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/cfg/ConstructorDetector.java

package com.fasterxml.jackson.databind.cfg;

import com.fasterxml.jackson.databind.util.ClassUtil;

/**
 * Configurable handler used to select aspects of selecting
 * constructor to use as "Creator" for POJOs.
 * Defines the API for handlers, a pre-defined set of standard instances
 * and methods for constructing alternative configurations.
 *
 * @since 2.12
 */
public final class ConstructorDetector
    implements java.io.Serializable
{
    private static final long serialVersionUID = 1L;

    /**
     * Definition of alternate handling modes of single-argument constructors
     * that are annotated with {@link com.fasterxml.jackson.annotation.JsonCreator}
     * but without "mode" definition (or explicit name for the argument):
     * this is the case where two interpretations
     * are possible -- "properties" (in which case the argument is named parameter
     * of a JSON Object) and "delegating (in which case the argument maps to the
     * whole JSON value).
     *<p>
     * Default choice is {@code HEURISTIC} (which is Jackson pre-2.12 always uses)
     *<p>
     * NOTE: does NOT have any effect if explicit {@code @JsonCreator}} annotation
     * is required.
     *
     * @since 2.12
     */
    public enum SingleArgConstructor {
        /**
         * Assume "delegating" mode if not explicitly annotated otherwise
         */
        DELEGATING,

        /**
         * Assume "properties" mode if not explicitly annotated otherwise
         */
        PROPERTIES,

        /**
         * Use heuristics to see if "properties" mode is to be used (POJO has a
         * property with the same name as the implicit name [if available] of
         * the constructor argument).
         * Note: this is the default choice for Jackson versions before 2.12.
         */
        HEURISTIC,

        /**
         * Refuse to decide implicit mode and instead throw a
         * {@link com.fasterxml.jackson.databind.exc.InvalidDefinitionException}
         * in ambiguous case.
         */
        REQUIRE_MODE;
    }

    /*
    /**********************************************************************
    /* Global default instances to use
    /**********************************************************************
     */

    /**
     * Instance used by default, which:
     *<ul>
     * <li>Uses {@link SingleArgConstructor#HEURISTIC} for single-argument constructor case
     *  </li>
     * <li>Does not require explicit {@code @JsonCreator} annotations (so allows
     * auto-detection of Visible constructors} (except for JDK types)
     *  </li>
     * <li>Does not allow auto-detection of Visible constructors for so-called JDK
     *   types; that is, classes in packages {@code java.*} and {@code javax.*}
     *  </li>
     *</ul>
     */
    public final static ConstructorDetector DEFAULT
        = new ConstructorDetector(SingleArgConstructor.HEURISTIC);

    /**
     * Instance similar to {@link #DEFAULT} except that for single-argument case
     * uses setting of {@link SingleArgConstructor#PROPERTIES}.
     */
    public final static ConstructorDetector USE_PROPERTIES_BASED
        = new ConstructorDetector(SingleArgConstructor.PROPERTIES);

    /**
     * Instance similar to {@link #DEFAULT} except that for single-argument case
     * uses setting of {@link SingleArgConstructor#DELEGATING}.
     */
    public final static ConstructorDetector USE_DELEGATING
        = new ConstructorDetector(SingleArgConstructor.DELEGATING);

    /**
     * Instance similar to {@link #DEFAULT} except that for single-argument case
     * uses setting of {@link SingleArgConstructor#REQUIRE_MODE}.
     */
    public final static ConstructorDetector EXPLICIT_ONLY
        = new ConstructorDetector(SingleArgConstructor.REQUIRE_MODE);

    /*
    /**********************************************************************
    /* Configuration
    /**********************************************************************
     */

    protected final SingleArgConstructor _singleArgMode;

    /**
     * Whether explicit {@link com.fasterxml.jackson.annotation.JsonCreator}
     * is always required for detecting constructors (even if visible) other
     * than the default (no argument) constructor.
     */
    protected final boolean _requireCtorAnnotation;

    /**
     * Whether auto-detection of constructors of "JDK types" (those in
     * packages {@code java.} and {@code javax.}) is allowed or not
     */
    protected final boolean _allowJDKTypeCtors;

    /*
    /**********************************************************************
    /* Life-cycle
    /**********************************************************************
     */

    protected ConstructorDetector(SingleArgConstructor singleArgMode,
            boolean requireCtorAnnotation,
            boolean allowJDKTypeCtors)
    {
        _singleArgMode = singleArgMode;
        _requireCtorAnnotation = requireCtorAnnotation;
        _allowJDKTypeCtors = allowJDKTypeCtors;
    }

    /**
     * Constructors used for default configurations which only varies
     * by {@code _singleArgMode}
     */
    protected ConstructorDetector(SingleArgConstructor singleArgMode) {
        this(singleArgMode, false, false);
    }

    public ConstructorDetector withSingleArgMode(SingleArgConstructor singleArgMode) {
        return new ConstructorDetector(singleArgMode,
                _requireCtorAnnotation, _allowJDKTypeCtors);
    }

    public ConstructorDetector withRequireAnnotation(boolean state) {
        return new ConstructorDetector(_singleArgMode,
                state, _allowJDKTypeCtors);
    }

    public ConstructorDetector withAllowJDKTypeConstructors(boolean state) {
        return new ConstructorDetector(_singleArgMode,
                _requireCtorAnnotation, state);
    }

    /*
    /**********************************************************************
    /* API
    /**********************************************************************
     */

    public SingleArgConstructor singleArgMode() {
        return _singleArgMode;
    }

    public boolean requireCtorAnnotation() {
        return _requireCtorAnnotation;
    }

    public boolean allowJDKTypeConstructors() {
        return _allowJDKTypeCtors;
    }

    public boolean singleArgCreatorDefaultsToDelegating() {
        return _singleArgMode == SingleArgConstructor.DELEGATING;
    }

    public boolean singleArgCreatorDefaultsToProperties() {
        return _singleArgMode == SingleArgConstructor.PROPERTIES;
    }

    /**
     * Accessor that combines checks for whether implicit creators are allowed
     * and, if so, whether JDK type constructors are allowed (if type is JDK type)
     * to determine whether implicit constructor
     * detection should be enabled for given type or not.
     * 
     * @param rawType Value type to consider
     *
     * @return True if implicit constructor detection should be enabled; false if not
     */
    public boolean shouldIntrospectorImplicitConstructors(Class<?> rawType) {
        // May not allow implicit creator introspection at all:
        if (_requireCtorAnnotation) {
            return false;
        }
        // But if it is allowed, may further limit use for JDK types
        if (!_allowJDKTypeCtors) {
            if (ClassUtil.isJDKClass(rawType)) {
                // 18-Sep-2020, tatu: Looks like must make an exception for Exception
                //    types (ha!) -- at this point, single-String-arg constructor
                //    is to be auto-detected
                if (!Throwable.class.isAssignableFrom(rawType)) {
                    return false;
                }
            }
        }
        return true;
    }
}

⏎ com/fasterxml/jackson/databind/cfg/ConstructorDetector.java

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