Hibernate how to use constants as part of the composite external reference

@Entity public class Master {
 @Id
 @Column(name = "SIGNIFICANT_KEY")
 private String realKey;

 @Id
 @Column(name = "CONSTANT_KEY")
 private String constantPartKey;
}

@Entity public class Detail {
 @ManyToOne
 @JoinColumnsOrFormulas(value={
 @JoinColumnOrFormula(column=
 @JoinColumn(name = "SIGNIFICANT_KEY",
 referencedColumnName = "SIGNIFICANT_KEY",
 insertable=false, updatable=false, nullable = false)),
 @JoinColumnOrFormula(formula=
 @JoinFormula(referencedColumnName="CONSTANT_KEY", value="'THE CONSTANT VALUE'"))
 })
 Master master;
}

@Entity
public class Strange {
 @Id
 private Long id;

 @Column
 private long constant = 345; // the constant that you want in yo ur database

 @OneToMany(mappedBy = "strange")
 private Set details;

 ...
 // no setter for constant!
}

@Entity
public class Detail {
 ...
 @ManyToOne
 @JoinColumn(name = "strange_id" )
 private Strange strange;
}

@Entity
public class Strange {
 @Id
 @Column(name = "strange_id")
 private Long id;

 @Id
 private long constant = 345; // the constant that you want in your database

 @OneToMany(mappedBy = "strange")
 private Set details ;

 ...
 // no setter for constant!
}

@Entity
public class Detail {
 ...
 @ManyToOne
 @JoinColumn(name = "strange_id", referencedColumnName = "strange_id")
 private Strange strange;
}

I have a main table A, which contains a The composite primary key consists of two columns. One of the columns is a constant (“constant value” in the code below). The table definition is as follows:

@Entity public class Master {
 @Id
 @Column(name = "SIGNIFICANT_KEY")
 private String realKey;

 @Id
 @Column(name = "CONSTANT_KEY")
 private String constantPartKey;
}

I have a detailed information table B that uses only one (non-constant) column to reference main table A. I want to use two Realize the usual ManyToOne and OneToMany relationships between tables.

Question: How to use Hibernate to handle this situation?

The only master reference solution I found relies on using the formula:

@Entity public class Detail {
 @ManyToOne
 @JoinColumnsOrFormulas(value={
 @JoinColumnOrFormula(column=
 @JoinColumn(name = "SIGNIFICANT_KEY",
 referencedColumnName = "SIGNIFICANT_KEY",
 insertable=false, updatable=false, nullable = false)),
 @JoinColumnOrFormula(formula=
 @JoinFormula(referencedColumnName="CONSTANT_KEY", value="'THE CONSTANT VALUE'"))
 })
 Master master;
}

Now I see other problems: due to the java.lang.ClassCastException I reported earlier, I cannot use this field in the OneToMany relationship: https://hibernate.onjira .com/browse/HHH-6811

I really want to know how useful it is to have a constant column value in the database, but anyway… < p>

What I want to do is only map the non-constant column to ID, and make the constant column a regular column with constant value:

@ Entity
public class Strange {
 @Id
 private Long id;

 @Column
 private long constant = 345; // the constant that you want in your database

 @OneToMany(mappedBy = "strange" )
 private Set details;

 ...
 // no setter for constant!
}

@Entity< br />public class Detail {
 ...
 @ManyToOne
 @JoinColumn(name = "strange_id")
 private Strange strange;
}

If other entities refer to the same Strange entity using its complete composite key, you only need to do the following:

@Entity
public class Strange {
 @Id
 @Column(name = "strange_id")
 private Long id;

 @Id
 private long constant = 345; // the constant that you want in your database

 @OneToMany(mappedBy = "strange")
 private Set details;

 ...
 // no setter for constant!
}

@Entity
public class Detail {
 ...
 @ManyToOne
 @JoinColumn(name = "strange_id", referencedColumnName = "strange_id")
 private Strange strange;
}

You can use entities other than PK to refer to other entities. Another unique column will also work. And because strange_id is unique, it meets the requirements. In this case, the referenced column name must be specified using the referencedColumnName property.

< /p>