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/ser/DefaultSerializerProvider.java

package com.fasterxml.jackson.databind.ser;

import java.io.IOException;
import java.util.*;
import java.util.concurrent.atomic.AtomicReference;

import com.fasterxml.jackson.annotation.ObjectIdGenerator;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.cfg.HandlerInstantiator;
import com.fasterxml.jackson.databind.introspect.Annotated;
import com.fasterxml.jackson.databind.introspect.BeanPropertyDefinition;
import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatVisitorWrapper;
import com.fasterxml.jackson.databind.jsonschema.SchemaAware;
import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
import com.fasterxml.jackson.databind.node.ObjectNode;
import com.fasterxml.jackson.databind.ser.impl.WritableObjectId;
import com.fasterxml.jackson.databind.util.ClassUtil;

/**
 * Standard implementation used by {@link ObjectMapper}:
 * adds methods only exposed to {@link ObjectMapper},
 * as well as constructors.
 *<p>
 * Note that class is abstract just because it does not
 * define {@link #createInstance} method.
 *<p>
 * Also note that all custom {@link SerializerProvider}
 * implementations must sub-class this class: {@link ObjectMapper}
 * requires this type, not basic provider type.
 */
public abstract class DefaultSerializerProvider
    extends SerializerProvider
    implements java.io.Serializable // since 2.1; only because ObjectWriter needs it
{
    private static final long serialVersionUID = 1L;

    /*
    /**********************************************************
    /* State, for non-blueprint instances
    /**********************************************************
     */

    /**
     * Per-serialization map Object Ids that have seen so far, iff
     * Object Id handling is enabled.
     */
    protected transient Map<Object, WritableObjectId> _seenObjectIds;
    
    protected transient ArrayList<ObjectIdGenerator<?>> _objectIdGenerators;

    /**
     * Generator used for serialization. Needed mostly for error reporting
     * purposes.
     *
     * @since 2.8
     */
    protected transient JsonGenerator _generator;

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

    protected DefaultSerializerProvider() { super(); }

    protected DefaultSerializerProvider(SerializerProvider src,
            SerializationConfig config,SerializerFactory f) {
        super(src, config, f);
    }

    protected DefaultSerializerProvider(DefaultSerializerProvider src) {
        super(src);
    }

    /**
     * Method that sub-classes need to implement: used to create a non-blueprint instances
     * from the blueprint.
     * This is needed to retain state during serialization.
     */
    public abstract DefaultSerializerProvider createInstance(SerializationConfig config,
            SerializerFactory jsf);

    /**
     * Method needed to ensure that {@link ObjectMapper#copy} will work
     * properly; specifically, that caches are cleared, but settings
     * will otherwise remain identical; and that no sharing of state
     * occurs.
     *
     * @since 2.5
     */
    public DefaultSerializerProvider copy() {
        throw new IllegalStateException("DefaultSerializerProvider sub-class not overriding copy()");
    }

    /*
    /**********************************************************
    /* Abstract method impls, factory methods
    /**********************************************************
     */
    
    @Override
    public JsonSerializer<Object> serializerInstance(Annotated annotated, Object serDef)
            throws JsonMappingException
    {
        if (serDef == null) {
            return null;
        }
        JsonSerializer<?> ser;
        
        if (serDef instanceof JsonSerializer) {
            ser = (JsonSerializer<?>) serDef;
        } else {
            // Alas, there's no way to force return type of "either class
            // X or Y" -- need to throw an exception after the fact
            if (!(serDef instanceof Class)) {
                reportBadDefinition(annotated.getType(),
                        "AnnotationIntrospector returned serializer definition of type "
                        +serDef.getClass().getName()+"; expected type JsonSerializer or Class<JsonSerializer> instead");
            }
            Class<?> serClass = (Class<?>)serDef;
            // there are some known "no class" markers to consider too:
            if (serClass == JsonSerializer.None.class || ClassUtil.isBogusClass(serClass)) {
                return null;
            }
            if (!JsonSerializer.class.isAssignableFrom(serClass)) {
                reportBadDefinition(annotated.getType(),
                        "AnnotationIntrospector returned Class "
                        +serClass.getName()+"; expected Class<JsonSerializer>");
            }
            HandlerInstantiator hi = _config.getHandlerInstantiator();
            ser = (hi == null) ? null : hi.serializerInstance(_config, annotated, serClass);
            if (ser == null) {
                ser = (JsonSerializer<?>) ClassUtil.createInstance(serClass,
                        _config.canOverrideAccessModifiers());
            }
        }
        return (JsonSerializer<Object>) _handleResolvable(ser);
    }

    @Override
    public Object includeFilterInstance(BeanPropertyDefinition forProperty,
            Class<?> filterClass)
    {
        if (filterClass == null) {
            return null;
        }
        HandlerInstantiator hi = _config.getHandlerInstantiator();
        Object filter = (hi == null) ? null : hi.includeFilterInstance(_config, forProperty, filterClass);
        if (filter == null) {
            filter = ClassUtil.createInstance(filterClass,
                    _config.canOverrideAccessModifiers());
        }
        return filter;
    }

    @Override
    public boolean includeFilterSuppressNulls(Object filter) throws JsonMappingException
    {
        if (filter == null) {
            return true;
        }
        // should let filter decide what to do with nulls:
        // But just in case, let's handle unexpected (from our perspective) problems explicitly
        try {
            return filter.equals(null);
        } catch (Exception e) {
            String msg = String.format(
"Problem determining whether filter of type '%s' should filter out `null` values: (%s) %s",
filter.getClass().getName(), e.getClass().getName(), ClassUtil.exceptionMessage(e));
            reportBadDefinition(filter.getClass(), msg, e);
            return false; // never gets here
        }
    }

    /*
    /**********************************************************
    /* Object Id handling
    /**********************************************************
     */
    
    @Override
    public WritableObjectId findObjectId(Object forPojo, ObjectIdGenerator<?> generatorType)
    {
        if (_seenObjectIds == null) {
            _seenObjectIds = _createObjectIdMap();
        } else {
            WritableObjectId oid = _seenObjectIds.get(forPojo);
            if (oid != null) {
                return oid;
            }
        }
        // Not seen yet; must add an entry, return it. For that, we need generator
        ObjectIdGenerator<?> generator = null;
        
        if (_objectIdGenerators == null) {
            _objectIdGenerators = new ArrayList<ObjectIdGenerator<?>>(8);
        } else {
            for (int i = 0, len = _objectIdGenerators.size(); i < len; ++i) {
                ObjectIdGenerator<?> gen = _objectIdGenerators.get(i);
                if (gen.canUseFor(generatorType)) {
                    generator = gen;
                    break;
                }
            }
        }
        if (generator == null) {
            generator = generatorType.newForSerialization(this);
            _objectIdGenerators.add(generator);
        }
        WritableObjectId oid = new WritableObjectId(generator);
        _seenObjectIds.put(forPojo, oid);
        return oid;
    }

    /**
     * Overridable helper method used for creating {@link java.util.Map}
     * used for storing mappings from serializable objects to their
     * Object Ids.
     * 
     * @since 2.3
     */
    protected Map<Object,WritableObjectId> _createObjectIdMap()
    {
        /* 06-Aug-2013, tatu: We may actually want to use equality,
         *   instead of identity... so:
         */
        if (isEnabled(SerializationFeature.USE_EQUALITY_FOR_OBJECT_ID)) {
            return new HashMap<Object,WritableObjectId>();
        }
        return new IdentityHashMap<Object,WritableObjectId>();
    }

    /*
    /**********************************************************
    /* Extended API: simple accesors
    /**********************************************************
     */

    /**
     * Method that can be called to see if this serializer provider
     * can find a serializer for an instance of given class.
     *<p>
     * Note that no Exceptions are thrown, including unchecked ones:
     * implementations are to swallow exceptions if necessary.
     */
    public boolean hasSerializerFor(Class<?> cls, AtomicReference<Throwable> cause)
    {
        // 07-Nov-2015, tatu: One special case, Object.class; will work only if
        //   empty beans are allowed or custom serializer registered. Easiest to
        //   check here.
        if (cls == Object.class) {
            if (!_config.isEnabled(SerializationFeature.FAIL_ON_EMPTY_BEANS)) {
                return true;
            }
        }
        
        try {
            JsonSerializer<?> ser = _findExplicitUntypedSerializer(cls);
            return (ser != null);
        } catch (JsonMappingException e) {
            if (cause != null) {
                cause.set(e);
            }
        } catch (RuntimeException e) {
            if (cause == null) { // earlier behavior
                throw e;
            }
            cause.set(e);
        }
        return false;
    }

    /**
     * Accessor for the {@link JsonGenerator} currently in use for serializing
     * content. Null for blueprint instances; non-null for actual active
     * provider instances.
     *
     * @since 2.8
     */
    @Override
    public JsonGenerator getGenerator() {
        return _generator;
    }

    /*
    /**********************************************************
    /* Extended API called by ObjectMapper: value serialization
    /**********************************************************
     */
    
    /**
     * The method to be called by {@link ObjectMapper} and {@link ObjectWriter}
     * for serializing given value, using serializers that
     * this provider has access to (via caching and/or creating new serializers
     * as need be).
     */
    public void serializeValue(JsonGenerator gen, Object value) throws IOException
    {
        _generator = gen;
        if (value == null) {
            _serializeNull(gen);
            return;
        }
        final Class<?> cls = value.getClass();
        // true, since we do want to cache root-level typed serializers (ditto for null property)
        final JsonSerializer<Object> ser = findTypedValueSerializer(cls, true, null);
        PropertyName rootName = _config.getFullRootName();
        if (rootName == null) { // not explicitly specified
            if (_config.isEnabled(SerializationFeature.WRAP_ROOT_VALUE)) {
                _serialize(gen, value, ser, _config.findRootName(cls));
                return;
            }
        } else if (!rootName.isEmpty()) {
            _serialize(gen, value, ser, rootName);
            return;
        }
        _serialize(gen, value, ser);
    }

    /**
     * The method to be called by {@link ObjectMapper} and {@link ObjectWriter}
     * for serializing given value (assumed to be of specified root type,
     * instead of runtime type of value),
     * using serializers that
     * this provider has access to (via caching and/or creating new serializers
     * as need be),
     * 
     * @param rootType Type to use for locating serializer to use, instead of actual
     *    runtime type. Must be actual type, or one of its super types
     */
    public void serializeValue(JsonGenerator gen, Object value, JavaType rootType) throws IOException
    {
        _generator = gen;
        if (value == null) {
            _serializeNull(gen);
            return;
        }
        // Let's ensure types are compatible at this point
        if (!rootType.getRawClass().isAssignableFrom(value.getClass())) {
            _reportIncompatibleRootType(value, rootType);
        }
        // root value, not reached via property:
        JsonSerializer<Object> ser = findTypedValueSerializer(rootType, true, null);
        PropertyName rootName = _config.getFullRootName();
        if (rootName == null) { // not explicitly specified
            if (_config.isEnabled(SerializationFeature.WRAP_ROOT_VALUE)) {
                _serialize(gen, value, ser, _config.findRootName(rootType));
                return;
            }
        } else if (!rootName.isEmpty()) {
            _serialize(gen, value, ser, rootName);
            return;
        }
        _serialize(gen, value, ser);
    }

    /**
     * The method to be called by {@link ObjectWriter}
     * for serializing given value (assumed to be of specified root type,
     * instead of runtime type of value), when it may know specific
     * {@link JsonSerializer} to use.
     * 
     * @param rootType Type to use for locating serializer to use, instead of actual
     *    runtime type, if no serializer is passed
     * @param ser Root Serializer to use, if not null
     * 
     * @since 2.1
     */
    public void serializeValue(JsonGenerator gen, Object value, JavaType rootType,
            JsonSerializer<Object> ser) throws IOException
    {
        _generator = gen;
        if (value == null) {
            _serializeNull(gen);
            return;
        }
        // Let's ensure types are compatible at this point
        if ((rootType != null) && !rootType.getRawClass().isAssignableFrom(value.getClass())) {
            _reportIncompatibleRootType(value, rootType);
        }
        // root value, not reached via property:
        if (ser == null) {
            ser = findTypedValueSerializer(rootType, true, null);
        }
        PropertyName rootName = _config.getFullRootName();
        if (rootName == null) { // not explicitly specified
            if (_config.isEnabled(SerializationFeature.WRAP_ROOT_VALUE)) {
                rootName = (rootType == null)
                        ? _config.findRootName(value.getClass())
                        : _config.findRootName(rootType);
                _serialize(gen, value, ser, rootName);
                return;
            }
        } else if (!rootName.isEmpty()) {
            _serialize(gen, value, ser, rootName);
            return;
        }
        _serialize(gen, value, ser);
    }

    /**
     * Alternate serialization call used for polymorphic types, when {@link TypeSerializer}
     * is already known, but the actual serializer may or may not be.
     *
     * @since 2.6
     */
    public void serializePolymorphic(JsonGenerator gen, Object value, JavaType rootType,
            JsonSerializer<Object> valueSer, TypeSerializer typeSer)
        throws IOException
    {
        _generator = gen;
        if (value == null) {
            _serializeNull(gen);
            return;
        }
        // Let's ensure types are compatible at this point
        if ((rootType != null) && !rootType.getRawClass().isAssignableFrom(value.getClass())) {
            _reportIncompatibleRootType(value, rootType);
        }
        /* 12-Jun-2015, tatu: nominal root type is necessary for Maps at least;
         *   possibly collections, but can cause problems for other polymorphic
         *   types. We really need to distinguish between serialization type,
         *   base type; but right we don't. Hence this check
         */
        if (valueSer == null) {
            if ((rootType != null) && rootType.isContainerType()) {
                valueSer = findValueSerializer(rootType, null);
            } else {
                valueSer = findValueSerializer(value.getClass(), null);
            }
        }

        final boolean wrap;
        PropertyName rootName = _config.getFullRootName();
        if (rootName == null) {
            wrap = _config.isEnabled(SerializationFeature.WRAP_ROOT_VALUE);
            if (wrap) {
                gen.writeStartObject();
                PropertyName pname = _config.findRootName(value.getClass());
                gen.writeFieldName(pname.simpleAsEncoded(_config));
            }
        } else if (rootName.isEmpty()) {
            wrap = false;
        } else {
            wrap = true;
            gen.writeStartObject();
            gen.writeFieldName(rootName.getSimpleName());
        }
        try {
            valueSer.serializeWithType(value, gen, this, typeSer);
            if (wrap) {
                gen.writeEndObject();
            }
        } catch (Exception e) {
            throw _wrapAsIOE(gen, e);
        }
    }

    private final void _serialize(JsonGenerator gen, Object value,
            JsonSerializer<Object> ser, PropertyName rootName)
        throws IOException
    {
        try {
            gen.writeStartObject();
            gen.writeFieldName(rootName.simpleAsEncoded(_config));
            ser.serialize(value, gen, this);
            gen.writeEndObject();
        } catch (Exception e) {
            throw _wrapAsIOE(gen, e);
        }
    }

    private final void _serialize(JsonGenerator gen, Object value,
            JsonSerializer<Object> ser)
        throws IOException
    {
        try {
            ser.serialize(value, gen, this);
        } catch (Exception e) {
            throw _wrapAsIOE(gen, e);
        }
    }

    /**
     * Helper method called when root value to serialize is null
     * 
     * @since 2.3
     */
    protected void _serializeNull(JsonGenerator gen) throws IOException
    {
        JsonSerializer<Object> ser = getDefaultNullValueSerializer();
        try {
            ser.serialize(null, gen, this);
        } catch (Exception e) {
            throw _wrapAsIOE(gen, e);
        }
    }

    private IOException _wrapAsIOE(JsonGenerator g, Exception e) {
        if (e instanceof IOException) {
            return (IOException) e;
        }
        String msg = ClassUtil.exceptionMessage(e);
        if (msg == null) {
            msg = "[no message for "+e.getClass().getName()+"]";
        }
        return new JsonMappingException(g, msg, e);
    }

    /*
    /********************************************************
    /* Access to caching details
    /********************************************************
     */

    /**
     * Method that can be used to determine how many serializers this
     * provider is caching currently
     * (if it does caching: default implementation does)
     * Exact count depends on what kind of serializers get cached;
     * default implementation caches all serializers, including ones that
     * are eagerly constructed (for optimal access speed)
     *<p> 
     * The main use case for this method is to allow conditional flushing of
     * serializer cache, if certain number of entries is reached.
     */
    public int cachedSerializersCount() {
        return _serializerCache.size();
    }

    /**
     * Method that will drop all serializers currently cached by this provider.
     * This can be used to remove memory usage (in case some serializers are
     * only used once or so), or to force re-construction of serializers after
     * configuration changes for mapper than owns the provider.
     */
    public void flushCachedSerializers() {
        _serializerCache.flush();
    }

    /*
    /**********************************************************
    /* Extended API called by ObjectMapper: other
    /**********************************************************
     */

    /**
     * The method to be called by {@link ObjectMapper} and {@link ObjectWriter}
     * to to expose the format of the given to to the given visitor
     *
     * @param javaType The type for which to generate format
     * @param visitor the visitor to accept the format
     */
    public void acceptJsonFormatVisitor(JavaType javaType, JsonFormatVisitorWrapper visitor)
        throws JsonMappingException
    {
        if (javaType == null) {
            throw new IllegalArgumentException("A class must be provided");
        }
        /* no need for embedded type information for JSON schema generation (all
         * type information it needs is accessible via "untyped" serializer)
         */
        visitor.setProvider(this);
        findValueSerializer(javaType, null).acceptJsonFormatVisitor(visitor, javaType);
    }

    /**
     * The method to be called by {@link ObjectMapper}
     * to generate <a href="http://json-schema.org/">JSON schema</a> for
     * given type.
     *
     * @param type The type for which to generate schema
     * 
     * @deprecated Should not be used any more
     */
    @Deprecated // since 2.6
    public com.fasterxml.jackson.databind.jsonschema.JsonSchema generateJsonSchema(Class<?> type)
        throws JsonMappingException
    {
        /* no need for embedded type information for JSON schema generation (all
         * type information it needs is accessible via "untyped" serializer)
         */
        JsonSerializer<Object> ser = findValueSerializer(type, null);
        JsonNode schemaNode = (ser instanceof SchemaAware) ?
                ((SchemaAware) ser).getSchema(this, null) : com.fasterxml.jackson.databind.jsonschema.JsonSchema.getDefaultSchemaNode();
        if (!(schemaNode instanceof ObjectNode)) {
            throw new IllegalArgumentException("Class " + type.getName()
                    +" would not be serialized as a JSON object and therefore has no schema");
        }
        return new com.fasterxml.jackson.databind.jsonschema.JsonSchema((ObjectNode) schemaNode);
    }
    
    
    /*
    /**********************************************************
    /* Helper classes
    /**********************************************************
     */

    /**
     * Concrete implementation that defines factory method(s),
     * defined as final.
     */
    public final static class Impl extends DefaultSerializerProvider {
        private static final long serialVersionUID = 1L;

        public Impl() { super(); }
        public Impl(Impl src) { super(src); }

        protected Impl(SerializerProvider src, SerializationConfig config,
                SerializerFactory f) {
            super(src, config, f);
        }

        @Override
        public DefaultSerializerProvider copy()
        {
            if (getClass() != Impl.class) {
                return super.copy();
            }
            return new Impl(this);
        }
        
        @Override
        public Impl createInstance(SerializationConfig config, SerializerFactory jsf) {
            return new Impl(this, config, jsf);
        }
    }
}

⏎ com/fasterxml/jackson/databind/ser/DefaultSerializerProvider.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
Download 

⇒ Jackson Annotations Source Code

⇐ Download and Install Jackson Binary Package

⇑ Downloading and Reviewing jackson-*.jar

⇑⇑ Jackson - Java JSON library