Implementation:Apache Flink ElementConverter Apply

Knowledge Sources	Apache Flink
Domains	Stream_Processing, Data_Transformation
Last Updated	2026-02-09 00:00 GMT

Overview

Concrete interface for converting pipeline elements to destination-specific request entries provided by the Apache Flink connector-base module.

Description

The ElementConverter is a @FunctionalInterface extending Serializable with two methods: apply for the conversion logic and open as an optional lifecycle hook for initialization. Connector implementations provide concrete converters (e.g., converting records to Kinesis PutRecordRequest objects).

Usage

Implement this interface when building a custom async sink connector. The converter is passed to the AsyncSinkBase constructor or builder.

Code Reference

Source Location

• Repository: Apache Flink
• File: flink-connectors/flink-connector-base/src/main/java/org/apache/flink/connector/base/sink/writer/ElementConverter.java
• Lines: L35-41

Signature

@PublicEvolving
public interface ElementConverter<InputT, RequestEntryT> extends Serializable {

    RequestEntryT apply(InputT element, SinkWriter.Context context);

    default void open(WriterInitContext context) {}
}

Import

import org.apache.flink.connector.base.sink.writer.ElementConverter;

I/O Contract

Inputs

Name	Type	Required	Description
element	InputT	Yes	Pipeline element to convert
context	SinkWriter.Context	Yes	Provides timestamp and watermark

Outputs

Name	Type	Description
requestEntry	RequestEntryT extends Serializable	Destination-specific request entry

Usage Examples

Custom Element Converter

ElementConverter<MyEvent, PutRecordsRequestEntry> converter =
    (element, context) -> {
        return PutRecordsRequestEntry.builder()
            .data(SdkBytes.fromUtf8String(element.toJson()))
            .partitionKey(element.getKey())
            .build();
    };

Related Pages

Implements Principle

• Principle:Apache_Flink_Element_Conversion