Finer-grain control of exception behaviour in view renderers

[acwwat]

This PR is one possible implementation of issue #1811. In short, I am standardizing the exception thrown by each ViewRenderer implementation as ViewRenderException, which is then caught and rethrown as WebApplicationException by ViewMessageBodyWriter.

To preserve previous behavior of returning an HTML error response on render exceptions, I have added a new ViewRenderExceptionMapper class which should be registered. Consequently I am still changing the original behavior by adding this registration requirement. Let me know if this is OK from backward-compatibility standpoint - if needed we can register the mapper in ViewBundle, although I don't know how I can register another exception mapper afterwards if I want custom behaviour. This also requires change to the documentation.

Otherwise, one can choose to provide their own ExceptionMapper to catch WebApplicationException and check that the cause is ViewRenderException, then do whatever is needed with its cause in the form of an exception thrown by the rendering code (Viewmarker, Mustache, etc.)

I tried updating the tests to verify both cases of with and without ViewRenderExceptionMapper, but I can't seem to get registration in each test case working like this:

target("/test/bad").regsiter(new ViewRenderExceptionMapper()).request().get(String.class);

I had to register the mapper in configure(). Please let me know if you have any solution to this so I can increase the test coverage.

Thanks.

[coveralls]

Coverage decreased (-0.1%) to 81.804% when pulling 46a0a14 on acwwat:view-exc into 867a101 on dropwizard:master.

[nickbabcock]

I think it would be worthwhile to have a test in dropwizard-e2e/src/main/java/com/example/app1 showing that the behavior can be changed.

[acwwat]

@nickbabcock I added a test/example to e2e on overriding the standard 503 response on missing mustache view with a 404 response.

[coveralls]

Coverage decreased (-0.09%) to 81.814% when pulling 534205f on acwwat:view-exc into 867a101 on dropwizard:master.

[dren-dk]

My preference would be to format the log message in my own ExceptionMapper, so could this go into the ExceptionMapper as well?

[acwwat]

That makes sense. I've removed the logging from ViewMessageBodyWriter and added the logging code to ViewRenderExceptionMapper to preserve the original exception logging behavior.

[coveralls]

Coverage decreased (-0.1%) to 81.794% when pulling 6d3a467 on acwwat:view-exc into 867a101 on dropwizard:master.

[arteam]

The pull request looks good to me. I don't think the code coverage is so important, what matters you provided relevant tests. And thank you very much for a very detailed documentation for ViewRenderException!