Guard against NPE for async; fixes gh-926

spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/instrument/async/TraceAsyncAspect.java

@@ -16,10 +16,11 @@
 
 package org.springframework.cloud.sleuth.instrument.async;
 
-import java.lang.reflect.Method;
-
 import brave.Span;
 import brave.Tracer;
+
+import java.lang.reflect.Method;
+
 import org.aspectj.lang.ProceedingJoinPoint;
 import org.aspectj.lang.annotation.Around;
 import org.aspectj.lang.annotation.Aspect;
@@ -53,9 +54,12 @@ public class TraceAsyncAspect {
 
 	@Around("execution (@org.springframework.scheduling.annotation.Async  * *.*(..))")
 	public Object traceBackgroundThread(final ProceedingJoinPoint pjp) throws Throwable {
-		String spanName = this.spanNamer.name(getMethod(pjp, pjp.getTarget()),
-				SpanNameUtil.toLowerHyphen(pjp.getSignature().getName()));
-		Span span = this.tracer.currentSpan().name(spanName);
+		String spanName = name(pjp);
+		Span span = this.tracer.currentSpan();
+		if (span == null) {
+			span = this.tracer.nextSpan();
+		}
+		span = span.name(spanName);
 		try(Tracer.SpanInScope ws = this.tracer.withSpanInScope(span)) {
 			span.tag(this.traceKeys.getAsync().getPrefix() +
 					this.traceKeys.getAsync().getClassNameKey(), pjp.getTarget().getClass().getSimpleName());
@@ -67,6 +71,11 @@ public class TraceAsyncAspect {
 		}
 	}
 
+	String name(ProceedingJoinPoint pjp) {
+		return this.spanNamer.name(getMethod(pjp, pjp.getTarget()),
+				SpanNameUtil.toLowerHyphen(pjp.getSignature().getName()));
+	}
+
 	private Method getMethod(ProceedingJoinPoint pjp, Object object) {
 		MethodSignature signature = (MethodSignature) pjp.getSignature();
 		Method method = signature.getMethod();

spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/instrument/async/TraceAsyncAspectTest.java

@@ -0,0 +1,52 @@
+package org.springframework.cloud.sleuth.instrument.async;
+
+import brave.Tracing;
+import brave.propagation.CurrentTraceContext;
+
+import org.aspectj.lang.ProceedingJoinPoint;
+import org.aspectj.lang.reflect.MethodSignature;
+import org.assertj.core.api.BDDAssertions;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.BDDMockito;
+import org.mockito.Mockito;
+import org.springframework.cloud.sleuth.DefaultSpanNamer;
+import org.springframework.cloud.sleuth.TraceKeys;
+import org.springframework.cloud.sleuth.util.ArrayListSpanReporter;
+
+/**
+ * @author Marcin Grzejszczak
+ */
+public class TraceAsyncAspectTest {
+
+	ArrayListSpanReporter reporter = new ArrayListSpanReporter();
+	Tracing tracing = Tracing.newBuilder()
+			.currentTraceContext(CurrentTraceContext.Default.create())
+			.spanReporter(this.reporter)
+			.build();
+	ProceedingJoinPoint point = Mockito.mock(ProceedingJoinPoint.class);
+
+	@Before
+	public void setup() throws NoSuchMethodException {
+		MethodSignature signature = Mockito.mock(MethodSignature.class);
+		BDDMockito.given(signature.getName()).willReturn("fooBar");
+		BDDMockito.given(signature.getMethod()).willReturn(TraceAsyncAspectTest.class.getMethod("setup"));
+		BDDMockito.given(this.point.getSignature()).willReturn(signature);
+		BDDMockito.given(this.point.getTarget()).willReturn("");
+	}
+
+	//Issue#926
+	@Test public void should_work() throws Throwable {
+		TraceAsyncAspect asyncAspect = new TraceAsyncAspect(this.tracing.tracer(),
+				new DefaultSpanNamer(), new TraceKeys()) {
+			@Override String name(ProceedingJoinPoint pjp) {
+				return "foo-bar";
+			}
+		};
+
+		asyncAspect.traceBackgroundThread(this.point);
+
+		BDDAssertions.then(this.reporter.getSpans()).hasSize(1);
+		BDDAssertions.then(this.reporter.getSpans().get(0).name()).isEqualTo("foo-bar");
+	}
+}