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/CoercionConfigs.java

package com.fasterxml.jackson.databind.cfg;

import java.util.HashMap;
import java.util.Map;

import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.MapperFeature;
import com.fasterxml.jackson.databind.type.LogicalType;

/**
 * @since 2.12
 */
public class CoercionConfigs
    implements java.io.Serializable
{
    private static final long serialVersionUID = 1L;

    private final static int TARGET_TYPE_COUNT = LogicalType.values().length;

    /**
     * Global default for cases not explicitly covered
     */
    protected CoercionAction _defaultAction;

    /**
     * Default coercion definitions used if no overrides found
     * by logical or physical type.
     */
    protected final MutableCoercionConfig _defaultCoercions;
    
    /**
     * Coercion definitions by logical type ({@link LogicalType})
     */
    protected MutableCoercionConfig[] _perTypeCoercions;

    /**
     * Coercion definitions by physical type (Class).
     */
    protected Map<Class<?>, MutableCoercionConfig> _perClassCoercions;

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

    public CoercionConfigs() {
        this(CoercionAction.TryConvert, new MutableCoercionConfig(),
                null, null);
    }

    protected CoercionConfigs(CoercionAction defaultAction,
            MutableCoercionConfig defaultCoercions,
            MutableCoercionConfig[] perTypeCoercions,
            Map<Class<?>, MutableCoercionConfig> perClassCoercions)
    {
        _defaultCoercions = defaultCoercions;
        _defaultAction = defaultAction;
        _perTypeCoercions = perTypeCoercions;
        _perClassCoercions = perClassCoercions;
    }

    /**
     * Method called to create a non-shared copy of configuration settings,
     * to be used by another {@link com.fasterxml.jackson.databind.ObjectMapper}
     * instance.
     *
     * @return A non-shared copy of configuration settings
     */
    public CoercionConfigs copy()
    {
        MutableCoercionConfig[] newPerType;
        if (_perTypeCoercions == null) {
            newPerType = null;
        } else {
            final int size = _perTypeCoercions.length;
            newPerType = new MutableCoercionConfig[size];
            for (int i = 0; i < size; ++i) {
                newPerType[i] = _copy(_perTypeCoercions[i]);
            }
        }
        Map<Class<?>, MutableCoercionConfig> newPerClass;
        if (_perClassCoercions == null) {
            newPerClass = null;
        } else {
            newPerClass = new HashMap<>();
            for (Map.Entry<Class<?>, MutableCoercionConfig> entry : _perClassCoercions.entrySet()) {
                newPerClass.put(entry.getKey(), entry.getValue().copy());
            }
        }
        return new CoercionConfigs(_defaultAction, _defaultCoercions.copy(),
                newPerType, newPerClass);
    }

    private static MutableCoercionConfig _copy(MutableCoercionConfig src) {
        if (src == null) {
            return null;
        }
        return src.copy();
    }

    /*
    /**********************************************************************
    /* Mutators: global defaults
    /**********************************************************************
     */

    public MutableCoercionConfig defaultCoercions() {
        return _defaultCoercions;
    }

    /*
    /**********************************************************************
    /* Mutators: per type
    /**********************************************************************
     */

    public MutableCoercionConfig findOrCreateCoercion(LogicalType type) {
        if (_perTypeCoercions == null) {
            _perTypeCoercions = new MutableCoercionConfig[TARGET_TYPE_COUNT];
        }
        MutableCoercionConfig config = _perTypeCoercions[type.ordinal()];
        if (config == null) {
            _perTypeCoercions[type.ordinal()] = config = new MutableCoercionConfig();
        }
        return config;
    }

    public MutableCoercionConfig findOrCreateCoercion(Class<?> type) {
        if (_perClassCoercions == null) {
            _perClassCoercions = new HashMap<>();
        }
        MutableCoercionConfig config = _perClassCoercions.get(type);
        if (config == null) {
            config = new MutableCoercionConfig();
            _perClassCoercions.put(type, config);
        }
        return config;
    }

    /*
    /**********************************************************************
    /* Access
    /**********************************************************************
     */

    /**
     * General-purpose accessor for finding what to do when specified coercion
     * from shape that is now always allowed to be coerced from is requested.
     *
     * @param config Currently active deserialization configuration
     * @param targetType Logical target type of coercion
     * @param targetClass Physical target type of coercion
     * @param inputShape Input shape to coerce from
     *
     * @return CoercionAction configured for specified coercion
     *
     * @since 2.12
     */
    public CoercionAction findCoercion(DeserializationConfig config,
            LogicalType targetType,
            Class<?> targetClass, CoercionInputShape inputShape)
    {
        // First, see if there is exact match for physical type
        if ((_perClassCoercions != null) && (targetClass != null)) {
            MutableCoercionConfig cc = _perClassCoercions.get(targetClass);
            if (cc != null) {
                CoercionAction act = cc.findAction(inputShape);
                if (act != null) {
                    return act;
                }
            }
        }

        // If not, maybe by logical type
        if ((_perTypeCoercions != null) && (targetType != null)) {
            MutableCoercionConfig cc = _perTypeCoercions[targetType.ordinal()];
            if (cc != null) {
                CoercionAction act = cc.findAction(inputShape);
                if (act != null) {
                    return act;
                }
            }
        }

        // Barring that, default coercion for input shape?
        CoercionAction act = _defaultCoercions.findAction(inputShape);
        if (act != null) {
            return act;
        }

        // Otherwise there are some legacy features that can provide answer
        switch (inputShape) {
        case EmptyArray:
            // Default for setting is false
            return config.isEnabled(DeserializationFeature.ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT) ?
                    CoercionAction.AsNull : CoercionAction.Fail;
        case Float:
            if (targetType == LogicalType.Integer) {
                // Default for setting in 2.x is true
                return config.isEnabled(DeserializationFeature.ACCEPT_FLOAT_AS_INT) ?
                        CoercionAction.TryConvert : CoercionAction.Fail;
            }
            break;
        case Integer:
            if (targetType == LogicalType.Enum) {
                if (config.isEnabled(DeserializationFeature.FAIL_ON_NUMBERS_FOR_ENUMS)) {
                    return CoercionAction.Fail;
                }
            }
            break;
        default:
        }

        // classic scalars are numbers, booleans; but date/time also considered
        // scalar for this particular purpose
        final boolean baseScalar = _isScalarType(targetType);

        if (baseScalar
                // Default for setting in 2.x is true
                && !config.isEnabled(MapperFeature.ALLOW_COERCION_OF_SCALARS)
                // 12-Oct-2022, carterkozak: As per [databind#3624]: Coercion from integer-shaped
                // data into a floating point type is not banned by the
                // ALLOW_COERCION_OF_SCALARS feature because '1' is a valid JSON representation of
                // '1.0' in a way that other types of coercion do not satisfy.
                && (targetType != LogicalType.Float || inputShape != CoercionInputShape.Integer)) {
            return CoercionAction.Fail;
        }

        if (inputShape == CoercionInputShape.EmptyString) {
            // Since coercion of scalar must be enabled (see check above), allow empty-string
            // coercions by default even without this setting
            if (baseScalar
                    // Default for setting is false
                    || config.isEnabled(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT)) {
                return CoercionAction.AsNull;
            }
            // 09-Jun-2020, tatu: Seems necessary to support backwards-compatibility with
            //     2.11, wrt "FromStringDeserializer" supported types
            if (targetType == LogicalType.OtherScalar) {
                return CoercionAction.TryConvert;
            }
            // But block from allowing structured types like POJOs, Maps etc
            return CoercionAction.Fail;
        }

        // and all else failing, return default
        return _defaultAction;
    }

    /**
     * More specialized accessor called in case of input being a blank
     * String (one consisting of only white space characters with length of at least one).
     * Will basically first determine if "blank as empty" is allowed: if not,
     * returns {@code actionIfBlankNotAllowed}, otherwise returns action for
     * {@link CoercionInputShape#EmptyString}.
     *
     * @param config Currently active deserialization configuration
     * @param targetType Logical target type of coercion
     * @param targetClass Physical target type of coercion
     * @param actionIfBlankNotAllowed Return value to use in case "blanks as empty"
     *    is not allowed
     *
     * @return CoercionAction configured for specified coercion from blank string
     */
    public CoercionAction findCoercionFromBlankString(DeserializationConfig config,
            LogicalType targetType,
            Class<?> targetClass,
            CoercionAction actionIfBlankNotAllowed)
    {
        Boolean acceptBlankAsEmpty = null;
        CoercionAction action = null;

        // First, see if there is exact match for physical type
        if ((_perClassCoercions != null) && (targetClass != null)) {
            MutableCoercionConfig cc = _perClassCoercions.get(targetClass);
            if (cc != null) {
                acceptBlankAsEmpty = cc.getAcceptBlankAsEmpty();
                action = cc.findAction(CoercionInputShape.EmptyString);
            }
        }

        // If not, maybe by logical type
        if ((_perTypeCoercions != null) && (targetType != null)) {
            MutableCoercionConfig cc = _perTypeCoercions[targetType.ordinal()];
            if (cc != null) {
                if (acceptBlankAsEmpty == null) {
                    acceptBlankAsEmpty = cc.getAcceptBlankAsEmpty();
                }
                if (action == null) {
                    action = cc.findAction(CoercionInputShape.EmptyString);
                }
            }
        }

        // Barring that, default coercion for input shape?
        if (acceptBlankAsEmpty == null) {
            acceptBlankAsEmpty = _defaultCoercions.getAcceptBlankAsEmpty();
        }
        if (action == null) {
            action = _defaultCoercions.findAction(CoercionInputShape.EmptyString);
        }

        // First: if using blank as empty is no-go, return what caller specified
        if (Boolean.FALSE.equals(acceptBlankAsEmpty)) {
            return actionIfBlankNotAllowed;
        }
        // Otherwise, if action found, return that
        if (action != null) {
            return action;
        }

        // 23-Sep-2021, tatu: [databind#3234] Should default to "allow" for Scalar types
        //    for backwards compatibility
        if (_isScalarType(targetType)) {
            return CoercionAction.AsNull;
        }

        // If not, one specific legacy setting to consider...
        if (config.isEnabled(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT)) {
            return CoercionAction.AsNull;
        }

        // But finally consider ultimate default to be "false" and so:
        return actionIfBlankNotAllowed;
    }

    protected boolean _isScalarType(LogicalType targetType) {
        return (targetType == LogicalType.Float)
                || (targetType == LogicalType.Integer)
                || (targetType == LogicalType.Boolean)
                || (targetType == LogicalType.DateTime);
    }
}

⏎ com/fasterxml/jackson/databind/cfg/CoercionConfigs.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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