Package org.apache.flink.api.java.typeutils.runtime

Class NullableSerializer<T>

  • Type Parameters:
    T - type to serialize
    All Implemented Interfaces:
    Serializable
    public class NullableSerializer<T>
extends TypeSerializer<T>
    Serializer wrapper to add support of null value serialization.

    If the target serializer does not support null values of its type, you can use this class to wrap this serializer. This is a generic treatment of null value serialization which comes with the cost of additional byte in the final serialized value. The NullableSerializer will intercept null value serialization case and prepend the target serialized value with a boolean flag marking whether it is null or not. 

    
 TypeSerializer<T> originalSerializer = ...;
 TypeSerializer<T> serializerWithNullValueSupport = NullableSerializer.wrap(originalSerializer);
 // or
 TypeSerializer<T> serializerWithNullValueSupport = NullableSerializer.wrapIfNullIsNotSupported(originalSerializer);
 
 }
    See Also:
    Serialized Form

    • Method Detail

      • wrapIfNullIsNotSupported

        public static <T> TypeSerializer<T> wrapIfNullIsNotSupported​(@Nonnull
                                                             TypeSerializer<T> originalSerializer,
                                                             boolean padNullValueIfFixedLen)
        This method tries to serialize null value with the originalSerializer and wraps it in case of NullPointerException, otherwise it returns the originalSerializer.
        Parameters:
        originalSerializer - serializer to wrap and add null support
        padNullValueIfFixedLen - pad null value to preserve the fixed length of original serializer
        Returns:
        serializer which supports null values

      • checkIfNullSupported

        public static <T> boolean checkIfNullSupported​(@Nonnull
                                               TypeSerializer<T> serializer)
        This method checks if serializer supports null value.
        Parameters:
        serializer - serializer to check

      • wrap

        public static <T> TypeSerializer<T> wrap​(@Nonnull
                                         TypeSerializer<T> originalSerializer,
                                         boolean padNullValueIfFixedLen)
        This method wraps the originalSerializer with the NullableSerializer if not already wrapped.
        Parameters:
        originalSerializer - serializer to wrap and add null support
        padNullValueIfFixedLen - pad null value to preserve the fixed length of original serializer
        Returns:
        wrapped serializer which supports null values

      • isImmutableType

        public boolean isImmutableType()
        Description copied from class: TypeSerializer
        Gets whether the type is an immutable type.
        Specified by:
        isImmutableType in class TypeSerializer<T>
        Returns:
        True, if the type is immutable.

      • duplicate

        public TypeSerializer<T> duplicate()
        Description copied from class: TypeSerializer
        Creates a deep copy of this serializer if it is necessary, i.e. if it is stateful. This can return itself if the serializer is not stateful.

        We need this because Serializers might be used in several threads. Stateless serializers are inherently thread-safe while stateful serializers might not be thread-safe.

        Specified by:
        duplicate in class TypeSerializer<T>

      • createInstance

        public T createInstance()
        Description copied from class: TypeSerializer
        Creates a new instance of the data type.
        Specified by:
        createInstance in class TypeSerializer<T>
        Returns:
        A new instance of the data type.

      • copy

        public T copy​(T from)
        Description copied from class: TypeSerializer
        Creates a deep copy of the given element in a new element.
        Specified by:
        copy in class TypeSerializer<T>
        Parameters:
        from - The element reuse be copied.
        Returns:
        A deep copy of the element.

      • copy

        public T copy​(T from,
              T reuse)
        Description copied from class: TypeSerializer
        Creates a copy from the given element. The method makes an attempt to store the copy in the given reuse element, if the type is mutable. This is, however, not guaranteed.
        Specified by:
        copy in class TypeSerializer<T>
        Parameters:
        from - The element to be copied.
        reuse - The element to be reused. May or may not be used.
        Returns:
        A deep copy of the element.

      • getLength

        public int getLength()
        Description copied from class: TypeSerializer
        Gets the length of the data type, if it is a fix length data type.
        Specified by:
        getLength in class TypeSerializer<T>
        Returns:
        The length of the data type, or -1 for variable length data types.

      • serialize

        public void serialize​(T record,
                      DataOutputView target)
               throws IOException
        Description copied from class: TypeSerializer
        Serializes the given record to the given target output view.
        Specified by:
        serialize in class TypeSerializer<T>
        Parameters:
        record - The record to serialize.
        target - The output view to write the serialized data to.
        Throws:
        IOException - Thrown, if the serialization encountered an I/O related error. Typically raised by the output view, which may have an underlying I/O channel to which it delegates.

      • deserialize

        public T deserialize​(DataInputView source)
              throws IOException
        Description copied from class: TypeSerializer
        De-serializes a record from the given source input view.
        Specified by:
        deserialize in class TypeSerializer<T>
        Parameters:
        source - The input view from which to read the data.
        Returns:
        The deserialized element.
        Throws:
        IOException - Thrown, if the de-serialization encountered an I/O related error. Typically raised by the input view, which may have an underlying I/O channel from which it reads.

      • deserialize

        public T deserialize​(T reuse,
                     DataInputView source)
              throws IOException
        Description copied from class: TypeSerializer
        De-serializes a record from the given source input view into the given reuse record instance if mutable.
        Specified by:
        deserialize in class TypeSerializer<T>
        Parameters:
        reuse - The record instance into which to de-serialize the data.
        source - The input view from which to read the data.
        Returns:
        The deserialized element.
        Throws:
        IOException - Thrown, if the de-serialization encountered an I/O related error. Typically raised by the input view, which may have an underlying I/O channel from which it reads.

      • copy

        public void copy​(DataInputView source,
                 DataOutputView target)
          throws IOException
        Description copied from class: TypeSerializer
        Copies exactly one record from the source input view to the target output view. Whether this operation works on binary data or partially de-serializes the record to determine its length (such as for records of variable length) is up to the implementer. Binary copies are typically faster. A copy of a record containing two integer numbers (8 bytes total) is most efficiently implemented as target.write(source, 8);.
        Specified by:
        copy in class TypeSerializer<T>
        Parameters:
        source - The input view from which to read the record.
        target - The target output view to which to write the record.
        Throws:
        IOException - Thrown if any of the two views raises an exception.

      • snapshotConfiguration

        public TypeSerializerSnapshot<T> snapshotConfiguration()
        Description copied from class: TypeSerializer
        Snapshots the configuration of this TypeSerializer. This method is only relevant if the serializer is used to state stored in checkpoints/savepoints.

        The snapshot of the TypeSerializer is supposed to contain all information that affects the serialization format of the serializer. The snapshot serves two purposes: First, to reproduce the serializer when the checkpoint/savepoint is restored, and second, to check whether the serialization format is compatible with the serializer used in the restored program.

        IMPORTANT: TypeSerializerSnapshots changed after Flink 1.6. Serializers implemented against Flink versions up to 1.6 should still work, but adjust to new model to enable state evolution and be future-proof. See the class-level comments, section "Upgrading TypeSerializers to the new TypeSerializerSnapshot model" for details.

        Specified by:
        snapshotConfiguration in class TypeSerializer<T>
        Returns:
        snapshot of the serializer's current configuration (cannot be null).
        See Also:
        TypeSerializerSnapshot.resolveSchemaCompatibility(TypeSerializerSnapshot)