Null serialisation is not disabled when spring.gson.serialize-nulls is set to false

[zhanglc]

fix: #13622

gson should not serialize null value when set spring.gson.serialize-nulls=false

test case:

       @Test
	public void serializeNullsFalse() {
		this.contextRunner.withPropertyValues("spring.gson.serialize-nulls:false")
				.run((context) -> {
					Gson gson = context.getBean(Gson.class);
					assertThat(gson.serializeNulls()).isFalse();
				});
	}

[zhanglc]

The code which I changed pass the Tests.

[INFO] Running org.springframework.boot.autoconfigure.gson.GsonAutoConfigurationTests
[INFO] Tests run: 18, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.268 s - in org.springframework.boot.autoconfigure.gson.GsonAutoConfigurationTests

But some test failed from the master branch:

[INFO] Running org.springframework.boot.autoconfigure.ImportAutoConfigurationTests
[ERROR] Tests run: 5, Failures: 2, Errors: 0, Skipped: 0, Time elapsed: 0.155 s <<< FAILURE! - in org.springframework.boot.autoconfigure.ImportAutoConfigurationTests
[ERROR] multipleAnnotationsShouldMergeCorrectly(org.springframework.boot.autoconfigure.ImportAutoConfigurationTests)  Time elapsed: 0.088 s  <<< FAILURE!
java.lang.AssertionError: 

Actual and expected have the same elements but not in the same order, at index 0 actual element was:
  <"ConfigC">
whereas expected element was:
  <"ConfigA">

[wilkinsona]

@zhanglc Thank you for your efforts to contribute to Spring Boot. They're much appreciated. Please note that there's no need to close a pull request and open a new one if you want to refine it. Doing so creates some extra noise for everyone watching the repository. Instead, please push new commits to the branch you have used for the pull request or amend an existing commit and force-push it.

[zhanglc]

@wilkinsona Sorry for that.

This is my first time contributing to the open source project and I am not too familiar with it.
The master branch can't build now.
What should I do next?

[wilkinsona]

No problem. That failure seems to be unrelated to the proposed change so please don't worry about it. Master is building against snapshots of Spring Framework so it may be that a change there as caused the test to start to fail.

[snicoll]

@zhanglc thank you for making your first contribution to Spring Boot. This is now merged in 2.1.x and master.