Gavin King ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) *created* an issue Hibernate ORM ( https://hibernate.atlassian.net/browse/HHH?atlOrigin=eyJpIjoiN2M0MjI3ZmM3... ) / Bug ( https://hibernate.atlassian.net/browse/HHH-16592?atlOrigin=eyJpIjoiN2M0Mj... ) HHH-16592 ( https://hibernate.atlassian.net/browse/HHH-16592?atlOrigin=eyJpIjoiN2M0Mj... ) @MapsId and @ManyToOne ( https://hibernate.atlassian.net/browse/HHH-16592?atlOrigin=eyJpIjoiN2M0Mj... ) Issue Type: Bug Assignee: Unassigned Components: hibernate-core Created: 11/May/2023 12:03 PM Priority: Major Reporter: Gavin King ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%... ) It seems very clear that the JPA spec expects the following mapping to work: @Entity static class Loan { @Id @Column(name = "LOAN_ID") private Long id; @OneToMany(cascade = CascadeType.ALL, mappedBy = "loan") private List<Extension> extensions = new ArrayList<>(); } @Entity static class Extension { @Id @Column(name = "EX_LOAN_ID") private Long exLoanId; @Id @Column(name = "EX_NO") private Long exNo; @Column(name = "EX_EXTENSION_DAYS") private Long exExtensionDays; @ManyToOne @MapsId @JoinColumn(name = "EX_LOAN_ID") private Loan loan; } The workaround is to use insertable=false, updateable=false instead of @MapsId. @Entity static class Loan { @Id @Column(name = "LOAN_ID") private Long id; @OneToMany(cascade = CascadeType.ALL, mappedBy = "loan") private List<Extension> extensions = new ArrayList<>(); } @Entity static class Extension { @Id @Column(name = "EX_LOAN_ID") private Long exLoanId; @Id @Column(name = "EX_NO") private Long exNo; @Column(name = "EX_EXTENSION_DAYS") private Long exExtensionDays; @ManyToOne @JoinColumn(name = "EX_LOAN_ID", insertable = false, updatable = false) private Loan loan; } ( https://hibernate.atlassian.net/browse/HHH-16592#add-comment?atlOrigin=ey... ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-16592#add-comment?atlOrigin=ey... ) Get Jira notifications on your phone! Download the Jira Cloud app for Android ( https://play.google.com/store/apps/details?id=com.atlassian.android.jira.... ) or iOS ( https://itunes.apple.com/app/apple-store/id1006972087?pt=696495&ct=Em... ) This message was sent by Atlassian Jira (v1001.0.0-SNAPSHOT#100225- sha1:84d3b45 )