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Graph Database API for Neo4j.
There is a newer version: 5.25.1
/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.graphdb;

import java.util.Map;

import org.neo4j.annotations.api.PublicApi;

/**
 * An Entity is a {@link Entity} that is persisted in the database, and identified by an {@link #getId() id}.
 * 
 * {@link Node Nodes} and {@link Relationship Relationships} are Entities.
 *
 * Entities are attached to transaction in which they were accessed. Outside of transaction its possible only to access entity id.
 * All other methods should be called only in the scope of the owning transaction.
 *
 * Defines a common API for handling properties on both {@link Node nodes} and
 * {@link Relationship relationships}.
 * 

 * Properties are key-value pairs. The keys are always strings. Valid property
 * value types are all the Java primitives (int, byte,
 * float, etc), java.lang.Strings, the Spatial
 * and Temporal types and arrays of any of these.
 * 

 * The complete list of currently supported property types is:
 * 

 * boolean
 * byte
 * short
 * int
 * long
 * float
 * double
 * char
 * java.lang.String
 * org.neo4j.graphdb.spatial.Point
 * java.time.LocalDate
 * java.time.OffsetTime
 * java.time.LocalTime
 * java.time.ZonedDateTime

 * It is also possible to use java.time.OffsetDateTime and it will
 * be converted to a ZonedDateTime internally.
 * 
 * java.time.LocalDateTime
 * java.time.temporal.TemporalAmount

 * There are two concrete implementations of this interface, java.time.Duration
 * and java.time.Period which will be converted to a single Neo4j Duration
 * type. This means loss of type information, so properties of this type, when read back using
 * {@link #getProperty(String) getProperty} will be only of type java.time.temporal.TemporalAmount.
 * 
 * Arrays of any of the above types, for example int[], String[] or LocalTime[]
 * 
 * 
 * Please note that Neo4j does NOT accept arbitrary objects as property
 * values. {@link #setProperty(String, Object) setProperty()} takes a
 * java.lang.Object only to avoid an explosion of overloaded
 * setProperty() methods.
 **/
@PublicApi
public interface Entity
{
    /**
     * Returns the unique id of this entity. Id's are reused over time so they are only guaranteed to be unique
     * during a specific transaction: if the entity is deleted, it is
     * likely that some new entity will reuse this id at some point.
     *
     * @return The id of this Entity.
     */
    long getId();

    /**
     * Returns true if this property container has a property
     * accessible through the given key, false otherwise. If key is
     * null, this method returns false.
     *
     * @param key the property key
     * @return true if this property container has a property
     *         accessible through the given key, false otherwise
     */
    boolean hasProperty( String key );

    /**
     * Returns the property value associated with the given key. The value is of
     * one of the valid property types, i.e. a Java primitive,
     * a {@link String String}, a {@link org.neo4j.graphdb.spatial.Point Point},
     * a valid temporal type, or an array of any of the valid types.
     * See the {@link Entity the class description}
     * for a full list of known types.
     * 

     * If there's no property associated with key an unchecked
     * exception is raised. The idiomatic way to avoid an exception for an
     * unknown key and instead get null back is to use a default
     * value: {@link #getProperty(String, Object) Object valueOrNull =
     * nodeOrRel.getProperty( key, null )}
     *
     * @param key the property key
     * @return the property value associated with the given key
     * @throws NotFoundException if there's no property associated with
     *             key
     */
    Object getProperty( String key );

    /**
     * Returns the property value associated with the given key, or a default
     * value. The value is of one of the valid property types, i.e. a Java primitive,
     * a {@link String String}, a {@link org.neo4j.graphdb.spatial.Point Point},
     * a valid temporal type, or an array of any of the valid types.
     * See the {@link Entity the class description}
     * for a full list of known types.
     *
     * @param key the property key
     * @param defaultValue the default value that will be returned if no
     *            property value was associated with the given key
     * @return the property value associated with the given key
     */
    Object getProperty( String key, Object defaultValue );

    /**
     * Sets the property value for the given key to value. The
     * property value must be one of the valid property types, i.e. a Java primitive,
     * a {@link String String}, a {@link org.neo4j.graphdb.spatial.Point Point},
     * a valid temporal type, or an array of any of the valid types.
     * See the {@link Entity the class description}
     * for a full list of known types.
     * 
     * This means that null is not an accepted property value.
     *
     * @param key the key with which the new property value will be associated
     * @param value the new property value, of one of the valid property types
     * @throws IllegalArgumentException if value is of an
     *             unsupported type (including null)
     */
    void setProperty( String key, Object value );

    /**
     * Removes the property associated with the given key and returns the old
     * value. If there's no property associated with the key, null
     * will be returned.
     *
     * @param key the property key
     * @return the property value that used to be associated with the given key
     */
    Object removeProperty( String key );

    /**
     * Returns all existing property keys, or an empty iterable if this property
     * container has no properties.
     *
     * @return all property keys on this property container
     */
    // TODO: figure out concurrency semantics
    Iterable getPropertyKeys();

    /**
     * Returns specified existing properties. The collection is mutable,
     * but changing it has no impact on the graph as the data is detached.
     *
     * @param keys the property keys to return
     * @return specified properties on this property container
     * @throws NullPointerException if the array of keys or any key is null
     */
    Map getProperties( String... keys );

    /**
     * Returns all existing properties.
     *
     * @return all properties on this property container
     */
    Map getAllProperties();
}