Package com.fasterxml.jackson.databind

Class JsonSerializer<T>

java.lang.Object
com.fasterxml.jackson.databind.JsonSerializer<T>
All Implemented Interfaces:
JsonFormatVisitable
Direct Known Subclasses:
JsonSerializer.None, Jsr310NullKeySerializer, OneBasedMonthSerializer, StdSerializer, TypeWrappedSerializer, ZonedDateTimeKeySerializer
public abstract class JsonSerializer<T> extends Object implements JsonFormatVisitable
Abstract class that defines API used by ObjectMapper (and other chained JsonSerializers too) to serialize Objects of arbitrary types into JSON, using provided JsonGenerator. StdSerializer instead of this class, since it will implement many of optional methods of this class.

NOTE: various serialize methods are never (to be) called with null values -- caller must handle null values, usually by calling SerializerProvider.findNullValueSerializer(com.fasterxml.jackson.databind.BeanProperty) 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.

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 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).

In addition, to support per-property annotations (to configure aspects of serialization on per-property basis), serializers may want to implement ContextualSerializer, which allows specialization of serializers: call to ContextualSerializer.createContextual(com.fasterxml.jackson.databind.SerializerProvider, com.fasterxml.jackson.databind.BeanProperty) is passed information on property, and can create a newly configured serializer for handling that particular property.

If both ResolvableSerializer and ContextualSerializer are implemented, resolution of serializers occurs before contextualization.

  • Constructor Details

    • JsonSerializer

      public JsonSerializer()

  • Method Details

    • unwrappingSerializer

      public JsonSerializer<T> unwrappingSerializer(NameTransformer unwrapper)
      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.

      Default implementation just returns serializer as-is, indicating that no unwrapped variant exists

      Parameters:
      unwrapper - Name transformation to use to convert between names of unwrapper properties

    • replaceDelegatee

      public JsonSerializer<T> replaceDelegatee(JsonSerializer<?> delegatee)
      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 UnsupportedOperationException (if operation does not make sense or is not allowed); or return this serializer as is.
      Since:
      2.1

    • withFilterId

      public JsonSerializer<?> withFilterId(Object filterId)
      Mutant factory method that is called if contextual configuration indicates that a specific filter (as specified by filterId) is to be used for serialization.

      Default implementation simply returns this; sub-classes that do support filtering will need to create and return new instance if filter changes.

      Since:
      2.6

    • withIgnoredProperties

      public JsonSerializer<?> withIgnoredProperties(Set<String> ignoredProperties)
      Mutant factory method called to create a new instance after excluding specified set of properties by name, if there is any.
      Parameters:
      ignoredProperties - Set of property names to ignore for serialization;
      Returns:
      Serializer instance that without specified set of properties to ignore (if any)
      Since:
      2.16

    • serialize

      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.
      Parameters:
      value - Value to serialize; can not be null.
      gen - Generator used to output resulting Json content
      serializers - Provider that can be used to get serializers for serializing Objects value contains, if any.
      Throws:
      IOException

    • serializeWithType

      public void serializeWithType(T value, JsonGenerator gen, SerializerProvider serializers, TypeSerializer typeSer) 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.

      Default implementation will throw UnsupportedOperationException to indicate that proper type handling needs to be implemented.

      For simple datatypes written as a single scalar value (JSON String, Number, Boolean), implementation would look like: 

        // 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);
      and implementations for type serialized as JSON Arrays or Objects would differ slightly, as START-ARRAY/END-ARRAY and START-OBJECT/END-OBJECT pairs need to be properly handled with respect to serializing of contents.
      Parameters:
      value - Value to serialize; can not be null.
      gen - Generator used to output resulting Json content
      serializers - Provider that can be used to get serializers for serializing Objects value contains, if any.
      typeSer - Type serializer to use for including type information
      Throws:
      IOException

    • handledType

      public Class<T> handledType()
      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).

      Default implementation will return null, which essentially means same as returning Object.class would; that is, that nothing is known about handled type.

    • isEmpty

      @Deprecated public boolean isEmpty(T value)
      Deprecated.
      Since 2.5 Use isEmpty(SerializerProvider, Object) instead; will be removed from 3.0
      Method called to check whether given serializable value is considered "empty" value (for purposes of suppressing serialization of empty values).

      Default implementation will consider only null values to be empty.

    • isEmpty

      public boolean isEmpty(SerializerProvider provider, T value)
      Method called to check whether given serializable value is considered "empty" value (for purposes of suppressing serialization of empty values).

      Default implementation will consider only null values to be empty.

      NOTE: replaces isEmpty(Object), which was deprecated in 2.5

      Since:
      2.5

    • usesObjectId

      public boolean usesObjectId()
      Method that can be called to see whether this serializer instance will use Object Id to handle cyclic references.

    • isUnwrappingSerializer

      public boolean isUnwrappingSerializer()
      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.

    • getDelegatee

      public JsonSerializer<?> getDelegatee()
      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.
      Returns:
      Serializer this serializer delegates calls to, if null; null otherwise.
      Since:
      2.1

    • properties

      public Iterator<PropertyWriter> properties()
      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 BeanPropertyWriter. Of standard Jackson serializers, only BeanSerializer exposes properties.
      Since:
      2.6

    • acceptJsonFormatVisitor

      public void acceptJsonFormatVisitor(JsonFormatVisitorWrapper visitor, JavaType type) throws JsonMappingException
      Default implementation simply calls JsonFormatVisitorWrapper.expectAnyFormat(JavaType).
      Specified by:
      acceptJsonFormatVisitor in interface JsonFormatVisitable
      Parameters:
      type - Type of element (entity like property) being visited
      Throws:
      JsonMappingException
      Since:
      2.1