From 1b1f8d49c19f307af79fabdb8f5201251cb8f93c Mon Sep 17 00:00:00 2001
From: wusheng <wu.sheng@foxmail.com>
Date: Sat, 8 Jul 2017 10:53:13 +0800
Subject: [PATCH] Add checker for extract and inject.

---
 .../apm/agent/core/context/ContextManager.java  | 17 ++++++++++++-----
 .../apm/agent/core/context/TracingContext.java  |  2 +-
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/ContextManager.java b/apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/ContextManager.java
index 082609b8ec..892a195b55 100644
--- a/apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/ContextManager.java
+++ b/apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/ContextManager.java
@@ -16,7 +16,9 @@ import org.skywalking.apm.util.StringUtil;
 /**
  * {@link ContextManager} controls the whole context of {@link TraceSegment}. Any {@link TraceSegment} relates to
  * single-thread, so this context use {@link ThreadLocal} to maintain the context, and make sure, since a {@link
- * TraceSegment} starts, all ChildOf spans are in the same context. <p> What is 'ChildOf'? {@see
+ * TraceSegment} starts, all ChildOf spans are in the same context.
+ * <p>
+ * What is 'ChildOf'? {@see
  * https://github.com/opentracing/specification/blob/master/specification.md#references-between-spans}
  *
  * <p> Also, {@link ContextManager} delegates to all {@link AbstractTracerContext}'s major methods.
@@ -107,12 +109,17 @@ public class ContextManager implements TracingContextListener, BootService, Igno
         return span;
     }
 
-    public static void inject(ContextCarrier contextCarrier) {
-        get().inject(contextCarrier);
+    public static void inject(ContextCarrier carrier) {
+        if (carrier != null && carrier.isValid()) {
+            get().inject(carrier);
+        }
     }
 
-    public static void extract(ContextCarrier contextCarrier) {
-        get().extract(contextCarrier);
+    public static void extract(ContextCarrier carrier) {
+        if (carrier == null) {
+            throw new IllegalArgumentException("ContextCarrier can't be null.");
+        }
+        get().extract(carrier);
     }
 
     public ContextSnapshot capture() {
diff --git a/apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/TracingContext.java b/apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/TracingContext.java
index 763b72dbf7..f84244a5f1 100644
--- a/apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/TracingContext.java
+++ b/apm-sniffer/apm-agent-core/src/main/java/org/skywalking/apm/agent/core/context/TracingContext.java
@@ -70,8 +70,8 @@ public class TracingContext implements AbstractTracerContext {
      * Inject the context into the given carrier, only when the active span is an exit one.
      *
      * @param carrier to carry the context for crossing process.
-     * @see {@link AbstractTracerContext#inject(ContextCarrier)}
      * @throws IllegalStateException, if the active span isn't an exit one.
+     * @see {@link AbstractTracerContext#inject(ContextCarrier)}
      */
     @Override
     public void inject(ContextCarrier carrier) {
-- 
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