Question

I java ee项目有两个实体类别:Employee和Shft,它们之间有许多重复工作。它希望:



    @Entity
    public class Employee implements Serializable {
    @ManyToMany(mappedBy="employees")
    private List shifts;
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String surname;
    private String firstname;

......



    @Entity

    public class Shift implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    @Temporal(javax.persistence.TemporalType.TIMESTAMP)
    private Date timeStart;
    @Temporal(javax.persistence.TemporalType.TIMESTAMP)
    private Date timeEnd;
    private int workers;
    private int overseers;
    @ManyToMany
    private List employees;

我有一个共同基金网页,希望把雇员(一个或一个)增到在我背后的传票上选择的班子:



    public void addToShift(Employee e){
            selectedShift.addEmployee(e);
            e.addShift(selectedShift);      
    }

After the method is called, i see nothing in the join table. I tried a few things, like looking up the entities again using entitymanager.find, but nothing really helped, i can t see anything in the join table and i can t see why. There were no problem managing employees and shift, it s "just" the connection...... Do you have any ideas?

Answer 1

Simply setting values to detached entities is not enough. You still have to call EntityManager.merge inside transaction. Then after when transaction is committed (or entitymanager is flushed) you will see results in database as well.

如果持续存在的情况仍然开放(在你看来不是这样),光靠流动是不够的,不需要合并。

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