Polishing.

Avoid nullability in RepositoryMethodContextHolder.getContext(). Introduce shortcut in RepositoryMethodContext to obtain the current thread-local context. Update documentation.

See #3175.
Original pull request: #3176

Author: mp911de

src/main/antora/modules/ROOT/pages/repositories/custom-implementations.adoc

@@ -271,7 +271,7 @@ package com.acme.search;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.data.domain.Limit;
-import org.springframework.data.repository.core.support.RepositoryMethodContext;
+import org.springframework.data.repository.core.RepositoryMethodContext;
 
 class DefaultSearchExtension<T> implements SearchExtension<T> {
 
@@ -282,7 +282,7 @@ class DefaultSearchExtension<T> implements SearchExtension<T> {
     }
 
     public List<T> search(String text, Limit limit) {
-        return search(RepositoryMethodContext.currentMethod(), text, limit);
+        return search(RepositoryMethodContext.getContext(), text, limit);
     }
 
     List<T> search(RepositoryMethodContext metadata, String text, Limit limit) {
@@ -297,12 +297,12 @@ class DefaultSearchExtension<T> implements SearchExtension<T> {
 }
 ----
 
-In the example above `RepositoryMethodContext.currentMethod()` is used to retrieve metadata for the actual method invocation.
+In the example above `RepositoryMethodContext.getContext()` is used to retrieve metadata for the actual method invocation.
 `RepositoryMethodContext` exposes information attached to the repository such as the domain type.
 In this case we use the repository domain type to identify the name of the index to be searched.
 
 Exposing invocation metadata is costly, hence it is disabled by default.
-To access `RepositoryMethodContext.currentMethod()` you need to advise the repository factory responsible for creating the actual repository to expose method metadata.
+To access `RepositoryMethodContext.getContext()` you need to advise the repository factory responsible for creating the actual repository to expose method metadata.
 
 .Expose Repository Metadata
 [tabs]
@@ -319,7 +319,7 @@ package com.acme.search;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.data.domain.Limit;
 import org.springframework.data.repository.core.support.RepositoryMetadataAccess;
-import org.springframework.data.repository.core.support.RepositoryMethodContext;
+import org.springframework.data.repository.core.RepositoryMethodContext;
 
 class DefaultSearchExtension<T> implements SearchExtension<T>, RepositoryMetadataAccess {
 

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

@@ -33,10 +33,24 @@
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author Oliver Drotbohm
- * @since 3.4.0
+ * @since 3.4
  */
 public interface RepositoryMethodContext {
 
+	/**
+	 * Try to return the current repository method metadata. This method is usable only if the calling method has been
+	 * invoked via a repository method, and the repository factory has been set to expose metadata. Otherwise, this method
+	 * will throw an IllegalStateException.
+	 *
+	 * @return the current repository method metadata (never returns {@code null})
+	 * @throws IllegalStateException if the repository method metadata cannot be found, because the method was invoked
+	 *           outside a repository method invocation context, or because the repository has not been configured to
+	 *           expose its metadata.
+	 */
+	static RepositoryMethodContext getContext() throws IllegalStateException {
+		return RepositoryMethodContextHolder.getContext();
+	}
+
 	/**
 	 * Returns the metadata for the repository.
 	 *

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

@@ -19,74 +19,68 @@
 import org.springframework.lang.Nullable;
 
 /**
+ * Associates a given {@link RepositoryMethodContext} with the current execution thread.
+ * <p>
+ * This class provides a series of static methods that interact with a thread-local storage of
+ * {@link RepositoryMethodContext}. The purpose of the class is to provide a convenient way to be used for an
+ * application.
+ *
  * @author Christoph Strobl
- * @since 3.4.0
+ * @author Mark Paluch
+ * @since 3.4
+ * @see RepositoryMethodContext
  */
 public class RepositoryMethodContextHolder {
 
-	private static ContextProvider contextSupplier;
-
-	static {
-		contextSupplier = new ThreadLocalContextProvider();
-	}
-
+	/**
+	 * ThreadLocal holder for repository method associated with this thread. Will contain {@code null} unless the
+	 * "exposeMetadata" property on the controlling repository factory configuration has been set to {@code true}.
+	 */
+	private static final ThreadLocal<RepositoryMethodContext> currentMethod = new NamedThreadLocal<>(
+			"Current Repository Method");
+
+	/**
+	 * Make the given repository method metadata available via the {@link #getContext()} method.
+	 * <p>
+	 * Note that the caller should be careful to keep the old value as appropriate.
+	 *
+	 * @param context the metadata to expose (or {@code null} to reset it)
+	 * @return the old metadata, which may be {@code null} if none was bound
+	 * @see #getContext()
+	 */
 	@Nullable
 	public static RepositoryMethodContext setContext(@Nullable RepositoryMethodContext context) {
-		return contextSupplier.set(context);
-	}
-
-	@Nullable
-	public static RepositoryMethodContext current() {
-		return contextSupplier.get();
-	}
-
-	public static void clearContext() {
-		contextSupplier.clear();
-	}
-
-	interface ContextProvider {
-
-		@Nullable
-		RepositoryMethodContext get();
 
-		@Nullable
-		RepositoryMethodContext set(@Nullable RepositoryMethodContext context);
-
-		void clear();
-	}
-
-	static class ThreadLocalContextProvider implements ContextProvider {
-
-		/**
-		 * ThreadLocal holder for repository method associated with this thread. Will contain {@code null} unless the
-		 * "exposeMetadata" property on the controlling repository factory configuration has been set to "true".
-		 */
-		private static final ThreadLocal<RepositoryMethodContext> currentMethod = new NamedThreadLocal<>(
-				"Current Repository Method");
-
-		@Override
-		@Nullable
-		public RepositoryMethodContext get() {
-			return currentMethod.get();
-		}
-
-		public void clear() {
+		RepositoryMethodContext old = currentMethod.get();
+		if (context != null) {
+			currentMethod.set(context);
+		} else {
 			currentMethod.remove();
 		}
 
-		@Override
-		@Nullable
-		public RepositoryMethodContext set(@Nullable RepositoryMethodContext context) {
-
-			RepositoryMethodContext old = currentMethod.get();
-
-			if (context != null) {
-				currentMethod.set(context);
-			} else {
-				currentMethod.remove();
-			}
+		return old;
+	}
 
-			return old;
+	/**
+	 * Try to return the current repository method metadata. This method is usable only if the calling method has been
+	 * invoked via a repository method, and the repository factory has been set to expose metadata. Otherwise, this method
+	 * will throw an IllegalStateException.
+	 *
+	 * @return the current repository method metadata (never returns {@code null})
+	 * @throws IllegalStateException if the repository method metadata cannot be found, because the method was invoked
+	 *           outside a repository method invocation context, or because the repository has not been configured to
+	 *           expose its metadata.
+	 */
+	public static RepositoryMethodContext getContext() {
+
+		RepositoryMethodContext metadata = currentMethod.get();
+
+		if (metadata == null) {
+			throw new IllegalStateException(
+					"Cannot find current repository method: Set 'exposeMetadata' property on RepositoryFactorySupport to 'true' to make it available, and "
+							+ "ensure that RepositoryMethodContext.getContext() is invoked in the same thread as the repository invocation.");
 		}
+
+		return metadata;
 	}
 }

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

@@ -27,7 +27,7 @@
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author Oliver Drotbohm
- * @since 3.4.0
+ * @since 3.4
  */
 public class DefaultRepositoryMethodContext implements RepositoryMethodContext {
 

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

@@ -121,7 +121,7 @@ public void setRepositoryBaseClass(Class<?> repositoryBaseClass) {
 	 * Default is "false", in order to avoid unnecessary extra interception. This means that no guarantees are provided
 	 * that {@code RepositoryMethodContext} access will work consistently within any method of the advised object.
 	 *
-	 * @since 3.4.0
+	 * @since 3.4
 	 */
 	public void setExposeMetadata(boolean exposeMetadata) {
 		this.exposeMetadata = exposeMetadata;

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

@@ -27,7 +27,7 @@
  *
  * @author Mark Paluch
  * @since 3.4
- * @see RepositoryMethodContext
+ * @see org.springframework.data.repository.core.RepositoryMethodContext
  */
 public interface RepositoryMetadataAccess {
 

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

@@ -256,7 +256,7 @@ void capturesRepositoryMetadata() {
 		record Metadata(RepositoryMethodContext context, MethodInvocation methodInvocation) {}
 
 		when(factory.queryOne.execute(any(Object[].class)))
-				.then(invocation -> new Metadata(RepositoryMethodContextHolder.current(),
+				.then(invocation -> new Metadata(RepositoryMethodContextHolder.getContext(),
 						ExposeInvocationInterceptor.currentInvocation()));
 
 		factory.setExposeMetadata(true);
@@ -279,7 +279,7 @@ record Metadata(RepositoryMethodContext context, MethodInvocation methodInvocati
 		}
 
 		when(factory.queryOne.execute(any(Object[].class)))
-				.then(invocation -> new Metadata(RepositoryMethodContextHolder.current(),
+				.then(invocation -> new Metadata(RepositoryMethodContextHolder.getContext(),
 						ExposeInvocationInterceptor.currentInvocation()));
 
 		var repository = factory.getRepository(ObjectRepository.class, new RepositoryMetadataAccess() {});