Package de.otto.synapse.state

Interface StateRepository<V>

Type Parameters:
V - The type of the event-sourced entities stored in the StateRepository
All Superinterfaces:
AutoCloseable
All Known Implementing Classes:
ChronicleMapStateRepository, ConcurrentMapStateRepository, DelegatingStateRepository, NitriteStateRepository
public interface StateRepository<V> extends AutoCloseable
A StateRepository is used to store the aggregated state of event-sourced entities.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    clear()
    Removes all of the mappings from this repository (optional operation).
    void
    close()
    Closes the StateRepository.
    Optional<V>
    compute(String key, BiFunction<? super String,? super Optional<V>,? extends V> remappingFunction)
    Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping).
    void
    consumeAll(BiConsumer<? super String,? super V> consumer)
    Computes each entry within the repository.
    Optional<V>
    get(String key)
    Returns the optional value to which the specified key is mapped, or Optional.empty() if this repository contains no mapping for the key.
    String
    getName()
    The unique name of the StateRepository.
    Set<String>
    keySet()
    Returns an immutable set of the keys in this repository.
    Optional<V>
    put(String key, V value)
    Associates the specified value with the specified key in this repository.
    Optional<V>
    remove(String key)
    Removes the mapping for a key from this repository if it is present.
    long
    size()
    Returns the number of key-value mappings in this repository.

  • Method Details

    • getName

      String getName()
      The unique name of the StateRepository.

      Using the same name for multiple repositories will lead to

      Returns:
      name

    • keySet

      Set<String> keySet()
      Returns an immutable set of the keys in this repository.
      Returns:
      a set view of the keys contained in this repository

    • get

      Optional<V> get(String key)
      Returns the optional value to which the specified key is mapped, or Optional.empty() if this repository contains no mapping for the key.

      More formally, if this repository contains a mapping from a key k to a value v such that (key==null ? k==null : key.equals(k)), then this method returns Optional.of(v); otherwise it returns Optional.empty(). (There can be at most one such mapping.)

      Parameters:
      key - the key whose associated value is to be returned
      Returns:
      the Optional containing the value to which the specified key is mapped, or Optional.empty() if this repository contains no mapping for the key
      Throws:
      NullPointerException - if the specified key is null

    • consumeAll

      void consumeAll(BiConsumer<? super String,? super V> consumer)
      Computes each entry within the repository.
      Parameters:
      consumer - the consumer that will be applied on each repository entry

    • put

      Optional<V> put(String key, V value)
      Associates the specified value with the specified key in this repository. If the repository previously contained a mapping for the key, the old value is replaced by the specified value. (A repository m is said to contain a mapping for a key k if and only if m.get(k) would return a non-empty value.)
      Parameters:
      key - key with which the specified value is to be associated
      value - value to be associated with the specified key
      Returns:
      the previous value associated with 'key', or 'Optional.empty()' if there was no mapping for 'key'
      Throws:
      ClassCastException - if the class of the specified value prevents it from being stored in this repository
      NullPointerException - if the specified key or value is null
      IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this repository

    • compute

      Optional<V> compute(String key, BiFunction<? super String,? super Optional<V>,? extends V> remappingFunction)
      Attempts to compute a mapping for the specified key and its current mapped value (or null if there is no current mapping). For example, to either create or append a String msg to a value mapping: 
       
 repository.compute(key, (k, v) -> (v == null) ? msg : v.concat(msg))

      If the function returns null, the mapping is removed (or remains absent if initially absent). If the function itself throws an (unchecked) exception, the exception is rethrown, and the current mapping is left unchanged.

      The default implementation is equivalent to performing the following steps for this repository, then returning the current value or null if absent: 

       
 OptionalV> oldValue = repository.get(key);
 V newValue = remappingFunction.apply(key, oldValue);
 if (!oldValue.isEmpty()) {
    if (newValue != null)
       repository.put(key, newValue);
    else
       repository.remove(key);
 } else {
    if (newValue != null)
       repository.put(key, newValue);
    else
       return Optional.empty();
 }
      Parameters:
      key - key with which the specified value is to be associated
      remappingFunction - the function to compute a value
      Returns:
      the Optional containing the new value associated with the specified key, or Optional.empty() if none
      Throws:
      NullPointerException - if the specified key is null, or the remappingFunction is null
      ClassCastException - if the class of the specified value prevents it from being stored in this repository

    • remove

      Optional<V> remove(String key)
      Removes the mapping for a key from this repository if it is present. More formally, if this repository contains a mapping from key 'k' to value 'v' such that (key==null ? k==null : key.equals(k)), that mapping is removed. (The repository can contain at most one such mapping.)

      Returns the optional value to which this repository previously associated the key, or 'Optional.empty()' if the repository contained no mapping for the key.

      The repository will not contain a mapping for the specified key once the call returns.

      Parameters:
      key - key whose mapping is to be removed from the repository
      Returns:
      the optional previous value associated with 'key', or 'Optional.empty()' if there was no mapping for 'key'.
      Throws:
      NullPointerException - if the specified key is null

    • clear

      void clear()
      Removes all of the mappings from this repository (optional operation). The repository will be empty after this call returns.
      Throws:
      UnsupportedOperationException - if the 'clear' operation is not supported by this repository

    • size

      long size()
      Returns the number of key-value mappings in this repository. If the repository contains more than 'Integer.MAX_VALUE' elements, returns 'Integer.MAX_VALUE'.
      Returns:
      the number of key-value mappings in this repository

    • close

      void close() throws Exception
      Closes the StateRepository.

      Depending on the implementation of the interface, it might be required to close() the repository on shutdown in order to prevent data loss.

      Specified by:
      close in interface AutoCloseable
      Throws:
      Exception - if closing the repository fails for some reason.