Fix SLF4J-414

slf4j-api/src/main/java/org/slf4j/helpers/BasicMDCAdapter.java

@@ -141,6 +141,10 @@ public class BasicMDCAdapter implements MDCAdapter {
     }
 
     public void setContextMap(Map<String, String> contextMap) {
-        inheritableThreadLocal.set(new HashMap<String, String>(contextMap));
+        Map<String, String> copy = null;
+        if(contextMap != null) {
+            copy = new HashMap<String, String>(contextMap);
+        }
+        inheritableThreadLocal.set(copy);
     }
 }

slf4j-api/src/main/java/org/slf4j/spi/MDCAdapter.java

@@ -83,6 +83,8 @@ public interface MDCAdapter {
      * map and then copying the map passed as parameter. The context map 
      * parameter must only contain keys and values of type String.
      * 
+     * Implementations must support null valued map passed as parameter.
+     * 
      * @param contextMap must contain only keys and values of type String
      * 
      * @since 1.5.1

slf4j-api/src/test/java/org/slf4j/helpers/BasicMDCAdapterTest.java

@@ -42,8 +42,13 @@ import org.slf4j.spi.MDCAdapter;
  * @author Lukasz Cwik
  */
 public class BasicMDCAdapterTest {
-    MDCAdapter mdc = new BasicMDCAdapter();
+    protected MDCAdapter mdc = instantiateMDC();
 
+    protected MDCAdapter instantiateMDC() {
+        return new BasicMDCAdapter();
+    }
+    
+    // leave MDC clean
     @After
     public void tearDown() throws Exception {
         mdc.clear();
@@ -103,6 +108,12 @@ public class BasicMDCAdapterTest {
         assertNull(mdc.get("childKey"));
     }
 
+    
+    @Test
+    public void testInvokingSetContextMap_WithANullMap_SLF4J_414() {
+        mdc.setContextMap(null);
+    }
+    
     @Test
     public void testMDCChildThreadCanOverwriteParentThread() throws Exception {
         mdc.put("sharedKey", "parentValue");

slf4j-log4j12/src/main/java/org/slf4j/log4j12/Log4jMDCAdapter.java

@@ -25,7 +25,6 @@
 package org.slf4j.log4j12;
 
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.Map;
 
 import org.apache.log4j.MDCFriend;
@@ -39,6 +38,7 @@ public class Log4jMDCAdapter implements MDCAdapter {
         }
     }
 
+    @Override
     public void clear() {
         @SuppressWarnings("rawtypes")
         Map map = org.apache.log4j.MDC.getContext();
@@ -47,6 +47,7 @@ public class Log4jMDCAdapter implements MDCAdapter {
         }
     }
 
+    @Override
     public String get(String key) {
         return (String) org.apache.log4j.MDC.get(key);
     }
@@ -63,10 +64,12 @@ public class Log4jMDCAdapter implements MDCAdapter {
      * @throws IllegalArgumentException
      *             in case the "key" or <b>"val"</b> parameter is null
      */
+    @Override
     public void put(String key, String val) {
         org.apache.log4j.MDC.put(key, val);
     }
 
+    @Override
     public void remove(String key) {
         org.apache.log4j.MDC.remove(key);
     }
@@ -82,13 +85,21 @@ public class Log4jMDCAdapter implements MDCAdapter {
     }
 
     @SuppressWarnings({ "rawtypes", "unchecked" })
-    public void setContextMap(Map contextMap) {
+    @Override
+    public void setContextMap(Map<String, String> contextMap) {
         Map old = org.apache.log4j.MDC.getContext();
+        
+        // we must cater for the case where the contextMap argument is null 
+        if(contextMap == null) {
+            if(old != null) {
+                old.clear();
+            }
+            return;
+        }
+        
         if (old == null) {
-            Iterator entrySetIterator = contextMap.entrySet().iterator();
-            while (entrySetIterator.hasNext()) {
-                Map.Entry mapEntry = (Map.Entry) entrySetIterator.next();
-                org.apache.log4j.MDC.put((String) mapEntry.getKey(), mapEntry.getValue());
+            for (Map.Entry<String, String> mapEntry : contextMap.entrySet()) {
+                org.apache.log4j.MDC.put(mapEntry.getKey(), mapEntry);
             }
         } else {
             old.clear();

slf4j-log4j12/src/test/java/org/slf4j/log4j12/Log4jMDCAdapterTest.java

@@ -0,0 +1,13 @@
+package org.slf4j.log4j12;
+
+import org.slf4j.helpers.BasicMDCAdapterTest;
+import org.slf4j.spi.MDCAdapter;
+
+public class Log4jMDCAdapterTest extends BasicMDCAdapterTest {
+    
+    protected MDCAdapter instantiateMDC() {
+        return new Log4jMDCAdapter();
+    }
+    
+
+}