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/jsontype/TypeResolverBuilder.java

package com.fasterxml.jackson.databind.jsontype;

import java.util.Collection;

import com.fasterxml.jackson.annotation.JsonTypeInfo;
import com.fasterxml.jackson.annotation.JsonTypeInfo.As;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.SerializationConfig;

/**
 * Interface that defines builders that are configured based on
 * annotations (like {@link com.fasterxml.jackson.annotation.JsonTypeInfo} or JAXB annotations),
 * and produce type serializers and deserializers used for
 * handling type information embedded in JSON to allow for safe
 * polymorphic type handling.
 *<p>
 * Builder is first initialized by calling {@link #init} method, and then
 * configured using 'set' methods like {@link #inclusion}.
 * Finally, after calling all configuration methods,
 * {@link #buildTypeSerializer} or {@link #buildTypeDeserializer}
 * will be called to get actual type resolver constructed
 * and used for resolving types for configured base type and its
 * subtypes.
 *<p>
 * Note that instances are used for two related but distinct use cases:
 *<ul>
 * <li>To create builders to use with explicit type information
 *    inclusion (usually via <code>@JsonTypeInfo</code> annotation)
 *   </li>
 * <li>To create builders when "default typing" is used; if so, type information
 *   is automatically included for certain kind of types, regardless of annotations
 *   </li>
 *</ul>
 * Important distinction between the cases is that in first case, calls to
 * create builders are only made when builders are certainly needed; whereas
 * in second case builder has to first verify whether type information is
 * applicable for given type, and if not, just return null to indicate this.
 */
public interface TypeResolverBuilder<T extends TypeResolverBuilder<T>>
{
    /*
    /**********************************************************
    /* Accessors
    /**********************************************************
     */

    /**
     * Accessor for currently configured default type; implementation
     * class that may be used in case no valid type information is
     * available during type resolution
     */
    public Class<?> getDefaultImpl();

    /*
    /**********************************************************
    /* Actual builder methods
    /**********************************************************
     */

    /**
     * Method for building type serializer based on current configuration
     * of this builder.
     * 
     * @param baseType Base type that constructed resolver will
     *    handle; super type of all types it will be used for.
     */
    public TypeSerializer buildTypeSerializer(SerializationConfig config,
            JavaType baseType, Collection<NamedType> subtypes);

    /**
     * Method for building type deserializer based on current configuration
     * of this builder.
     * 
     * @param baseType Base type that constructed resolver will
     *    handle; super type of all types it will be used for.
     * @param subtypes Known subtypes of the base type.
     */
    public TypeDeserializer buildTypeDeserializer(DeserializationConfig config,
            JavaType baseType, Collection<NamedType> subtypes);
    
    /*
    /**********************************************************
    /* Initialization method(s) that must be called before other
    /* configuration
    /**********************************************************
     */

    /**
     * Initialization method that is called right after constructing
     * the builder instance.
     *
     * @param idType Which type metadata is used
     * @param res (optional) Custom type id resolver used, if any
     * 
     * @return Resulting builder instance (usually this builder,
     *   but not necessarily)
     */
    public T init(JsonTypeInfo.Id idType, TypeIdResolver res);

    /*
    /**********************************************************
    /* Methods for configuring resolver to build 
    /**********************************************************
     */
    
    /**
     * Method for specifying mechanism to use for including type metadata
     * in JSON.
     * If not explicitly called, setting defaults to
     * {@link As#PROPERTY}.
     * 
     * @param includeAs Mechanism used for including type metadata in JSON
     * 
     * @return Resulting builder instance (usually this builder,
     *   but may be a newly constructed instance for immutable builders}
     */
    public T inclusion(As includeAs);

    /**
     * Method for specifying name of property used for including type
     * information. Not used for all inclusion mechanisms;
     * usually only used with {@link As#PROPERTY}.
     *<p>
     * If not explicitly called, name of property to use is based on
     * defaults for {@link com.fasterxml.jackson.annotation.JsonTypeInfo.Id} configured.
     * 
     * @param propName Name of JSON property to use for including
     *    type information
     * 
     * @return Resulting builder instance (usually this builder,
     *   but may be a newly constructed instance for immutable builders}
     */
    public T typeProperty(String propName);

    /**
     * Method for specifying default implementation to use if type id 
     * is either not available, or cannot be resolved.
     *
     * @return Resulting builder instance (usually this builder,
     *   but may be a newly constructed instance for immutable builders}
     */
    public T defaultImpl(Class<?> defaultImpl);

    /**
     * Method for specifying whether type id should be visible to
     * {@link com.fasterxml.jackson.databind.JsonDeserializer}s or not.
     * 
     * @return Resulting builder instance (usually this builder,
     *   but may be a newly constructed instance for immutable builders}
     * 
     * @since 2.0
     */
    public T typeIdVisibility(boolean isVisible);

    /*
    /**********************************************************************
    /* Mutant factories (2.13+)
    /**********************************************************************
     */

    /**
     * "Mutant factory" method for creating a new instance with different default
     * implementation.
     *
     * @since 2.13
     *
     * @return Either this instance (if nothing changed) or a new instance with
     *    different default implementation
     */
    public default T withDefaultImpl(Class<?> defaultImpl) {
        // 18-Sep-2021, tatu: Not sure if this should be left failing, or use
        //    possibly unsafe variant
        return defaultImpl(defaultImpl);
    }
}

⏎ com/fasterxml/jackson/databind/jsontype/TypeResolverBuilder.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
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