如何使用JPA保留两个实体

当持久保存关系的非所有权方的一个实例（包含“ mappedBy”并且在您的情况下为“消费者”）时，您必须 始终
确保将关系的双方都设置为具有预期的级联工作。

您当然应该总是这样做，以确保您的域模型正确。

Consumer c = new Consumer();ProfilePicure p = new ProfilePicture();c.setProfilePicture(p);//see implementation//persist c

消费者.java

    @Entity    @Table(name = "Consumer")    @NamedQueries({...})    public class Consumer implements Serializable {        @Id        @GeneratedValue(strategy = GenerationType.IDENTITY)        @Basic(optional = false)        @Column(name = "id")        private Integer id;        @Basic(optional = false)        @NotNull        @Size(min = 1, max = 50)        @Column(name = "userName")        private String userName;        @oneToOne(cascade = CascadeType.ALL, mappedBy = "consumer")        private ProfilePicture profilePicture;        public void setProfilePicture(ProfilePicture profilePicture){ //SET BOTH SIDES OF THE RELATIonSHIP this.profilePicture = profilePicture; profilePicture.setConsumer(this);        }}

始终封装添加/删除关系，然后可以确保正确性：

public class Parent{private Set<Child> children;public Set<Child> getChildren(){    return Collections.unmodifiableSet(children); //no direct access:force clients to use add/remove methods}public void addChild(Child child){    child.setParent(this);     children.add(child);}public class Child(){    private Parent parent;}