From 9a3e8357cc2a7f700232efdd93914d971432cc45 Mon Sep 17 00:00:00 2001
From: Alvin <329772643@qq.com>
Date: Wed, 31 Mar 2021 07:11:30 +0800
Subject: [PATCH] Fix NullPointerException when call
 "ReactiveRequestHolder.getHeaders" (#6651)

---
 CHANGES.md                                                 | 1 +
 .../plugin/spring/mvc/commons/ReactiveRequestHolder.java   | 7 ++++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/CHANGES.md b/CHANGES.md
index d5c1d8188..97231e226 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -27,6 +27,7 @@ Release Notes.
 * Replace hbase-1.x-plugin with hbase-1.x-2.x-plugin to adapt hbase client 2.x
 * Remove the close_before_method and close_after_method parameters of custom-enhance-plugin to avoid memory leaks.
 * Fix bug that springmvn-annotation-4.x-plugin, witness class does not exist in some versions.
+* Fix NullPointerException with `ReactiveRequestHolder.getHeaders`.
 
 #### OAP-Backend
 * Allow user-defined `JAVA_OPTS` in the startup script.
diff --git a/apm-sniffer/apm-sdk-plugin/spring-plugins/mvc-annotation-commons/src/main/java/org/apache/skywalking/apm/plugin/spring/mvc/commons/ReactiveRequestHolder.java b/apm-sniffer/apm-sdk-plugin/spring-plugins/mvc-annotation-commons/src/main/java/org/apache/skywalking/apm/plugin/spring/mvc/commons/ReactiveRequestHolder.java
index d7130775c..b5e1876ae 100644
--- a/apm-sniffer/apm-sdk-plugin/spring-plugins/mvc-annotation-commons/src/main/java/org/apache/skywalking/apm/plugin/spring/mvc/commons/ReactiveRequestHolder.java
+++ b/apm-sniffer/apm-sdk-plugin/spring-plugins/mvc-annotation-commons/src/main/java/org/apache/skywalking/apm/plugin/spring/mvc/commons/ReactiveRequestHolder.java
@@ -20,6 +20,7 @@ package org.apache.skywalking.apm.plugin.spring.mvc.commons;
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 
@@ -37,7 +38,11 @@ public class ReactiveRequestHolder implements RequestHolder {
 
     @Override
     public Enumeration<String> getHeaders(final String headerName) {
-        return Collections.enumeration(this.serverHttpRequest.getHeaders().get(headerName));
+        List<String> values = this.serverHttpRequest.getHeaders().get(headerName);
+        if (values == null) {
+            return Collections.enumeration(Collections.EMPTY_LIST);
+        }
+        return Collections.enumeration(values);
     }
 
     @Override