Ensure JsonMapper is autoconfigured when non-JSON ObjectMapper beans …

[yangfeng123456]

Fixes an issue where the presence of a non-JSON ObjectMapper (such as CsvMapper)
prevents the auto-configuration of the default JsonMapper.

Previously, any ObjectMapper bean caused JsonMapper auto-configuration to back off,
which could lead to unexpected JSON serialization failures in web applications.

This change ensures that JsonMapper is still auto-configured when non-JSON
ObjectMapper beans are present.

A test has been added to verify the correct behavior.

[wilkinsona]

This appears to be a duplicate of #47379 and we already have a test for this:

spring-boot/module/spring-boot-jackson/src/test/java/org/springframework/boot/jackson/autoconfigure/JacksonAutoConfigurationTests.java

Lines 130 to 137 in eab6923

	@EnumSource
	@ParameterizedTest
	void mapperDoesNotBackOffWhenObjectMapperIsDefined(MapperType mapperType) {
	this.contextRunner.withBean(ObjectMapper.class).run((context) -> {
	assertThat(context).hasSingleBean(mapperType.mapperClass);
	assertThat(context.getBeansOfType(ObjectMapper.class)).hasSize(MapperType.values().length + 1);
	});
	}

Furthermore, the proposed fix won't result in a change in behavior as the condition uses the method's return type by default. The test is also faulty as it asserts that there's a single ObjectMapper bean. There will be and should be multiple.

[yangfeng123456]

This appears to be a duplicate of #47379 and we already have a test for this:

spring-boot/module/spring-boot-jackson/src/test/java/org/springframework/boot/jackson/autoconfigure/JacksonAutoConfigurationTests.java

Lines 130 to 137 in eab6923

	@EnumSource
	@ParameterizedTest
	void mapperDoesNotBackOffWhenObjectMapperIsDefined(MapperType mapperType) {
	this.contextRunner.withBean(ObjectMapper.class).run((context) -> {
	assertThat(context).hasSingleBean(mapperType.mapperClass);
	assertThat(context.getBeansOfType(ObjectMapper.class)).hasSize(MapperType.values().length + 1);
	});
	}

Furthermore, the proposed fix won't result in a change in behavior as the condition uses the method's return type by default. The test is also faulty as it asserts that there's a single ObjectMapper bean. There will be and should be multiple.

Thank you very much for the detailed explanation and for taking the time to review this.

[wilkinsona]

No problem, but please be more considerate of our time in future. Opening a PR that includes a test that doesn't pass isn't a good use of our time or yours. You should run the build locally and make sure that everything's working before submitting something for review.

[yangfeng123456]

No problem, but please be more considerate of our time in future. Opening a PR that includes a test that doesn't pass isn't a good use of our time or yours. You should run the build locally and make sure that everything's working before submitting something for review.

Apologies for the oversight, and thank you for the feedback.