org.springframework.cloud.stream.binder.kafka.streams.annotations

Annotation Type KafkaStreamsStateStore

@Target(value={TYPE,METHOD,ANNOTATION_TYPE})
 @Retention(value=RUNTIME)
public @interface KafkaStreamsStateStore

Interface for Kafka Stream state store. This interface can be used to inject a state store specification into KStream building process so that the desired store can be built by StreamBuilder and added to topology for later use by processors. This is particularly useful when need to combine stream DSL with low level processor APIs. In those cases, if a writable state store is desired in processors, it needs to be created using this annotation. Here is the example.

     @StreamListener("input")
     @KafkaStreamsStateStore(name="mystate", type= KafkaStreamsStateStoreProperties.StoreType.WINDOW,
                                                                size=300000)
           public void process(KStream<Object, Product> input) {
         ......
     }
 

With that, you should be able to read/write this state store in your processor/transformer code.

                new Processor<Object, Product>() {
                        WindowStore<Object, String> state;
                        @Override
                        public void init(ProcessorContext processorContext) {
                        state = (WindowStore)processorContext.getStateStore("mystate");
                                ......
                        }
                }
 

Author:

Lei Chen

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
boolean	cache Whether catching is enabled or not.
String	keySerde Serde used for key.
long	lengthMs Length in milli-second of Windowed store window.
boolean	logging Whether logging is enabled or not.
String	name Provides name of the state store.
long	retentionMs Retention period for Windowed store windows.
KafkaStreamsStateStoreProperties.StoreType	type State store type.
String	valueSerde Serde used for value.

Element Detail

name

public abstract String name

Provides name of the state store.

Returns:

name of state store.

Default:

""

type

public abstract KafkaStreamsStateStoreProperties.StoreType type

State store type.

Returns:

KafkaStreamsStateStoreProperties.StoreType of state store.

Default:

org.springframework.cloud.stream.binder.kafka.streams.properties.KafkaStreamsStateStoreProperties.StoreType.KEYVALUE

keySerde

public abstract String keySerde

Serde used for key.

Returns:

key serde of state store.

Default:

"org.apache.kafka.common.serialization.Serdes$StringSerde"

valueSerde

public abstract String valueSerde

Serde used for value.

Returns:

value serde of state store.

Default:

"org.apache.kafka.common.serialization.Serdes$StringSerde"

lengthMs

public abstract long lengthMs

Length in milli-second of Windowed store window.

Returns:

length in milli-second of window(for windowed store).

Default:

0L

retentionMs

public abstract long retentionMs

Retention period for Windowed store windows.

Returns:

the maximum period of time in milli-second to keep each window in this store(for windowed store).

Default:

0L

cache

public abstract boolean cache

Whether catching is enabled or not.

Returns:

whether caching should be enabled on the created store.

Default:

false

logging

public abstract boolean logging

Whether logging is enabled or not.

Returns:

whether logging should be enabled on the created store.

Default:

true