Allow injection of RepositoryMethodContext.

RepositoryMethodContext are now made available for dependency injection via RepositoryConfigurationExtensionSupport.registerBeansForRoot(…). Moved RMC into repository.core package (previously repository.core.support) and only expose factory methods on DefaultRepositoryMethodContext. DRMC also exposes a injection proxy lookup method that creates a proxy equipped with a TargetSource delegating to DRMC.getInstance() (previously ….getContext()). An additional, static DRMC.forMethod(…) allows the creation of a default instance for testing purposes.

Rename getRepository() to getMetadata() on RMC.

Fixes GH-3175.

Author: odrotbohm

src/main/java/org/springframework/data/repository/config/RepositoryConfigurationExtensionSupport.java

@@ -31,12 +31,15 @@
 import org.springframework.beans.factory.support.AbstractBeanDefinition;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.log.LogMessage;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.repository.core.RepositoryMetadata;
+import org.springframework.data.repository.core.RepositoryMethodContext;
 import org.springframework.data.repository.core.support.AbstractRepositoryMetadata;
+import org.springframework.data.repository.core.support.DefaultRepositoryMethodContext;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
@@ -106,7 +109,13 @@ public String getDefaultNamedQueryLocation() {
 	}
 
 	public void registerBeansForRoot(BeanDefinitionRegistry registry,
-			RepositoryConfigurationSource configurationSource) {}
+			RepositoryConfigurationSource configurationSource) {
+
+		// A proxy RepositoryMethodContext for dependency injection
+		registerIfNotAlreadyRegistered(
+				() -> new RootBeanDefinition(RepositoryMethodContext.class, DefaultRepositoryMethodContext::getInjectionProxy),
+				registry, "repositoryMethodContextFactory", configurationSource);
+	}
 
 	/**
 	 * Returns the prefix of the module to be used to create the default location for Spring Data named queries.

src/main/java/org/springframework/data/repository/core/RepositoryMethodContext.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2024 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.repository.core;
+
+import java.lang.reflect.Method;
+
+/**
+ * Interface containing methods and value objects to obtain information about the current repository method invocation.
+ * <p>
+ * The {@link #currentMethod()} method is usable if the repository factory is configured to expose the current
+ * repository method metadata (not the default). It returns the invoked repository method. Target objects or advice can
+ * use this to make advised calls.
+ * <p>
+ * Spring Data's framework does not expose method metadata by default, as there is a performance cost in doing so.
+ * <p>
+ * The functionality in this class might be used by a target object that needed access to resources on the invocation.
+ * However, this approach should not be used when there is a reasonable alternative, as it makes application code
+ * dependent on usage in particular.
+ *
+ * @author Christoph Strobl
+ * @author Mark Paluch
+ * @author Oliver Drotbohm
+ * @since 3.4.0
+ */
+public interface RepositoryMethodContext {
+
+	/**
+	 * Returns the metadata for the repository.
+	 *
+	 * @return the repository metadata, will never be {@literal null}.
+	 */
+	RepositoryMetadata getMetadata();
+
+	/**
+	 * Returns the current method that is being invoked.
+	 * <p>
+	 * The method object represents the method as being invoked on the repository interface. It doesn't match the backing
+	 * repository implementation in case the method invocation is delegated to an implementation method.
+	 *
+	 * @return the current method, will never be {@literal null}..
+	 */
+	Method getMethod();
+}

src/main/java/org/springframework/data/repository/core/support/DefaultRepositoryMethodContext.java

@@ -17,18 +17,22 @@
 
 import java.lang.reflect.Method;
 
+import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.core.NamedThreadLocal;
 import org.springframework.data.repository.core.RepositoryMetadata;
+import org.springframework.data.repository.core.RepositoryMethodContext;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 
 /**
  * Class containing value objects providing information about the current repository method invocation.
  *
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Oliver Drotbohm
  * @since 3.4.0
  */
-class DefaultRepositoryMethodContext implements RepositoryMethodContext {
+public class DefaultRepositoryMethodContext implements RepositoryMethodContext {
 
 	/**
 	 * ThreadLocal holder for repository method associated with this thread. Will contain {@code null} unless the
@@ -46,15 +50,41 @@ class DefaultRepositoryMethodContext implements RepositoryMethodContext {
 		this.method = method;
 	}
 
+	/**
+	 * Creates a new {@link RepositoryMethodContext} for the given {@link Method}.
+	 *
+	 * @param method must not be {@literal null}.
+	 * @return will never be {@literal null}.
+	 */
+	public static RepositoryMethodContext forMethod(Method method) {
+
+		Assert.notNull(method, "Method must not be null!");
+
+		return new DefaultRepositoryMethodContext(AbstractRepositoryMetadata.getMetadata(method.getDeclaringClass()),
+				method);
+	}
+
+	/**
+	 * Creates a proxy {@link RepositoryMethodContext} instance suitable for dependency injection.
+	 *
+	 * @return will never be {@literal null}.
+	 */
+	public static RepositoryMethodContext getInjectionProxy() {
+
+		return ProxyFactory.getProxy(RepositoryMethodContext.class,
+				new DynamicLookupTargetSource<>(RepositoryMethodContext.class, () -> getInstance()));
+	}
+
 	@Nullable
-	static RepositoryMethodContext getMetadata() {
+	static RepositoryMethodContext getInstance() {
 		return currentMethod.get();
 	}
 
 	@Nullable
 	static RepositoryMethodContext setMetadata(@Nullable RepositoryMethodContext metadata) {
 
 		RepositoryMethodContext old = currentMethod.get();
+
 		if (metadata != null) {
 			currentMethod.set(metadata);
 		} else {
@@ -65,13 +95,12 @@ static RepositoryMethodContext setMetadata(@Nullable RepositoryMethodContext met
 	}
 
 	@Override
-	public RepositoryMetadata getRepository() {
+	public RepositoryMetadata getMetadata() {
 		return repositoryMetadata;
 	}
 
 	@Override
 	public Method getMethod() {
 		return method;
 	}
-
 }

src/main/java/org/springframework/data/repository/core/support/DynamicLookupTargetSource.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2024 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.repository.core.support;
+
+import java.util.function.Supplier;
+
+import org.springframework.aop.TargetSource;
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * A {@link TargetSource}, that will re-obtain an instance using the configured supplier.
+ *
+ * @author Oliver Drotbohm
+ * @since 3.4.0
+ */
+class DynamicLookupTargetSource<T> implements TargetSource {
+
+	private final Class<T> type;
+	private final Supplier<? extends T> supplier;
+
+	/**
+	 * Creates a new {@link DynamicLookupTargetSource} for the given type and {@link Supplier}.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @param supplier must not be {@literal null}.
+	 */
+	public DynamicLookupTargetSource(Class<T> type, Supplier<? extends T> supplier) {
+
+		Assert.notNull(type, "Type must not be null!");
+		Assert.notNull(supplier, "Supplier must not be null!");
+
+		this.type = type;
+		this.supplier = supplier;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.aop.TargetSource#isStatic()
+	 */
+	@Override
+	public boolean isStatic() {
+		return false;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.aop.TargetSource#getTarget()
+	 */
+	@Override
+	@Nullable
+	public Object getTarget() throws Exception {
+		return supplier.get();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.aop.TargetSource#getTargetClass()
+	 */
+	@Override
+	@NonNull
+	public Class<?> getTargetClass() {
+		return type;
+	}
+}

src/main/java/org/springframework/data/repository/core/support/RepositoryFactorySupport.java

@@ -51,6 +51,7 @@
 import org.springframework.data.repository.core.NamedQueries;
 import org.springframework.data.repository.core.RepositoryInformation;
 import org.springframework.data.repository.core.RepositoryMetadata;
+import org.springframework.data.repository.core.RepositoryMethodContext;
 import org.springframework.data.repository.core.support.RepositoryComposition.RepositoryFragments;
 import org.springframework.data.repository.core.support.RepositoryInvocationMulticaster.DefaultRepositoryInvocationMulticaster;
 import org.springframework.data.repository.core.support.RepositoryInvocationMulticaster.NoOpRepositoryInvocationMulticaster;
@@ -668,15 +669,18 @@ public ExposeMetadataInterceptor(RepositoryMetadata repositoryMetadata) {
 		public Object invoke(MethodInvocation invocation) throws Throwable {
 
 			RepositoryMethodContext oldMetadata = null;
+
 			try {
-				oldMetadata = RepositoryMethodContext
-						.setCurrentMetadata(new DefaultRepositoryMethodContext(repositoryMetadata, invocation.getMethod()));
+
+				oldMetadata = DefaultRepositoryMethodContext
+						.setMetadata(new DefaultRepositoryMethodContext(repositoryMetadata, invocation.getMethod()));
+
 				return invocation.proceed();
+
 			} finally {
-				RepositoryMethodContext.setCurrentMetadata(oldMetadata);
+				DefaultRepositoryMethodContext.setMetadata(oldMetadata);
 			}
 		}
-
 	}
 
 	/**