Polish

See gh-30152

Author: wilkinsona

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jackson/JacksonAutoConfiguration.java

@@ -48,7 +48,6 @@
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.jackson.JsonComponentModule;
 import org.springframework.boot.jackson.JsonMixinModule;
-import org.springframework.boot.jackson.JsonMixinScanPackages;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -98,10 +97,8 @@ public JsonComponentModule jsonComponentModule() {
 
 	@Bean
 	public JsonMixinModule jsonMixinModule(ApplicationContext context) {
-		List<String> packages = JsonMixinScanPackages.get(context).getPackageNames();
-		if (packages.isEmpty() && AutoConfigurationPackages.has(context)) {
-			packages = AutoConfigurationPackages.get(context);
-		}
+		List<String> packages = AutoConfigurationPackages.has(context) ? AutoConfigurationPackages.get(context)
+				: Collections.emptyList();
 		return new JsonMixinModule(context, packages);
 	}
 

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

@@ -47,8 +47,10 @@
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.databind.util.StdDateFormat;
 import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;
+import org.assertj.core.api.InstanceOfAssertFactories;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.boot.autoconfigure.AutoConfigurationPackage;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.autoconfigure.http.HttpMessageConvertersAutoConfiguration;
 import org.springframework.boot.jackson.JsonComponent;
@@ -92,8 +94,13 @@ void doubleModuleRegistration() {
 	}
 
 	@Test
-	void jsonMixinModuleShouldBeAutoconfigured() {
-		this.contextRunner.run((context) -> assertThat(context).hasSingleBean(JsonMixinModule.class));
+	void jsonMixinModuleShouldBeAutoConfiguredWithBasePackages() {
+		this.contextRunner.withUserConfiguration(MixinConfiguration.class).run((context) -> {
+			assertThat(context).hasSingleBean(JsonMixinModule.class);
+			JsonMixinModule module = context.getBean(JsonMixinModule.class);
+			assertThat(module).extracting("basePackages", InstanceOfAssertFactories.list(String.class))
+					.containsExactly(MixinConfiguration.class.getPackage().getName());
+		});
 	}
 
 	@Test
@@ -637,4 +644,9 @@ void setBirthDate(Date birthDate) {
 
 	}
 
+	@AutoConfigurationPackage
+	static class MixinConfiguration {
+
+	}
+
 }

spring-boot-project/spring-boot-docs/src/docs/asciidoc/features/json.adoc

@@ -40,6 +40,14 @@ include::code:object/MyJsonComponent[]
 
 
 
+[[features.json.jackson.mixins]]
+==== Mixins
+Jackson has support for mixins that can be used to mix additional annotations into those already declared on a target class.
+Spring Boot's Jackson auto-configuration will scan your application's packages for classes annotated with `@JsonMixin` and register them with the auto-configured `ObjectMapper`.
+The registration is performed by Spring Boot's `JsonMixinModule`.
+
+
+
 [[features.json.gson]]
 === Gson
 Auto-configuration for Gson is provided.

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/jackson/JsonMixinModule.java

@@ -16,7 +16,6 @@
 
 package org.springframework.boot.jackson;
 
-import java.io.IOException;
 import java.util.Collection;
 
 import com.fasterxml.jackson.databind.Module;
@@ -29,15 +28,16 @@
 import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
 import org.springframework.core.annotation.MergedAnnotation;
 import org.springframework.core.annotation.MergedAnnotations;
-import org.springframework.core.type.classreading.MetadataReader;
+import org.springframework.core.type.filter.AnnotationTypeFilter;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
- * Spring Bean and Jackson {@link Module} to register {@link JsonMixin @JsonMixin}
- * annotated beans.
+ * Spring Bean and Jackson {@link Module} to find and
+ * {@link SimpleModule#setMixInAnnotation(Class, Class) register}
+ * {@link JsonMixin @JsonMixin}-annotated classes.
  *
  * @author Guirong Hu
  * @since 2.7.0
@@ -68,7 +68,6 @@ public void afterPropertiesSet() throws Exception {
 		JsonMixinComponentScanner scanner = new JsonMixinComponentScanner();
 		scanner.setEnvironment(this.context.getEnvironment());
 		scanner.setResourceLoader(this.context);
-
 		for (String basePackage : this.basePackages) {
 			if (StringUtils.hasText(basePackage)) {
 				for (BeanDefinition candidate : scanner.findCandidateComponents(basePackage)) {
@@ -81,25 +80,20 @@ public void afterPropertiesSet() throws Exception {
 	private void addJsonMixin(Class<?> mixinClass) {
 		MergedAnnotation<JsonMixin> annotation = MergedAnnotations
 				.from(mixinClass, MergedAnnotations.SearchStrategy.TYPE_HIERARCHY).get(JsonMixin.class);
-		Class<?>[] targetTypes = annotation.getClassArray("type");
-		if (ObjectUtils.isEmpty(targetTypes)) {
-			return;
-		}
-		for (Class<?> targetType : targetTypes) {
+		for (Class<?> targetType : annotation.getClassArray("type")) {
 			setMixInAnnotation(targetType, mixinClass);
 		}
 	}
 
 	static class JsonMixinComponentScanner extends ClassPathScanningCandidateComponentProvider {
 
-		@Override
-		protected boolean isCandidateComponent(MetadataReader metadataReader) throws IOException {
-			return true;
+		JsonMixinComponentScanner() {
+			addIncludeFilter(new AnnotationTypeFilter(JsonMixin.class));
 		}
 
 		@Override
 		protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) {
-			return beanDefinition.getMetadata().hasAnnotation(JsonMixin.class.getName());
+			return true;
 		}
 
 	}