ManyToOne
多对一，是最常见的表间关系，对应关系数据库中的外键关系。通常用于建立子实体和其父实体的关联关系
@Entity(name = "Person")public static class Person { ???@Id ???@GeneratedValue ???private Long id; ???//Getters and setters are omitted for brevity}@Entity(name = "Phone")public static class Phone { ???@Id ???@GeneratedValue ???private Long id; ???@Column(name = "`number`") ???private String number; ???@ManyToOne ???@JoinColumn(name = "person_id", ???????????foreignKey = @ForeignKey(name = "PERSON_ID_FK") ???) ???private Person person; ???//Getters and setters are omitted for brevity}CREATE TABLE Person ( ???id BIGINT NOT NULL , ???PRIMARY KEY ( id ))CREATE TABLE Phone ( ???id BIGINT NOT NULL , ???number VARCHAR(255) , ???person_id BIGINT , ???PRIMARY KEY ( id ) )ALTER TABLE PhoneADD CONSTRAINT PERSON_ID_FKFOREIGN KEY (person_id) REFERENCES Person
例子：
Person person = new Person();entityManager.persist( person );Phone phone = new Phone( "123-456-7890" );phone.setPerson( person );entityManager.persist( phone );entityManager.flush();phone.setPerson( null );INSERT INTO Person ( id )VALUES ( 1 )INSERT INTO Phone ( number, person_id, id )VALUES ( ‘123-456-7890‘, 1, 2 )UPDATE PhoneSET ???number = ‘123-456-7890‘, ??????person_id = NULLWHERE ?id = 2
OneToMany
一对多用于建立父实体和子实体之间的关系。如果子实体侧没有对应的ManyToOne配置，则这个OneToMany是单向的。如果子实体侧有对应的ManyToOne配置，则这个OneToMany是双向的。双向的关系，可以让开发者在两侧都能获取关联关系。
单向的一对多关系，实例：
@Entity(name = "Person")public static class Person { ???@Id ???@GeneratedValue ???private Long id; ???@OneToMany(cascade = CascadeType.ALL, orphanRemoval = true) ???private List<Phone> phones = new ArrayList<>(); ???//Getters and setters are omitted for brevity}@Entity(name = "Phone")public static class Phone { ???@Id ???@GeneratedValue ???private Long id; ???@Column(name = "`number`") ???private String number; ???//Getters and setters are omitted for brevity}CREATE TABLE Person ( ???id BIGINT NOT NULL , ???PRIMARY KEY ( id ))CREATE TABLE Person_Phone ( ???Person_id BIGINT NOT NULL , ???phones_id BIGINT NOT NULL)CREATE TABLE Phone ( ???id BIGINT NOT NULL , ???number VARCHAR(255) , ???PRIMARY KEY ( id ))ALTER TABLE Person_PhoneADD CONSTRAINT UK_9uhc5itwc9h5gcng944pcaslfUNIQUE (phones_id)ALTER TABLE Person_PhoneADD CONSTRAINT FKr38us2n8g5p9rj0b494sd3391FOREIGN KEY (phones_id) REFERENCES PhoneALTER TABLE Person_PhoneADD CONSTRAINT FK2ex4e4p7w1cj310kg2woisjl2FOREIGN KEY (Person_id) REFERENCES PersonHibernate对单向的一对多关系，两个实体对应两个表，关联关系使用一个中间表来表达。单向一对多在级联操作上比较低效。
双向一对多
Hibernate处理双向一对多关系，按多对一的关系来处理，本质上还是主外键关系。双向的一对多使父子双方都能能力来获取关联关系。使操作更方便，效率等同多对一。
@Entity(name = "Person")public static class Person { ???@Id ???@GeneratedValue ???private Long id; ???@OneToMany(mappedBy = "person", cascade = CascadeType.ALL, orphanRemoval = true) ???private List<Phone> phones = new ArrayList<>(); ???//Getters and setters are omitted for brevity ???public void addPhone(Phone phone) { ???????phones.add( phone ); ???????phone.setPerson( this ); ???} ???public void removePhone(Phone phone) { ???????phones.remove( phone ); ???????phone.setPerson( null ); ???}}@Entity(name = "Phone")public static class Phone { ???@Id ???@GeneratedValue ???private Long id; ???@NaturalId ???@Column(name = "`number`", unique = true) ???private String number; ???@ManyToOne ???private Person person; ???//Getters and setters are omitted for brevity ???@Override ???public boolean equals(Object o) { ???????if ( this == o ) { ???????????return true; ???????} ???????if ( o == null || getClass() != o.getClass() ) { ???????????return false; ???????} ???????Phone phone = (Phone) o; ???????return Objects.equals( number, phone.number ); ???} ???@Override ???public int hashCode() { ???????return Objects.hash( number ); ???}}CREATE TABLE Person ( ???id BIGINT NOT NULL , ???PRIMARY KEY ( id ))CREATE TABLE Phone ( ???id BIGINT NOT NULL , ???number VARCHAR(255) , ???person_id BIGINT , ???PRIMARY KEY ( id ))ALTER TABLE PhoneADD CONSTRAINT UK_l329ab0g4c1t78onljnxmbnp6UNIQUE (number)ALTER TABLE PhoneADD CONSTRAINT FKmw13yfsjypiiq0i1osdkaeqpgFOREIGN KEY (person_id) REFERENCES PersonHibernate之表间关系
原文地址：https://www.cnblogs.com/hengwu/p/9864489.html