How to handle exception in Struts - exception

How can we handle exceptions in Struts? Please share the sample code.

The following URL should help http://www.objectsource.com/j2eechapters/Ch18-Exception_Handling.htm

Use log4j to log the exceptions,
Never use System.out.println in struts application to catch exceptions, as it is expensive ,
Tutorials for log4j> http://logging.apache.org/log4j/1.2/manual.html
to handle the errors:
in struts project to handle the error objet by using ActionError object and to handle the errors by using ActionErrors object.
for suppose
ActionError ae1=new ActionError("err.one");
ActionError ae2=new ActionError("err.two");
Action Errors aes=new ActionErrors();
aes.add(ae1);
aes.add(ae2);
saveErrors(request,aes);//store the errors object in request object
to handle exception:
1)using try and cach blocks
2)using declarative exception handling technique
to handle the exceptions by using global exceptons tag in struts-config.xml
whenever that exception will be came it executes the gen.jsp page.

Related

custom exception message in spring cloud function deployed in aws-lambda

I have a java project written using spring-cloud-function and deployed in aws-lambda.
I am trying to return a custom exception with some fields in the exception message body, something like"
{
reason: <exception reason>
code: <error code>
<some other fields>
}
#ExceptionHandler, that is generally used in spring boot doesn't seem to work here.
I can return the exception in the required format by creating a class for building the exception message in required format but in that case the error code will always be 200 since it will not be an exception object per se. Instead it will be my custom error object.
Is there a way I can set this up so that the above required format of exception object is returned and correct error code can be returned too?
Thanks in advance
First, the exception has nothing to do with Spring Boot. It's part of spring-web, so yes it would not work here since s-c-function is a general purpose framework, where the same function could be deployed and triggered via web, streaming, aws-lambda etc. .
Now, yes we had a problem returning JSON error (as you show) or object that represents the same, but that was fixed. So please update s-c-function to 3.2.3.

How to handle the exceptions thrown from item reader?

I want to catch the exceptions thrown from item reader (e.g. reader not open , incorrect token exceptions etc) and handle it. Currently spring batch is throwing them as fatal exceptons and come out of the step.
Please let me know if there is any way to do it?
I faced the same issue whereby I wanted to catch the
org.springframework.batch.item.file.FlatFileParseException
thrown by the FlatFileItemReader and perform some custom handling & logging. Did some research and almost reached the conclusion that I might have to write a custom reader instead of the default reader I was currently using, until I stumbled upon a gem of a section in the Spring Batch documentation: http://docs.spring.io/spring-batch/reference/html/configureStep.html#interceptingStepExecution
You can write a custom implementation of the ItemReadListener<T> interface and over-ride the onReadError(Exception ex) method and then register this listener class in the corresponding step. As such, this method will then be called when the reader encounters an exception while reading from the file. The exception reference will be passed to the method as well using which you can do as you please like logging etc.
Similarly, writing a #OnReadError annotated method is also an alternative if you don't want to implement the ItemReadListener interface separately.
On a different note, if your whole purpose is to skip such exceptions that might occur while reading, you can try adding following to the chunk configuration in the XML:
<skippable-exception-classes>
<include class="org.springframework.batch.item.file.FlatFileParseException"/>
</skippable-exception-classes>
Ref: http://docs.spring.io/spring-batch/reference/html/configureStep.html#configuringSkip
Problem solved! :)

Spring Integration Exception Handling

What is the concept behind exception handling in Spring Integration or any other EAI framework: Are they treated as a Message?
Lets say that a JMS timeout exception was thrown from jms-outbound-gateway. Now it has to be moved all the way upto the parent custom gateway addEmployeeGateway which defines a method called addEmployee which throws a custom exception called SystemDownException. These two components are connected through request and reply channels and thats the only medium of communication. Does it mean that Exceptions are also treated as messages?
Also, if i had to map the JMS timeout exception to my custom exception SystemDownException and rethrow the SystemDownException how and where would i achieve this. I dont want to use an errorchannel.
The general mechanism for handling exceptions is an error-channel on the inbound (or some intermediate) endpoint; the ErrorMessage payload has failedMessage and cause properties.
The mechanism is similar to try {...} catch {...} in Java.
I dont want to use an errorchannel.
Alternatively, you can configure a custom request handler advice on the JMS outbound gateway; there, you can do whatever you want, including throwing your SystemDownException after catching an exception on callback.execute().

Handle specific exception that is not related to an exchange

I created a custom component for a proprietary service. If this service is down i get noticed via a call of a callback function. I am throwing a custom exception at this point.
Sending exchanges to the producer/ consumer will yield no errors or exceptions (all seems to fine).
So i need to implement an emergency stop if my custom exception is thrown. I read a bit about exception handling in camel. I think i need a context-scoped onException(MyException.class).??? but what then?
Is this working on exceptions that are called without relation to an exchange? If this is working how to handle it. I want to stop certain routes in this case.
here you can find to stop routes from a route: http://camel.apache.org/how-can-i-stop-a-route-from-a-route.html.
If you do the call of the proprietary service in a route you do have an exchange btw.
kind regards,
soilworker
I created a little workaround: I set a boolean i the callback method is called. On each call of process i check this boolean and if true i throw an exception.
With this the exception is within normal camel exception handling and onException could be used.

WCF Exception Handling Strategies

We are developing a proxy in WCF that will serve as a means of communication for some handhelds running our custom client application. I am curious what error handling strategies people use as I would rather not wrap EVERY proxy call in try/catch.
When I develop ASP .NET I dont catch the majority of exceptions, I leverage Application_Error in Global asax which can then log the exception, send an email, and redirect the user to a custom error landing page. What I am looking for in WCF is similar to this, except that it would allow me to pass a general faultreason to the client from a central location.
Basically I am curious how people centralize their exception handling in WCF apps.
Thanks
You might find the IErrorHandler interface useful here. We've been using this to do pretty much what you mention - centralised exception logging and providing generalised fault reasons without having to litter the code with numerous try/catches to try and deal with the problem locally.
So here is what I did. We have a few custom exceptions in our application such as BusinessRuleException and ProcessException, WCF supports both FaultException and FaultException<T>.
General practice seems to be that you always throw FaultException to the client in the case of a general error or an error that you dont want to display exactly what happened. In other cases you can pass FaultException<T> where T is a class with information about the particular exception.
I created this concept of Violations in the application, which basically meant that any custom exception had a property containing the corresponding Violation instance. This instance was then passed down to the client enabling the client to recognize when a recoverable error had occured.
This solved part of the problem, but I still wanted a general catch all that would allow me to centeralize logging. I found this by using the IErrorHandle interface and adding my own custom error handler to WCF. Here is the code:
public class ServiceHostGeneralErrorHandler : IErrorHandler
{
public void ProvideFault(Exception ex, MessageVersion version, ref Message fault)
{
if (ex is FaultException)
return;
// a general message to the client
var faultException = new FaultException("A General Error Occured");
MessageFault messageFault = faultException.CreateMessageFault();
fault = Message.CreateMessage(version, messageFault, null);
}
public bool HandleError(Exception ex)
{
// log the exception
// mark as handled
return true;
}
}
Using this method, I can convert the exception from whatever it is to something that can be easily displayed on the client while at the same time logging the real exception for the IT staff to see. So far this approach is working quite well and follows the same structure as other modules in the application.
We use the Exception Handling Application block and shield most faults from clients to avoid disclosing sensitive information, this article might be a good starting point for you, as with "best practices" - you should use what fits your domain.