hibernater 复习,总结
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hibernater 注解总结
@Entity
@Table
@Id
@GeneratedValue (主键策略)
@Access 访问策略.不直接访问属性(不用设置)
@Proxy (proxyClass 指定接口,延迟加载)
@DynamicInsert 指定insert 动态插入,一般不开启,费时间
@DynamicUpdate 同上(可以指定乐观锁策略 p401)
SelectBeforeUpdate 先更新,在select 这个不是很懂
@Polymorphism 隐式查询
@Where 过滤条件
@BachSize 抓取是的个数.支持延迟加载
@OptimisticLock 乐观锁
@Check
@Subselect 只读实体 有点像mybaits构成实体 有用
@Column (length nuable name)
@Formula 只读表达式 (数据库的max那些函数)
@Generated 指定数据列的值是否有数据库生成 p402 自动生成时间(感觉有点用,但是需要数据库脚本支持)
@Transient 不保存的属性
@Enumerated 枚举,有保存序号,和保存名称两种
@Basic 大数据 byte[] 对于大数据要延迟加载
@Lob char[]
@Temporal 时间
@SequenceGenerator() 主键生成器 oracle 还是GeneratedValue 简单
@TableGenerator
@ElementCollection 集合属性
@CollectionTable
@JoinColumn 外键 常用属性 unable unique(为该列指定唯一约束) referecceedName 该列所参照的主键的列名字
对于nuable 如果持久化对象能过管得到,则nuable true,对于外键.则可以为false
List Map
@OrderColumn list 集合索引
@MapKeyColumn map 集合索引
Set 无序,不用索引
eg:
@ElementCollection(targetClass = String.class)
@CollectionTable(name = "school_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "school_name")
@OrderColumn(name = "list_order")
private List<String> schools = new ArrayList<>();
//OrderColumn 索引的column,采用默认的Cascady.ALL 采用联合主键 person_id list_order
对于数组也是一样的
eg:
@ElementCollection(targetClass = String.class)
@CollectionTable(name = "school_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "school_name")
@OrderColumn(name = "list_order")
private String[] schools;
对于Set 因为是无序的所以不用 OrderColumn 采用的外键,和 school_name 作为联合主键
@ElementCollection(targetClass = String.class)
@CollectionTable(name = "school_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "school_name")
private Set<String> schools = new HashSet<>();
对于Map 采用key 和外键作为主键 延迟加载
@ElementCollection(targetClass = Float.class,fetch = FetchType.EAGER)
@CollectionTable(name = "school_inf",
joinColumns = @JoinColumn(name = "scrop_inf",nullable = false))
@MapKeyColumn(name = "subject_name")
@MapKeyClass(String.class)
@Column(name = "mark")
private Map<String,Float> scores = new HashMap<>();
什么时候有那个list map set
在1 n 的时候,控制映射关系,在n 时候,则采用set,反向集合
hibernater 对于TreeSet TreeMap
@SortNatural
@SortComparator()
eg:TreeSet
@ElementCollection(targetClass = String.class,fetch = FetchType.EAGER)
@CollectionTable(name = "training_inf",
joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "training_name",nullable = false)
@SortNatural
private SortedSet<String> trainings = new TreeSet<>();
@OrderBy 对排序 的支持
@ElementCollection(targetClass = String.class,fetch = FetchType.EAGER)
@CollectionTable(name = "training_inf",
joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "training_name",nullable = false)
@OrderBy("training_name desc")
private Set<String> trainings = new HashSet<>();
映射组件 在组件端,添加注释,使之为 组件
Perosn 端
privater Name name; //直接声明
Name 端
对于组件,他是附件在主表上面的
@Embeddable Name{
....
@Parent
privater Person owner;
}
hibernater 提供的另外的一种组件
直接在Perosn 里面添加
@Embedded
@AttributeOverrides({
@AssociationOverride(name="first",column = @Column(name="person_firstname")),
@AssociationOverride(name="last",column = @Column(name="person_lastname"))
})
不需要在Name 添加什么东西(感觉还不如直接申明为属性)
集合属性的元素作为组件
@ElementCollection(targetClass = Scrore.clasa)
@CollectionTable(name = "score_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@MapKeyColumn(name = "subject_name")
@MapKeyClass(String.class)
private Map<String,Score> scores = new HashMap<>();
@ElementCollection(targetClass = Name.class)
@CollectionTable(name = "nick_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@OrderColumn(name = "list_order")
private List<Name> nicks = new ArrayList<>();
比较之前的list 他没有 @Column(name = "school_name")
它会默认采取list 的属性名称 就更一把的一样,其实这个,就是吧组件的两个属性
默认添加到附表的结构中 这是组件的一种性质吧
将组件作为map key
@ElementCollection(targetClass = Integer.class)
@CollectionTable(name = "nick_power_inf",
joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "nick_power",nullable = false)
@MapKeyClass(Name.class)
private Map<Name,Integer> nicjPower = new HashMap<>();
对于Name 要复写hashcode 和equals 方法.并且,要将Name 声明为 @Embedable
还是一样.组件,作为附表的一部分 p430
组件作为复合主键
@EmbeddedId
@AttributeOverrides({
@AttributeOverride(name = "frist",column = @Column(name = "person_firstName")),
@AttributeOverride(name = "last",column = @Column(name = "person_lastName"))
})
private Name name;
// @EmbeddedId 声明为主键.对于这种,就不需要在Name 上面做任何操作,只需要复写hashcode 和 equals
对于这种,组件的属性直接被添加到主表里面
----------------------------------------------------
hibernater 深入
@ManyToOne cascade fetch
无连接表的 n - 1 在n 端添加关系
多个人对应一个地址,只需要通过人找到地址就行,这是在 person 端,在地址端,不做任何操作
@ManyToOne(targetEntity = Address.class,cascade = CascadeType.ALL)
@JoinColumn(name = "address_id",nullable = false)
private Address address;
对于cascade.all ,只需要,在person 端,设置address 直接保存person.后,address,自动级连保存,先插入从表,在保存主表
有连接表的 n - 1 person 端
@ManyToOne(targetEntity = Address.class,cascade = CascadeType.ALL)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "person_id",unique = true),
inverseJoinColumns = @JoinColumn(name = "address_id",referencedColumnName = "address_id"))
private Address address;
对于 joinColumns 都是映射的主键和外建 unique 以perosn_id 作为唯一性列的参考 只许表中只有一个person id
单向的 1 1 的映射
@OneToOne(targetEntity = Address.class)
@JoinColumn(name = "address_id",referencedColumnName = "address_id",unique = true)
private Address address;
使用unquie 控制唯一性关系
对于mappedBy 表示不控制关系 orphanRemoval 删除孤儿实体 和cascade 两者存在一个就行
无连接表 单项 1 n 在n 端控制 信息.默认的在n 端添加外键
@OneToMany(targetEntity = Address.class)
@JoinColumn(name = "person_id",referencedColumnName = "person_id")
private Set<Address> addresses = new HashSet<>();
对于无连接表中,都已吧控制信息写在n 端,然后在 1 端,接受数据 referencedColumnName 映射到外面去的
对于这样的信息,没有cascade.all 所 (此外必须要先通过先实例化address_inf 才行)insert 外键为空address_inf ,然后在update address_inf 将person 的主键作为
address_inf 的外键.出现这样的原因,是应为 address_inf 不知 perosn_inf ,一直,没有将 person_id 作为自己的属性
可以通过双向的 1 n 链接解决问题 但是 1 端会 多出一条update 性能要比 n端低 p 447 (有点懵逼)
有链接表的单向 1 n 关联 person unique = true.address 关联一个address 地址,但是person 可以关联多个address
没有cascade 但是应为出现链接表,所以,无论实例化那个都可以 就是会不会出现幽灵数据,可以通过 cascade.all
来阻止这种情况发生 解决,以为有链接表,所以先实例哪一个对象,都可以,对于one 端 cascade.all 写不写,都是要删除附加表的信息
如果,要实现附表的删除,则需要手动删除
@OneToMany(targetEntity = Address.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "person_id"),
inverseJoinColumns = @JoinColumn(name = "address_id",
referencedColumnName = "address_id",unique = true))
private Set<Address> addresses = new HashSet<>();
对于单项的 n n ,必须使用连接表 不能使用 unquie ,如果使用 unquie 则变为 形式上变为 one to many
@ManyToMany(targetEntity = Address.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "person_id"),
inverseJoinColumns = @JoinColumn(name = "adress_id",referencedColumnName = "address_id"))
private Set<Address> addresses = new HashSet<>();
对于有链接表的,级连操作,都是第三张表
无连接表的双向1 n 连接
一般采用这种方式 mappedBy 放弃映射关系,可以直接使用
Peron
@OneToMany(targetEntity = Address.class,mappedBy = "person")
private Set<Address> addresses = new HashSet<>();
Address n 端控制关系 先持久化 person ,在持久化 address 这样可以保证效率
如果先持久化address 再持久化 person 所以,会产生三条语句,insert address insert person update address
@ManyToOne(targetEntity = Person.class)
@JoinColumn(name = "person_id",referencedColumnName = "person_id",nullable = false)
private Person person;
有链接表的双向 1 n
Peron
@OneToMany(targetEntity = Address.class,mappedBy = "person")
private Set<Address> addresses = new HashSet<>();
address
@ManyToOne(targetEntity = Person.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "address_id",referencedColumnName = "address_id",unique = true),
inverseJoinColumns = @JoinColumn(name = "person_id",referencedColumnName = "person_id"))
private Perosn person;
address_id和 person_id 作为主列键 对于有三表,一般都可以吧
看来joinColumns 有多种意思 我觉得这里不应该unique = true ,这里是正确的
就是对于多个属性的限制,只是在入库的时候,更加严格,
双向 n n 关联 因为是 n n 所以不能用 unquie
这里的 person_id 和address_id 都是主列键,谁先谁后,都一样,只是,按照一样的顺序,可以少写代码
@ManyToMany(targetEntity = Address.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "id"),
inverseJoinColumns = @JoinColumn(name = "address_id",referencedColumnName = "id"))
private Set<Address> addresses = new HashSet<>();
@ManyToMany(targetEntity = Person.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "id"),
inverseJoinColumns = @JoinColumn(name = "address_id",referencedColumnName = "id"))
private Set<Person> Person = new HashSet<>();
双向 1 1 对于主表,一端,应该放弃控制关系,要不然,会造成update的性能下降
peroson
@OneToOne(targetEntity = Address.class,mappedBy = "person")
private Address address;
address
@OneToOne(targetEntity = Person.class)
@JoinColumn(name = "person_id",referencedColumnName = "id",unique = true);
private Person person;
https://www.cnblogs.com/SpringSmallGrass/archive/2013/04/06/3002199.html
对于mapped 复习,双边关系,只需要一端维护就可以,拥有段,不用维护,被拥有段需要维护, 在被拥有段建立外键
one one many many one many 都可以建立 但是 many to one (控制关系都是n 端维护,) 没有这个属性,,这样的好处是,减少一条的update 语句.性能更好
对于这种级联删除,在拥有段控制关系,对于孤儿,可以通过one to many one to one ,启动级联.也就是主表
从表的生命周期完全在主表类可以采用 CascadeTpye.ALL 加 orphanRemoval =true
多主键,多外键,控制关系
Person
@Id
private String firstName;
@Id
private String lastName;
@OneToMany(targetEntity = Address,mappedBy = "person",cascade = CascadeType.ALL)
private Set<Address> addresses = new HashSet<>();
Address
@ManyToOne(targetEntity = Person.class)
@JoinColumns({
@JoinColumn(name = "person_first",referencedColumnName = "firstName",nullable = false),
@JoinColumn(name = "person_last",referencedColumnName = "lastName",nullable = false)
})
private Person perosn;
将成员为主键
@Entity
@Table
@Id
@GeneratedValue (主键策略)
@Access 访问策略.不直接访问属性(不用设置)
@Proxy (proxyClass 指定接口,延迟加载)
@DynamicInsert 指定insert 动态插入,一般不开启,费时间
@DynamicUpdate 同上(可以指定乐观锁策略 p401)
SelectBeforeUpdate 先更新,在select 这个不是很懂
@Polymorphism 隐式查询
@Where 过滤条件
@BachSize 抓取是的个数.支持延迟加载
@OptimisticLock 乐观锁
@Check
@Subselect 只读实体 有点像mybaits构成实体 有用
@Column (length nuable name)
@Formula 只读表达式 (数据库的max那些函数)
@Generated 指定数据列的值是否有数据库生成 p402 自动生成时间(感觉有点用,但是需要数据库脚本支持)
@Transient 不保存的属性
@Enumerated 枚举,有保存序号,和保存名称两种
@Basic 大数据 byte[] 对于大数据要延迟加载
@Lob char[]
@Temporal 时间
@SequenceGenerator() 主键生成器 oracle 还是GeneratedValue 简单
@TableGenerator
@ElementCollection 集合属性
@CollectionTable
@JoinColumn 外键 常用属性 unable unique(为该列指定唯一约束) referecceedName 该列所参照的主键的列名字
对于nuable 如果持久化对象能过管得到,则nuable true,对于外键.则可以为false
List Map
@OrderColumn list 集合索引
@MapKeyColumn map 集合索引
Set 无序,不用索引
eg:
@ElementCollection(targetClass = String.class)
@CollectionTable(name = "school_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "school_name")
@OrderColumn(name = "list_order")
private List<String> schools = new ArrayList<>();
//OrderColumn 索引的column,采用默认的Cascady.ALL 采用联合主键 person_id list_order
对于数组也是一样的
eg:
@ElementCollection(targetClass = String.class)
@CollectionTable(name = "school_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "school_name")
@OrderColumn(name = "list_order")
private String[] schools;
对于Set 因为是无序的所以不用 OrderColumn 采用的外键,和 school_name 作为联合主键
@ElementCollection(targetClass = String.class)
@CollectionTable(name = "school_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "school_name")
private Set<String> schools = new HashSet<>();
对于Map 采用key 和外键作为主键 延迟加载
@ElementCollection(targetClass = Float.class,fetch = FetchType.EAGER)
@CollectionTable(name = "school_inf",
joinColumns = @JoinColumn(name = "scrop_inf",nullable = false))
@MapKeyColumn(name = "subject_name")
@MapKeyClass(String.class)
@Column(name = "mark")
private Map<String,Float> scores = new HashMap<>();
什么时候有那个list map set
在1 n 的时候,控制映射关系,在n 时候,则采用set,反向集合
hibernater 对于TreeSet TreeMap
@SortNatural
@SortComparator()
eg:TreeSet
@ElementCollection(targetClass = String.class,fetch = FetchType.EAGER)
@CollectionTable(name = "training_inf",
joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "training_name",nullable = false)
@SortNatural
private SortedSet<String> trainings = new TreeSet<>();
@OrderBy 对排序 的支持
@ElementCollection(targetClass = String.class,fetch = FetchType.EAGER)
@CollectionTable(name = "training_inf",
joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "training_name",nullable = false)
@OrderBy("training_name desc")
private Set<String> trainings = new HashSet<>();
映射组件 在组件端,添加注释,使之为 组件
Perosn 端
privater Name name; //直接声明
Name 端
对于组件,他是附件在主表上面的
@Embeddable Name{
....
@Parent
privater Person owner;
}
hibernater 提供的另外的一种组件
直接在Perosn 里面添加
@Embedded
@AttributeOverrides({
@AssociationOverride(name="first",column = @Column(name="person_firstname")),
@AssociationOverride(name="last",column = @Column(name="person_lastname"))
})
不需要在Name 添加什么东西(感觉还不如直接申明为属性)
集合属性的元素作为组件
@ElementCollection(targetClass = Scrore.clasa)
@CollectionTable(name = "score_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@MapKeyColumn(name = "subject_name")
@MapKeyClass(String.class)
private Map<String,Score> scores = new HashMap<>();
@ElementCollection(targetClass = Name.class)
@CollectionTable(name = "nick_inf",joinColumns = @JoinColumn(name = "person_id",nullable = false))
@OrderColumn(name = "list_order")
private List<Name> nicks = new ArrayList<>();
比较之前的list 他没有 @Column(name = "school_name")
它会默认采取list 的属性名称 就更一把的一样,其实这个,就是吧组件的两个属性
默认添加到附表的结构中 这是组件的一种性质吧
将组件作为map key
@ElementCollection(targetClass = Integer.class)
@CollectionTable(name = "nick_power_inf",
joinColumns = @JoinColumn(name = "person_id",nullable = false))
@Column(name = "nick_power",nullable = false)
@MapKeyClass(Name.class)
private Map<Name,Integer> nicjPower = new HashMap<>();
对于Name 要复写hashcode 和equals 方法.并且,要将Name 声明为 @Embedable
还是一样.组件,作为附表的一部分 p430
组件作为复合主键
@EmbeddedId
@AttributeOverrides({
@AttributeOverride(name = "frist",column = @Column(name = "person_firstName")),
@AttributeOverride(name = "last",column = @Column(name = "person_lastName"))
})
private Name name;
// @EmbeddedId 声明为主键.对于这种,就不需要在Name 上面做任何操作,只需要复写hashcode 和 equals
对于这种,组件的属性直接被添加到主表里面
----------------------------------------------------
hibernater 深入
@ManyToOne cascade fetch
无连接表的 n - 1 在n 端添加关系
多个人对应一个地址,只需要通过人找到地址就行,这是在 person 端,在地址端,不做任何操作
@ManyToOne(targetEntity = Address.class,cascade = CascadeType.ALL)
@JoinColumn(name = "address_id",nullable = false)
private Address address;
对于cascade.all ,只需要,在person 端,设置address 直接保存person.后,address,自动级连保存,先插入从表,在保存主表
有连接表的 n - 1 person 端
@ManyToOne(targetEntity = Address.class,cascade = CascadeType.ALL)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "person_id",unique = true),
inverseJoinColumns = @JoinColumn(name = "address_id",referencedColumnName = "address_id"))
private Address address;
对于 joinColumns 都是映射的主键和外建 unique 以perosn_id 作为唯一性列的参考 只许表中只有一个person id
单向的 1 1 的映射
@OneToOne(targetEntity = Address.class)
@JoinColumn(name = "address_id",referencedColumnName = "address_id",unique = true)
private Address address;
使用unquie 控制唯一性关系
对于mappedBy 表示不控制关系 orphanRemoval 删除孤儿实体 和cascade 两者存在一个就行
无连接表 单项 1 n 在n 端控制 信息.默认的在n 端添加外键
@OneToMany(targetEntity = Address.class)
@JoinColumn(name = "person_id",referencedColumnName = "person_id")
private Set<Address> addresses = new HashSet<>();
对于无连接表中,都已吧控制信息写在n 端,然后在 1 端,接受数据 referencedColumnName 映射到外面去的
对于这样的信息,没有cascade.all 所 (此外必须要先通过先实例化address_inf 才行)insert 外键为空address_inf ,然后在update address_inf 将person 的主键作为
address_inf 的外键.出现这样的原因,是应为 address_inf 不知 perosn_inf ,一直,没有将 person_id 作为自己的属性
可以通过双向的 1 n 链接解决问题 但是 1 端会 多出一条update 性能要比 n端低 p 447 (有点懵逼)
有链接表的单向 1 n 关联 person unique = true.address 关联一个address 地址,但是person 可以关联多个address
没有cascade 但是应为出现链接表,所以,无论实例化那个都可以 就是会不会出现幽灵数据,可以通过 cascade.all
来阻止这种情况发生 解决,以为有链接表,所以先实例哪一个对象,都可以,对于one 端 cascade.all 写不写,都是要删除附加表的信息
如果,要实现附表的删除,则需要手动删除
@OneToMany(targetEntity = Address.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "person_id"),
inverseJoinColumns = @JoinColumn(name = "address_id",
referencedColumnName = "address_id",unique = true))
private Set<Address> addresses = new HashSet<>();
对于单项的 n n ,必须使用连接表 不能使用 unquie ,如果使用 unquie 则变为 形式上变为 one to many
@ManyToMany(targetEntity = Address.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "person_id"),
inverseJoinColumns = @JoinColumn(name = "adress_id",referencedColumnName = "address_id"))
private Set<Address> addresses = new HashSet<>();
对于有链接表的,级连操作,都是第三张表
无连接表的双向1 n 连接
一般采用这种方式 mappedBy 放弃映射关系,可以直接使用
Peron
@OneToMany(targetEntity = Address.class,mappedBy = "person")
private Set<Address> addresses = new HashSet<>();
Address n 端控制关系 先持久化 person ,在持久化 address 这样可以保证效率
如果先持久化address 再持久化 person 所以,会产生三条语句,insert address insert person update address
@ManyToOne(targetEntity = Person.class)
@JoinColumn(name = "person_id",referencedColumnName = "person_id",nullable = false)
private Person person;
有链接表的双向 1 n
Peron
@OneToMany(targetEntity = Address.class,mappedBy = "person")
private Set<Address> addresses = new HashSet<>();
address
@ManyToOne(targetEntity = Person.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "address_id",referencedColumnName = "address_id",unique = true),
inverseJoinColumns = @JoinColumn(name = "person_id",referencedColumnName = "person_id"))
private Perosn person;
address_id和 person_id 作为主列键 对于有三表,一般都可以吧
看来joinColumns 有多种意思 我觉得这里不应该unique = true ,这里是正确的
就是对于多个属性的限制,只是在入库的时候,更加严格,
双向 n n 关联 因为是 n n 所以不能用 unquie
这里的 person_id 和address_id 都是主列键,谁先谁后,都一样,只是,按照一样的顺序,可以少写代码
@ManyToMany(targetEntity = Address.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "id"),
inverseJoinColumns = @JoinColumn(name = "address_id",referencedColumnName = "id"))
private Set<Address> addresses = new HashSet<>();
@ManyToMany(targetEntity = Person.class)
@JoinTable(name = "person_address",
joinColumns = @JoinColumn(name = "person_id",referencedColumnName = "id"),
inverseJoinColumns = @JoinColumn(name = "address_id",referencedColumnName = "id"))
private Set<Person> Person = new HashSet<>();
双向 1 1 对于主表,一端,应该放弃控制关系,要不然,会造成update的性能下降
peroson
@OneToOne(targetEntity = Address.class,mappedBy = "person")
private Address address;
address
@OneToOne(targetEntity = Person.class)
@JoinColumn(name = "person_id",referencedColumnName = "id",unique = true);
private Person person;
https://www.cnblogs.com/SpringSmallGrass/archive/2013/04/06/3002199.html
对于mapped 复习,双边关系,只需要一端维护就可以,拥有段,不用维护,被拥有段需要维护, 在被拥有段建立外键
one one many many one many 都可以建立 但是 many to one (控制关系都是n 端维护,) 没有这个属性,,这样的好处是,减少一条的update 语句.性能更好
对于这种级联删除,在拥有段控制关系,对于孤儿,可以通过one to many one to one ,启动级联.也就是主表
从表的生命周期完全在主表类可以采用 CascadeTpye.ALL 加 orphanRemoval =true
多主键,多外键,控制关系
Person
@Id
private String firstName;
@Id
private String lastName;
@OneToMany(targetEntity = Address,mappedBy = "person",cascade = CascadeType.ALL)
private Set<Address> addresses = new HashSet<>();
Address
@ManyToOne(targetEntity = Person.class)
@JoinColumns({
@JoinColumn(name = "person_first",referencedColumnName = "firstName",nullable = false),
@JoinColumn(name = "person_last",referencedColumnName = "lastName",nullable = false)
})
private Person perosn;
将成员为主键
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