Fix NPE when building a client with a query param with no values

[jebeaudet]

Using feign-core 7.1.0, when creating a feign client with a query param with no values, the builder throws a NPE. I didn't want to include Apache CollectionsUtils so I just added a null check. Thanks for the great library btw, hope this PR is OK!

TestApi.java:

public interface TestApi
{
    @RequestLine("POST /api/{parameter}?in_error")
    void updateInError(@Named("parameter")String parameter);
}

Builder :

Feign.builder()
         .decoder(new GsonDecoder())
         .encoder(new GsonEncoder())
         .logLevel(Level.FULL)
         .target(TestApi.class, "http://localhost:8888");

throws this stackstrace :

java.lang.NullPointerException: null
    at feign.RequestTemplate.allValuesAreNull(RequestTemplate.java:494) ~[feign-core-7.1.0.jar:7.1.0]
    at feign.RequestTemplate.pullAnyQueriesOutOfUrl(RequestTemplate.java:476) ~[feign-core-7.1.0.jar:7.1.0]
    at feign.RequestTemplate.append(RequestTemplate.java:207) ~[feign-core-7.1.0.jar:7.1.0]
    at feign.Contract$Default.processAnnotationOnMethod(Contract.java:137) ~[feign-core-7.1.0.jar:7.1.0]
    at feign.Contract$BaseContract.parseAndValidatateMetadata(Contract.java:62) ~[feign-core-7.1.0.jar:7.1.0]
    at feign.Contract$BaseContract.parseAndValidatateMetadata(Contract.java:48) ~[feign-core-7.1.0.jar:7.1.0]
    at feign.ReflectiveFeign$ParseHandlersByName.apply(ReflectiveFeign.java:143) ~[feign-core-7.1.0.jar:7.1.0]
    at feign.ReflectiveFeign.newInstance(ReflectiveFeign.java:58) ~[feign-core-7.1.0.jar:7.1.0]
    at feign.Feign$Builder.target(Feign.java:265) ~[feign-core-7.1.0.jar:7.1.0]
    at feign.Feign$Builder.target(Feign.java:261) ~[feign-core-7.1.0.jar:7.1.0]

[cloudbees-pull-request-builder]

NetflixOSS » feign » feign-pull-requests #60 SUCCESS
This pull request looks good

[codefromthecrypt]

Thanks for the help! Looks good. just might want to add a test in DefaultContractTest to ensure query w/o value continues to work later :)

A couple small notes

1. most likely, you'll want to put your changes on a branch besides master. that way, things like squashing commits are contained.
2. when your commit is final, reword it so that it says what it supports. ex.

Supports query params without values

Fixes an NPE when building a client with a query param with no values.

The above Supports query params without values header looks nicer in the commit log, but the details are still present. Reads like "this commit Supports query params without values"

Make sense?

Thanks again!

[codefromthecrypt]

Oh yeah and don't forget to update CHANGES.md for the next minor version of 7.x

[jebeaudet]

Thanks for the tips! I'll close this one and reopen another from a different branch.