Refine ReactorResourceFactory

1. Rename globalResources to useGlobalResources.
2. Use of global resources is mutually exlusive with explicit config.
3. Allow Consumer<HttpResources> to configure global resources.
4. Allow ConnectionProvider + LoopResources Supplier to customize
   creation and initialization.
5. Do not manage externally provided ConnectionProvider + LoopResources
   instances.

Issue: SPR-17243

spring-web/src/main/java/org/springframework/http/client/reactive/ReactorResourceFactory.java

@@ -15,6 +15,9 @@
  */
 package org.springframework.http.client.reactive;
 
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+
 import reactor.netty.http.HttpResources;
 import reactor.netty.resources.ConnectionProvider;
 import reactor.netty.resources.LoopResources;
@@ -37,7 +40,16 @@ import org.springframework.util.Assert;
  */
 public class ReactorResourceFactory implements InitializingBean, DisposableBean {
 
-	private boolean globalResources = true;
+	private boolean useGlobalResources = true;
+
+	@Nullable
+	private Consumer<HttpResources> globalResourcesConsumer;
+
+
+	private Supplier<ConnectionProvider> connectionProviderSupplier = () -> ConnectionProvider.elastic("http");
+
+	private Supplier<LoopResources> loopResourcesSupplier = () -> LoopResources.create("reactor-http");
+
 
 	@Nullable
 	private ConnectionProvider connectionProvider;
@@ -45,52 +57,78 @@ public class ReactorResourceFactory implements InitializingBean, DisposableBean
 	@Nullable
 	private LoopResources loopResources;
 
-	private String threadPrefix = "reactor-http";
+
+	private boolean manageConnectionProvider = false;
+
+	private boolean manageLoopResources = false;
 
 
 	/**
-	 * Whether to expose and manage the global Reactor Netty resources from the
-	 * {@link HttpResources} holder.
-	 * <p>Default is "true" in which case this factory helps to configure and
-	 * shut down the global Reactor Netty resources within the lifecycle of a
-	 * Spring {@code ApplicationContext}.
-	 * <p>If set to "false" then the factory creates and manages its own
-	 * {@link LoopResources} and {@link ConnectionProvider}, independent of the
-	 * global ones in the {@link HttpResources} holder.
-	 * @param globalResources whether to expose and manage the global resources
+	 * Whether to use global Reactor Netty resources via {@link HttpResources}.
+	 * <p>Default is "true" in which case this factory initializes and stops the
+	 * global Reactor Netty resources within Spring's {@code ApplicationContext}
+	 * lifecycle. If set to "false" the factory manages its resources independent
+	 * of the global ones.
+	 * @param useGlobalResources whether to expose and manage the global resources
+	 * @see #addGlobalResourcesConsumer(Consumer)
 	 */
-	public void setGlobalResources(boolean globalResources) {
-		this.globalResources = globalResources;
+	public void setUseGlobalResources(boolean useGlobalResources) {
+		this.useGlobalResources = useGlobalResources;
 	}
 
 	/**
-	 * Configure the {@link ConnectionProvider} to use.
-	 * <p>By default, initialized with {@link ConnectionProvider#elastic(String)}.
-	 * @param connectionProvider the connection provider to use
+	 * Add a Consumer for configuring the global Reactor Netty resources on
+	 * startup. When this option is used, {@link #setUseGlobalResources} is also
+	 * enabled.
+	 * @param consumer the consumer to apply
+	 * @see #setUseGlobalResources(boolean)
 	 */
-	public void setConnectionProvider(@Nullable ConnectionProvider connectionProvider) {
-		this.connectionProvider = connectionProvider;
+	public void addGlobalResourcesConsumer(Consumer<HttpResources> consumer) {
+		this.useGlobalResources = true;
+		this.globalResourcesConsumer = this.globalResourcesConsumer != null ?
+				this.globalResourcesConsumer.andThen(consumer) : consumer;
 	}
 
 	/**
-	 * Configure the {@link LoopResources} to use.
-	 * <p>By default, initialized with {@link LoopResources#create(String)}.
-	 * @param loopResources the loop resources to use
+	 * Use this option when you don't want to participate in global resources and
+	 * you want to customize the creation of the managed {@code ConnectionProvider}.
+	 * <p>By default, {@code ConnectionProvider.elastic("http")} is used.
+	 * <p>Note that this option is ignored if {@code userGlobalResources=false} or
+	 * {@link #setConnectionProvider(ConnectionProvider)} is set.
+	 * @param supplier the supplier to use
 	 */
-	public void setLoopResources(@Nullable LoopResources loopResources) {
-		this.loopResources = loopResources;
+	public void setConnectionProviderSupplier(@Nullable Supplier<ConnectionProvider> supplier) {
+		this.connectionProviderSupplier = supplier;
+	}
+
+	/**
+	 * Use this option when you don't want to participate in global resources and
+	 * you want to customize the creation of the managed {@code LoopResources}.
+	 * <p>By default, {@code LoopResources.create("reactor-http")} is used.
+	 * <p>Note that this option is ignored if {@code userGlobalResources=false} or
+	 * {@link #setLoopResources(LoopResources)} is set.
+	 * @param supplier the supplier to use
+	 */
+	public void setLoopResourcesSupplier(@Nullable Supplier<LoopResources> supplier) {
+		this.loopResourcesSupplier = supplier;
+	}
+
+	/**
+	 * Use this option when you want to provide an externally managed
+	 * {@link ConnectionProvider} instance.
+	 * @param connectionProvider the connection provider to use as is
+	 */
+	public void setConnectionProvider(@Nullable ConnectionProvider connectionProvider) {
+		this.connectionProvider = connectionProvider;
 	}
 
 	/**
-	 * Configure the thread prefix to initialize {@link LoopResources} with. This
-	 * is used only when a {@link LoopResources} instance isn't
-	 * {@link #setLoopResources(LoopResources) provided}.
-	 * <p>By default set to "reactor-http".
-	 * @param threadPrefix the thread prefix to use
+	 * Use this option when you want to provide an externally managed
+	 * {@link LoopResources} instance.
+	 * @param loopResources the loop resources to use as is
 	 */
-	public void setThreadPrefix(String threadPrefix) {
-		Assert.notNull(threadPrefix, "Thread prefix is required");
-		this.threadPrefix = threadPrefix;
+	public void setLoopResources(@Nullable LoopResources loopResources) {
+		this.loopResources = loopResources;
 	}
 
 
@@ -98,57 +136,58 @@ public class ReactorResourceFactory implements InitializingBean, DisposableBean
 	 * Whether this factory exposes the global
 	 * {@link reactor.netty.http.HttpResources HttpResources} holder.
 	 */
-	public boolean isGlobalResources() {
-		return this.globalResources;
+	public boolean isUseGlobalResources() {
+		return this.useGlobalResources;
 	}
 
 	/**
 	 * Return the configured {@link ConnectionProvider}.
 	 */
-	@Nullable
 	public ConnectionProvider getConnectionProvider() {
+		Assert.notNull(this.connectionProvider, "ConnectionProvider not initialized yet via InitializingBean.");
 		return this.connectionProvider;
 	}
 
 	/**
 	 * Return the configured {@link LoopResources}.
 	 */
-	@Nullable
 	public LoopResources getLoopResources() {
+		Assert.notNull(this.loopResources, "LoopResources not initialized yet via InitializingBean.");
 		return this.loopResources;
 	}
 
-	/**
-	 * Return the configured prefix for event loop threads.
-	 */
-	public String getThreadPrefix() {
-		return this.threadPrefix;
-	}
-
 
 	@Override
 	public void afterPropertiesSet() throws Exception {
-		if (this.loopResources == null) {
-			this.loopResources = LoopResources.create(this.threadPrefix);
-		}
-		if (this.connectionProvider == null) {
-			this.connectionProvider = ConnectionProvider.elastic("http");
+		if (this.useGlobalResources) {
+			Assert.isTrue(this.loopResources == null && this.connectionProvider == null,
+					"'useGlobalResources' is mutually exclusive with explicitly configured resources.");
+			HttpResources httpResources = HttpResources.get();
+			if (this.globalResourcesConsumer != null) {
+				this.globalResourcesConsumer.accept(httpResources);
+			}
 		}
-		if (this.globalResources) {
-			HttpResources.set(this.loopResources);
-			HttpResources.set(this.connectionProvider);
+		else {
+			if (this.loopResources == null) {
+				this.manageLoopResources = true;
+				this.loopResources = this.loopResourcesSupplier.get();
+			}
+			if (this.connectionProvider == null) {
+				this.manageConnectionProvider = true;
+				this.connectionProvider = this.connectionProviderSupplier.get();
+			}
 		}
 	}
 
 	@Override
 	public void destroy() {
-		if (this.globalResources) {
+		if (this.useGlobalResources) {
 			HttpResources.disposeLoopsAndConnections();
 		}
 		else {
 			try {
 				ConnectionProvider provider = this.connectionProvider;
-				if (provider != null) {
+				if (provider != null && this.manageConnectionProvider) {
 					provider.dispose();
 				}
 			}
@@ -158,7 +197,7 @@ public class ReactorResourceFactory implements InitializingBean, DisposableBean
 
 			try {
 				LoopResources resources = this.loopResources;
-				if (resources != null) {
+				if (resources != null && this.manageLoopResources) {
 					resources.dispose();
 				}
 			}

src/docs/asciidoc/web/webflux-webclient.adoc

@@ -94,7 +94,7 @@ concurrency. In this mode global resources remain active until the process exits
 If the server is timed with the process, there is typically no need for an explicit
 shutdown. However if the server can start or stop in-process, e.g. Spring MVC
 application deployed as a WAR, you can declare a Spring-managed bean of type
-`ReactorResourceFactory` with `globalResources=true` (the default) to ensure the Reactor
+`ReactorResourceFactory` with `useGlobalResources=true` (the default) to ensure the Reactor
 Netty global resources are shut down when the Spring `ApplicationContext` is closed:
 
 [source,java,intent=0]