/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.logging.log4j.core.jackson;

import java.io.IOException;
import java.util.Map;

import org.apache.logging.log4j.util.ReadOnlyStringMap;
import org.apache.logging.log4j.util.TriConsumer;

import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.ser.std.StdSerializer;

/**
 * <p>
 * <em>Consider this class private.</em>
 * </p>
 */
public class ContextDataSerializer extends StdSerializer<ReadOnlyStringMap> {

    private static final long serialVersionUID = 1L;

    protected ContextDataSerializer() {
        super(Map.class, false);
    }

    @Override
    public void serialize(final ReadOnlyStringMap contextData, final JsonGenerator jgen,
            final SerializerProvider provider) throws IOException, JsonGenerationException {

        jgen.writeStartObject();
        contextData.forEach(WRITE_STRING_FIELD_INTO, jgen);
        jgen.writeEndObject();
    }

    private static final TriConsumer<String, Object, JsonGenerator> WRITE_STRING_FIELD_INTO =
            (key, value, jsonGenerator) -> {
        try {
            jsonGenerator.writeStringField(key, String.valueOf(value));
        } catch (final Exception ex) {
            throw new IllegalStateException("Problem with key " + key, ex);
        }
    };
}

@@ -1986,16 +1986,125 @@
   try %7B%0A
+            if (value == null) %7B%0A                jsonGenerator.writeNullField(key);%0A            %7D else %7B%0A    
         
@@ -2167,16 +2167,30 @@
 alue));%0A
+            %7D%0A
         

Allow JsonLayout output JSON `null` for ContextMap (#496)