/*
 * Copyright 2008-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.data.jpa.domain;

import java.io.Serializable;

import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;
import javax.persistence.Transient;

import org.springframework.data.domain.Persistable;
import org.springframework.data.util.ProxyUtils;
import org.springframework.lang.Nullable;

Abstract base class for entities. Allows parameterization of id type, chooses auto-generation and implements equals(Object) and hashCode() based on that id. 
Author:
Oliver Gierke, Thomas Darimont, Mark Paluch
Type parameters:
<PK> – the type of the identifier./**
 * Abstract base class for entities. Allows parameterization of id type, chooses auto-generation and implements
 * {@link #equals(Object)} and {@link #hashCode()} based on that id.
 *
 * @author Oliver Gierke
 * @author Thomas Darimont
 * @author Mark Paluch
 * @param <PK> the type of the identifier.
 */
@MappedSuperclass
public abstract class AbstractPersistable<PK extends Serializable> implements Persistable<PK> {

	private static final long serialVersionUID = -5554308939380869754L;

	@Id @GeneratedValue private @Nullable PK id;

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Persistable#getId()
	 */
	@Nullable
	@Override
	public PK getId() {
		return id;
	}

	
Sets the id of the entity.
Params:
id – the id to set/**
	 * Sets the id of the entity.
	 *
	 * @param id the id to set
	 */
	protected void setId(@Nullable PK id) {
		this.id = id;
	}

	
Must be Transient in order to ensure that no JPA provider complains because of a missing setter. 
See Also:
Persistable.isNew()/**
	 * Must be {@link Transient} in order to ensure that no JPA provider complains because of a missing setter.
	 *
	 * @see org.springframework.data.domain.Persistable#isNew()
	 */
	@Transient // DATAJPA-622
	@Override
	public boolean isNew() {
		return null == getId();
	}

	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {
		return String.format("Entity of type %s with id: %s", this.getClass().getName(), getId());
	}

	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#equals(java.lang.Object)
	 */
	@Override
	public boolean equals(Object obj) {

		if (null == obj) {
			return false;
		}

		if (this == obj) {
			return true;
		}

		if (!getClass().equals(ProxyUtils.getUserClass(obj))) {
			return false;
		}

		AbstractPersistable<?> that = (AbstractPersistable<?>) obj;

		return null == this.getId() ? false : this.getId().equals(that.getId());
	}

	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#hashCode()
	 */
	@Override
	public int hashCode() {

		int hashCode = 17;

		hashCode += null == getId() ? 0 : getId().hashCode() * 31;

		return hashCode;
	}
}