This adds the `Feign.Builder.decode404()` flag which indicates decoders
should process responses with 404 status. It also changes all
first-party decoders (like gson) to return well-known empty values by
default. Further customization is possible by wrapping or creating a
custom decoder.
Prior to this change, we used custom invocation handlers as the way to
add fallback values based on exception or return status. `feign-hystrix`
uses this to return `HystrixCommand<X>`, but the general pattern applies
to anything that has a type representing both success and failure, such
as `Try<X>` or `Observable<X>`.
As we define it here, 404 status is not a retry or fallback policy, it
is just empty semantics. By limiting Feign's special processing to 404,
we gain a lot with very little supporting code.
If instead we opened all codes, Feign could easily turn bad request,
redirect, or server errors silently to null. This sort of configuration
issue is hard to troubleshoot. 404 -> empty is a very safe policy vs
all codes.
Moreover, we don't create a cliff, where folks seeking fallback policy
eventually realize they can't if only given a response code. Fallback
systems like Hystrix address exceptions that occur before or in lieu of
a response. By special-casing 404, we avoid a slippery slope of half-
implementing Hystrix.
Finally, 404 handling has been commonly requested: it has a clear use-
case, and through that value. This design supports that without breaking
compatibility, or impacting existing integrations such as Hystrix or
Ribbon.
See #238#287
Files had various formatting differences, as did pull requests. Rather than
create our own style, this inherits and requires the well documented Google
Java Style.
Feign has `MethodMetadata.bodyType()`, but never passed it to encoders.
Encoders that register type adapters need to do so based on the
interface desired as opposed to the implementation class. This change
breaks api compatibility for < 8.x, by requiring an additional arg
on `Encoder.encode`.
see https://github.com/square/retrofit/issues/713
Dagger 1.x and 2.x are incompatible. Rather than choose one over the
other, this change removes Dagger completely. Users can now choose any
injector, constructing Feign via its Builder.
This change also drops support for javax.inject.Named, which has
been replaced by feign.Param.
see #120
AssertJ has more powerful test assertions and does not run the risk of
interfering with the classpath of main code, such as guava does. This
removes guava from test and example code and adjusts using AssertJ in
some cases.
JUnit Rules, such as MockWebServerRule, reduce boilerplate setup present
in our tests. By migrating off TestNG, and onto rules, our tests become
more maintainable as JUnit is well understood.
Adrian Cole
Adrian Cole
Rob Spieldenner
Whitaker, Greg