package org.neo4j.graphdb.event;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.PropertyContainer;
import org.neo4j.graphdb.Relationship;
/**
* Represents a changed property.
*
* Instances of this interface represent the property as it is after the
* transaction when returned from
* {@link TransactionData#assignedNodeProperties()} or
* {@link TransactionData#assignedRelationshipProperties()}. Instances of this
* interface represent the property as it was before the transaction as well as
* how it will be after the transaction has been committed.
*
* @author Tobias Ivarsson
*
* @param <T> The type of the entity the property belongs to, either
* {@link Node} or {@link Relationship}.
*/
public interface PropertyEntry<T extends PropertyContainer>
{
/**
* Get the entity that this property was modified on. The entity is either a
* {@link Node} or a {@link Relationship}, depending on the generic type of
* this instance.
*
* @return the {@link Node} or {@link Relationship} that the property was
* modified on.
*/
T entity();
/**
* Get the key of the modified property.
*
* @return the key of the modified property.
*/
String key();
/**
* Get the value of the modified property as it was before the transaction
* (which modified it) started. If this {@link PropertyEntry} was returned
* from {@link TransactionData#assignedNodeProperties()} or
* {@link TransactionData#assignedRelationshipProperties()}, the value
* returned from this method is the value that was set for {@code key} on
* {@code entity} before the transaction started, or {@code null} if such a
* property wasn't set.
*
* If this {@link PropertyEntry} was returned from
* {@link TransactionData#removedNodeProperties()} or
* {@link TransactionData#removedRelationshipProperties()} the value
* returned from this method is the value that was stored at this property
* before the transaction started.
*
* @return The value of the property as it was before the transaction
* started.
*/
Object previouslyCommitedValue();
/**
* Get the value of the modified property. If this {@link PropertyEntry}
* was returned from {@link TransactionData#assignedNodeProperties()} or
* {@link TransactionData#assignedRelationshipProperties()}, the value
* returned from this method is the value that will be assigned to the
* property after the transaction is committed. If this
* {@link PropertyEntry} was returned from
* {@link TransactionData#removedNodeProperties()} or
* {@link TransactionData#removedRelationshipProperties()} an
* {@link IllegalStateException} will be thrown.
*
* @return The value of the modified property.
* @throws IllegalStateException if this method is called where this
* instance represents a removed property.
*/
Object value();
}