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/std/EnumDeserializer.java

package com.fasterxml.jackson.databind.deser.std;

import java.io.IOException;
import java.util.Objects;

import com.fasterxml.jackson.annotation.JsonFormat;

import com.fasterxml.jackson.core.*;

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;
import com.fasterxml.jackson.databind.cfg.CoercionAction;
import com.fasterxml.jackson.databind.cfg.CoercionInputShape;
import com.fasterxml.jackson.databind.deser.ContextualDeserializer;
import com.fasterxml.jackson.databind.deser.SettableBeanProperty;
import com.fasterxml.jackson.databind.deser.ValueInstantiator;
import com.fasterxml.jackson.databind.introspect.AnnotatedMethod;
import com.fasterxml.jackson.databind.type.LogicalType;
import com.fasterxml.jackson.databind.util.ClassUtil;
import com.fasterxml.jackson.databind.util.CompactStringObjectMap;
import com.fasterxml.jackson.databind.util.EnumResolver;

/**
 * Deserializer class that can deserialize instances of
 * specified Enum class from Strings and Integers.
 */
@JacksonStdImpl // was missing until 2.6
public class EnumDeserializer
    extends StdScalarDeserializer<Object>
    implements ContextualDeserializer
{
    private static final long serialVersionUID = 1L;

    protected Object[] _enumsByIndex;
    
    /**
     * @since 2.8
     */
    private final Enum<?> _enumDefaultValue;

    /**
     * @since 2.7.3
     */
    protected final CompactStringObjectMap _lookupByName;

    /**
     * Alternatively, we may need a different lookup object if "use toString"
     * is defined.
     *
     * @since 2.7.3
     */
    protected CompactStringObjectMap _lookupByToString;

    protected final Boolean _caseInsensitive;

    /**
     * Marker flag for cases where we expect actual integral value for Enum,
     * based on {@code @JsonValue} (and equivalent) annotated accessor.
     *
     * @since 2.13
     */
    protected final boolean _isFromIntValue;

    /**
     * @since 2.9
     */
    public EnumDeserializer(EnumResolver byNameResolver, Boolean caseInsensitive)
    {
        super(byNameResolver.getEnumClass());
        _lookupByName = byNameResolver.constructLookup();
        _enumsByIndex = byNameResolver.getRawEnums();
        _enumDefaultValue = byNameResolver.getDefaultValue();
        _caseInsensitive = caseInsensitive;
        _isFromIntValue = byNameResolver.isFromIntValue();
    }

    /**
     * @since 2.9
     */
    protected EnumDeserializer(EnumDeserializer base, Boolean caseInsensitive)
    {
        super(base);
        _lookupByName = base._lookupByName;
        _enumsByIndex = base._enumsByIndex;
        _enumDefaultValue = base._enumDefaultValue;
        _caseInsensitive = caseInsensitive;
        _isFromIntValue = base._isFromIntValue;
    }

    /**
     * @deprecated Since 2.9
     */
    @Deprecated
    public EnumDeserializer(EnumResolver byNameResolver) {
        this(byNameResolver, null);
    }

    /**
     * @deprecated Since 2.8
     */
    @Deprecated
    public static JsonDeserializer<?> deserializerForCreator(DeserializationConfig config,
            Class<?> enumClass, AnnotatedMethod factory) {
        return deserializerForCreator(config, enumClass, factory, null, null);
    }

    /**
     * Factory method used when Enum instances are to be deserialized
     * using a creator (static factory method)
     * 
     * @return Deserializer based on given factory method
     *
     * @since 2.8
     */
    public static JsonDeserializer<?> deserializerForCreator(DeserializationConfig config,
            Class<?> enumClass, AnnotatedMethod factory,
            ValueInstantiator valueInstantiator, SettableBeanProperty[] creatorProps)
    {
        if (config.canOverrideAccessModifiers()) {
            ClassUtil.checkAndFixAccess(factory.getMember(),
                    config.isEnabled(MapperFeature.OVERRIDE_PUBLIC_ACCESS_MODIFIERS));
        }
        return new FactoryBasedEnumDeserializer(enumClass, factory,
                factory.getParameterType(0),
                valueInstantiator, creatorProps);
    }

    /**
     * Factory method used when Enum instances are to be deserialized
     * using a zero-/no-args factory method
     * 
     * @return Deserializer based on given no-args factory method
     *
     * @since 2.8
     */
    public static JsonDeserializer<?> deserializerForNoArgsCreator(DeserializationConfig config,
            Class<?> enumClass, AnnotatedMethod factory)
    {
        if (config.canOverrideAccessModifiers()) {
            ClassUtil.checkAndFixAccess(factory.getMember(),
                    config.isEnabled(MapperFeature.OVERRIDE_PUBLIC_ACCESS_MODIFIERS));
        }
        return new FactoryBasedEnumDeserializer(enumClass, factory);
    }

    /**
     * @since 2.9
     */
    public EnumDeserializer withResolved(Boolean caseInsensitive) {
        if (Objects.equals(_caseInsensitive, caseInsensitive)) {
            return this;
        }
        return new EnumDeserializer(this, caseInsensitive);
    }
    
    @Override // since 2.9
    public JsonDeserializer<?> createContextual(DeserializationContext ctxt,
            BeanProperty property) throws JsonMappingException
    {
        Boolean caseInsensitive = findFormatFeature(ctxt, property, handledType(),
                JsonFormat.Feature.ACCEPT_CASE_INSENSITIVE_PROPERTIES);
        if (caseInsensitive == null) {
            caseInsensitive = _caseInsensitive;
        }
        return withResolved(caseInsensitive);
    }

    /*
    /**********************************************************
    /* Default JsonDeserializer implementation
    /**********************************************************
     */

    /**
     * Because of costs associated with constructing Enum resolvers,
     * let's cache instances by default.
     */
    @Override
    public boolean isCachable() { return true; }

    @Override // since 2.12
    public LogicalType logicalType() {
        return LogicalType.Enum;
    }

    @Override // since 2.12
    public Object getEmptyValue(DeserializationContext ctxt) throws JsonMappingException {
        return _enumDefaultValue;
    }

    @Override
    public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException
    {
        // Usually should just get string value:
        // 04-Sep-2020, tatu: for 2.11.3 / 2.12.0, removed "FIELD_NAME" as allowed;
        //   did not work and gave odd error message.
        if (p.hasToken(JsonToken.VALUE_STRING)) {
            return _fromString(p, ctxt, p.getText());
        }

        // But let's consider int acceptable as well (if within ordinal range)
        if (p.hasToken(JsonToken.VALUE_NUMBER_INT)) {
            // 26-Sep-2021, tatu: [databind#1850] Special case where we get "true" integer
            //    enumeration and should avoid use of {@code Enum.index()}
            if (_isFromIntValue) {
                // ... whether to rely on "getText()" returning String, or get number, convert?
                // For now assume all format backends can produce String:
                return _fromString(p, ctxt, p.getText());
            }
            return _fromInteger(p, ctxt, p.getIntValue());
        }
        // 29-Jun-2020, tatu: New! "Scalar from Object" (mostly for XML)
        if (p.isExpectedStartObjectToken()) {
            return _fromString(p, ctxt,
                    ctxt.extractScalarFromObject(p, this, _valueClass));
        }
        return _deserializeOther(p, ctxt);
    }

    protected Object _fromString(JsonParser p, DeserializationContext ctxt,
            String text)
        throws IOException
    {
        CompactStringObjectMap lookup = ctxt.isEnabled(DeserializationFeature.READ_ENUMS_USING_TO_STRING)
                ? _getToStringLookup(ctxt) : _lookupByName;
        Object result = lookup.find(text);
        if (result == null) {
            String trimmed = text.trim();
            if ((trimmed == text) || (result = lookup.find(trimmed)) == null) {
                return _deserializeAltString(p, ctxt, lookup, trimmed);
            }
        }
        return result;
    }

    protected Object _fromInteger(JsonParser p, DeserializationContext ctxt,
            int index)
        throws IOException
    {
        final CoercionAction act = ctxt.findCoercionAction(logicalType(), handledType(),
                CoercionInputShape.Integer);

        // First, check legacy setting for slightly different message
        if (act == CoercionAction.Fail) {
            if (ctxt.isEnabled(DeserializationFeature.FAIL_ON_NUMBERS_FOR_ENUMS)) {
                return ctxt.handleWeirdNumberValue(_enumClass(), index,
                        "not allowed to deserialize Enum value out of number: disable DeserializationConfig.DeserializationFeature.FAIL_ON_NUMBERS_FOR_ENUMS to allow"
                        );
            }
            // otherwise this will force failure with new setting
            _checkCoercionFail(ctxt, act, handledType(), index,
                    "Integer value ("+index+")");
        }
        switch (act) {
        case AsNull:
            return null;
        case AsEmpty:
            return getEmptyValue(ctxt);
        case TryConvert:
        default:
        }
        if (index >= 0 && index < _enumsByIndex.length) {
            return _enumsByIndex[index];
        }
        if ((_enumDefaultValue != null)
                && ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE)) {
            return _enumDefaultValue;
        }
        if (!ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL)) {
            return ctxt.handleWeirdNumberValue(_enumClass(), index,
                    "index value outside legal index range [0..%s]",
                    _enumsByIndex.length-1);
        }
        return null;
    }
        /*
    return _checkCoercionFail(ctxt, act, rawTargetType, value,
            "empty String (\"\")");
            */
    
    /*
    /**********************************************************
    /* Internal helper methods
    /**********************************************************
     */
    
    private final Object _deserializeAltString(JsonParser p, DeserializationContext ctxt,
            CompactStringObjectMap lookup, String nameOrig) throws IOException
    {
        String name = nameOrig.trim();
        if (name.isEmpty()) { // empty or blank
            // 07-Jun-2021, tatu: [databind#3171] Need to consider Default value first
            //   (alas there's bit of duplication here)
            if ((_enumDefaultValue != null)
                    && ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE)) {
                return _enumDefaultValue;
            }
            if (ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL)) {
                return null;
            }

            CoercionAction act;
            if (nameOrig.isEmpty()) {
                act = _findCoercionFromEmptyString(ctxt);
                act = _checkCoercionFail(ctxt, act, handledType(), nameOrig,
                        "empty String (\"\")");
            } else {
                act = _findCoercionFromBlankString(ctxt);
                act = _checkCoercionFail(ctxt, act, handledType(), nameOrig,
                        "blank String (all whitespace)");
            }
            switch (act) {
            case AsEmpty:
            case TryConvert:
                return getEmptyValue(ctxt);
            case AsNull:
            default: // Fail already handled earlier
            }
            return null;
//            if (ctxt.isEnabled(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT)) {
        } else {
            // [databind#1313]: Case insensitive enum deserialization
            if (Boolean.TRUE.equals(_caseInsensitive)) {
                Object match = lookup.findCaseInsensitive(name);
                if (match != null) {
                    return match;
                }
            } else if (!ctxt.isEnabled(DeserializationFeature.FAIL_ON_NUMBERS_FOR_ENUMS)
                    && !_isFromIntValue) {
                // [databind#149]: Allow use of 'String' indexes as well -- unless prohibited (as per above)
                char c = name.charAt(0);
                if (c >= '0' && c <= '9') {
                    try {
                        int index = Integer.parseInt(name);
                        if (!ctxt.isEnabled(MapperFeature.ALLOW_COERCION_OF_SCALARS)) {
                            return ctxt.handleWeirdStringValue(_enumClass(), name,
"value looks like quoted Enum index, but `MapperFeature.ALLOW_COERCION_OF_SCALARS` prevents use"
                                    );
                        }
                        if (index >= 0 && index < _enumsByIndex.length) {
                            return _enumsByIndex[index];
                        }
                    } catch (NumberFormatException e) {
                        // fine, ignore, was not an integer
                    }
                }
            }
        }
        if ((_enumDefaultValue != null)
                && ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE)) {
            return _enumDefaultValue;
        }
        if (ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL)) {
            return null;
        }
        return ctxt.handleWeirdStringValue(_enumClass(), name,
                "not one of the values accepted for Enum class: %s",  lookup.keys());
    }

    protected Object _deserializeOther(JsonParser p, DeserializationContext ctxt) throws IOException
    {
        // [databind#381]
        if (p.hasToken(JsonToken.START_ARRAY)) {
            return _deserializeFromArray(p, ctxt);
        }
        return ctxt.handleUnexpectedToken(_enumClass(), p);
    }

    protected Class<?> _enumClass() {
        return handledType();
    }

    protected CompactStringObjectMap _getToStringLookup(DeserializationContext ctxt)
    {
        CompactStringObjectMap lookup = _lookupByToString;
        // note: exact locking not needed; all we care for here is to try to
        // reduce contention for the initial resolution
        if (lookup == null) {
            synchronized (this) {
                lookup = EnumResolver.constructUsingToString(ctxt.getConfig(), _enumClass())
                    .constructLookup();
            }
            _lookupByToString = lookup;
        }
        return lookup;
    }
}

⏎ com/fasterxml/jackson/databind/deser/std/EnumDeserializer.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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