org.apache.flink.api.common.serialization

Interface DeserializationSchema<T>

Type Parameters:

T - The type created by the deserialization schema.

All Superinterfaces:

ResultTypeQueryable<T>, Serializable

All Known Subinterfaces:

DeserializationSchema<T>

All Known Implementing Classes:

AbstractDeserializationSchema, AbstractDeserializationSchema, AvroDeserializationSchema, AvroRowDataDeserializationSchema, AvroRowDeserializationSchema, CanalJsonDeserializationSchema, ChangelogCsvDeserializer, ConfluentRegistryAvroDeserializationSchema, CsvRowDataDeserializationSchema, CsvRowDeserializationSchema, DebeziumAvroDeserializationSchema, DebeziumJsonDeserializationSchema, EventDeSerializationSchema, JsonDeserializationSchema, JsonNodeDeserializationSchema, JsonRowDataDeserializationSchema, JsonRowDeserializationSchema, KafkaEventSchema, MaxwellJsonDeserializationSchema, OggJsonDeserializationSchema, PbRowDataDeserializationSchema, RawFormatDeserializationSchema, RegistryAvroDeserializationSchema, SimpleStringSchema, SimpleStringSchema, TypeInformationSerializationSchema, TypeInformationSerializationSchema

@Public
public interface DeserializationSchema<T>
extends Serializable, ResultTypeQueryable<T>

The deserialization schema describes how to turn the byte messages delivered by certain data sources (for example Apache Kafka) into data types (Java/Scala objects) that are processed by Flink.

In addition, the DeserializationSchema describes the produced type (ResultTypeQueryable.getProducedType()), which lets Flink create internal serializers and structures to handle the type.

Note: In most cases, one should start from AbstractDeserializationSchema, which takes care of producing the return type information automatically.

A DeserializationSchema must be Serializable because its instances are often part of an operator or transformation function.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	DeserializationSchema.InitializationContext A contextual information provided for open(InitializationContext) method.

Method Summary

Modifier and Type	Method and Description
T	deserialize(byte[] message) Deserializes the byte message.
default void	deserialize(byte[] message, Collector<T> out) Deserializes the byte message.
boolean	isEndOfStream(T nextElement) Method to decide whether the element signals the end of the stream.
default void	open(DeserializationSchema.InitializationContext context) Initialization method for the schema.

Methods inherited from interface org.apache.flink.api.java.typeutils.ResultTypeQueryable

getProducedType

Method Detail

open

@PublicEvolving
default void open(DeserializationSchema.InitializationContext context)
                           throws Exception

Initialization method for the schema. It is called before the actual working methods deserialize(byte[]) and thus suitable for one time setup work.

The provided DeserializationSchema.InitializationContext can be used to access additional features such as e.g. registering user metrics.

Parameters:

context - Contextual information that can be used during initialization.

Throws:

Exception

deserialize

T deserialize(byte[] message)
       throws IOException

Deserializes the byte message.

Parameters:

message - The message, as a byte array.

Returns:

The deserialized message as an object (null if the message cannot be deserialized).

Throws:

IOException

deserialize

@PublicEvolving
default void deserialize(byte[] message,
                                         Collector<T> out)
                                  throws IOException

Deserializes the byte message.

Can output multiple records through the Collector. Note that number and size of the produced records should be relatively small. Depending on the source implementation records can be buffered in memory or collecting records might delay emitting checkpoint barrier.

Parameters:

message - The message, as a byte array.

out - The collector to put the resulting messages.

Throws:

IOException

isEndOfStream

boolean isEndOfStream(T nextElement)

Method to decide whether the element signals the end of the stream. If true is returned the element won't be emitted.

Parameters:

nextElement - The element to test for the end-of-stream signal.

Returns:

True, if the element signals end of stream, false otherwise.