net.morimekta.providence.server

Class ExceptionHandler

java.lang.Object

net.morimekta.providence.server.ExceptionHandler

public class ExceptionHandler
extends Object

Handle exceptions for HTTP responses. Note that using this instead of a proper service handler will easily hide exceptions, or transform unknown exceptions into known exceptions outside of service implementations. But it provides a handy way of normalizing non-default responses onto HTTP status and message format.

Overridable Methods

• writeErrorResponse(Throwable, Serializer, HttpServletRequest, HttpServletResponse): Complete handling of exceptions thrown by the PServiceCallHandler.handleCall(PServiceCall, PService) method or similar. Calling super on this will fall back to default exception handling, using the methods below. This will per default serialize PMessage exceptions normally, and just call HttpServletResponse.sendError(int,String) for all the others using the Throwable.getMessage() message.
• getResponseException(Throwable): Get the response exception given the specific thrown exception. This method can be used to unwrap wrapped exceptions, or transform non- message exceptions into providence message exceptions.
• statusCodeForException(Throwable): Get the HTTP status code to be used for the error response. Override to specialize, and call super to get default behavior. The default will handle PApplicationException errors, and otherwise return 500 Internal Server Error.

Field Summary

Fields

Modifier and Type	Field and Description
static ExceptionHandler	INSTANCE

Constructor Summary

Constructors

Constructor and Description
ExceptionHandler()

Method Summary

Modifier and Type	Method and Description
protected Throwable	getResponseException(Throwable e) Get the exception to ge handled on failed requests.
void	handleException(Throwable rex, net.morimekta.providence.serializer.Serializer responseSerializer, javax.servlet.http.HttpServletRequest httpRequest, javax.servlet.http.HttpServletResponse httpResponse) Handle exceptions from the handle method.
protected int	statusCodeForException(Throwable exception) With default exception handling, this can simply change the status code used for the response.
protected void	writeErrorResponse(Throwable rex, net.morimekta.providence.serializer.Serializer responseSerializer, javax.servlet.http.HttpServletRequest httpRequest, javax.servlet.http.HttpServletResponse httpResponse) Write the error response.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INSTANCE

public static final ExceptionHandler INSTANCE

Constructor Detail

ExceptionHandler

public ExceptionHandler()

Method Detail

handleException

public void handleException(@Nonnull
                            Throwable rex,
                            @Nonnull
                            net.morimekta.providence.serializer.Serializer responseSerializer,
                            @Nonnull
                            javax.servlet.http.HttpServletRequest httpRequest,
                            @Nonnull
                            javax.servlet.http.HttpServletResponse httpResponse)
                     throws IOException

Handle exceptions from the handle method. This method can be overridden if a thrown exception must be handled before it is transformed with getResponseException(Throwable). Otherwise override writeErrorResponse(Throwable, Serializer, HttpServletRequest, HttpServletResponse) instead.

Parameters:

rex - The response exception, which is the thrown exception or one of it's causes. See getResponseException(Throwable).

responseSerializer - The serializer to use to serialize message output.

httpRequest - The HTTP request.

httpResponse - The HTTP response.

Throws:

IOException - If writing the response failed.

writeErrorResponse

protected void writeErrorResponse(@Nonnull
                                  Throwable rex,
                                  @Nonnull
                                  net.morimekta.providence.serializer.Serializer responseSerializer,
                                  @Nonnull
                                  javax.servlet.http.HttpServletRequest httpRequest,
                                  @Nonnull
                                  javax.servlet.http.HttpServletResponse httpResponse)
                           throws IOException

Write the error response. Override this method in order to write the response or response headers specifically. Callers must call super if response not written. It is fine to set headers and call super too.

Parameters:

rex - The response exception.

responseSerializer - The response serializer.

httpRequest - The request.

httpResponse - The response.

Throws:

IOException - If writing the response failed.

getResponseException

@Nonnull
protected Throwable getResponseException(Throwable e)

Get the exception to ge handled on failed requests.

Parameters:

e - The exception seen.

Returns:

The exception to use as response base.

statusCodeForException

protected int statusCodeForException(@Nonnull
                                     Throwable exception)

With default exception handling, this can simply change the status code used for the response.

Parameters:

exception - The exception seen.

Returns:

The status code to be used.