[logging-log4j2] 01/02: LOG4J2-2939: Fix NPE in MDCContextMap (#430)

[ck...@apache.org]

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ckozak pushed a commit to branch release-2.x
in repository https://gitbox.apache.org/repos/asf/logging-log4j2.git

commit ec34bd2f1ebc34bc80cde64d51ec6060d7bd250e
Author: Constantin Hirsch (SemVox) <63...@users.noreply.github.com>
AuthorDate: Tue Oct 6 16:34:38 2020 +0200

    LOG4J2-2939: Fix NPE in MDCContextMap (#430)
    
    Accomodate for the fact that MDC.getCopyOfContextMap() may return null
---
 .../org/apache/logging/slf4j/MDCContextMap.java    |  6 ++--
 .../java/org/apache/logging/slf4j/LoggerTest.java  | 41 +++++++++++++++++++++-
 2 files changed, 44 insertions(+), 3 deletions(-)

diff --git a/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/MDCContextMap.java b/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/MDCContextMap.java
index f03ee54..b04d358 100644
--- a/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/MDCContextMap.java
+++ b/log4j-to-slf4j/src/main/java/org/apache/logging/slf4j/MDCContextMap.java
@@ -71,7 +71,8 @@ public class MDCContextMap implements CleanableThreadContextMap {
 
     @Override
     public boolean containsKey(final String key) {
-        return MDC.getCopyOfContextMap().containsKey(key);
+        Map<String, String> map = MDC.getCopyOfContextMap();
+        return map != null && map.containsKey(key);
     }
 
     @Override
@@ -88,7 +89,8 @@ public class MDCContextMap implements CleanableThreadContextMap {
 
     @Override
     public boolean isEmpty() {
-        return MDC.getCopyOfContextMap().isEmpty();
+        Map<String, String> map = MDC.getCopyOfContextMap();
+        return map == null || map.isEmpty();
     }
 
     @Override
diff --git a/log4j-to-slf4j/src/test/java/org/apache/logging/slf4j/LoggerTest.java b/log4j-to-slf4j/src/test/java/org/apache/logging/slf4j/LoggerTest.java
index 77b9c4e..1f14110 100644
--- a/log4j-to-slf4j/src/test/java/org/apache/logging/slf4j/LoggerTest.java
+++ b/log4j-to-slf4j/src/test/java/org/apache/logging/slf4j/LoggerTest.java
@@ -33,6 +33,7 @@ import org.apache.logging.log4j.spi.MessageFactory2Adapter;
 import org.junit.Before;
 import org.junit.ClassRule;
 import org.junit.Test;
+import org.slf4j.MDC;
 
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
@@ -183,5 +184,43 @@ public class LoggerTest {
         assertThat(list.strList, hasSize(2));
         assertTrue("Incorrect year", list.strList.get(0).startsWith("2010"));
     }
-}
 
+    @Test
+    public void mdcNullBackedIsEmpty() {
+        assertNull("Setup wrong", MDC.getCopyOfContextMap());
+        assertTrue(ThreadContext.isEmpty());
+    }
+
+    @Test
+    public void mdcNullBackedContainsKey() {
+        assertNull("Setup wrong", MDC.getCopyOfContextMap());
+        assertFalse(ThreadContext.containsKey("something"));
+    }
+
+    @Test
+    public void mdcNullBackedContainsNullKey() {
+        assertNull("Setup wrong", MDC.getCopyOfContextMap());
+        assertFalse(ThreadContext.containsKey(null));
+    }
+
+    @Test
+    public void mdcContainsNullKey() {
+        try {
+            ThreadContext.put("some", "thing");
+            assertNotNull("Setup wrong", MDC.getCopyOfContextMap());
+            assertFalse(ThreadContext.containsKey(null));
+        } finally {
+            ThreadContext.clearMap();
+        }
+    }
+
+    @Test
+    public void mdcCannotContainNullKey() {
+        try {
+            ThreadContext.put(null, "something");
+            fail("should throw");
+        } catch (IllegalArgumentException | NullPointerException e) {
+            // expected
+        }
+    }
+}