driver-legacy/src/main/com/mongodb/util/JSONSerializers.java
public static ObjectSerializer getLegacy() {

        ClassMapBasedObjectSerializer serializer = addCommonSerializers();

        serializer.addObjectSerializer(Date.class, new LegacyDateSerializer(serializer));
        serializer.addObjectSerializer(BSONTimestamp.class, new LegacyBSONTimestampSerializer(serializer));
        serializer.addObjectSerializer(Binary.class, new LegacyBinarySerializer());
        serializer.addObjectSerializer(byte[].class, new LegacyBinarySerializer());
        return serializer;
    }
public static ObjectSerializer getLegacy() {

        ClassMapBasedObjectSerializer serializer = addCommonSerializers();

        serializer.addObjectSerializer(Date.class, new LegacyDateSerializer(serializer));
        serializer.addObjectSerializer(BSONTimestamp.class, new LegacyBSONTimestampSerializer(serializer));
        serializer.addObjectSerializer(Binary.class, new LegacyBinarySerializer());
        serializer.addObjectSerializer(byte[].class, new LegacyBinarySerializer());
        return serializer;
    }
Returns an {@code ObjectSerializer} that mostly conforms to the strict JSON format defined in
<a href="http://docs.mongodb.org/manual/reference/mongodb-extended-json/">extended JSON</a>, but with a few differences to keep
compatibility with previous versions of the driver.  Clients should generally prefer {@code getStrict} in preference to this method.

@return object serializer
@mongodb.driver.manual reference/mongodb-extended-json/ MongoDB Extended JSON
@see #getStrict()