Add support for automatic context-propagation with Micrometer

Closes gh-16665

web/src/main/java/org/springframework/security/web/server/ServerWebExchangeThreadLocalAccessor.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2002-2025 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.security.web.server;
+
+import io.micrometer.context.ThreadLocalAccessor;
+
+import org.springframework.util.Assert;
+import org.springframework.web.server.ServerWebExchange;
+
+/**
+ * A {@link ThreadLocalAccessor} for accessing a {@link ServerWebExchange}.
+ * <p>
+ * This class adapts the existing Reactor Context attribute
+ * {@code ServerWebExchange.class} to the {@link ThreadLocalAccessor} contract to allow
+ * Micrometer Context Propagation to automatically propagate a {@link ServerWebExchange}
+ * in Reactive applications. It is automatically registered with the
+ * {@link io.micrometer.context.ContextRegistry} through the
+ * {@link java.util.ServiceLoader} mechanism when context-propagation is on the classpath.
+ *
+ * @author Steve Riesenberg
+ * @since 6.5
+ * @see io.micrometer.context.ContextRegistry
+ */
+public final class ServerWebExchangeThreadLocalAccessor implements ThreadLocalAccessor<ServerWebExchange> {
+
+	private static final ThreadLocal<ServerWebExchange> threadLocal = new ThreadLocal<>();
+
+	@Override
+	public Object key() {
+		return ServerWebExchange.class;
+	}
+
+	@Override
+	public ServerWebExchange getValue() {
+		return threadLocal.get();
+	}
+
+	@Override
+	public void setValue(ServerWebExchange exchange) {
+		Assert.notNull(exchange, "exchange cannot be null");
+		threadLocal.set(exchange);
+	}
+
+	@Override
+	public void setValue() {
+		threadLocal.remove();
+	}
+
+}

web/src/main/resources/META-INF/services/io.micrometer.context.ThreadLocalAccessor

@@ -0,0 +1 @@
+org.springframework.security.web.server.ServerWebExchangeThreadLocalAccessor