I have classes Car that has field Driver driver and Driver that inherites from Employee. Employee has field id.
I have to find and provide to frontend the driver's id for the car using JPA Criteria and metamodel. It turnes out difficult because id is inherited from superclass. The query should be made by:
public static <U, T, P> Specification<U> isEqualTo(SingularAtribute<U, T> joinField, SingularAtribute<T, P>, field, P param{
if (param == null){
return null;
}
return (root, query, cb) -> cb.equal(root.join(joinField).get(field), param);
}
However when I want to use it in:
static Specification<Car> hasDriverId(Long value){
return isEqualTo(Car_.driver, Driver_id, value);
}
I get error:
method isEqualTo cannot be aplied to given types;
required: SingularAtribute<U,T>, SingularAtribute<T,P>, P
found: SingularAtribute<Car, Driver>, SingularAtribute<Employee, Long>, Long
reason: inference variable T has incompatible equality constraints Employee, Driver
I know that inheritance can cause problems in ORM however I cannot change it in project. Is there way to overcome this?
Related
In my code Appointment is a entity and Long id is its primary key.
In the below code when i write findById(Long id), the return type required is Optional.
But when i write findAppointmentById(Long id), the return type required is Appointment.
What is difference between findById(Long id) and findAppointmentById(Long id) ??
public interface AppointmentDao extends CrudRepository<Appointment, Long>{
Optional<Appointment> findById(Long id);
}
What is difference between findById(Long id) and findAppointmentById(Long id) ??
The difference is findById(id) is already declared in the CrudRepository interface as returning an Optional, and overriding a return type of Optional with an unrelated Appointment type is not allowed in Java
But why does findAppointmentById(Long id) return Appointment ? Is it because its a derived query and since i wrote Appointment in the query ,it will return Appoinment?
No, it's because you declared it to return Appointment. You can declare it to return Optional<Appointment> and it will work just as well. You can put anything you like between find... and ...By, Spring Data will simply ignore it.
I am trying to retrieve a USER from my database using the ID in the WHERE clause. However I am receiving an error and my program is failing.
This is the error I'm receiving when I run my program:
ERROR [org.jboss.as.ejb3.invocation] (default task-19)
JBAS014134: EJB Invocation failed on component CustomerServiceBeanImpl
for method public abstract package.name.entity.ICustomer
package.name.bean.CustomerServiceBean.getCustomerById(long):
javax.ejb.EJBException: java.lang.IllegalArgumentException:
Parameter value [19533] did not match expected type [package.name.entity.User (n/a)]
Note: [19533] is a test value I used.
This is the method that is having the error in the CustomerServiceBeanImpl.java:
#Override
public Customer getCustomerById (final long id)
{
return Customer.getById (this.em, id);
}
This is the method that's being called by the component CustomerServiceBeanImpl:
public static Customer getById (final EntityManager em, final long id)
{
for (final Customer c : em.createNamedQuery ("Customer.getById", Customer.class)
.setParameter ("id", id).setMaxResults (1).getResultList ())
{
return c;
}
return null;
}
The name query is this:
#NamedQuery (name = "Customer.getById",
query = "SELECT o FROM gnf.Customer o WHERE o.user = :id")
In the Customer.java class itself the relevant column is this one:
#ManyToOne (fetch = FetchType.LAZY)
#JoinColumn (name = "user_id")
private User user;
Doing a quick check of my ERD the "id" column in my "customer" table has a data type of BIGINT. However I'm not sure if that matters. (PostgreSQL database by the way.)
How can I fix this error?
The WHERE clause in your named query seems to be the problem. The attribute user in your Customer.class is of type User and your query expects it to be a type compatible to long.
...
Parameter value [19533] did not match expected type [package.name.entity.User ...
So if you need more help on this it would be great to see the complete entities User and Customer.
It is happening because in your database the parameter will be a #oneToOne object and you have to call the id inside the Object so you have to give the query as following :
"select user from User user where user.customer.id=:param"
i have entity Request that have #ManyToMany Set<Region> regions, and Region entity have field region of type RegionEnum of enum type with constants of regions.
I need to create criteria to get requests, where its regions are in collection of RegionEnum;
In my choice:
List<RegionEnum> regs=...; // from method parameter
CriteriaBuilder cb=em.getCriteriaBuilder();
CriteriaQuery<Request> cq=cb.createQuery(Request.class);
Root<Request> from=cq.from(Request.class);
cq.where(cb.isTrue(from.join("regions").get("region").in(regs)));
return em.createQuery(cq).getResultList();
I have an java.lang.IllegalArgumentException: PREDICATE_PASSED_TO_EVALUATION (There is no English translation for this message.)
enum:
public enum RegionEnum {
CENTRAL("Центральный"),
SOUTH("Южный"),
NWEST("Северо-Западный"),
FEAST("Дальневосточный"),
SIB("Сибирский"),
URFO("Уральский"),
VOLGA("Волжский"),
NCAU("Северо-Кавказский");
private final String value;
private Region(String value) {
this.value=value;
}
public String value() {
return this.value;
}
}
is my criteria right and problem with enum? or criteria is bad?
I have faced with the same exception today so I tried to solve the problem.
Let's assume we have the following instances already initialized (as in your example):
CriteriaBuilder cb;
List<String> values;
Root<Entity> r; // where Entity has String name attribute
Now we can create a Predicate instance this way which is working using EclipseLink 2.6.2 library:
Predicate good = r.get("name").in(values);
But if we try to wrap the predicate into the cb.isTrue() method (as you did it) which require an "Expression<Boolean>" parameter like this:
Predicate wrong = cb.isTrue(r.get("name").in(values));
the mentioned exception PREDICATE_PASSED_TO_EVALUATION will be raised as you have received it even the expression has right syntax.
I think because Expression is an Ancestor of Predicate class but this just an idea. At least the exception message says something like this.
So just remove the cb.isTrue() wrapping and probably it will work for you as it works for me.
I've ran into a problem while creating an data access layer for my application. I am working with derived entities in Entity Framework. If I try to create an ObjectSet for a derived Entity, I get this Exception:
Blockquote There are no EntitySets defined for the specified entity type 'Type Name'. If 'Type Name' is a derived type, use the base type instead.
I've tried to resolve this problem via Reflection. (if the Entity Type is derived by an Entity Type => get an ObjectSet for the base Type)
I found this: How can I obtain ObjectSet<T> from Entity-Framework at runtime where T is dynamic? but I haven't found how to use Include and Where on the built up ObjectSet.
protected IEnumerable<IDataObject> GetData(Type entityType, Expression<Func<dynamic, bool>> whereClause, Expression<Func<dynamic, dynamic>>[] includes)
{
if (typeof(IDataObject).IsAssignableFrom(entityType.BaseType))
{
return GetData(entityType.BaseType, whereClause, includes);
}
var contextType = this.Context.GetType();
MethodInfo createObjectSetMethod = contextType.GetMethod("CreateObjectSet", new Type[] {}).MakeGenericMethod(entityType);
// Builds up an ObjectSet<EntityType>
dynamic objectSet = createObjectSetMethod.Invoke(this.Context, new object[] { });
dynamic query = objectSet;
if (includes != null)
{
foreach (var include in includes)
{
query = query.Include(include);
}
}
if (whereClause == null)
{
whereClause = (item) => true;
}
query = query.Where(whereClause);
return query.ToList().OfType<IDataObject>();
}
The code runs as intended, as long I don't use the Includes and WhereClause.
When I call this function I dont know the resolved ObjectSet (T-Parameter) at compile time.
Is there any way to use dynamic Expressions in an generic ObjectSet?
Thanks in advance.
The issue looks to be with the
query = query.Include(include);
the var include would be an Expression<Func<dynamic,dynamic>>
The Include Method you access is expecting a string or
Expression<Func<T, TProperty>>
Have you tried to pass the include as a string path? I would expect that to work.
Otherwise you need to construct the expression tree with code
since you cant pass Dynamic objects to
public static IQueryable<T> Include<T, TProperty>(this IQueryable<T> source, Expression<Func<T, TProperty>> path) where T : class;
There is also dynamic linq library to can check out.
System.Linq.Dynamic can be found at following links
http://msdn.microsoft.com/en-US/vstudio/bb894665.aspx
with an intro here http://www.scottgu.com/blogposts/dynquery/dynamiclinqcsharp.zip
This is an easier alternative using text to build expression trees.
Building expressions trees with code is more powerful and flexible but harder.
Basically I want to use a dynamic data website to maintain data in an EF4 model where the entities are in their own assembly. Model and context are in another assembly.
I tried this Entity Framework 4 + Self-Tracking Entities + ASP.NET Dynamic Data = Error
but get an "ambiguous match" error from reflection:
System.Reflection.AmbiguousMatchException was unhandled by user code
Message=Ambiguous match found.
Source=mscorlib
StackTrace:
at System.RuntimeType.GetPropertyImpl(String name, BindingFlags bindingAttr, Binder binder, Type returnType, Type[] types, ParameterModifier[] modifiers)
at System.Type.GetProperty(String name)
at System.Web.DynamicData.ModelProviders.EFTableProvider..ctor(EFDataModelProvider dataModel, EntitySet entitySet, EntityType entityType, Type entityClrType, Type parentEntityClrType, Type rootEntityClrType, String name)
at System.Web.DynamicData.ModelProviders.EFDataModelProvider.CreateTableProvider(EntitySet entitySet, EntityType entityType)
at System.Web.DynamicData.ModelProviders.EFDataModelProvider..ctor(Object contextInstance, Func1 contextFactory)
at System.Web.DynamicData.ModelProviders.SchemaCreator.CreateDataModel(Object contextInstance, Func1 contextFactory)
at System.Web.DynamicData.MetaModel.RegisterContext(Func`1 contextFactory, ContextConfiguration configuration)
at WebApplication1.Global.RegisterRoutes(RouteCollection routes) in C:\dev\Puffin\Puffin.Prototype.Web\Global.asax.cs:line 42
at WebApplication1.Global.Application_Start(Object sender, EventArgs e) in C:\dev\Puffin\Puffin.Prototype.Web\Global.asax.cs:line 78
InnerException:
I came across a similar problem to this recently. It had to do with inheritance in my model. I had a Resource entity that had derived types of Person, Equipment, etc. and in those I had overridden a couple properties, but by mistake gave them different signatures. I'll describe my scenario and hopefully it will help.
To be able to debug deep enough into the framework, and see all the variable values, you will have to disable optimizations:
Link
I was seeing the Ambiguous Match error when registering the Context in Global.asax as you were:
public static void RegisterRoutes(RouteCollection routes)
{
// IMPORTANT: DATA MODEL REGISTRATION
// Uncomment this line to register an ADO.NET Entity Framework model for ASP.NET Dynamic Data.
// Set ScaffoldAllTables = true only if you are sure that you want all tables in the
// data model to support a scaffold (i.e. templates) view. To control scaffolding for
// individual tables, create a partial class for the table and apply the
// [ScaffoldTable(true)] attribute to the partial class.
// Note: Make sure that you change "YourDataContextType" to the name of the data context
// class in your application.
DefaultModel.RegisterContext(typeof(EntityModelContainer), new ContextConfiguration() { ScaffoldAllTables = true });
Stepping into the RegisterContext method, I got to System.Web.DynamicData.ModelProviders.EFDataModelProvider there is section of code that loads all the Entities in the model by traversing the inheritance hierarchy in the constuctor for EFDataModelProvider.
while (objectStack.Any()) {
EntityType entityType = objectStack.Pop();
if (entityType != null) {
// Update the entity set when we are at another root type (a type without a base type).
if (entityType.BaseType == null) {
currentEntitySet = entitySetLookup[entityType];
}
var table = CreateTableProvider(currentEntitySet, entityType);
tables.Add(table);
}
foreach (EntityType derivedEntityType in derivedTypesLookup[entityType]) {
// Push the derived entity types on the stack
objectStack.Push(derivedEntityType);
}
}
I put a breakpoint in here and was able to see that Ambiguous Match was occurring for me when calling CreateTableProvider on my Equipment entity (which was derived from Resource).
Looking back at the Stack Trace from the original exception (which I should have done in the first place!) I put a breakpoint in the constructor for System.Web.DynamicData.ModelProviders.EFTableProvider.IsPublicProperty and watched to see which property/method/whatever was causing the ambiguous match -- for me this ended up being a navigation property called Resources (Resources are themselves a hierarchy) that I had overridden in Equipment.
private static bool IsPublicProperty(Type entityClrType, string propertyName) {
var property = entityClrType.GetProperty(propertyName);
return property != null && property.GetGetMethod() != null;
}
In the partial class for Equipment, I had:
public partial class Equipment
{
public new IEnumerable<Resource> Resources
{
but in the parent class, Resource, Resources was defined as:
public virtual ICollection<Resource> Resources
{
When these Properties are being loaded by the .GetProperty(propertyName) in IsPublicProperty, they have the same name but different signatures (because I had given them different return type by mistake) so it isn't clear which shoudl be loaded based on name alone. I corrected my mistake and made Resources in my Equipment class return an ICollection, and boom -- no more ambiguous match.
Not sure if this will help or not, but if you step through in a similar way you should be able to find exactly what is causing the ambiguous match.