Question

I have multiple tables with a lot of data in it. I’m only mentioning things pertinent to the question. For rendering data on the jsp, I only need selective data from different tables.

In reference to travel-vacation, lets say I have to retrieve and render holiday package name, itinerary duration and total price per defaults.

• Holiday package name is in table HolidayPackage (id, name)
• Itinerary duration in table Itinerary Itinerary (idPkg, idItinerary, dayNum) = (SUM aggregate of itinerary rows for a given package )
• Price is defined in two different tables base price and total price

  = (Sum( base(idPkg) + total(idPkg) ))

How can I retrieve selective data from these database tables to render the name, itinerary duration and total price for a given holiday package ?

I am using Hibernate with mysql as my database.

Thoughts:

Can I use a view to fetch data into my custom java object Result where Result is defined as:

class Result{
 String name;
 Intger itineraryDuration;
 BigDecimal totalPrice;
}

Also, can I use functions as the definition of column values in views ?

Answer 1

What I do with views is I create an immutable hibernate model class and associated DAO to query the model class.

I annotate the model class as follows:

@Entity
@Immutable
@Table(name = "CLASSIFICATION_LABELS_V", schema = "CORPORATE")

I also set the setters to protected, but this is optional.

If the view is structured similar to an existing model class, you can use a named query and map it to your model using the resultClass attribute. The following is for Oracle so if using anything else, the query parameter would be different.

@NamedNativeQueries({
    @NamedNativeQuery(name = "create_product_from_template", query = "call pkg_authoring.sp_create_prod_from_template(?, :productId, :templateId)", resultClass = TblProduct.class, callable = true)
})

In hibernate, you can use functions as follows:

@Formula(value = "(select fnHasProducts(customerId) from dual)")
    @AccessType("property")
    private Integer products = 0;

@Formula(value = "(select fnAssigneeForProduct(productId) from dual)")
    private Integer assignee = 0;