http://github.com/FasterXML/jackson: General data-binding functionality for Jackson: works on core streaming API (FasterXML)
  • Tatu Saloranta
  • Christopher Currie
  • Paul Brown 
package com.fasterxml.jackson.databind.ser.std;

import java.io.IOException;

import com.fasterxml.jackson.core.*;
import com.fasterxml.jackson.databind.*;


Specialized serializer that can be used as the generic key serializer, when serializing Maps to JSON Objects. 
Deprecated:Since 2.8, use Default instead.
/**
 * Specialized serializer that can be used as the generic key serializer,
 * when serializing {@link java.util.Map}s to JSON Objects.
 *
 * @deprecated Since 2.8, use {@link StdKeySerializers.Default} instead.
 */
@SuppressWarnings("serial")
@Deprecated // since 2.8,
public class StdKeySerializer extends StdSerializer<Object>
{
    public StdKeySerializer() { super(Object.class); }

    @Override
    public void serialize(Object value, JsonGenerator g, SerializerProvider provider) throws IOException {
        // 19-Oct-2016, tatu: Simplified to bare essentials since this is deprecated
        g.writeFieldName(value.toString());
    }
}