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/StdKeyDeserializer.java

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

import java.io.IOException;
import java.io.Serializable;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URL;
import java.util.*;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.io.NumberInput;

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;
import com.fasterxml.jackson.databind.introspect.AnnotatedMethod;
import com.fasterxml.jackson.databind.util.ClassUtil;
import com.fasterxml.jackson.databind.util.EnumResolver;
import com.fasterxml.jackson.databind.util.TokenBuffer;

/**
 * Default {@link KeyDeserializer} implementation used for most {@link java.util.Map}
 * types Jackson supports.
 * Implemented as "chameleon" (or swiss pocket knife) class; not particularly elegant,
 * but helps reduce number of classes and jar size (class metadata adds significant
 * per-class overhead; much more than bytecode).
 */
@JacksonStdImpl
public class StdKeyDeserializer extends KeyDeserializer
    implements java.io.Serializable
{
    private static final long serialVersionUID = 1L;

    public final static int TYPE_BOOLEAN = 1;
    public final static int TYPE_BYTE = 2;
    public final static int TYPE_SHORT = 3;
    public final static int TYPE_CHAR = 4;
    public final static int TYPE_INT = 5;
    public final static int TYPE_LONG = 6;
    public final static int TYPE_FLOAT = 7;
    public final static int TYPE_DOUBLE = 8;
    public final static int TYPE_LOCALE = 9;
    public final static int TYPE_DATE = 10;
    public final static int TYPE_CALENDAR = 11;
    public final static int TYPE_UUID = 12;
    public final static int TYPE_URI = 13;
    public final static int TYPE_URL = 14;
    public final static int TYPE_CLASS = 15;
    public final static int TYPE_CURRENCY = 16;
    public final static int TYPE_BYTE_ARRAY = 17; // since 2.9

    final protected int _kind;
    final protected Class<?> _keyClass;

    /**
     * Some types that are deserialized using a helper deserializer.
     */
    protected final FromStringDeserializer<?> _deser;
    
    protected StdKeyDeserializer(int kind, Class<?> cls) {
        this(kind, cls, null);
    }

    protected StdKeyDeserializer(int kind, Class<?> cls, FromStringDeserializer<?> deser) {
        _kind = kind;
        _keyClass = cls;
        _deser = deser;
    }

    public static StdKeyDeserializer forType(Class<?> raw)
    {
        int kind;

        // first common types:
        if (raw == String.class || raw == Object.class
                || raw == CharSequence.class
                // see [databind#2115]:
                || raw == Serializable.class) {
            return StringKD.forType(raw);
        }
        if (raw == UUID.class) {
            kind = TYPE_UUID;
        } else if (raw == Integer.class) {
            kind = TYPE_INT;
        } else if (raw == Long.class) {
            kind = TYPE_LONG;
        } else if (raw == Date.class) {
            kind = TYPE_DATE;
        } else if (raw == Calendar.class) {
            kind = TYPE_CALENDAR;
        // then less common ones...
        } else if (raw == Boolean.class) {
            kind = TYPE_BOOLEAN;
        } else if (raw == Byte.class) {
            kind = TYPE_BYTE;
        } else if (raw == Character.class) {
            kind = TYPE_CHAR;
        } else if (raw == Short.class) {
            kind = TYPE_SHORT;
        } else if (raw == Float.class) {
            kind = TYPE_FLOAT;
        } else if (raw == Double.class) {
            kind = TYPE_DOUBLE;
        } else if (raw == URI.class) {
            kind = TYPE_URI;
        } else if (raw == URL.class) {
            kind = TYPE_URL;
        } else if (raw == Class.class) {
            kind = TYPE_CLASS;
        } else if (raw == Locale.class) {
            FromStringDeserializer<?> deser = FromStringDeserializer.findDeserializer(Locale.class);
            return new StdKeyDeserializer(TYPE_LOCALE, raw, deser);
        } else if (raw == Currency.class) {
            FromStringDeserializer<?> deser = FromStringDeserializer.findDeserializer(Currency.class);
            return new StdKeyDeserializer(TYPE_CURRENCY, raw, deser);
        } else if (raw == byte[].class) {
            kind = TYPE_BYTE_ARRAY;
        } else {
            return null;
        }
        return new StdKeyDeserializer(kind, raw);
    }

    @Override
    public Object deserializeKey(String key, DeserializationContext ctxt)
        throws IOException
    {
        if (key == null) { // is this even legal call?
            return null;
        }
        try {
            Object result = _parse(key, ctxt);
            if (result != null) {
                return result;
            }
        } catch (Exception re) {
            return ctxt.handleWeirdKey(_keyClass, key, "not a valid representation, problem: (%s) %s",
                    re.getClass().getName(),
                    ClassUtil.exceptionMessage(re));
        }
        if (ClassUtil.isEnumType(_keyClass)
                && ctxt.getConfig().isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL)) {
            return null;
        }
        return ctxt.handleWeirdKey(_keyClass, key, "not a valid representation");
    }

    public Class<?> getKeyClass() { return _keyClass; }

    protected Object _parse(String key, DeserializationContext ctxt) throws Exception
    {
        switch (_kind) {
        case TYPE_BOOLEAN:
            if ("true".equals(key)) {
                return Boolean.TRUE;
            }
            if ("false".equals(key)) {
                return Boolean.FALSE;
            }
            return ctxt.handleWeirdKey(_keyClass, key, "value not 'true' or 'false'");
        case TYPE_BYTE:
            {
                int value = _parseInt(key);
                // allow range up to 255, inclusive (to support "unsigned" byte)
                if (value < Byte.MIN_VALUE || value > 255) {
                    return ctxt.handleWeirdKey(_keyClass, key, "overflow, value cannot be represented as 8-bit value");
                }
                return Byte.valueOf((byte) value);
            }
        case TYPE_SHORT:
            {
                int value = _parseInt(key);
                if (value < Short.MIN_VALUE || value > Short.MAX_VALUE) {
                    return ctxt.handleWeirdKey(_keyClass, key, "overflow, value cannot be represented as 16-bit value");
                    // fall-through and truncate if need be
                }
                return Short.valueOf((short) value);
            }
        case TYPE_CHAR:
            if (key.length() == 1) {
                return Character.valueOf(key.charAt(0));
            }
            return ctxt.handleWeirdKey(_keyClass, key, "can only convert 1-character Strings");
        case TYPE_INT:
            return _parseInt(key);

        case TYPE_LONG:
            return _parseLong(key);

        case TYPE_FLOAT:
            // Bounds/range checks would be tricky here, so let's not bother even trying...
            return Float.valueOf((float) _parseDouble(key));
        case TYPE_DOUBLE:
            return _parseDouble(key);
        case TYPE_LOCALE:
            try {
                return _deser._deserialize(key, ctxt);
            } catch (IllegalArgumentException e) {
                return _weirdKey(ctxt, key, e);
            }
        case TYPE_CURRENCY:
            try {
                return _deser._deserialize(key, ctxt);
            } catch (IllegalArgumentException e) {
                return _weirdKey(ctxt, key, e);
            }
        case TYPE_DATE:
            return ctxt.parseDate(key);
        case TYPE_CALENDAR:
            return ctxt.constructCalendar(ctxt.parseDate(key));
        case TYPE_UUID:
            try {
                return UUID.fromString(key);
            } catch (Exception e) {
                return _weirdKey(ctxt, key, e);
            }
        case TYPE_URI:
            try {
                return URI.create(key);
            } catch (Exception e) {
                return _weirdKey(ctxt, key, e);
            }
        case TYPE_URL:
            try {
                return new URL(key);
            } catch (MalformedURLException e) {
                return _weirdKey(ctxt, key, e);
            }
        case TYPE_CLASS:
            try {
                return ctxt.findClass(key);
            } catch (Exception e) {
                return ctxt.handleWeirdKey(_keyClass, key, "unable to parse key as Class");
            }
        case TYPE_BYTE_ARRAY:
            try {
                return ctxt.getConfig().getBase64Variant().decode(key);
            } catch (IllegalArgumentException e) {
                return _weirdKey(ctxt, key, e);
            }
        default:
            throw new IllegalStateException("Internal error: unknown key type "+_keyClass);
        }
    }

    /*
    /**********************************************************
    /* Helper methods for sub-classes
    /**********************************************************
     */

    protected int _parseInt(String key) throws IllegalArgumentException {
        return NumberInput.parseInt(key);
    }

    protected long _parseLong(String key) throws IllegalArgumentException {
        return NumberInput.parseLong(key);
    }

    protected double _parseDouble(String key) throws IllegalArgumentException {
        return NumberInput.parseDouble(key);
    }

    // @since 2.9
    protected Object _weirdKey(DeserializationContext ctxt, String key, Exception e) throws IOException {
        return ctxt.handleWeirdKey(_keyClass, key, "problem: %s",
                ClassUtil.exceptionMessage(e));
    }

    /*
    /**********************************************************
    /* First: the standard "String as String" deserializer
    /**********************************************************
     */

    @JacksonStdImpl
    final static class StringKD extends StdKeyDeserializer
    {
        private static final long serialVersionUID = 1L;
        private final static StringKD sString = new StringKD(String.class);
        private final static StringKD sObject = new StringKD(Object.class);
        
        private StringKD(Class<?> nominalType) { super(-1, nominalType); }

        public static StringKD forType(Class<?> nominalType)
        {
            if (nominalType == String.class) {
                return sString;
            }
            if (nominalType == Object.class) {
                return sObject;
            }
            return new StringKD(nominalType);
        }

        @Override
        public Object deserializeKey(String key, DeserializationContext ctxt) throws IOException {
            return key;
        }
    }    

    /*
    /**********************************************************
    /* Key deserializer implementations; other
    /**********************************************************
     */

    /**
     * Key deserializer that wraps a "regular" deserializer (but one
     * that must recognize FIELD_NAMEs as text!) to reuse existing
     * handlers as key handlers.
     */
    final static class DelegatingKD
        extends KeyDeserializer // note: NOT the std one
        implements java.io.Serializable
    {
        private static final long serialVersionUID = 1L;

        final protected Class<?> _keyClass;

        protected final JsonDeserializer<?> _delegate;
        
        protected DelegatingKD(Class<?> cls, JsonDeserializer<?> deser) {
            _keyClass = cls;
            _delegate = deser;
        }

        @SuppressWarnings("resource")
        @Override
        public final Object deserializeKey(String key, DeserializationContext ctxt)
            throws IOException
        {
            if (key == null) { // is this even legal call?
                return null;
            }
            TokenBuffer tb = ctxt.bufferForInputBuffering();
            tb.writeString(key);
            try {
                // Ugh... should not have to give parser which may or may not be correct one...
                JsonParser p = tb.asParser();
                p.nextToken();
                Object result = _delegate.deserialize(p, ctxt);
                if (result != null) {
                    return result;
                }
                return ctxt.handleWeirdKey(_keyClass, key, "not a valid representation");
            } catch (Exception re) {
                return ctxt.handleWeirdKey(_keyClass, key, "not a valid representation: %s", re.getMessage());
            }
        }

        public Class<?> getKeyClass() { return _keyClass; }
    }

    @JacksonStdImpl
    final static class EnumKD extends StdKeyDeserializer
    {
        private static final long serialVersionUID = 1L;

        protected final EnumResolver _byNameResolver;

        protected final AnnotatedMethod _factory;

        /**
         * Lazily constructed alternative in case there is need to
         * use 'toString()' method as the source.
         *
         * @since 2.7.3
         */
        protected EnumResolver _byToStringResolver;

        protected final Enum<?> _enumDefaultValue;
        
        protected EnumKD(EnumResolver er, AnnotatedMethod factory) {
            super(-1, er.getEnumClass());
            _byNameResolver = er;
            _factory = factory;
            _enumDefaultValue = er.getDefaultValue();
        }

        @Override
        public Object _parse(String key, DeserializationContext ctxt) throws IOException
        {
            if (_factory != null) {
                try {
                    return _factory.call1(key);
                } catch (Exception e) {
                    ClassUtil.unwrapAndThrowAsIAE(e);
                }
            }
            EnumResolver res = ctxt.isEnabled(DeserializationFeature.READ_ENUMS_USING_TO_STRING)
                    ? _getToStringResolver(ctxt) : _byNameResolver;
            Enum<?> e = res.findEnum(key);
            if (e == null) {
                if ((_enumDefaultValue != null)
                        && ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE)) {
                    e = _enumDefaultValue;
                } else if (!ctxt.isEnabled(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL)) {
                    return ctxt.handleWeirdKey(_keyClass, key, "not one of the values accepted for Enum class: %s",
                        res.getEnumIds());
                }
                // fall-through if problems are collected, not immediately thrown
            }
            return e;
        }

        private EnumResolver _getToStringResolver(DeserializationContext ctxt)
        {
            EnumResolver res = _byToStringResolver;
            if (res == null) {
                synchronized (this) {
                    res = EnumResolver.constructUsingToString(ctxt.getConfig(),
                            _byNameResolver.getEnumClass());
                    _byToStringResolver = res;
                }
            }
            return res;
        }
    }
    
    /**
     * Key deserializer that calls a single-string-arg constructor
     * to instantiate desired key type.
     */
    final static class StringCtorKeyDeserializer extends StdKeyDeserializer
    {
        private static final long serialVersionUID = 1L;

        protected final Constructor<?> _ctor;

        public StringCtorKeyDeserializer(Constructor<?> ctor) {
            super(-1, ctor.getDeclaringClass());
            _ctor = ctor;
        }

        @Override
        public Object _parse(String key, DeserializationContext ctxt) throws Exception
        {
            return _ctor.newInstance(key);
        }
    }

    /**
     * Key deserializer that calls a static no-args factory method
     * to instantiate desired key type.
     */
    final static class StringFactoryKeyDeserializer extends StdKeyDeserializer
    {
        private static final long serialVersionUID = 1L;

        final Method _factoryMethod;

        public StringFactoryKeyDeserializer(Method fm) {
            super(-1, fm.getDeclaringClass());
            _factoryMethod = fm;
        }

        @Override
        public Object _parse(String key, DeserializationContext ctxt) throws Exception
        {
            return _factoryMethod.invoke(null, key);
        }
    }
}

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