Hibernate JPA：无法将字段x设置为x

Question

我有一个项目班：

@Entity
public class Project implements Serializable{

private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name="id", unique=true )
private Long id;

@Column(name="name", nullable=false, unique = true)
private String name;

@OneToMany(mappedBy="projectid", fetch = FetchType.EAGER)
private Set<Collaborator> collaborators = new HashSet<>();

public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}
}

然后是合作者：

@Entity
public class Collaborator implements Serializable{

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "id", unique = true, nullable = false)
private Long id;

@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(nullable = true)
private Project projectid;

public Long getId() {
    return id;
}

public void setId(Long id) {
    this.id = id;
}
}


public Project getProjectid() {
    return projectid;
}

public void setProjectid(Project projectid) {
    this.projectid = projectid;
}

在我的DAO中,我想执行以下查询：

@Query("select c from Collaborator as c where c.projectid = ?1 and  c.showable = true")
List<Collaborator> findAllShowableCollaboratorsByProjectidAndShowableTrue(Long projectId);

null

如有任何帮助，我将不胜感激。谢谢。

Answer 1

您的协作者中的ProjectID是Project对象，而不是Long对象。因此将存储库方法更改为：

@Query("select c from Collaborator as c where c.projectid.id = ?1 and  c.showable = true")
List<Collaborator> findAllShowableCollaboratorsByProjectidAndShowableTrue(Long projectId);  

>

注意，不建议使用位置参数绑定，因为参数的顺序无法更改（在您的情况下，似乎没有问题，因为只有一个参数）。我建议你改变一下：

@Query("select c from Collaborator as c where c.projectid.id = :pid and  c.showable = true")
List<Collaborator> findAllShowableCollaboratorsByProjectidAndShowableTrue(@Param("pid") Long pid);  

使用projectID作为类型为project的字段名有点混乱。将名称更改为project这样的名称更好。