Class/Object

com.lightbend.lagom.scaladsl.persistence

PersistentEntity

Related Docs: object PersistentEntity | package persistence

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abstract class PersistentEntity extends AnyRef

A PersistentEntity has a stable entity identifier, with which it can be accessed from anywhere in the cluster. It is run by an actor and the state is persistent using event sourcing.

initialState and behavior are abstract methods that your concrete subclass must implement. The behavior is defined as a set of actions given a state. The actions are functions to process incoming commands and persisted events.

The PersistentEntity receives commands of type Command that can be validated before persisting state changes as events of type Event. The functions that process incoming commands are registered in the Actions using onCommand of the Actions.

A command may also be read-only and only perform some side-effect, such as replying to the request. Such command handlers are registered using onReadOnlyCommand of the Actions. Replies are sent with the reply method of the context that is passed to the command handler function.

A command handler returns a Persist directive that defines what event or events, if any, to persist. Use the thenPersist, thenPersistAll or done methods of the context that is passed to the command handler function to create the Persist directive.

When an event has been persisted successfully the state of type State is updated by applying the event to the current state. The functions for updating the state are registered with the onEvent method of the Actions. The event handler returns the new state. The state must be immutable, so you return a new instance of the state. Current state is passed as parameter to the event handler. The same event handlers are also used when the entity is started up to recover its state from the stored events.

After persisting an event, external side effects can be performed in the afterPersist function that can be defined when creating the Persist directive. A typical side effect is to reply to the request to confirm that it was performed successfully. Replies are sent with the reply method of the context that is passed to the command handler function.

The event handlers are typically only updating the state, but they may also change the behavior of the entity in the sense that new functions for processing commands and events may be defined for a given state. This is useful when implementing finite state machine (FSM) like entities.

When the entity is started the state is recovered by replaying stored events. To reduce this recovery time the entity may start the recovery from a snapshot of the state and then only replaying the events that were stored after the snapshot. Such snapshots are automatically saved after a configured number of persisted events.

Source
PersistentEntity.scala
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Instance Constructors

  1. new PersistentEntity()

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Type Members

  1. class Actions extends (State) ⇒ Actions

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    Actions consists of functions to process incoming commands and persisted events.

    Actions consists of functions to process incoming commands and persisted events. Actions is an immutable class.

  2. type Behavior = (State) ⇒ Actions

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  3. abstract type Command

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  4. abstract class CommandContext[R] extends ReadOnlyCommandContext[R]

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    The context that is used by command handler function.

    The context that is used by command handler function. Events are persisted with the context and replies are sent with the context.

    R

    the reply type of the command

  5. abstract type Event

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  6. type EventHandler = PartialFunction[(Event, State), State]

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  7. trait Persist extends AnyRef

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    A command handler returns a Persist directive that defines what event or events, if any, to persist.

    A command handler returns a Persist directive that defines what event or events, if any, to persist. Use the thenPersist, thenPersistAll or done methods of the context that is passed to the command handler function to create the Persist directive.

  8. abstract class ReadOnlyCommandContext[R] extends AnyRef

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    The context that is used by read-only command handlers.

    The context that is used by read-only command handlers. Replies are sent with the context.

    R

    the reply type of the command

  9. abstract type State

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Abstract Value Members

  1. abstract def behavior: Behavior

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    Abstract method that must be implemented by concrete subclass to define the behavior of the entity.

  2. abstract def initialState: State

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Concrete Value Members

  1. final def !=(arg0: Any): Boolean

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    Definition Classes
    AnyRef → Any
  2. final def ##(): Int

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    Definition Classes
    AnyRef → Any
  3. def +(other: String): String

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    Implicit information
    This member is added by an implicit conversion from PersistentEntity to any2stringadd[PersistentEntity] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (PersistentEntity, B)

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    Implicit information
    This member is added by an implicit conversion from PersistentEntity to ArrowAssoc[PersistentEntity] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  5. final def ==(arg0: Any): Boolean

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    Definition Classes
    AnyRef → Any
  6. object Actions

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  7. final def asInstanceOf[T0]: T0

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    Definition Classes
    Any
  8. def clone(): AnyRef

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    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  9. def ensuring(cond: (PersistentEntity) ⇒ Boolean, msg: ⇒ Any): PersistentEntity

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    Implicit information
    This member is added by an implicit conversion from PersistentEntity to Ensuring[PersistentEntity] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  10. def ensuring(cond: (PersistentEntity) ⇒ Boolean): PersistentEntity

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    Implicit information
    This member is added by an implicit conversion from PersistentEntity to Ensuring[PersistentEntity] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: Boolean, msg: ⇒ Any): PersistentEntity

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    Implicit information
    This member is added by an implicit conversion from PersistentEntity to Ensuring[PersistentEntity] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. def ensuring(cond: Boolean): PersistentEntity

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    Implicit information
    This member is added by an implicit conversion from PersistentEntity to Ensuring[PersistentEntity] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  13. final def entityId: String

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    Attributes
    protected
  14. def entityTypeName: String

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    The name of this entity type.

    The name of this entity type. It should be unique among the entity types of the service. By default it is using the short class name of the concrete PersistentEntity class. Subclass may override to define other type names. It is needed to override and retain the original name when the class name is changed because this name is part of the key of the store data (it is part of the persistenceId of the underlying PersistentActor).

  15. final def eq(arg0: AnyRef): Boolean

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    Definition Classes
    AnyRef
  16. def equals(arg0: Any): Boolean

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    Definition Classes
    AnyRef → Any
  17. def finalize(): Unit

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    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  18. def formatted(fmtstr: String): String

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    Implicit information
    This member is added by an implicit conversion from PersistentEntity to StringFormat[PersistentEntity] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  19. final def getClass(): Class[_]

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    Definition Classes
    AnyRef → Any
  20. def hashCode(): Int

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    Definition Classes
    AnyRef → Any
  21. final def isInstanceOf[T0]: Boolean

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    Definition Classes
    Any
  22. final def ne(arg0: AnyRef): Boolean

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    Definition Classes
    AnyRef
  23. final def notify(): Unit

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    Definition Classes
    AnyRef
  24. final def notifyAll(): Unit

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    Definition Classes
    AnyRef
  25. def recoveryCompleted(state: State): State

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    This method is called to notify the entity that the recovery process is finished.

  26. final def synchronized[T0](arg0: ⇒ T0): T0

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    Definition Classes
    AnyRef
  27. def toString(): String

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    Definition Classes
    AnyRef → Any
  28. final def wait(): Unit

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    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  29. final def wait(arg0: Long, arg1: Int): Unit

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    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  30. final def wait(arg0: Long): Unit

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    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  31. def [B](y: B): (PersistentEntity, B)

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    Implicit information
    This member is added by an implicit conversion from PersistentEntity to ArrowAssoc[PersistentEntity] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from PersistentEntity to any2stringadd[PersistentEntity]

Inherited by implicit conversion StringFormat from PersistentEntity to StringFormat[PersistentEntity]

Inherited by implicit conversion Ensuring from PersistentEntity to Ensuring[PersistentEntity]

Inherited by implicit conversion ArrowAssoc from PersistentEntity to ArrowAssoc[PersistentEntity]

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