具有Web服务的应用程序中的异常处理的最佳方式

Question

I have an application which consists of SOAP and REST web services and a simple HTTP access. All of them convert incoming requests and send them to a handler. The most painful thing is exception handling. In order to return the right response, I have to wrap every method with try-catch block and create a response there.

I thought that I could create a filter which could do it. But how can the filter recognise the source of it (soap, rest frontend) so I knew that I should return a SOAP or other response?

Answer 1

It depends on the WS framework you use. All I know have some sort of interceptors/aspects that you can inject and handle exceptions in one place. For instance in apache-cxf there is even a special outbound error chain where you can plug your own interceptors.

Obviously try-catch in every method is a bad idea.

Answer 2

In layer of below Web-Service Layer , you have to create your custom Exception and in Web-Service layer you have to use try-catch approach for achieve occurred exception and in catch block log and convert it to your custom web service layer exception. I show this approach in following:

@WebService
public class EmployeeWS
{
    @WebMethod
    public void add(Employee em) throws CustomWebServiceException
    {
       try
       {
         // call facade layer method  
       }
       catch(Exception e)
       {
          logger.error(e.getMessage());
          throw new CustomWebServiceException(e);
       }        
    }
}

Alternative using try catch in any Web-Method ,you can use AOP approch(for sample Spring AOP ) or interceptor approach in Web-Service frameworks (for sample SOAPHandler<T> in JAX-WS ).

Note : In JAX-WS standard, you can't throw a RuntimeException because Exception must specify in final WSDL and if you throw a RuntimeException your web service client don't achieve your CustomException , in another your Web-Method need to throws in itself signature.

You can see selected Web-Service faramework documents for more information.

Answer 3

It sounds that you are not using any framework because that was typical frameworks provide. For example Spring allows you to decouple the code from exception handling and define your custom exception handlers.

In your case you generally have 2 solutions.

(1) You can use Decorator pattern: wrap each service with decorator where each method is implemented as

try {
    call real method
} catch() {
   send error to client
}

Since it is very verbose you can save time using Dynamic proxy (feature that was introduced in java 5). So, you can dynamically wrap each service (if your services have defined interface).

(2) You can solve it using servlet API's error page:

javax.servlet.ServletException /servlet/ErrorDisplay

for more details see http://java.sun.com/developer/technicalArticles/Servlets/servletapi2.3/

Answer 4

You can customize your class!! Do it!

Take easy on diagnostic errors, like insert a protocol number, message Log, message client, etc...

http://java.globinch.com/enterprise-java/web-services/jax-ws/jax-ws-exceptions-faults-annotation-exception-and-fault-handling-examples/#Pre-Requisites