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/ReferenceTypeDeserializer.java

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

import java.io.IOException;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.deser.ContextualDeserializer;
import com.fasterxml.jackson.databind.deser.ValueInstantiator;
import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
import com.fasterxml.jackson.databind.type.LogicalType;
import com.fasterxml.jackson.databind.type.ReferenceType;
import com.fasterxml.jackson.databind.util.AccessPattern;

/**
 * Base deserializer implementation for properties {@link ReferenceType} values.
 * Implements most of functionality, only leaving couple of abstract
 * methods for sub-classes to implement
 *
 * @since 2.8
 */
public abstract class ReferenceTypeDeserializer<T>
    extends StdDeserializer<T>
    implements ContextualDeserializer
{
    private static final long serialVersionUID = 2L; // 2.9

    /**
     * Full type of property (or root value) for which this deserializer
     * has been constructed and contextualized.
     */
    protected final JavaType _fullType;

    protected final ValueInstantiator _valueInstantiator;

    protected final TypeDeserializer _valueTypeDeserializer;
    protected final JsonDeserializer<Object> _valueDeserializer;

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

    @SuppressWarnings("unchecked")
    public ReferenceTypeDeserializer(JavaType fullType, ValueInstantiator vi,
            TypeDeserializer typeDeser, JsonDeserializer<?> deser)
    {
        super(fullType);
        _valueInstantiator = vi;
        _fullType = fullType;
        _valueDeserializer = (JsonDeserializer<Object>) deser;
        _valueTypeDeserializer = typeDeser;
    }

    @Deprecated // since 2.9
    public ReferenceTypeDeserializer(JavaType fullType,
            TypeDeserializer typeDeser, JsonDeserializer<?> deser)
    {
        this(fullType, null, typeDeser, deser);
    }

    @Override
    public JsonDeserializer<?> createContextual(DeserializationContext ctxt, BeanProperty property)
            throws JsonMappingException
    {
        JsonDeserializer<?> deser = _valueDeserializer;
        if (deser == null) {
            deser = ctxt.findContextualValueDeserializer(_fullType.getReferencedType(), property);
        } else { // otherwise directly assigned, probably not contextual yet:
            deser = ctxt.handleSecondaryContextualization(deser, property, _fullType.getReferencedType());            
        }
        TypeDeserializer typeDeser = _valueTypeDeserializer;
        if (typeDeser != null) {
            typeDeser = typeDeser.forProperty(property);
        }
        // !!! 23-Oct-2016, tatu: TODO: full support for configurable ValueInstantiators?
        if ((deser == _valueDeserializer) && (typeDeser == _valueTypeDeserializer)) {
            return this;
        }
        return withResolved(typeDeser, deser);
    }

    /*
    /**********************************************************
    /* Partial NullValueProvider impl
    /**********************************************************
     */

    /**
     * Null value varies dynamically (unlike with scalar types),
     * so let's indicate this.
     */
    @Override
    public AccessPattern getNullAccessPattern() {
        return AccessPattern.DYNAMIC;
    }

    @Override
    public AccessPattern getEmptyAccessPattern() {
        return AccessPattern.DYNAMIC;
    }

    /*
    /**********************************************************
    /* Abstract methods for sub-classes to implement
    /**********************************************************
     */
    
    /**
     * Mutant factory method called when changes are needed; should construct
     * newly configured instance with new values as indicated.
     *<p>
     * NOTE: caller has verified that there are changes, so implementations
     * need NOT check if a new instance is needed.
     */
    protected abstract ReferenceTypeDeserializer<T> withResolved(TypeDeserializer typeDeser,
            JsonDeserializer<?> valueDeser);

    @Override
    public abstract T getNullValue(DeserializationContext ctxt) throws JsonMappingException;

    @Override
    public Object getEmptyValue(DeserializationContext ctxt) throws JsonMappingException {
        return getNullValue(ctxt);
    }

    // 02-Sep-2021, tatu: Related to [databind#3214] we may want to add this... but
    //    with 2.13.0 so close will not yet do that, but wait for 2.14
//    @Override
//    public Object getAbsentValue(DeserializationContext ctxt) throws JsonMappingException {
//        return null;
//    }

    public abstract T referenceValue(Object contents);

    /**
     * Method called in case of "merging update", in which we should try
     * update reference instead of creating a new one. If this does not
     * succeed, should just create a new instance.
     *
     * @since 2.9
     */
    public abstract T updateReference(T reference, Object contents);

    /**
     * Method that may be called to find contents of specified reference,
     * if any; or `null` if none. Note that method should never fail, so
     * for types that use concept of "absence" vs "presence", `null` is
     * to be returned for both "absent" and "reference to `null`" cases.
     *
     * @since 2.9
     */
    public abstract Object getReferenced(T reference);

    /*
    /**********************************************************
    /* Overridden accessors
    /**********************************************************
     */

    @Override
    public ValueInstantiator getValueInstantiator() { return _valueInstantiator; }

    @Override
    public JavaType getValueType() { return _fullType; }

    @Override // since 2.12
    public LogicalType logicalType() {
        if (_valueDeserializer != null) {
            return _valueDeserializer.logicalType();
        }
        return super.logicalType();
    }

    /**
     * By default we assume that updateability mostly relies on value
     * deserializer; if it supports updates, typically that's what
     * matters. So let's just delegate.
     */
    @Override // since 2.9
    public Boolean supportsUpdate(DeserializationConfig config) {
        return (_valueDeserializer == null) ? null
                : _valueDeserializer.supportsUpdate(config);
    }

    /*
    /**********************************************************
    /* Deserialization
    /**********************************************************
     */

    @Override
    public T deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        // 23-Oct-2016, tatu: ValueInstantiator only defined for non-vanilla instances,
        //    but do check... might work
        if (_valueInstantiator != null) {
            @SuppressWarnings("unchecked")
            T value = (T) _valueInstantiator.createUsingDefault(ctxt);
            return deserialize(p, ctxt, value);
        }
        Object contents = (_valueTypeDeserializer == null)
                ? _valueDeserializer.deserialize(p, ctxt)
                : _valueDeserializer.deserializeWithType(p, ctxt, _valueTypeDeserializer);
        return referenceValue(contents);
    }

    @Override
    public T deserialize(JsonParser p, DeserializationContext ctxt, T reference) throws IOException
    {
        Object contents;
        // 26-Oct-2016, tatu: first things first; see if we should be able to merge:
        Boolean B = _valueDeserializer.supportsUpdate(ctxt.getConfig());
        // if explicitly stated that merge won't work...
        if (B.equals(Boolean.FALSE) ||  (_valueTypeDeserializer != null)) {
            contents = (_valueTypeDeserializer == null)
                    ? _valueDeserializer.deserialize(p, ctxt)
                    : _valueDeserializer.deserializeWithType(p, ctxt, _valueTypeDeserializer);
        } else {
            // Otherwise, see if we can merge the value
            contents = getReferenced(reference);
            // Whether to error or not... for now, just go back to default then
            if (contents == null) {
                contents = (_valueTypeDeserializer == null)
                        ? _valueDeserializer.deserialize(p, ctxt)
                        : _valueDeserializer.deserializeWithType(p, ctxt, _valueTypeDeserializer);
                return referenceValue(contents);
            } else {
                contents = _valueDeserializer.deserialize(p, ctxt, contents);
            }
        }
        return updateReference(reference, contents);
    }

    @Override
    public Object deserializeWithType(JsonParser p, DeserializationContext ctxt,
            TypeDeserializer typeDeserializer) throws IOException
    {
        if (p.hasToken(JsonToken.VALUE_NULL)) { // can this actually happen?
            return getNullValue(ctxt);
        }
        // 22-Oct-2015, tatu: This handling is probably not needed (or is wrong), but
        //   could be result of older (pre-2.7) Jackson trying to serialize natural types.
        //  Because of this, let's allow for now, unless proven problematic
        /*
        if ((t != null) && t.isScalarValue()) {
            return deserialize(p, ctxt);
        }
        */
        // 19-Apr-2016, tatu: Alas, due to there typically really being anything for Reference wrapper
        //   itself, need to just ignore `typeDeser`, use TypeDeserializer we do have for contents
        //   and it might just work.

        if (_valueTypeDeserializer == null) {
            return deserialize(p, ctxt);
        }
        return referenceValue(_valueTypeDeserializer.deserializeTypedFromAny(p, ctxt));
    }
}

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