add TraceWebAspect to wrap Callable's returned in Controllers.

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/TraceWebAspect.java

@@ -0,0 +1,82 @@
+package org.springframework.cloud.sleuth.instrument.web;
+
+import java.util.concurrent.Callable;
+
+import lombok.extern.apachecommons.CommonsLog;
+
+import org.aspectj.lang.ProceedingJoinPoint;
+import org.aspectj.lang.annotation.Around;
+import org.aspectj.lang.annotation.Aspect;
+import org.aspectj.lang.annotation.Pointcut;
+import org.springframework.cloud.sleuth.Trace;
+import org.springframework.cloud.sleuth.TraceContextHolder;
+import org.springframework.cloud.sleuth.instrument.TraceCallable;
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.client.RestOperations;
+
+/**
+ * Aspect that adds correlation id to
+ * <p/>
+ * <ul>
+ * <li>{@link RestController} annotated classes with public {@link Callable} methods</li>
+ * <li>{@link Controller} annotated classes with public {@link Callable} methods</li>
+ * </ul>
+ * <p/>
+ * For controllers an around aspect is created that wraps the {@link Callable#call()}
+ * method execution in {@link TraceCallable}
+ * <p/>
+ *
+ * @see RestController
+ * @see Controller
+ * @see RestOperations
+ * @see TraceCallable
+ * @see Trace
+ *
+ * @author Tomasz Nurkewicz, 4financeIT
+ * @author Marcin Grzejszczak, 4financeIT
+ * @author Michal Chmielarz, 4financeIT
+ * @author Spencer Gibb
+ */
+@Aspect
+@CommonsLog
+public class TraceWebAspect {
+
+	private final Trace trace;
+
+	public TraceWebAspect(Trace trace) {
+		this.trace = trace;
+	}
+
+	@Pointcut("@target(org.springframework.web.bind.annotation.RestController)")
+	private void anyRestControllerAnnotated() {
+	}
+
+	@Pointcut("@target(org.springframework.stereotype.Controller)")
+	private void anyControllerAnnotated() {
+	}
+
+	@Pointcut("execution(public java.util.concurrent.Callable *(..))")
+	private void anyPublicMethodReturningCallable() {
+	}
+
+	@Pointcut("(anyRestControllerAnnotated() || anyControllerAnnotated()) && anyPublicMethodReturningCallable()")
+	private void anyControllerOrRestControllerWithPublicAsyncMethod() {
+	}
+
+	@Around("anyControllerOrRestControllerWithPublicAsyncMethod()")
+	@SuppressWarnings("unchecked")
+	public Object wrapWithCorrelationId(ProceedingJoinPoint pjp) throws Throwable {
+		Callable callable = (Callable) pjp.proceed();
+		if (TraceContextHolder.isTracing()) {
+			log.debug("Wrapping callable with span ["
+					+ TraceContextHolder.getCurrentSpan() + "]");
+
+			return new TraceCallable(this.trace, callable);
+		}
+		else {
+			return callable;
+		}
+	}
+
+}

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/web/TraceWebAutoConfiguration.java

@@ -52,6 +52,12 @@ public class TraceWebAutoConfiguration {
 	@Autowired
 	private Trace trace;
 
+	@Bean
+	@ConditionalOnMissingBean
+	public TraceWebAspect traceWebAspect() {
+		return new TraceWebAspect(trace);
+	}
+
 	@Bean
 	@ConditionalOnMissingBean
 	public TraceHandlerInterceptor traceHandlerInterceptor() {