java - hibernate 查询。 Actor 类

Question

有hql查询

List<Developer> developers = session.createQuery("from Developer d " +
              "left join ProjectDeveloper pd on pd.developer.id = d.id " +
              "where pd.project.id = " + project.getId()).getResultList();

它可以工作并获取对象列表，但不是开发人员。

其实，i get 得到的对象看起来像是一个数组列表，其中包含了对象数组，其中又包含了开发者类对象和ProjectDeveloper(mtm类)。不幸的是，我无法放置与图像的链接，但架构如下所示:

developers = {ArrayList@4889} size = 4 
 \/ 0 = {object[2]4897} //what does this do in ArrayList<**Developer**>>??
    -> 0 = {Developer@4901} //This is exactly the class I expect in ArrayList
    -> 1 = {ProjectDeveloper}//?????
 -> 1 = {object[2]4898}

开发者类别:

@Table(name = "developers")
@Entity
public class Developer implements GenerallyTable{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private long id;
    @Column(name = "first_name")
    private String name;     
    @Column(name = "age")
    private int age;     
    @Column(name = "sex")
    private boolean sex;    
    @Column(name = "salary")
    private BigDecimal salary;
//...getters + setters
}

这怎么可能(Developer.class 如何转换为结构未知的数组)，以及如何才能准确获取 Developers 的 ArrayList？

Answer 1

尝试使用 createQuery 定义类型 https://docs.jboss.org/hibernate/orm/5.2/javadocs/org/hibernate/Session.html#createQuery-java.lang.String-java.lang.Class-

List<Developer> developers = session.createQuery("select d from Developer d " +
                    "left join ProjectDeveloper pd on pd.developer.id = d.id " +
                    "where pd.project.id = " + project.getId(), Developer.class)
                    .getResultList();

您还应该使用setParameter方法

List<Developer> developers = session.createQuery("select d from Developer d " +
                    "left join ProjectDeveloper pd on pd.developer.id = d.id " +
                    "where pd.project.id = :proj_id", Developer.class)
                    .setParameter("proj_id", project.getId())
                    .getResultList();