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/impl/TypeDeserializerBase.java

package com.fasterxml.jackson.databind.jsontype.impl;

import java.io.IOException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import com.fasterxml.jackson.annotation.JsonTypeInfo;

import com.fasterxml.jackson.core.*;

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.deser.std.NullifyingDeserializer;
import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
import com.fasterxml.jackson.databind.jsontype.TypeIdResolver;
import com.fasterxml.jackson.databind.util.ClassUtil;

/**
 * Base class for all standard Jackson {@link TypeDeserializer}s.
 */
public abstract class TypeDeserializerBase
    extends TypeDeserializer
    implements java.io.Serializable
{
    private static final long serialVersionUID = 1;

    protected final TypeIdResolver _idResolver;

    protected final JavaType _baseType;

    /**
     * Property that contains value for which type information
     * is included; null if value is a root value.
     * Note that this value is not assigned during construction
     * but only when {@link #forProperty} is called to create
     * a copy.
     */
    protected final BeanProperty _property;

    /**
     * Type to use as the default implementation, if type id is
     * missing or cannot be resolved.
     */
    protected final JavaType _defaultImpl;

    /**
     * Name of type property used; needed for non-property versions too,
     * in cases where type id is to be exposed as part of JSON.
     */
    protected final String _typePropertyName;

    protected final boolean _typeIdVisible;

    /**
     * For efficient operation we will lazily build mappings from type ids
     * to actual deserializers, once needed.
     */
    protected final Map<String,JsonDeserializer<Object>> _deserializers;

    protected JsonDeserializer<Object> _defaultImplDeserializer;

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

    /**
     * @since 2.8
     */
    protected TypeDeserializerBase(JavaType baseType, TypeIdResolver idRes,
            String typePropertyName, boolean typeIdVisible, JavaType defaultImpl)
    {
        _baseType = baseType;
        _idResolver = idRes;
        _typePropertyName = ClassUtil.nonNullString(typePropertyName);
        _typeIdVisible = typeIdVisible;
        // defaults are fine, although shouldn't need much concurrency
        _deserializers = new ConcurrentHashMap<String, JsonDeserializer<Object>>(16, 0.75f, 2);
        _defaultImpl = defaultImpl;
        _property = null;
    }

    protected TypeDeserializerBase(TypeDeserializerBase src, BeanProperty property)
    {
        _baseType = src._baseType;
        _idResolver = src._idResolver;
        _typePropertyName = src._typePropertyName;
        _typeIdVisible = src._typeIdVisible;
        _deserializers = src._deserializers;
        _defaultImpl = src._defaultImpl;
        _defaultImplDeserializer = src._defaultImplDeserializer;
        _property = property;
    }

    @Override
    public abstract TypeDeserializer forProperty(BeanProperty prop);

    /*
    /**********************************************************
    /* Accessors
    /**********************************************************
     */
    
    @Override
    public abstract JsonTypeInfo.As getTypeInclusion();

    public String baseTypeName() { return _baseType.getRawClass().getName(); }

    @Override
    public final String getPropertyName() { return _typePropertyName; }
    
    @Override    
    public TypeIdResolver getTypeIdResolver() { return _idResolver; }

    @Override
    public Class<?> getDefaultImpl() {
        return ClassUtil.rawClass(_defaultImpl);
    }

    @Override
    public boolean hasDefaultImpl() {
        return (_defaultImpl != null);
    }

    /**
     * @since 2.9
     */
    public JavaType baseType() {
        return _baseType;
    }

    @Override
    public String toString()
    {
        StringBuilder sb = new StringBuilder();
        sb.append('[').append(getClass().getName());
        sb.append("; base-type:").append(_baseType);
        sb.append("; id-resolver: ").append(_idResolver);
        sb.append(']');
        return sb.toString();
    }
    
    /*
    /**********************************************************
    /* Helper methods for sub-classes
    /**********************************************************
     */

    protected final JsonDeserializer<Object> _findDeserializer(DeserializationContext ctxt,
            String typeId) throws IOException
    {
        JsonDeserializer<Object> deser = _deserializers.get(typeId);
        if (deser == null) {
            /* As per [databind#305], need to provide contextual info. But for
             * backwards compatibility, let's start by only supporting this
             * for base class, not via interface. Later on we can add this
             * to the interface, assuming deprecation at base class helps.
             */
            JavaType type = _idResolver.typeFromId(ctxt, typeId);
            if (type == null) {
                // use the default impl if no type id available:
                deser = _findDefaultImplDeserializer(ctxt);
                if (deser == null) {
                    // 10-May-2016, tatu: We may get some help...
                    JavaType actual = _handleUnknownTypeId(ctxt, typeId);
                    if (actual == null) { // what should this be taken to mean?
                        // 17-Jan-2019, tatu: As per [databind#2221], better NOT return `null` but...
                        return NullifyingDeserializer.instance;
                    }
                    // ... would this actually work?
                    deser = ctxt.findContextualValueDeserializer(actual, _property);
                }
            } else {
                /* 16-Dec-2010, tatu: Since nominal type we get here has no (generic) type parameters,
                 *   we actually now need to explicitly narrow from base type (which may have parameterization)
                 *   using raw type.
                 *
                 *   One complication, though; cannot change 'type class' (simple type to container); otherwise
                 *   we may try to narrow a SimpleType (Object.class) into MapType (Map.class), losing actual
                 *   type in process (getting SimpleType of Map.class which will not work as expected)
                 */
                if ((_baseType != null)
                        && _baseType.getClass() == type.getClass()) {
                    /* 09-Aug-2015, tatu: Not sure if the second part of the check makes sense;
                     *   but it appears to check that JavaType impl class is the same which is
                     *   important for some reason?
                     *   Disabling the check will break 2 Enum-related tests.
                     */
                    // 19-Jun-2016, tatu: As per [databind#1270] we may actually get full
                    //   generic type with custom type resolvers. If so, should try to retain them.
                    //  Whether this is sufficient to avoid problems remains to be seen, but for
                    //  now it should improve things.
                    if (!type.hasGenericTypes()) {
                        try { // [databind#2668]: Should not expose generic RTEs
                            type = ctxt.constructSpecializedType(_baseType, type.getRawClass());
                        } catch (IllegalArgumentException e) {
                            // 29-Mar-2020, tatu: I hope this is not misleading for other cases, but
                            //   for [databind#2668] seems reasonable
                            throw ctxt.invalidTypeIdException(_baseType, typeId, e.getMessage());
                        }
                    }
                }
                deser = ctxt.findContextualValueDeserializer(type, _property);
            }
            _deserializers.put(typeId, deser);
        }
        return deser;
    }

    protected final JsonDeserializer<Object> _findDefaultImplDeserializer(DeserializationContext ctxt) throws IOException
    {
        // 06-Feb-2013, tatu: As per [databind#148], consider default implementation value of
        //   {@link java.lang.Void} to mean "serialize as null"; as well as DeserializationFeature
        //   to do swift mapping to null
        if (_defaultImpl == null) {
            if (!ctxt.isEnabled(DeserializationFeature.FAIL_ON_INVALID_SUBTYPE)) {
                return NullifyingDeserializer.instance;
            }
            return null;
        }
        Class<?> raw = _defaultImpl.getRawClass();
        if (ClassUtil.isBogusClass(raw)) {
            return NullifyingDeserializer.instance;
        }
        
        synchronized (_defaultImpl) {
            if (_defaultImplDeserializer == null) {
                _defaultImplDeserializer = ctxt.findContextualValueDeserializer(
                        _defaultImpl, _property);
            }
            return _defaultImplDeserializer;
        }
    }

    /**
     * Helper method called when {@link JsonParser} indicates that it can use
     * so-called native type ids. Assumption from there is that only native
     * type ids are to be used.
     * 
     * @since 2.3
     */
    @Deprecated
    protected Object _deserializeWithNativeTypeId(JsonParser jp, DeserializationContext ctxt) throws IOException {
        return _deserializeWithNativeTypeId(jp, ctxt, jp.getTypeId());
    }

    /**
     * Helper method called when {@link JsonParser} indicates that it can use
     * so-called native type ids, and such type id has been found.
     * 
     * @since 2.4
     */
    protected Object _deserializeWithNativeTypeId(JsonParser p, DeserializationContext ctxt, Object typeId)
        throws IOException
    {
        JsonDeserializer<Object> deser;
        if (typeId == null) {
            // 04-May-2014, tatu: Should error be obligatory, or should there be another method
            //   for "try to deserialize with native type id"?
            deser = _findDefaultImplDeserializer(ctxt);
            if (deser == null) {
                return ctxt.reportInputMismatch(baseType(),
                        "No (native) type id found when one was expected for polymorphic type handling");
            }
        } else {
            String typeIdStr = (typeId instanceof String) ? (String) typeId : String.valueOf(typeId);
            deser = _findDeserializer(ctxt, typeIdStr);
        }
        return deser.deserialize(p, ctxt);
    }

    /**
     * Helper method called when given type id cannot be resolved into 
     * concrete deserializer either directly (using given {@link  TypeIdResolver}),
     * or using default type.
     * Default implementation simply throws a {@link com.fasterxml.jackson.databind.JsonMappingException} to
     * indicate the problem; sub-classes may choose
     *
     * @return If it is possible to resolve type id into a {@link JsonDeserializer}
     *   should return that deserializer; otherwise throw an exception to indicate
     *   the problem.
     *
     * @since 2.8
     */
    protected JavaType _handleUnknownTypeId(DeserializationContext ctxt, String typeId)
        throws IOException
    {
        String extraDesc = _idResolver.getDescForKnownTypeIds();
        if (extraDesc == null) {
            extraDesc = "type ids are not statically known";
        } else {
            extraDesc = "known type ids = " + extraDesc;
        }
        if (_property != null) {
            extraDesc = String.format("%s (for POJO property '%s')", extraDesc,
                    _property.getName());
        }
        return ctxt.handleUnknownTypeId(_baseType, typeId, _idResolver, extraDesc);
    }

    /**
     * @since 2.9
     */
    protected JavaType _handleMissingTypeId(DeserializationContext ctxt, String extraDesc)
        throws IOException
    {
        return ctxt.handleMissingTypeId(_baseType, _idResolver, extraDesc);
    }
}

⏎ com/fasterxml/jackson/databind/jsontype/impl/TypeDeserializerBase.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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