fix: register the HAL beans when HateoasProperties is absent

CHANGELOG.md

@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- #3328, #3337 – `/v3/api-docs` fails with a `NullPointerException` when spring-hateoas is on the classpath without `HateoasProperties`
 - #3320 – `@Order` and `Ordered` ignored when applying customizers
 - #3319 – A `Page` nested in another schema is not replaced by `PagedModel`
 - #3313 – Springdoc auto-configurations rely on unspecified auto-configuration ordering

springdoc-openapi-starter-common/src/main/java/org/springdoc/core/configuration/SpringDocHateoasConfiguration.java

@@ -42,6 +42,7 @@
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
 import org.springframework.boot.hateoas.autoconfigure.HateoasProperties;
 import org.springframework.context.annotation.Bean;
@@ -58,23 +59,62 @@
 @Configuration(proxyBeanMethods = false)
 @AutoConfigureAfter(SpringDocConfiguration.class)
 @ConditionalOnExpression("${springdoc.api-docs.enabled:true} and ${springdoc.enable-hateoas:true}")
-@ConditionalOnClass({LinkRelationProvider.class, HateoasProperties.class})
+@ConditionalOnClass(LinkRelationProvider.class)
 @ConditionalOnWebApplication
 @ConditionalOnBean(SpringDocConfiguration.class)
 public class SpringDocHateoasConfiguration {
 
 	/**
-	 * Hateoas hal provider hateoas hal provider.
+	 * Configuration for HateoasHalProvider when HateoasProperties is on the classpath.
 	 *
-	 * @param hateoasPropertiesOptional the hateoas properties optional
-	 * @param objectMapperProvider      the object mapper provider
-	 * @return the hateoas hal provider
+	 * @author bnasslahsen
 	 */
-	@Bean
-	@ConditionalOnMissingBean
-	@Lazy(false)
-	HateoasHalProvider hateoasHalProvider(Optional<HateoasProperties> hateoasPropertiesOptional, ObjectMapperProvider objectMapperProvider) {
-		return new HateoasHalProvider(hateoasPropertiesOptional, objectMapperProvider);
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass(name = {
+			"org.springframework.hateoas.server.LinkRelationProvider",
+			"org.springframework.boot.hateoas.autoconfigure.HateoasProperties"
+	})
+	static class HateoasPropertiesConfiguration {
+
+		/**
+		 * Hateoas hal provider hateoas hal provider.
+		 *
+		 * @param hateoasPropertiesOptional the hateoas properties optional
+		 * @param objectMapperProvider      the object mapper provider
+		 * @return the hateoas hal provider
+		 */
+		@Bean
+		@ConditionalOnMissingBean
+		@Lazy(false)
+		HateoasHalProvider hateoasHalProvider(Optional<HateoasProperties> hateoasPropertiesOptional, ObjectMapperProvider objectMapperProvider) {
+			return new HateoasHalProvider(hateoasPropertiesOptional, objectMapperProvider);
+		}
+
+	}
+
+	/**
+	 * Fallback configuration for HateoasHalProvider when HateoasProperties is absent.
+	 *
+	 * @author bnasslahsen
+	 */
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass(name = "org.springframework.hateoas.server.LinkRelationProvider")
+	@ConditionalOnMissingClass("org.springframework.boot.hateoas.autoconfigure.HateoasProperties")
+	static class NoHateoasPropertiesConfiguration {
+
+		/**
+		 * Hateoas hal provider hateoas hal provider.
+		 *
+		 * @param objectMapperProvider the object mapper provider
+		 * @return the hateoas hal provider
+		 */
+		@Bean
+		@ConditionalOnMissingBean
+		@Lazy(false)
+		HateoasHalProvider hateoasHalProvider(ObjectMapperProvider objectMapperProvider) {
+			return new HateoasHalProvider(Optional.empty(), objectMapperProvider);
+		}
+
 	}
 
 	/**

springdoc-openapi-starter-common/src/main/java/org/springdoc/core/utils/SpringDocDataRestUtils.java

@@ -265,6 +265,8 @@ private void updateRequestBodySchemaProperties(String key, Schema referencedSche
 	 * @return the schema
 	 */
 	private Schema updateResponseSchema(String className, Schema existingSchema, Components components, boolean openapi31) {
+		if (existingSchema == null)
+			return null;
 		Map<String, Schema> properties = existingSchema.getProperties();
 		EntityInfo entityInfo = entityInoMap.get(className);
 		if (!CollectionUtils.isEmpty(properties)) {
@@ -292,15 +294,16 @@ else if (EMBEDDED.equals(propId)) {
 	 */
 	private void updateResponseSchemaEmbedded(Components components, EntityInfo entityInfo, Entry<String, Schema> entry, boolean openapi31) {
 		String entityClassName = linkRelationProvider.getCollectionResourceRelFor(entityInfo.getDomainType()).value();
+		Map<String, Schema> embeddedProperties = entry.getValue().getProperties();
+		if (CollectionUtils.isEmpty(embeddedProperties))
+			return;
 		Schema itemsSchema = null;
 		if (openapi31) {
-			JsonSchema jsonSchema = (JsonSchema) entry.getValue().getProperties().get(entityClassName);
-			if (jsonSchema != null)
+			if (embeddedProperties.get(entityClassName) instanceof JsonSchema jsonSchema)
 				itemsSchema = jsonSchema.getItems();
 		}
 		else {
-			ArraySchema arraySchema = (ArraySchema) entry.getValue().getProperties().get(entityClassName);
-			if (arraySchema != null)
+			if (embeddedProperties.get(entityClassName) instanceof ArraySchema arraySchema)
 				itemsSchema = arraySchema.getItems();
 		}
 		if (itemsSchema != null) {

springdoc-openapi-starter-common/src/test/java/org/springdoc/core/configuration/SpringDocHateoasConfigurationTest.java

@@ -1,11 +1,17 @@
 package org.springdoc.core.configuration;
 
 import org.junit.jupiter.api.Test;
+import org.springdoc.core.configuration.SpringDocHateoasConfiguration.HateoasPropertiesConfiguration;
+import org.springdoc.core.configuration.SpringDocHateoasConfiguration.NoHateoasPropertiesConfiguration;
+import org.springdoc.core.converters.CollectionModelContentConverter;
 import org.springdoc.core.customizers.GlobalOpenApiCustomizer;
 import org.springdoc.core.customizers.OpenApiHateoasLinksCustomizer;
 import org.springdoc.core.properties.SpringDocConfigProperties;
+import org.springdoc.core.providers.HateoasHalProvider;
 
 import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.hateoas.autoconfigure.HateoasProperties;
+import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.webmvc.autoconfigure.WebMvcAutoConfiguration;
 import org.springframework.hateoas.config.HateoasConfiguration;
@@ -82,4 +88,50 @@ void linksSchemaCustomizerShouldNotBeRegisteredIfBeanWithSameNameAlreadyExists()
 					assertThat(context.getBean(LINKS_SCHEMA_CUSTOMIZER)).isNotExactlyInstanceOf(OpenApiHateoasLinksCustomizer.class);
 				});
 	}
+
+	@Test
+	void halBeansShouldBeRegisteredWhenHateoasPropertiesIsPresent() {
+		hateoasContextRunner()
+				.run(context -> {
+					assertThat(context).hasNotFailed();
+					assertThat(context).hasSingleBean(HateoasHalProvider.class);
+					assertThat(context).hasSingleBean(CollectionModelContentConverter.class);
+					assertThat(context).hasSingleBean(HateoasPropertiesConfiguration.class);
+					assertThat(context).doesNotHaveBean(NoHateoasPropertiesConfiguration.class);
+				});
+	}
+
+	/**
+	 * spring-hateoas can be on the classpath without the Spring Boot auto-configuration
+	 * module that carries {@link HateoasProperties}, which is what happens with
+	 * spring-boot-starter-data-rest alone. The HAL beans, and above all the
+	 * {@code _embedded} converter, must still be registered then.
+	 */
+	@Test
+	void halBeansShouldBeRegisteredWhenHateoasPropertiesIsAbsent() {
+		hateoasContextRunner()
+				.withClassLoader(new FilteredClassLoader(HateoasProperties.class))
+				.run(context -> {
+					assertThat(context).hasNotFailed();
+					assertThat(context).hasSingleBean(HateoasHalProvider.class);
+					assertThat(context).hasSingleBean(CollectionModelContentConverter.class);
+					assertThat(context).hasSingleBean(NoHateoasPropertiesConfiguration.class);
+					assertThat(context).doesNotHaveBean(HateoasPropertiesConfiguration.class);
+				});
+	}
+
+	private WebApplicationContextRunner hateoasContextRunner() {
+		return new WebApplicationContextRunner()
+				.withPropertyValues(
+						"springdoc.api-docs.enabled=true",
+						"springdoc.enable-hateoas=true"
+				)
+				.withConfiguration(AutoConfigurations.of(
+						WebMvcAutoConfiguration.class,
+						HateoasConfiguration.class,
+						SpringDocConfiguration.class,
+						SpringDocConfigProperties.class,
+						SpringDocHateoasConfiguration.class
+				));
+	}
 }