Support to receive aggregate references as request parameters.

We now support using AggregateReference as type to bind request parameters taking URIs pointing to related aggregates. The default resolution will try to resolve the entire URI via UriToEntityConverter but one can also provide a function that can extract any part of the URI to be then resolved into either an identifier, aggregate instance or jMolecules Association against the ConversionService.

Fixes #2239.

spring-data-rest-webmvc/src/test/java/org/springframework/data/rest/webmvc/config/StringToAggregateReferenceConverterUnitTests.java

@@ -0,0 +1,141 @@
+/*
+ * Copyright 2023 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 static org.assertj.core.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.*;
+import static org.mockito.Mockito.*;
+
+import java.net.URI;
+import java.util.UUID;
+
+import org.jmolecules.ddd.types.Association;
+import org.jmolecules.ddd.types.Identifier;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.core.ResolvableType;
+import org.springframework.core.convert.ConversionFailedException;
+import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.core.convert.support.DefaultConversionService;
+import org.springframework.data.rest.core.AggregateReference;
+import org.springframework.data.rest.core.AssociationAggregateReference;
+
+/**
+ * Unit tests for {@link StringToAggregateReferenceConverter}.
+ *
+ * @author Oliver Drotbohm
+ */
+@ExtendWith(MockitoExtension.class)
+class StringToAggregateReferenceConverterUnitTests {
+
+	@Mock ConversionService conversionService;
+
+	StringToAggregateReferenceConverter converter = new StringToAggregateReferenceConverter(() -> conversionService);
+
+	@Test // GH-2239
+	void convertsUriIntoAggregateReference() {
+
+		var aggregate = new Object();
+
+		when(conversionService.convert(any(), any(), eq(toTypeDescriptor(Long.class)))).thenReturn(42L);
+		when(conversionService.convert(any(), any(), eq(toTypeDescriptor(Object.class)))).thenReturn(aggregate);
+
+		var source = "/foo/42";
+
+		var result = converter.convert(source, TypeDescriptor.valueOf(String.class),
+				toTypeDescriptor(AggregateReference.class, Object.class, Long.class));
+
+		assertThat(result.getUri()).isEqualTo(URI.create(source));
+		assertThat(result.resolveId()).isEqualTo(42L);
+		assertThat(result.resolveAggregate()).isEqualTo(aggregate);
+	}
+
+	@Test // GH-2239
+	void convertsUriIntoAggregateReferenceUsingCustomExtractor() {
+
+		var aggregate = new Object();
+
+		when(conversionService.convert(any(), any(), eq(toTypeDescriptor(Long.class)))).thenReturn(42L);
+		when(conversionService.convert(any(), any(), eq(toTypeDescriptor(Object.class)))).thenReturn(aggregate);
+
+		var source = "/foo/42";
+
+		var result = converter.convert(source, TypeDescriptor.valueOf(String.class),
+				toTypeDescriptor(AggregateReference.class, Object.class, Long.class));
+
+		result = result.withIdSource(it -> it.getPathSegments().get(1));
+
+		assertThat(result.getUri()).isEqualTo(URI.create(source));
+		assertThat(result.resolveId()).isEqualTo(42L);
+		assertThat(result.resolveAggregate()).isEqualTo(aggregate);
+	}
+
+	@Test // GH-2239
+	void createsAssociationAggregateReference() {
+
+		var identifier = new CustomIdentifier();
+
+		when(conversionService.convert(any(), any(), eq(toTypeDescriptor(CustomIdentifier.class)))).thenReturn(identifier);
+
+		var source = "/foo/42";
+
+		var result = converter.convert(source, TypeDescriptor.valueOf(String.class),
+				toTypeDescriptor(AssociationAggregateReference.class, Object.class, CustomIdentifier.class));
+
+		assertThat(result).isInstanceOfSatisfying(AssociationAggregateReference.class, it -> {
+			assertThat(it.resolveAssociation()).isNotNull()
+					.extracting(Association::getId).isEqualTo(identifier);
+		});
+	}
+
+	@Test // GH-2239
+	void rejectsNullSource() {
+
+		assertThatExceptionOfType(ConversionFailedException.class)
+				.isThrownBy(() -> converter.convert(null, TypeDescriptor.valueOf(String.class),
+						toTypeDescriptor(AggregateReference.class, Object.class, UUID.class)));
+	}
+
+	@Test // GH-2239
+	void rejectsInvalidURI() {
+
+		assertThatExceptionOfType(ConversionFailedException.class)
+				.isThrownBy(() -> converter.convert("@\\", TypeDescriptor.valueOf(String.class),
+						toTypeDescriptor(AggregateReference.class, Object.class, UUID.class)));
+	}
+
+	@Test // GH-2239
+	void registersConversions() {
+
+		var service = new DefaultConversionService();
+		service.addConverter(converter);
+
+		assertThat(service.canConvert(String.class, AggregateReference.class)).isTrue();
+		assertThat(service.canConvert(String.class, AssociationAggregateReference.class)).isTrue();
+	}
+
+	private static TypeDescriptor toTypeDescriptor(Class<?> type, Class<?>... generics) {
+
+		var resolvableType = ResolvableType.forClassWithGenerics(type, generics);
+
+		return new TypeDescriptor(resolvableType, null, null);
+	}
+
+	private static class CustomIdentifier implements Identifier {}
+}