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Howo to query tables with onetomany and manytoone relationships using Ebean

I am using Play Framework 2.1.0 and Ebean, and I had a problem requesting the following scripts listed below:

I have 3 classes that represent tables in a database.

class project {
   ...
   @OneToMany
   public SubProject sub;   
}

class SubProject {
   ...
   @ManyToOne
   public Project project;

   @OneToMany 
   public MiniProject mini;    
}   

class MiniProject {
  ...
  @ManyToOne
  public SubProject sub;    
}

Using ebean as

  • get all the subprojects of the project list?

  • get all the miniprojects of the project?

  • given a list of subprojects, how to get all miniprojects?

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3 answers

First of all, you incorrectly defined your classes. Your @OneToMany annotations must be defined above the item lists. I adjusted these mappings, and then I wrote a testing method, getting the right queries. Here is the code:

Project Class:

@Entity  
public class Project {

    @Id
    public Long id;

   @OneToMany(mappedBy="project")
   public List<SubProject> subprojects;
}

SubProject Class:

@Entity 
public class SubProject {

    @Id
    public Long id;

    @ManyToOne
    public Project project;

    @OneToMany(mappedBy="subproject") 
    public List<MiniProject> miniprojects; 
}

MiniProject:

@Entity 
public class MiniProject {

    @Id
    public Long id;

    @ManyToOne
    public SubProject subproject;
}

:

@Test
public void subTest () {
    FakeApplication app = Helpers.fakeApplication(Helpers.inMemoryDatabase());
    Helpers.start(app);

    Project p1 = new Project();
    p1.id=1L;

    SubProject s1 = new SubProject();
    SubProject s2 = new SubProject();
    s1.id=1L;
    s2.id=2L;

    p1.subprojects.add(s1);
    p1.subprojects.add(s2);
    s1.project = p1;
    s2.project = p1;

    MiniProject m1 = new MiniProject();
    MiniProject m2 = new MiniProject();
    MiniProject m3 = new MiniProject();
    MiniProject m4 = new MiniProject();

    m1.id=1L;
    m2.id=2L;
    m3.id=3L;
    m4.id=4L;

    s1.miniprojects.add(m1);
    s1.miniprojects.add(m2);
    s2.miniprojects.add(m3);
    s2.miniprojects.add(m4);

    m1.subproject =s1;
    m2.subproject =s1;
    m3.subproject =s2;
    m4.subproject =s2;

    Ebean.save(p1);
    Ebean.save(s1);
    Ebean.save(s2); 
    Ebean.save(m1);
    Ebean.save(m2);
    Ebean.save(m3);
    Ebean.save(m4);

    // retrieve all the subprojects of a list of Projects
    List<Long> projectIds = new ArrayList<Long>();
    projectIds.add(1L);     
    List<SubProject> subList = Ebean.createQuery(SubProject.class).where(Expr.in("project.id", projectIds)).findList();

    // retrieve all the miniprojects of a Project 
    Long projectId = 1L;
    List<MiniProject> miniList = Ebean.createQuery(MiniProject.class).where(Expr.eq("subproject.project.id", projectId)).findList();

    // given a list of sub projects , how to retrieve all the miniprojects
    List<Long> subprojectIds = new ArrayList<Long>();
    subprojectIds.add(1L);      
    List<MiniProject> miniSubList = Ebean.createQuery(MiniProject.class).where(Expr.in("subproject.id", subprojectIds)).findList();


    for(SubProject sub: subList) {
        System.out.println("subproject: "+sub.id);
    }
    System.out.println("-----------");
    for(MiniProject mini: miniList) {
        System.out.println("miniproject: "+mini.id);
    }
    System.out.println("-----------");
    for(MiniProject mini: miniSubList) {
        System.out.println("miniproject: "+mini.id);
    }
}
+3

, , List<SubProject> Set<SubProject> OneToMany ( MiniProject):

?

select s from Project p inner join p.subProjects s where p.id in :projectIds

?

select m from Project p 
inner join p.subProjects s 
inner join s.miniProjects m
where p.id = :projectId

, .

:

select m from SubProject s inner join s.miniProjects m where s.id in :subProjectIds
0

Define a helper in your classes

public static Finder<Long, YourClass> find = new Finder<Long, YourClass>(Long.class, YourClass.class);

Requests:

SubProject.find.where().in("project", listOfProject)
MiniProject.find.where().eq("sub.project",yourProject)
MiniProject.find.where().in("sub", listOfSubProject)
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