(playframework 2.0.2-java) EBean - No ScalarType registered error when querying with enum values

问题

I have Role entity class:

@Entity
public class Role extends Model {

    @Id
    @Constraints.Required
    public Integer id;

    @Constraints.Required
    @Formats.NonEmpty
    @Enumerated(EnumType.STRING)
    public RoleNameEnum name; // name is enum value
}

In some test I try to find users by role:

List<User> users = User.findByRole(Role.findByRoleName(RoleNameEnum.ADMIN));

where method findByRoleName() is following:

public static List<User> findByRole(Role role) {
    return find.where().eq("role", role).findList();
}

I receive error:

[error] Test UserTest.findUsersByRole failed: No ScalarType registered for class models.Role
[error]     at com.avaje.ebeaninternal.server.persist.Binder.bindObject(Binder.java:183)
[error]     at com.avaje.ebeaninternal.server.query.CQueryPredicates.bind(CQueryPredicates.java:162)
[error]     at com.avaje.ebeaninternal.server.query.CQuery.prepareBindExecuteQuery(CQuery.java:413)
[error]     at com.avaje.ebeaninternal.server.query.CQueryEngine.findMany(CQueryEngine.java:198)
[error]     at com.avaje.ebeaninternal.server.query.DefaultOrmQueryEngine.findMany(DefaultOrmQueryEngine.java:104)
[error]     at com.avaje.ebeaninternal.server.core.OrmQueryRequest.findList(OrmQueryRequest.java:344)
[error]     at com.avaje.ebeaninternal.server.core.DefaultServer.findList(DefaultServer.java:1469)
[error]     at com.avaje.ebeaninternal.server.querydefn.DefaultOrmQuery.findList(DefaultOrmQuery.java:906)
[error]     at com.avaje.ebeaninternal.util.DefaultExpressionList.findList(DefaultExpressionList.java:201)
[error]     at models.User.findByRole(User.java:63)
[error]     at UserTest$4.run(UserTest.java:62)
[error]     at play.test.Helpers.running(Helpers.java:294)
[error]     at UserTest.findUsersByRole(UserTest.java:58)

Does anybody have an idea what might be a problem?

回答1:

The quickest solution, assuming that you are mapping EnumValue exactly the same as the enum names:

public enum RoleNameEnum {
    @EnumValue("REGULAR")
    REGULAR,
    @EnumValue("ADMIN")
    ADMIN
}

Then you can implement the findByRole method as following:

public static List<User> findByRole(Role role) {
    return find.where().eq("role", role.name()).findList();
}

where the magic is just using the mapped string value instead of the enum instance for the role name.

I posted a bug on the ebean issue tracker: http://www.avaje.org/bugdetail-427.html, binder should detect the enum object and interpret it as its mapped value automatically.

EDIT:

In case that you need some other mapping than the simple enum value, here it is the utility code to get the value set using the @EnumValue annotation

public static <T extends Enum<T>> String serialize(T theEnum) {
    try {
        for (Field f : theEnum.getDeclaringClass().getDeclaredFields()) {
            if (theEnum.equals(f.get(theEnum))) {
                EnumValue enumValue = f.getAnnotation(EnumValue.class);
                if (enumValue != null)
                    return enumValue.value();
            }
        }
    } catch (Exception e) {
    }
    return null;
}

Then you can implement findByRole using the serialize method

public static List<User> findByRole(Role role) {
    return find.where().eq("role", serialize(role)).findList();
}

回答2:

Looks like the issue is that you have a roles list, not a single property on your user.

@Constraints.Required
@ManyToMany
public List<Role> roles = new ArrayList<Role>();

To query against that list, try:

public static List<User> findByRole(Role role) {
    return find.where().in("roles", role).findList();
}

来源：https://stackoverflow.com/questions/11960329/playframework-2-0-2-java-ebean-no-scalartype-registered-error-when-querying

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