[36] Override the ThreadContextMap in the provider.

resolves #36

Signed-off-by: James R. Perkins <jperkins@redhat.com>

src/main/java/org/jboss/logmanager/log4j/JBossProvider.java

@@ -20,6 +20,7 @@
 package org.jboss.logmanager.log4j;
 
 import org.apache.logging.log4j.spi.Provider;
+import org.apache.logging.log4j.spi.ThreadContextMap;
 
 /**
  * @author <a href="mailto:jperkins@redhat.com">James R. Perkins</a>
@@ -29,4 +30,14 @@ public class JBossProvider extends Provider {
     public JBossProvider() {
         super(500, "2.6.0", JBossLoggerContextFactory.class);
     }
+
+    @Override
+    public String getThreadContextMap() {
+        return ThreadContextMDCMap.class.getName();
+    }
+
+    @Override
+    public Class<? extends ThreadContextMap> loadThreadContextMap() {
+        return ThreadContextMDCMap.class;
+    }
 }

src/main/java/org/jboss/logmanager/log4j/ThreadContextMDCMap.java

@@ -0,0 +1,78 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ *
+ * Copyright 2023 Red Hat, Inc., and individual contributors
+ * as indicated by the @author tags.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jboss.logmanager.log4j;
+
+import org.apache.logging.log4j.spi.ThreadContextMap;
+import org.jboss.logmanager.MDC;
+
+import java.util.Map;
+
+/**
+ * A {@link ThreadContextMap} implementation which delegates to {@link MDC}.
+ *
+ * @author <a href="mailto:jperkins@redhat.com">James R. Perkins</a>
+ */
+public class ThreadContextMDCMap implements ThreadContextMap {
+    @Override
+    public void clear() {
+        MDC.clear();
+    }
+
+    @Override
+    public boolean containsKey(final String key) {
+        return MDC.get(key) != null;
+    }
+
+    @Override
+    public String get(final String key) {
+        return MDC.get(key);
+    }
+
+    @Override
+    public Map<String, String> getCopy() {
+        return MDC.copy();
+    }
+
+    @Override
+    public Map<String, String> getImmutableMapOrNull() {
+        final Map<String, String> copy = MDC.copy();
+        return copy.isEmpty() ? null : Map.copyOf(copy);
+    }
+
+    @Override
+    public boolean isEmpty() {
+        // TODO (jrp) this is not fast and should be thought about, should we add this to the log managers MDC?
+        return MDC.copy().isEmpty();
+    }
+
+    @Override
+    public void put(final String key, final String value) {
+        if (value == null) {
+            MDC.remove(key);
+        } else {
+            MDC.put(key, value);
+        }
+    }
+
+    @Override
+    public void remove(final String key) {
+        MDC.remove(key);
+    }
+}