ExceptionHandler is the central point for handling unexpected Exceptions that are thrown during the Faces lifecycle. The ExceptionHandler must not be notified of any Exceptions that occur during application startup or shutdown.
See the specification prose document for the requirements for the default implementation. Exceptions may be passed to the ExceptionHandler in one of two ways:
1.)By ensuring that Exceptions are not caught, or are caught and re-thrown.
This approach allows the ExceptionHandler facility specified in section JSF.6.2 to operate on the Exception.
2.)By using the system event facility to publish an ExceptionQueuedEvent that wraps the Exception.
This approach requires manually publishing the ExceptionQueuedEvent, but allows more information about the Exception to be stored in the event. The following code is an example of how to do this.
Global Exception Handler – Exception Handling is a cross-cutting concern, it should be done for all the pointcuts in our application. We have already looked into Spring AOP and that’s why Spring provides #ControllerAdvice annotation that we can use with any class to define our global exception handler.
The handler methods in Global Controller Advice is same as Controller based exception handler methods and used when controller class is not able to handle the exception.
Sample Code
#ExceptionHandler(Exception.class)
public ModelAndView getExceptionPage(Exception e, HttpServletRequest request) {
request.setAttribute("errorMessageObject", e.toString());
return model;
}
** Here we can catch the base exception class Exception.class or any other exception class. Also we can throw and catch our own custom defines exception class.
I have a default catch exception strategy for my entire flow/subflows. However, I'd like to be able to tell what component/endpoint threw an exception so I can try to restart the flow at that point (I have yet to figure out how to do that as well.)
Is there any easy way to tell what component/endpoint threw the exception, and be able to tell if it was in a foreach, and at what point (by looking at the "counter" variable.)
Thanks!
You can set a variable at the start of flow like this:
<set-variable variableName="flowName" value="Your_flow_name"/>
And the get the flow name like #[flowName] in your exception strategy.
EDIT:
To trigger a flow, create a java component implementing Callable interface, from the context get the MuleClient and use send or dispatch method to send payload to flow. Send causes MuleClient to wait for response while dispatch doesn't.
More info here: http://www.mulesoft.org/documentation/display/current/Using+the+Mule+Client
I have error_messages table, which contains the site-wide error messages.
I use the error messages across application. So, I created singleton bean of error messages (ErrorMessagesLoad.java)
ErrorMessagesLoad uses ErrorMessageDao to retrieve the error messages from database.
Should I create static variable in ErrorMessagesLoad to hold all the error messages and use it in all classes? or is there better way of doing it?
Thanks,
Satya
You should use your own implementation of MessageSource in Spring to resolve any messages. Here is a good point to start.
When implemented, you just wire your bean to any service or controller and it handles messages for you, with ability to iternationalize them.
In general global static variables should be avoided. Error handling can get tricky. Many applications try to put a global catch handler somewhere near the top (e.g. web applications the top would be filters) which has the ErrorMessagesLoad injected into it. That handler catches underlying exceptions, translates them into something user readable and then throws that higher.
Some examples include Spring's exception translation filter and Jersey's exception mapping mechanism.
My code is throwing an exception (due to a bug). In the log, I see:
org.jboss.resteasy.spi.UnhandledException: java.lang.NullPointerException
at org.jboss.resteasy.core.SynchronousDispatcher.handleApplicationException(SynchronousDispatcher.java:323)
at org.jboss.resteasy.core.SynchronousDispatcher.handleException(SynchronousDispatcher.java:199)
at org.jboss.resteasy.core.SynchronousDispatcher.handleInvokerException(SynchronousDispatcher.java:175)
at org.jboss.resteasy.core.SynchronousDispatcher.getResponse(SynchronousDispatcher.java:529)
etc...
The stack of the actual exception is not logged. If I wrap my code in a try..catch and log the caught exception I can verify that my code is at fault. No other library in my system does this, even for deeply-wrapped exceptions, so it must be a problem in RESTEasy, perhaps in UnhandledException?
Is there a way to get around this behavior? I can't think of a good reason why it should be hiding the actual exception.
Jetty
Java
Spring 3.0.3
RESTEasy 2.0.1GA
Do you have an ExceptionMapper? See Chapter 27, Exception Handling, in the RESTEasy documentation.
I used RESTEasy to add REST to an existing system, and the existing system has a weird way of wrapping exceptions within exceptions, so my ExceptionMappers do a lot of unwrapping.
Throwable t = exception;
while (t.getCause() != null) {
t = t.getCause();
}
t.printStackTrace();
I don't use RESTeasy, but it appears to be a dispatch mechanism for RESTful web services.
Assuming this is the case, then it has different design goals from other libraries: they are invoked from your application, but RESTeasy is responsible for invoking your application. It therefore has to protect itself from poorly written code. A "last ditch" exception handler is a common way to do this; you'll see the same thing in Swing.
Whether or not it should log the uncaught exceptions is a different matter. Perhaps there's a configuration option to do this. Or perhaps you need to add a couple lines of code. It is open-source, after all, and I'm sure the maintainers would appreciate a well-written bug report with patch.
Yes, your exception is swallowed by RESTeasy, wrapped in UnhandledException and logged. But your exception lies too deep within to be included in the stacktracs.
To print out your exception to the console, you could append the following to 'WEB-INF/classes/logging.properties'
org.apache.catalina.core.ContainerBase.[Catalina].level = FINEST
org.apache.catalina.core.ContainerBase.[Catalina].handlers = java.util.logging.ConsoleHandler