Question

我有两个表具有ManyToOne关系。我需要显示我的ManyToOne关系的特定行，但是在页面和控制台中都不会显示任何内容。（它甚至没有显示生成的SQL，尽管Hibernate显示了生成的代码的其他部分的SQL）

Project.java

@Entity
@Table(name = "Project")
@DynamicUpdate
public class Project implements Serializable{ 

  private int id;
  private String Name;
  private Developer developer;

  @Id
  @GeneratedValue
  public int getID() {
      return id; 
  }

  @ManyToOne(cascade = CascadeType.ALL)
  public Developer getDeveloper() {
     return developer;
  }
  ....

}

Developer.Java

@Entity()
@Table(name = "developer")
@DynamicUpdate
public class Developer implements Serializable {    
  private int id;
  private String name;

  @Id
  @GeneratedValue
  public int getID() {
      return id; 
  }
  .....
}

Model.Java

        Criteria criteria = session.createCriteria(Project.class, "project")
                .createAlias("project.developer", "developer");
        try{
        ProjectionList pl = Projections.projectionList();
        pl.add(Projections.property("project.id").as("id"));
        pl.add(Projections.property("project.name").as("name"));

        criteria.setProjection(pl);

        criteria.setResultTransformer(new
             AliasToBeanResultTransformer(ListOfProjectsSearchResult.class));

         criteria.add(Restrictions.eq("developer.id", 1));
        }catch(Exception e){

          e.printStackTrace();
        }

        return criteria.list();

Answer 1

由于您未在投影列表中包含Developer的任何字段，因此Hibernate不会返回该表的任何字段。但是由于WHERE子句，它会使用Developer表创建内部联接，如此生成的SQL查询所示：

select
    this_.id as y0_,
    this_.name as y1_
from Project this_
    inner join developer developer1_
        on this_.developer_id=developer1_.id
where developer1_.id=?

如果您在投影列表中添加Developer字段，Hibernate会将该字段添加到生成的查询的SELECT子句中。

添加您的代码：

pl.add(Projections.property("developer.name").as("developerName"));

在developerName课程中添加ListOfProjectsSearchResult属性（如果该属性不存在）并再次执行您的代码。生成的SQL查询应该类似于：

select
    this_.id as y0_,
    this_.name as y1_,
    developer1_.name as y2_
from Project this_
    inner join developer developer1_
        on this_.developer_id=developer1_.id
where developer1_.id=?

Hibernate不会在ManyToOne关系上显示select的结果

1 个答案: