JPA复合键可为空的列

@Entity
public class MyEntity {
    @EmbeddedId
    private MyCompoundKey id;

    // other fields and methods

    @Embeddable
    public static class MyCompoundKey implements Serializable {
        @Column(name = "column1")
        private String column1;

        @Column(name = "column2")
        private String column2;

        // constructor, getters, setters, equals, hashCode, etc.

        @AttributeOverride(name = "column1", column = @Column(name = "column1", nullable = true))
        public String getColumn1() {
            return column1;
        }

        @AttributeOverride(name = "column2", column = @Column(name = "column2", nullable = true))
        public String getColumn2() {
            return column2;
        }
    }
}