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/JsonSerializer.java

package com.fasterxml.jackson.databind;

import java.io.IOException;
import java.util.Iterator;

import com.fasterxml.jackson.core.*;

import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatVisitable;
import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatVisitorWrapper;
import com.fasterxml.jackson.databind.jsontype.TypeSerializer;
import com.fasterxml.jackson.databind.ser.PropertyWriter;
import com.fasterxml.jackson.databind.util.ClassUtil;
import com.fasterxml.jackson.databind.util.NameTransformer;

/**
 * Abstract class that defines API used by {@link ObjectMapper} (and
 * other chained {@link JsonSerializer}s too) to serialize Objects of
 * arbitrary types into JSON, using provided {@link JsonGenerator}.
 * {@link com.fasterxml.jackson.databind.ser.std.StdSerializer} instead
 * of this class, since it will implement many of optional
 * methods of this class.
 *<p>
 * NOTE: various <code>serialize</code> methods are never (to be) called
 * with null values -- caller <b>must</b> handle null values, usually
 * by calling {@link SerializerProvider#findNullValueSerializer} to obtain
 * serializer to use.
 * This also means that custom serializers cannot be directly used to change
 * the output to produce when serializing null values.
 *<p>
 * If serializer is an aggregate one -- meaning it delegates handling of some
 * of its contents by using other serializer(s) -- it typically also needs
 * to implement {@link com.fasterxml.jackson.databind.ser.ResolvableSerializer},
 * which can locate secondary serializers needed. This is important to allow dynamic
 * overrides of serializers; separate call interface is needed to separate
 * resolution of secondary serializers (which may have cyclic link back
 * to serializer itself, directly or indirectly).
 *<p>
 * In addition, to support per-property annotations (to configure aspects
 * of serialization on per-property basis), serializers may want
 * to implement 
 * {@link com.fasterxml.jackson.databind.ser.ContextualSerializer},
 * which allows specialization of serializers: call to
 * {@link com.fasterxml.jackson.databind.ser.ContextualSerializer#createContextual}
 * is passed information on property, and can create a newly configured
 * serializer for handling that particular property.
 *<p>
 * If both
 * {@link com.fasterxml.jackson.databind.ser.ResolvableSerializer} and
 * {@link com.fasterxml.jackson.databind.ser.ContextualSerializer}
 * are implemented, resolution of serializers occurs before
 * contextualization.
 */
public abstract class JsonSerializer<T>
    implements JsonFormatVisitable // since 2.1
{
    /*
    /**********************************************************
    /* Fluent factory methods for constructing decorated versions
    /**********************************************************
     */

    /**
     * Method that will return serializer instance that produces
     * "unwrapped" serialization, if applicable for type being
     * serialized (which is the case for some serializers
     * that produce JSON Objects as output).
     * If no unwrapped serializer can be constructed, will simply
     * return serializer as-is.
     *<p>
     * Default implementation just returns serializer as-is,
     * indicating that no unwrapped variant exists
     * 
     * @param unwrapper Name transformation to use to convert between names
     *   of unwrapper properties
     */
    public JsonSerializer<T> unwrappingSerializer(NameTransformer unwrapper) {
        return this;
    }

    /**
     * Method that can be called to try to replace serializer this serializer
     * delegates calls to. If not supported (either this serializer does not
     * delegate anything; or it does not want any changes), should either
     * throw {@link UnsupportedOperationException} (if operation does not
     * make sense or is not allowed); or return this serializer as is.
     * 
     * @since 2.1
     */
    public JsonSerializer<T> replaceDelegatee(JsonSerializer<?> delegatee) {
        throw new UnsupportedOperationException();
    }

    /**
     * Mutant factory method that is called if contextual configuration indicates that
     * a specific filter (as specified by <code>filterId</code>) is to be used for
     * serialization.
     *<p>
     * Default implementation simply returns <code>this</code>; sub-classes that do support
     * filtering will need to create and return new instance if filter changes.
     *
     * @since 2.6
     */
    public JsonSerializer<?> withFilterId(Object filterId) {
        return this;
    }

    /*
    /**********************************************************
    /* Serialization methods
    /**********************************************************
     */

    /**
     * Method that can be called to ask implementation to serialize
     * values of type this serializer handles.
     *
     * @param value Value to serialize; can <b>not</b> be null.
     * @param gen Generator used to output resulting Json content
     * @param serializers Provider that can be used to get serializers for
     *   serializing Objects value contains, if any.
     */
    public abstract void serialize(T value, JsonGenerator gen, SerializerProvider serializers)
        throws IOException;

    /**
     * Method that can be called to ask implementation to serialize
     * values of type this serializer handles, using specified type serializer
     * for embedding necessary type information.
     *<p>
     * Default implementation will throw {@link UnsupportedOperationException}
     * to indicate that proper type handling needs to be implemented.
     *<p>
     * For simple datatypes written as a single scalar value (JSON String, Number, Boolean),
     * implementation would look like:
     *<pre>
     *  // note: method to call depends on whether this type is serialized as JSON scalar, object or Array!
     *  typeSer.writeTypePrefixForScalar(value, gen);
     *  serialize(value, gen, provider);
     *  typeSer.writeTypeSuffixForScalar(value, gen);
     *</pre>
     * and implementations for type serialized as JSON Arrays or Objects would differ slightly,
     * as <code>START-ARRAY</code>/<code>END-ARRAY</code> and
     * <code>START-OBJECT</code>/<code>END-OBJECT</code> pairs
     * need to be properly handled with respect to serializing of contents.
     *
     * @param value Value to serialize; can <b>not</b> be null.
     * @param gen Generator used to output resulting Json content
     * @param serializers Provider that can be used to get serializers for
     *   serializing Objects value contains, if any.
     * @param typeSer Type serializer to use for including type information
     */
    public void serializeWithType(T value, JsonGenerator gen, SerializerProvider serializers,
            TypeSerializer typeSer)
        throws IOException
    {
        Class<?> clz = handledType();
        if (clz == null) {
            clz = value.getClass();
        }
        serializers.reportBadDefinition(clz, String.format(
                "Type id handling not implemented for type %s (by serializer of type %s)",
                clz.getName(), getClass().getName()));
    }

    /*
    /**********************************************************
    /* Other accessors
    /**********************************************************
     */

    /**
     * Method for accessing type of Objects this serializer can handle.
     * Note that this information is not guaranteed to be exact -- it
     * may be a more generic (super-type) -- but it should not be
     * incorrect (return a non-related type).
     *<p>
     * Default implementation will return null, which essentially means
     * same as returning <code>Object.class</code> would; that is, that
     * nothing is known about handled type.
     *<p>
     */
    public Class<T> handledType() { return null; }

    /**
     * Method called to check whether given serializable value is
     * considered "empty" value (for purposes of suppressing serialization
     * of empty values).
     *<p>
     * Default implementation will consider only null values to be empty.
     * 
     * @deprecated Since 2.5 Use {@link #isEmpty(SerializerProvider, Object)} instead;
     *   will be removed from 3.0
     */
    @Deprecated
    public boolean isEmpty(T value) {
        return isEmpty(null, value);
    }

    /**
     * Method called to check whether given serializable value is
     * considered "empty" value (for purposes of suppressing serialization
     * of empty values).
     *<p>
     * Default implementation will consider only null values to be empty.
     *<p>
     * NOTE: replaces {@link #isEmpty(Object)}, which was deprecated in 2.5
     * 
     * @since 2.5
     */
    public boolean isEmpty(SerializerProvider provider, T value) {
        return (value == null);
    }
    
    /**
     * Method that can be called to see whether this serializer instance
     * will use Object Id to handle cyclic references.
     */
    public boolean usesObjectId() {
        return false;
    }

    /**
     * Accessor for checking whether this serializer is an
     * "unwrapping" serializer; this is necessary to know since
     * it may also require caller to suppress writing of the
     * leading property name.
     */
    public boolean isUnwrappingSerializer() {
        return false;
    }
    
    /**
     * Accessor that can be used to determine if this serializer uses
     * another serializer for actual serialization, by delegating
     * calls. If so, will return immediate delegate (which itself may
     * delegate to further serializers); otherwise will return null.
     * 
     * @return Serializer this serializer delegates calls to, if null;
     *   null otherwise.
     * 
     * @since 2.1
     */
    public JsonSerializer<?> getDelegatee() {
        return null;
    }

    /**
     * Accessor for iterating over logical properties that the type
     * handled by this serializer has, from serialization perspective.
     * Actual type of properties, if any, will be
     * {@link com.fasterxml.jackson.databind.ser.BeanPropertyWriter}.
     * Of standard Jackson serializers, only {@link com.fasterxml.jackson.databind.ser.BeanSerializer}
     * exposes properties.
     *
     * @since 2.6
     */
    public Iterator<PropertyWriter> properties() {
        return ClassUtil.emptyIterator();
    }

    /*
    /**********************************************************
    /* Default JsonFormatVisitable implementation
    /**********************************************************
     */

    /**
     * Default implementation simply calls {@link JsonFormatVisitorWrapper#expectAnyFormat(JavaType)}.
     * 
     * @since 2.1
     */
    @Override
    public void acceptJsonFormatVisitor(JsonFormatVisitorWrapper visitor, JavaType type)
        throws JsonMappingException
    {
        visitor.expectAnyFormat(type);
    }

    /*
    /**********************************************************
    /* Helper class(es)
    /**********************************************************
     */

    /**
     * This marker class is only to be used with annotations, to
     * indicate that <b>no serializer is configured</b>.
     *<p>
     * Specifically, this class is to be used as the marker for
     * annotation {@link com.fasterxml.jackson.databind.annotation.JsonSerialize}.
     */
    public abstract static class None
        extends JsonSerializer<Object> { }
}

⏎ com/fasterxml/jackson/databind/JsonSerializer.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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