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/impl/PropertyValueBuffer.java

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

import java.io.IOException;
import java.util.BitSet;

import com.fasterxml.jackson.core.JsonParser;

import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.deser.SettableAnyProperty;
import com.fasterxml.jackson.databind.deser.SettableBeanProperty;
import com.fasterxml.jackson.databind.introspect.AnnotatedMember;

/**
 * Simple container used for temporarily buffering a set of
 * <code>PropertyValue</code>s.
 * Using during construction of beans (and Maps) that use Creators, 
 * and hence need buffering before instance (that will have properties
 * to assign values to) is constructed.
 */
public class PropertyValueBuffer
{
    /*
    /**********************************************************
    /* Configuration
    /**********************************************************
     */

    protected final JsonParser _parser;
    protected final DeserializationContext _context;

    protected final ObjectIdReader _objectIdReader;
    
    /*
    /**********************************************************
    /* Accumulated properties, other stuff
    /**********************************************************
     */

    /**
     * Buffer used for storing creator parameters for constructing
     * instance.
     */
    protected final Object[] _creatorParameters;
    
    /**
     * Number of creator parameters for which we have not yet received
     * values.
     */
    protected int _paramsNeeded;

    /**
     * Bitflag used to track parameters found from incoming data
     * when number of parameters is
     * less than 32 (fits in int).
     */
    protected int _paramsSeen;

    /**
     * Bitflag used to track parameters found from incoming data
     * when number of parameters is
     * 32 or higher.
     */
    protected final BitSet _paramsSeenBig;

    /**
     * If we get non-creator parameters before or between
     * creator parameters, those need to be buffered. Buffer
     * is just a simple linked list
     */
    protected PropertyValue _buffered;

    /**
     * In case there is an Object Id property to handle, this is the value
     * we have for it.
     */
    protected Object _idValue;

    /*
    /**********************************************************
    /* Life-cycle
    /**********************************************************
     */
    
    public PropertyValueBuffer(JsonParser p, DeserializationContext ctxt, int paramCount,
            ObjectIdReader oir)
    {
        _parser = p;
        _context = ctxt;
        _paramsNeeded = paramCount;
        _objectIdReader = oir;
        _creatorParameters = new Object[paramCount];
        if (paramCount < 32) {
            _paramsSeenBig = null;
        } else {
            _paramsSeenBig = new BitSet();
        }
    }

    /**
     * Returns {@code true} if the given property was seen in the JSON source by
     * this buffer.
     *
     * @since 2.8
     */
    public final boolean hasParameter(SettableBeanProperty prop)
    {
        if (_paramsSeenBig == null) {
            return ((_paramsSeen >> prop.getCreatorIndex()) & 1) == 1;
        }
        return _paramsSeenBig.get(prop.getCreatorIndex());
    }

    /**
     * A variation of {@link #getParameters(SettableBeanProperty[])} that
     * accepts a single property.  Whereas the plural form eagerly fetches and
     * validates all properties, this method may be used (along with
     * {@link #hasParameter(SettableBeanProperty)}) to let applications only
     * fetch the properties defined in the JSON source itself, and to have some
     * other customized behavior for missing properties.
     *
     * @since 2.8
     */
    public Object getParameter(SettableBeanProperty prop)
        throws JsonMappingException
    {
        Object value;
        if (hasParameter(prop)) {
            value = _creatorParameters[prop.getCreatorIndex()];
        } else {
            value = _creatorParameters[prop.getCreatorIndex()] = _findMissing(prop);
        }
        if (value == null && _context.isEnabled(DeserializationFeature.FAIL_ON_NULL_CREATOR_PROPERTIES)) {
            return _context.reportInputMismatch(prop,
                "Null value for creator property '%s' (index %d); `DeserializationFeature.FAIL_ON_NULL_CREATOR_PROPERTIES` enabled",
                prop.getName(), prop.getCreatorIndex());
        }
        return value;
    }

    /**
     * Method called to do necessary post-processing such as injection of values
     * and verification of values for required properties,
     * after either {@link #assignParameter(SettableBeanProperty, Object)}
     * returns <code>true</code> (to indicate all creator properties are found), or when
     * then whole JSON Object has been processed,
     */
    public Object[] getParameters(SettableBeanProperty[] props)
        throws JsonMappingException
    {
        // quick check to see if anything else is needed
        if (_paramsNeeded > 0) {
            if (_paramsSeenBig == null) {
                int mask = _paramsSeen;
                // not optimal, could use `Integer.trailingZeroes()`, but for now should not
                // really matter for common cases
                for (int ix = 0, len = _creatorParameters.length; ix < len; ++ix, mask >>= 1) {
                    if ((mask & 1) == 0) {
                        _creatorParameters[ix] = _findMissing(props[ix]);
                    }
                }
            } else {
                final int len = _creatorParameters.length;
                for (int ix = 0; (ix = _paramsSeenBig.nextClearBit(ix)) < len; ++ix) {
                    _creatorParameters[ix] = _findMissing(props[ix]);
                }
            }
        }

        if (_context.isEnabled(DeserializationFeature.FAIL_ON_NULL_CREATOR_PROPERTIES)) {
            for (int ix = 0; ix < props.length; ++ix) {
                if (_creatorParameters[ix] == null) {
                    SettableBeanProperty prop = props[ix];
                    _context.reportInputMismatch(prop,
                            "Null value for creator property '%s' (index %d); `DeserializationFeature.FAIL_ON_NULL_CREATOR_PROPERTIES` enabled",
                            prop.getName(), props[ix].getCreatorIndex());
                }
            }
        }
        return _creatorParameters;
    }

    protected Object _findMissing(SettableBeanProperty prop) throws JsonMappingException
    {
        // First: do we have injectable value?
        Object injectableValueId = prop.getInjectableValueId();
        if (injectableValueId != null) {
            return _context.findInjectableValue(prop.getInjectableValueId(),
                    prop, null);
        }
        // Second: required?
        if (prop.isRequired()) {
            _context.reportInputMismatch(prop, "Missing required creator property '%s' (index %d)",
                    prop.getName(), prop.getCreatorIndex());
        }
        if (_context.isEnabled(DeserializationFeature.FAIL_ON_MISSING_CREATOR_PROPERTIES)) {
            _context.reportInputMismatch(prop,
                    "Missing creator property '%s' (index %d); `DeserializationFeature.FAIL_ON_MISSING_CREATOR_PROPERTIES` enabled",
                    prop.getName(), prop.getCreatorIndex());
        }
        try {
            // Third: NullValueProvider? (22-Sep-2019, [databind#2458])
            // 08-Aug-2021, tatu: consider [databind#3214]; not null but "absent" value...
            Object absentValue = prop.getNullValueProvider().getAbsentValue(_context);
            if (absentValue != null) {
                return absentValue;
            }

            // Fourth: default value
            JsonDeserializer<Object> deser = prop.getValueDeserializer();
            return deser.getAbsentValue(_context);
        } catch (DatabindException e) {
            // [databind#2101]: Include property name, if we have it
            AnnotatedMember member = prop.getMember();
            if (member != null) {
                e.prependPath(member.getDeclaringClass(), prop.getName());
            }
            throw e;
        }
    }

    /*
    /**********************************************************
    /* Other methods
    /**********************************************************
     */

    /**
     * Helper method called to see if given non-creator property is the "id property";
     * and if so, handle appropriately.
     * 
     * @since 2.1
     */
    public boolean readIdProperty(String propName) throws IOException
    {
        if ((_objectIdReader != null) && propName.equals(_objectIdReader.propertyName.getSimpleName())) {
            _idValue = _objectIdReader.readObjectReference(_parser, _context);
            return true;
        }
        return false;
    }

    /**
     * Helper method called to handle Object Id value collected earlier, if any
     */
    public Object handleIdValue(final DeserializationContext ctxt, Object bean) throws IOException
    {
        if (_objectIdReader != null) {
            if (_idValue != null) {
                ReadableObjectId roid = ctxt.findObjectId(_idValue, _objectIdReader.generator, _objectIdReader.resolver);
                roid.bindItem(bean);
                // also: may need to set a property value as well
                SettableBeanProperty idProp = _objectIdReader.idProperty;
                if (idProp != null) {
                    return idProp.setAndReturn(bean, _idValue);
                }
            } else {
                // 07-Jun-2016, tatu: Trying to improve error messaging here...
                ctxt.reportUnresolvedObjectId(_objectIdReader, bean);
            }
        }
        return bean;
    }
    
    protected PropertyValue buffered() { return _buffered; }

    public boolean isComplete() { return _paramsNeeded <= 0; }

    /**
     * Method called to buffer value for given property, as well as check whether
     * we now have values for all (creator) properties that we expect to get values for.
     *
     * @return True if we have received all creator parameters
     * 
     * @since 2.6
     */
    public boolean assignParameter(SettableBeanProperty prop, Object value)
    {
        final int ix = prop.getCreatorIndex();
        _creatorParameters[ix] = value;
        if (_paramsSeenBig == null) {
            int old = _paramsSeen;
            int newValue = (old | (1 << ix));
            if (old != newValue) {
                _paramsSeen = newValue;
                if (--_paramsNeeded <= 0) {
                    // 29-Nov-2016, tatu: But! May still require Object Id value
                    return (_objectIdReader == null) || (_idValue != null);
                }
            }
        } else {
            if (!_paramsSeenBig.get(ix)) {
                _paramsSeenBig.set(ix);
                if (--_paramsNeeded <= 0) {
                    // 29-Nov-2016, tatu: But! May still require Object Id value
                }
            }
        }
        return false;
    }

    public void bufferProperty(SettableBeanProperty prop, Object value) {
        _buffered = new PropertyValue.Regular(_buffered, value, prop);
    }
    
    public void bufferAnyProperty(SettableAnyProperty prop, String propName, Object value) {
        _buffered = new PropertyValue.Any(_buffered, value, prop, propName);
    }

    public void bufferMapProperty(Object key, Object value) {
        _buffered = new PropertyValue.Map(_buffered, value, key);
    }
}

⏎ com/fasterxml/jackson/databind/deser/impl/PropertyValueBuffer.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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