Jackson is "the Java JSON library" or "the best JSON parser for Java". Or simply as "JSON for Java".

Jackson Annotations Source Code files are provided in the source packge (jackson-annotations-2.12.4-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Annotations Source Code below:

⏎ com/fasterxml/jackson/databind/deser/impl/BeanAsArrayDeserializer.java

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

import java.io.IOException;
import java.util.Set;

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.deser.*;
import com.fasterxml.jackson.databind.util.ClassUtil;
import com.fasterxml.jackson.databind.util.NameTransformer;

/**
 * Variant of {@link BeanDeserializer} used for handling deserialization
 * of POJOs when serialized as JSON Arrays, instead of JSON Objects.
 * 
 * @since 2.1
 */
public class BeanAsArrayDeserializer
    extends BeanDeserializerBase
{
    private static final long serialVersionUID = 1L;

    /**
     * Deserializer we delegate operations that we cannot handle.
     */
    protected final BeanDeserializerBase _delegate;

    /**
     * Properties in order expected to be found in JSON array.
     */
    protected final SettableBeanProperty[] _orderedProperties;
    
    /*
    /**********************************************************
    /* Life-cycle, construction, initialization
    /**********************************************************
     */

    /**
     * Main constructor used both for creating new instances (by
     * {@link BeanDeserializer#asArrayDeserializer}) and for
     * creating copies with different delegate.
     */
    public BeanAsArrayDeserializer(BeanDeserializerBase delegate,
            SettableBeanProperty[] ordered)
    {
        super(delegate);
        _delegate = delegate;
        _orderedProperties = ordered;
    }
    
    @Override
    public JsonDeserializer<Object> unwrappingDeserializer(NameTransformer unwrapper)
    {
        /* We can't do much about this; could either replace _delegate
         * with unwrapping instance, or just replace this one. Latter seems
         * more sensible.
         */
        return _delegate.unwrappingDeserializer(unwrapper);
    }

    @Override
    public BeanDeserializerBase withObjectIdReader(ObjectIdReader oir) {
        return new BeanAsArrayDeserializer(_delegate.withObjectIdReader(oir),
                _orderedProperties);
    }

    @Override
    public BeanDeserializerBase withByNameInclusion(Set<String> ignorableProps,
            Set<String> includableProps) {
        return new BeanAsArrayDeserializer(_delegate.withByNameInclusion(ignorableProps, includableProps),
                _orderedProperties);
    }

    @Override
    public BeanDeserializerBase withIgnoreAllUnknown(boolean ignoreUnknown) {
        return new BeanAsArrayDeserializer(_delegate.withIgnoreAllUnknown(ignoreUnknown),
                _orderedProperties);
    }

    @Override
    public BeanDeserializerBase withBeanProperties(BeanPropertyMap props) {
        return new BeanAsArrayDeserializer(_delegate.withBeanProperties(props),
                _orderedProperties);
    }
    
    @Override
    protected BeanDeserializerBase asArrayDeserializer() {
        return this;
    }

    /*
    /**********************************************************
    /* JsonDeserializer implementation
    /**********************************************************
     */
    
    @Override
    public Object deserialize(JsonParser p, DeserializationContext ctxt)
        throws IOException
    {
        // Let's delegate just in case we got a JSON Object (could error out, alternatively?)
        if (!p.isExpectedStartArrayToken()) {
            return _deserializeFromNonArray(p, ctxt);
        }
        if (!_vanillaProcessing) {
            return _deserializeNonVanilla(p, ctxt);
        }
        final Object bean = _valueInstantiator.createUsingDefault(ctxt);
        // [databind#631]: Assign current value, to be accessible by custom serializers
        p.setCurrentValue(bean);

        final SettableBeanProperty[] props = _orderedProperties;
        int i = 0;
        final int propCount = props.length;
        while (true) {
            if (p.nextToken() == JsonToken.END_ARRAY) {
                return bean;
            }
            if (i == propCount) {
                break;
            }
            SettableBeanProperty prop = props[i];
            if (prop != null) { // normal case
                try {
                    prop.deserializeAndSet(p, ctxt, bean);
                } catch (Exception e) {
                    wrapAndThrow(e, bean, prop.getName(), ctxt);
                }
            } else { // just skip?
                p.skipChildren();
            }
            ++i;
        }
        // Ok; extra fields? Let's fail, unless ignoring extra props is fine
        if (!_ignoreAllUnknown && ctxt.isEnabled(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)) {
            ctxt.reportWrongTokenException(this, JsonToken.END_ARRAY,
                    "Unexpected JSON values; expected at most %d properties (in JSON Array)",
                    propCount);
            // never gets here
        }
        // otherwise, skip until end
        do {
            p.skipChildren();
        } while (p.nextToken() != JsonToken.END_ARRAY);
        return bean;
    }

    @Override
    public Object deserialize(JsonParser p, DeserializationContext ctxt, Object bean)
        throws IOException
    {
        // [databind#631]: Assign current value, to be accessible by custom serializers
        p.setCurrentValue(bean);

        if (!p.isExpectedStartArrayToken()) {
            return _deserializeFromNonArray(p, ctxt);
        }
        
        /* No good way to verify that we have an array... although could I guess
         * check via JsonParser. So let's assume everything is working fine, for now.
         */
        if (_injectables != null) {
            injectValues(ctxt, bean);
        }
        final SettableBeanProperty[] props = _orderedProperties;
        int i = 0;
        final int propCount = props.length;
        while (true) {
            if (p.nextToken() == JsonToken.END_ARRAY) {
                return bean;
            }
            if (i == propCount) {
                break;
            }
            SettableBeanProperty prop = props[i];
            if (prop != null) { // normal case
                try {
                    prop.deserializeAndSet(p, ctxt, bean);
                } catch (Exception e) {
                    wrapAndThrow(e, bean, prop.getName(), ctxt);
                }
            } else { // just skip?
                p.skipChildren();
            }
            ++i;
        }
        
        // Ok; extra fields? Let's fail, unless ignoring extra props is fine
        if (!_ignoreAllUnknown && ctxt.isEnabled(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)) {
            ctxt.reportWrongTokenException(this, JsonToken.END_ARRAY,
                    "Unexpected JSON values; expected at most %d properties (in JSON Array)",
                    propCount);
            // never gets here
        }
        // otherwise, skip until end
        do {
            p.skipChildren();
        } while (p.nextToken() != JsonToken.END_ARRAY);
        return bean;
    }

    // needed since 2.1
    @Override
    public Object deserializeFromObject(JsonParser p, DeserializationContext ctxt)
        throws IOException
    {
        return _deserializeFromNonArray(p, ctxt);
    }

    /*
    /**********************************************************
    /* Helper methods, non-standard creation
    /**********************************************************
     */

    /**
     * Alternate deserialization method that has to check many more configuration
     * aspects than the "vanilla" processing.
     */
    protected Object _deserializeNonVanilla(JsonParser p, DeserializationContext ctxt)
        throws IOException
    {
        if (_nonStandardCreation) {
            return deserializeFromObjectUsingNonDefault(p, ctxt);
        }
        final Object bean = _valueInstantiator.createUsingDefault(ctxt);
        // [databind#631]: Assign current value, to be accessible by custom serializers
        p.setCurrentValue(bean);
        if (_injectables != null) {
            injectValues(ctxt, bean);
        }
        Class<?> activeView = _needViewProcesing ? ctxt.getActiveView() : null;
        final SettableBeanProperty[] props = _orderedProperties;
        int i = 0;
        final int propCount = props.length;

        while (true) {
            if (p.nextToken() == JsonToken.END_ARRAY) {
                return bean;
            }
            if (i == propCount) {
                break;
            }
            SettableBeanProperty prop = props[i];
            ++i;
            if (prop != null) { // normal case
                if (activeView == null || prop.visibleInView(activeView)) {
                    try {
                        prop.deserializeAndSet(p, ctxt, bean);
                    } catch (Exception e) {
                        wrapAndThrow(e, bean, prop.getName(), ctxt);
                    }
                    continue;
                }
            }
            // otherwise, skip it (view-filtered, no prop etc)
            p.skipChildren();
        }
        // Ok; extra fields? Let's fail, unless ignoring extra props is fine
        if (!_ignoreAllUnknown) {
            ctxt.reportWrongTokenException(this, JsonToken.END_ARRAY,
                    "Unexpected JSON values; expected at most %d properties (in JSON Array)",
                    propCount);
            // will never reach here as exception has been thrown
        }
        // otherwise, skip until end
        do {
            p.skipChildren();
        } while (p.nextToken() != JsonToken.END_ARRAY);
        return bean;
    }

    /**
     * Method called to deserialize bean using "property-based creator":
     * this means that a non-default constructor or factory method is
     * called, and then possibly other setters. The trick is that
     * values for creator method need to be buffered, first; and 
     * due to non-guaranteed ordering possibly some other properties
     * as well.
     */
    @Override
    protected final Object _deserializeUsingPropertyBased(final JsonParser p, final DeserializationContext ctxt)
        throws IOException
    {
        final PropertyBasedCreator creator = _propertyBasedCreator;
        PropertyValueBuffer buffer = creator.startBuilding(p, ctxt, _objectIdReader);

        final SettableBeanProperty[] props = _orderedProperties;
        final int propCount = props.length;
        int i = 0;
        Object bean = null;
        final Class<?> activeView = _needViewProcesing ? ctxt.getActiveView() : null;

        for (; p.nextToken() != JsonToken.END_ARRAY; ++i) {
            SettableBeanProperty prop = (i < propCount) ? props[i] : null;
            if (prop == null) { // we get null if there are extra elements; maybe otherwise too?
                p.skipChildren();
                continue;
            }
            if ((activeView != null) && !prop.visibleInView(activeView)) {
                p.skipChildren();
                continue;
            }

            // if we have already constructed POJO, things are simple:
            if (bean != null) {
                try {
                    prop.deserializeAndSet(p, ctxt, bean);
                } catch (Exception e) {
                    wrapAndThrow(e, bean, prop.getName(), ctxt);
                }
                continue;
            }
            final String propName = prop.getName();
            // if not yet, maybe we got a creator property?
            final SettableBeanProperty creatorProp = creator.findCreatorProperty(propName);
            // Object Id property?
            if (buffer.readIdProperty(propName) && creatorProp == null) {
                continue;
            }
            if (creatorProp != null) {
                // Last creator property to set?
                if (buffer.assignParameter(creatorProp, creatorProp.deserialize(p, ctxt))) {
                    try {
                        bean = creator.build(ctxt, buffer);
                    } catch (Exception e) {
                        wrapAndThrow(e, _beanType.getRawClass(), propName, ctxt);
                        continue; // never gets here
                    }
                    // [databind#631]: Assign current value, to be accessible by custom serializers
                    p.setCurrentValue(bean);
                    
                    //  polymorphic?
                    if (bean.getClass() != _beanType.getRawClass()) {
                        /* 23-Jul-2012, tatu: Not sure if these could ever be properly
                         *   supported (since ordering of elements may not be guaranteed);
                         *   but make explicitly non-supported for now.
                         */
                        ctxt.reportBadDefinition(_beanType, String.format(
                                "Cannot support implicit polymorphic deserialization for POJOs-as-Arrays style: "
                                +"nominal type %s, actual type %s",
                                ClassUtil.getTypeDescription(_beanType),
                                ClassUtil.getClassDescription(bean)));
                    }
                }
                continue;
            }
            // regular property? needs buffering
            buffer.bufferProperty(prop, prop.deserialize(p, ctxt));
        }

        // In case we didn't quite get all the creator properties, we may have to do this:
        if (bean == null) {
            try {
                bean = creator.build(ctxt, buffer);
            } catch (Exception e) {
                return wrapInstantiationProblem(e, ctxt);
            }
        }
        return bean;
    }

    /*
    /**********************************************************
    /* Helper methods, error reporting
    /**********************************************************
     */

    protected Object _deserializeFromNonArray(JsonParser p, DeserializationContext ctxt)
        throws IOException
    {
        String message = "Cannot deserialize a POJO (of type %s) from non-Array representation (token: %s): "
                +"type/property designed to be serialized as JSON Array";
        return ctxt.handleUnexpectedToken(getValueType(ctxt), p.currentToken(), p,
                message, ClassUtil.getTypeDescription(_beanType), p.currentToken());
        // in future, may allow use of "standard" POJO serialization as well; if so, do:
        //return _delegate.deserialize(p, ctxt);
    }
}

⏎ com/fasterxml/jackson/databind/deser/impl/BeanAsArrayDeserializer.java

 

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