jpa map 关系映射

一时失言乱红尘 2023-06-27 13:59 33阅读 0赞

jpa Map 类型的映射关系总结

参考：[https://thoughts-on-java.org/map-association-java-util-map/][https_thoughts-on-java.org_map-association-java-util-map]

1. key 、value 都是基础类型

@Setter
    @NoArgsConstructor
    @ToString
    @Entity
    @Table(name = "company")
    public class Company {
    
        private Long id;
        private String name;
        private Map<String, String> addresses = new HashMap<>();
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        public Long getId() {
            return id;
        }
    
        @Column(name = "name")
        public String getName() {
            return name;
        }
        
        /**
         * key, value 都是基础类型 
         */
        @ElementCollection
        @CollectionTable(name = "company_address", joinColumns = @JoinColumn(name = "company_id"))
        @MapKeyColumn(name = "address_no")
        @Column(name = "address")
        public Map<String, String> getAddresses() {
            return addresses;
        }
    }

mysql> select * from company;
    +----+------+
    | id | name |
    +----+------+
    |  1 | Alo7 |
    +----+------+
    1 row in set (0.00 sec)
    
    mysql> select * from  company_address;
    +------------+----------+------------+
    | company_id | address  | address_no |
    +------------+----------+------------+
    |          1 | beijing  | 001        |
    |          1 | shanghai | 002        |
    +------------+----------+------------+
    2 rows in set (0.00 sec)

2. key 是基础类型，value 是 Embeddable 类

@Embeddable
    @Data
    @ToString
    @NoArgsConstructor
    @AllArgsConstructor
    public class Address {
    
        private String country;
        private String street;
    }
    
    
    @ToString
    @Setter
    @NoArgsConstructor
    @Entity
    @Table(name = "schooler")
    public class Schooler {
    
        private Long id;
        private String name;
        private Map<String, Address> addressMap = new HashMap<>();
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        public Long getId() {
            return id;
        }
    
        @Column(name = "name")
        public String getName() {
            return name;
        }
    
        /**
         * key 是基础类型， value 是 Embeddable 类
         */
        @ElementCollection
        @CollectionTable(name = "schooler_address", joinColumns = {@JoinColumn(name = "schooler_id")})
        @MapKeyColumn(name = "address_no")
        public Map<String, Address> getAddressMap() {
            return addressMap;
        }
    }

mysql> select * from scholler;
    +----+---------+
    | id | name    |
    +----+---------+
    |  1 | qinghua |
    +----+---------+
    1 row in set (0.00 sec)
    
    mysql> select * from schooler_address;
    +-------------+---------+--------+------------+
    | schooler_id | country | street | address_no |
    +-------------+---------+--------+------------+
    |           1 | CH      | Nj     | 01         |
    |           1 | US      | NY     | 02         |
    +-------------+---------+--------+------------+

3. key 是基础类型，value 是 entity

@ToString
    @Setter
    @NoArgsConstructor
    @Entity
    @Table(name = "author")
    public class Author {
    
        private Long id;
        private String aname;
        private Map<String, Book> books = new HashMap<>();
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        public Long getId() {
            return id;
        }
    
        @Column(name = "aname")
        public String getAname() {
            return aname;
        }
    
        @ManyToMany
        @JoinTable(name = "author_book",
                joinColumns = {@JoinColumn(name = "author_id", referencedColumnName = "id")},
                inverseJoinColumns = {@JoinColumn(name = "book_id", referencedColumnName = "id")}
        )
        @MapKeyColumn(name = "book_name")
        public Map<String, Book> getBooks() {
            return books;
        }
    }
    
    
    @ToString
    @Setter
    @NoArgsConstructor
    @Entity
    @Table(name = "book")
    public class Book {
    
        private Long id;
        private String bname;
    
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        public Long getId() {
            return id;
        }
    
        @Column(name = "bname")
        public String getBname() {
            return bname;
        }
    }

mysql> select * from author_book;
    +-----------+---------+-----------+
    | author_id | book_id | book_name |
    +-----------+---------+-----------+
    |         1 |       1 | java      |
    |         1 |       2 | c#        |
    +-----------+---------+-----------+
    2 rows in set (0.00 sec)
    
    mysql> select * from book;
    +----+-------+
    | id | bname |
    +----+-------+
    |  1 | java  |
    |  2 | c#    |
    +----+-------+
    2 rows in set (0.00 sec)
    
    mysql> select * from author;
    +----+-------+
    | id | aname |
    +----+-------+
    |  1 | wang  |
    +----+-------+
    1 row in set (0.00 sec)

[https_thoughts-on-java.org_map-association-java-util-map]: https://thoughts-on-java.org/map-association-java-util-map/