Jackson is "the Java JSON library" or "the best JSON parser for Java". Or simply as "JSON for Java".

Jackson Databind Source Code files are provided in the source packge (jackson-databind-2.14.0-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Databind Source Code below:

⏎ com/fasterxml/jackson/databind/deser/ContextualKeyDeserializer.java

package com.fasterxml.jackson.databind.deser;

import com.fasterxml.jackson.databind.*;

/**
 * Add-on interface that {@link KeyDeserializer}s can implement to get a callback
 * that can be used to create contextual instances of key deserializer to use for
 * handling Map keys of supported type. This can be useful
 * for key deserializers that can be configured by annotations, or should otherwise
 * have differing behavior depending on what kind of Map property keys are being deserialized.
 */
public interface ContextualKeyDeserializer
{
    /**
     * Method called to see if a different (or differently configured) key deserializer
     * is needed to deserialize keys of specified Map property.
     * Note that instance that this method is called on is typically shared one and
     * as a result method should <b>NOT</b> modify this instance but rather construct
     * and return a new instance. This instance should only be returned as-is, in case
     * it is already suitable for use.
     * 
     * @param ctxt Deserialization context to access configuration, additional 
     *    deserializers that may be needed by this deserializer
     * @param property Method, field or constructor parameter that declared Map for which
     *   contextual instance will be used. Will not be available when deserializing root-level
     *   Map value; otherwise should not be null.
     * 
     * @return Key deserializer to use for deserializing keys specified Map property,
     *   may be this instance or a new instance.
     */
    public KeyDeserializer createContextual(DeserializationContext ctxt,
            BeanProperty property)
        throws JsonMappingException;
}

⏎ com/fasterxml/jackson/databind/deser/ContextualKeyDeserializer.java

Or download all of them as a single archive file:

File name: jackson-databind-2.14.0-sources.jar
File size: 1187952 bytes
Release date: 2022-11-05
Download 

⇒ Jackson Annotations Source Code

⇐ Download and Install Jackson Binary Package

⇑ Downloading and Reviewing jackson-*.jar

⇑⇑ Jackson - Java JSON library