How to handle unidirectional many-to-many relations with Ebean

Question

I have a problem with Ebean. I have the usual Objects PsecUser, PsecRoles and PsecPermission. A user can have many Permissions or Roles and a Role can have many Permission. Here the code (extract):

@Entity
public class PsecPermission {

    @Id
    @GeneratedValue
    private Long id;

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

    @Column(nullable=false)
    private String type = PsecBasicPermission.class.getName();

    @Column(nullable=false)
    private String target;

    @Column(nullable=false)
    private String actions;

}


@Entity
public class PsecRole  {

    @Id
    @GeneratedValue
    private Long id;

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

    @Temporal(TemporalType.TIMESTAMP)
    private Date lastUpdate;

    @ManyToMany(fetch=FetchType.EAGER)
    private List<PsecPermission> psecPermissions;

    private boolean defaultRole = false;

}

I wrote the following helper-method:

public PsecRole createOrUpdateRole(String name, boolean defaultRole, String... permissions) {
        PsecRole result = server.find(PsecRole.class).
                where().eq("name", name).findUnique();
        if (result == null) {
            result = new PsecRole();
            result.setName(name);
        }
        final List<PsecPermission> permissionObjects = server.find(PsecPermission.class).
                where().in("name", (Object[])permissions).findList();
        result.setPsecPermissions(permissionObjects);
        result.setDefaultRole(defaultRole);
        final Set <ConstraintViolation <PsecRole>> errors = 
                Validation.getValidator().validate(result);
        if (errors.isEmpty()) {
            server.save(result);
            server.saveManyToManyAssociations(result, "psecPermissions");
        } else {
            log.error("Can't save role: " + name +"!");
            for (ConstraintViolation <PsecRole> constraintViolation : errors) {
                log.error("   " + constraintViolation);
            }
        }
        return result;
}

and try the following test:

@Test
public void testCreateOrUpdateRole() {
    String[] permNames = {"Test1", "Test2", "Test3"};
    List <PsecPermission> permissions = new ArrayList <PsecPermission>();
    for (int i = 0; i < permNames.length; i++) {
        helper.createOrUpdatePermission(permNames[i], "target"+ i, "actions" +i);
        PsecPermission perm = server.find(PsecPermission.class).where().eq("name", permNames[i]).findUnique();
        assertThat(perm.getTarget()).isEqualTo("target" + i);
        assertThat(perm.getActions()).isEqualTo("actions" + i);
        permissions.add(perm);
    }

    PsecRole orgRole = helper.createOrUpdateRole(ROLE, false, permNames);
    testRole(permNames, orgRole);
    PsecRole role = server.find(PsecRole.class).where().eq("name", ROLE).findUnique();
    testRole(permNames, role);

}
private void testRole(String[] permNames, PsecRole role) {
    assertThat(role).isNotNull();
    assertThat(role.getName()).isEqualTo(ROLE);
    assertThat(role.isDefaultRole()).isEqualTo(false);
    assertThat(role.getPermissions()).hasSize(permNames.length);
}

Which fails if it checks the number of permissions at the readed role. It's always 0. I looked into the database and found that psec_role_psec_permission is alway empty.

Any idea what's wrong with the code?

You can get a pure Ebean-example from https://github.com/opensource21/ebean-samples/downloads it uses the eclipse-plugin from ebean.

Answer 1

There are two solutions for this problem:

Simply add cascade option at PsceRole

@ManyToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL)
private List<PsecPermission> psecPermissions;

and remove server.saveManyToManyAssociations(result, "psecPermissions"); you find it in the cascade-solution-branch.

The cleaner solution, because you don't need to define cascase- perhaps you don't want it: Just don't replace the list, just add your entries to the list. Better is to add new and remove old one. This mean in createOrUpdateRole:

result.getPsecPermissions().addAll(permissionObjects);

instead of

result.setPsecPermissions(permissionObjects);