英文:
Prevent creation of foreign keys in mapping tables?
问题
如何在Hibernate中防止创建外键？我需要将一些尚不存在的子项插入到我的“oneToMany”关系中。Hibernate应该忽略子项尚不存在的事实。
目前，当我尝试插入这些不存在的子项时，我会收到外键异常。因此，我需要禁用外键的创建和使用。
如何实现这一点？
@Entity@Table(name = "chunk", uniqueConstraints = {@UniqueConstraint(columnNames={"x", "y"})}, indexes = {@Index(columnList = "x,y")})@Access(value = AccessType.FIELD)@SelectBeforeUpdate(false)public class Chunk extends HibernateComponent{public int x;public int y;public Date createdOn;@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)@Fetch(FetchMode.JOIN)@BatchSize(size = 50)public Set<Identity> inChunk = new LinkedHashSet<>();@Transientpublic Set<ChunkLoader> loadedBy = new LinkedHashSet<>();public Chunk() {}public Chunk(int x, int y, Date createdOn) {this.x = x;this.y = y;this.createdOn = createdOn;}}
我们如何实现这一点？
英文:
How do we prevent the creation of foreign keys in hibernate ?
I need to insert some childs into my "oneToMany" relationship which do not exist yet. Hibernate should just ignore the fact that the childs do not exist yet.
Currently i receive a foreign key exception once i try to insert those non existing childs. So i need to disable the foreign key creation/useage.
@Entity@Table(name = "chunk", uniqueConstraints = {@UniqueConstraint(columnNames={"x", "y"})}, indexes = {@Index(columnList = "x,y")})@Access(value = AccessType.FIELD)@SelectBeforeUpdate(false)public class Chunk extends HibernateComponent{public int x;public int y;public Date createdOn;@OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)@Fetch(FetchMode.JOIN)@BatchSize(size = 50)public Set<Identity> inChunk = new LinkedHashSet<>();@Transientpublic Set<ChunkLoader> loadedBy = new LinkedHashSet<>();public Chunk() {}public Chunk(int x, int y, Date createdOn) {this.x = x;this.y = y;this.createdOn = createdOn;}}
How do we achieve this ?
答案1
得分: 0
我找到了一个解决方案... 不必让 hibernate 完全自己创建联接表，你可以通过使用 "JoinTable" 来修改创建过程。
@Entity@Table(name = "chunk", uniqueConstraints = {@UniqueConstraint(columnNames={"x", "y"})}, indexes = {@Index(columnList = "x,y")})@Access(value = AccessType.FIELD)@SelectBeforeUpdate(false)public class Chunk extends HibernateComponent{public int x;public int y;public Date createdOn;@OneToMany(fetch = FetchType.EAGER, cascade = {})@JoinTable(name = "chunk_identity", joinColumns = @JoinColumn(name = "identity_id"), inverseJoinColumns = @JoinColumn(name = "id"), inverseForeignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT))@Fetch(FetchMode.JOIN)@BatchSize(size = 50)public Set<Identity> inChunk = new LinkedHashSet<>();@Transientpublic Set<ChunkLoader> loadedBy = new LinkedHashSet<>();public Chunk() {}public Chunk(int x, int y, Date createdOn) {this.x = x;this.y = y;this.createdOn = createdOn;}}
这样我们就可以定义是否需要外键，或者是否可以简单地忽略它。
英文:
I found an solution... instead of letting hibernate create the join table completly by yourself you can modify the creation with "JoinTable".
@Entity@Table(name = "chunk", uniqueConstraints = {@UniqueConstraint(columnNames={"x", "y"})}, indexes = {@Index(columnList = "x,y")})@Access(value = AccessType.FIELD)@SelectBeforeUpdate(false)public class Chunk extends HibernateComponent{public int x;public int y;public Date createdOn;@OneToMany(fetch = FetchType.EAGER, cascade = {})@JoinTable(name = "chunk_identity", joinColumns = @JoinColumn(name = "identity_id"), inverseJoinColumns = @JoinColumn(name = "id"), inverseForeignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT))@Fetch(FetchMode.JOIN)@BatchSize(size = 50)public Set<Identity> inChunk = new LinkedHashSet<>();@Transientpublic Set<ChunkLoader> loadedBy = new LinkedHashSet<>();public Chunk() {}public Chunk(int x, int y, Date createdOn) {this.x = x;this.y = y;this.createdOn = createdOn;}}
This way we can define if we need an foreign key or if we can simply ignore it.
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