From 65d4d71895629dc839761c59a5f22be153c5269f Mon Sep 17 00:00:00 2001
From: Oliver Drotbohm <odrotbohm@vmware.com>
Date: Wed, 24 Feb 2021 17:58:39 +0100
Subject: [PATCH] Support for jMolecules Identifier types.

We now properly handle jMolecules Identifier instances by integration with the corresponding Converter implementations provided by the jmolecules-spring integrations library.

Fixes GH-1982.
---
 spring-data-rest-webmvc/pom.xml               |   7 +
 .../webmvc/config/JMoleculesConfigurer.java   | 163 ++++++++++++++++++
 .../config/RestControllerImportSelector.java  |   9 +-
 3 files changed, 178 insertions(+), 1 deletion(-)
 create mode 100644 spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/config/JMoleculesConfigurer.java

diff --git a/spring-data-rest-webmvc/pom.xml b/spring-data-rest-webmvc/pom.xml
index da4c7f128..42ef27ddf 100644
--- a/spring-data-rest-webmvc/pom.xml
+++ b/spring-data-rest-webmvc/pom.xml
@@ -35,6 +35,13 @@
 			<groupId>org.springframework</groupId>
 			<artifactId>spring-webmvc</artifactId>
 		</dependency>
+		
+		<dependency>
+			<groupId>org.jmolecules.integrations</groupId>
+			<artifactId>jmolecules-spring</artifactId>
+			<version>${jmolecules-integration}</version>
+			<optional>true</optional>
+		</dependency>
 
 		<dependency>
 			<groupId>javax.servlet</groupId>
diff --git a/spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/config/JMoleculesConfigurer.java b/spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/config/JMoleculesConfigurer.java
new file mode 100644
index 000000000..65efcc50a
--- /dev/null
+++ b/spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/config/JMoleculesConfigurer.java
@@ -0,0 +1,163 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.rest.webmvc.config;
+
+import java.io.Serializable;
+import java.util.function.Supplier;
+
+import org.jmolecules.ddd.types.Entity;
+import org.jmolecules.ddd.types.Identifier;
+import org.jmolecules.spring.IdentifierToPrimitivesConverter;
+import org.jmolecules.spring.PrimitivesToIdentifierConverter;
+import org.springframework.beans.factory.ObjectFactory;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Lazy;
+import org.springframework.core.ResolvableType;
+import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.core.convert.support.ConfigurableConversionService;
+import org.springframework.data.mapping.PersistentEntity;
+import org.springframework.data.mapping.PersistentProperty;
+import org.springframework.data.mapping.context.PersistentEntities;
+import org.springframework.data.rest.webmvc.spi.BackendIdConverter;
+import org.springframework.format.FormatterRegistry;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+
+/**
+ * Configuration for JMolecules integration. Registers the following components:
+ * <ul>
+ * <li>{@link IdentifierToPrimitivesConverter} and {@link PrimitivesToIdentifierConverter} in case not already present
+ * in the Spring MVC {@link ConversionService}</li>
+ * <li>the same converters on the {@link ConversionService} exposed to {@link RepositoryRestConfigurer}.</li>
+ * <li>a {@link BackendIdConverter} using those converters</li>
+ * </ol>
+ *
+ * @author Oliver Drotbohm
+ * @since 3.5
+ */
+@Configuration(proxyBeanMethods = false)
+class JMoleculesConfigurer implements WebMvcConfigurer, RepositoryRestConfigurer {
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.web.servlet.config.annotation.WebMvcConfigurer#addFormatters(org.springframework.format.FormatterRegistry)
+	 */
+	@Override
+	public void addFormatters(FormatterRegistry registry) {
+
+		ConversionService conversionService = (ConversionService) registry;
+		Supplier<ConversionService> supplier = () -> conversionService;
+
+		if (!conversionService.canConvert(Identifier.class, String.class)) {
+			registry.addConverter(new IdentifierToPrimitivesConverter(supplier));
+		}
+
+		if (!conversionService.canConvert(String.class, Identifier.class)) {
+			registry.addConverter(new PrimitivesToIdentifierConverter(supplier));
+		}
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.rest.webmvc.config.RepositoryRestConfigurer#configureConversionService(org.springframework.core.convert.support.ConfigurableConversionService)
+	 */
+	@Override
+	public void configureConversionService(ConfigurableConversionService conversionService) {
+
+		Supplier<ConversionService> supplier = () -> conversionService;
+
+		conversionService.addConverter(new PrimitivesToIdentifierConverter(supplier));
+		conversionService.addConverter(new IdentifierToPrimitivesConverter(supplier));
+	}
+
+	@Lazy
+	@Bean
+	BackendIdConverter jMoleculesEntitiesBackendIdConverter(PersistentEntities entities,
+			@Qualifier("mvcConversionService") ObjectFactory<ConversionService> conversionService) {
+		return new JMoleculesBackendIdentifierConverter(entities, () -> conversionService.getObject());
+	}
+
+	/**
+	 * A {@link BackendIdConverter} to convert from and to JMolecules' Identifier
+	 *
+	 * @author Oliver Drotbohm
+	 */
+	private static final class JMoleculesBackendIdentifierConverter implements BackendIdConverter {
+
+		private static final TypeDescriptor STRING_DESCRIPTOR = TypeDescriptor.valueOf(String.class);
+		private static final ResolvableType IDENTIFIER_TYPE = ResolvableType.forClass(Identifier.class);
+
+		private final PrimitivesToIdentifierConverter identifierConverter;
+		private final IdentifierToPrimitivesConverter primitivesConverter;
+		private final PersistentEntities entities;
+
+		/**
+		 * Creates a new {@link JMoleculesBackendIdentifierConverter} for the given {@link PersistentEntities} and
+		 * {@link ConversionService}.
+		 *
+		 * @param entities must not be {@literal null}.
+		 * @param conversionService must not be {@literal null}.
+		 */
+		public JMoleculesBackendIdentifierConverter(PersistentEntities entities,
+				Supplier<? extends ConversionService> conversionService) {
+
+			this.identifierConverter = new PrimitivesToIdentifierConverter(conversionService);
+			this.primitivesConverter = new IdentifierToPrimitivesConverter(conversionService);
+			this.entities = entities;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.rest.webmvc.spi.BackendIdConverter#fromRequestId(java.lang.String, java.lang.Class)
+		 */
+		@Override
+		public Serializable fromRequestId(String id, Class<?> entityType) {
+
+			PersistentEntity<?, ? extends PersistentProperty<?>> entity = entities.getRequiredPersistentEntity(entityType);
+			Class<?> idType = entity.getRequiredIdProperty().getType();
+
+			return (Serializable) identifierConverter.convert(id, TypeDescriptor.forObject(id),
+					TypeDescriptor.valueOf(idType));
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.rest.webmvc.spi.BackendIdConverter#toRequestId(java.io.Serializable, java.lang.Class)
+		 */
+		@Override
+		public String toRequestId(Serializable id, Class<?> entityType) {
+			return (String) primitivesConverter.convert(id, TypeDescriptor.forObject(id), STRING_DESCRIPTOR);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.plugin.core.Plugin#supports(java.lang.Object)
+		 */
+		@Override
+		public boolean supports(Class<?> delimiter) {
+
+			if (!Entity.class.isAssignableFrom(delimiter)) {
+				return false;
+			}
+
+			return IDENTIFIER_TYPE.isAssignableFrom(ResolvableType.forClass(delimiter)
+					.as(Entity.class)
+					.getGeneric(1));
+		}
+	}
+}
diff --git a/spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/config/RestControllerImportSelector.java b/spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/config/RestControllerImportSelector.java
index 9f46e7976..801ce7812 100644
--- a/spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/config/RestControllerImportSelector.java
+++ b/spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/config/RestControllerImportSelector.java
@@ -34,6 +34,7 @@ import org.springframework.util.ClassUtils;
 class RestControllerImportSelector implements ImportSelector {
 
 	private static final String HAL_EXPLORER_CONFIGURATION = "org.springframework.data.rest.webmvc.halexplorer.HalExplorerConfiguration";
+	private static final String JMOLECULES_SPRING = "org.jmolecules.spring.IdentifierToPrimitivesConverter";
 
 	/*
 	 * (non-Javadoc)
@@ -45,10 +46,16 @@ class RestControllerImportSelector implements ImportSelector {
 		List<String> configurations = new ArrayList<>();
 		configurations.add(RestControllerConfiguration.class.getName());
 
-		if (ClassUtils.isPresent(HAL_EXPLORER_CONFIGURATION, importingClassMetadata.getClass().getClassLoader())) {
+		ClassLoader classLoader = importingClassMetadata.getClass().getClassLoader();
+
+		if (ClassUtils.isPresent(HAL_EXPLORER_CONFIGURATION, classLoader)) {
 			configurations.add(HAL_EXPLORER_CONFIGURATION);
 		}
 
+		if (ClassUtils.isPresent(JMOLECULES_SPRING, classLoader)) {
+			configurations.add(JMoleculesConfigurer.class.getName());
+		}
+
 		return configurations.toArray(new String[configurations.size()]);
 	}
 }