@UniqueConstraints 更新失败

Question

我有一个实体类，在其中添加了 uniqueconstraint 注释，

@Table(uniqueConstraints={@UniqueConstraint(columnNames={"staffRecord_id", "defaultLabel_id","company_id","keyCode"})})
public class AllowanceDeduction implements Serializable{
---

我注意到当我尝试保存在表上时 使用

 if (allowanceDeduction.getId() == null) {
            this.entityManager.persist(allowanceDeduction);
        } else {

            this.entityManager.merge(allowanceDeduction);
        }


when the save or update fails due to a unique constraint. Isn't it only supposed to fail when trying to save a new record that is identical to a record that already exist.

为什么尝试合并或更新时会失败？ 请需要帮助

Answer 1

我不能肯定地说，但看起来你正试图保留一个 null id

if (allowanceDeduction.getId() == null) {
        this.entityManager.persist(allowanceDeduction);
        /* don't you need the id set to a non-null value in order to persist it? */
    } else {