Package io.ebean

Interface FetchGroup<T>

Type Parameters:

T - The bean type the Fetch group can be applied to

public interface FetchGroup<T>

Defines what part of the object graph to load (select and fetch clauses).

Using a FetchGroup effectively sets the select() and fetch() clauses for a query. It is alternative to specifying the select() and fetch() clauses on the query allowing for more re-use of "what to load" that can be defined separately from the query and combined with other FetchGroups.

Select example

 FetchGroup<Customer> fetchGroup = FetchGroup.of(Customer.class, "name, status");

 Customer.query()
   .select(fetchGroup)
   .findList();

 

Select and fetch example

 FetchGroup<Customer> fetchGroup = FetchGroup.of(Customer.class)
   .select("name, status")
   .fetch("contacts", "firstName, lastName, email")
   .build();

 Customer.query()
   .select(fetchGroup)
   .findList();

 

Combining FetchGroups

FetchGroups can be combined together to form another FetchGroup.

  FetchGroup<Address> FG_ADDRESS = FetchGroup.of(Address.class)
    .select("line1, line2, city")
    .fetch("country", "name")
    .build();

  FetchGroup<Customer> FG_CUSTOMER = FetchGroup.of(Customer.class)
    .select("name, version")
    .fetch("billingAddress", FG_ADDRESS)
    .build();


  Customer.query()
    .select(FG_CUSTOMER)
    .findList();

 

Method Summary

Static Methods

Modifier and Type	Method	Description
static <T> FetchGroupBuilder<T>	of(Class<T> cls)	Return the FetchGroupBuilder with the given select clause that we can add fetch clauses to.
static <T> FetchGroup<T>	of(Class<T> cls, String select)	Return the FetchGroup with the given select clause.
static <T> SpiFetchGroupQuery<T>	queryFor(Class<T> beanType)	Return a query to be used by query beans for constructing FetchGroup.

Method Detail

of

@Nonnull
static <T> FetchGroup<T> of(Class<T> cls,
                            String select)

Return the FetchGroup with the given select clause.

We use this for simple FetchGroup that only select() properties and do not have additional fetch() clause.

 FetchGroup<Customer> fetchGroup = FetchGroup.of(Customer.class, "name, status");

 Customer.query()
   .select(fetchGroup)
   .findList();

 

Parameters:

select - The select clause of the FetchGroup

Returns:

The FetchGroup with the given select clause

of

@Nonnull
static <T> FetchGroupBuilder<T> of(Class<T> cls)

Return the FetchGroupBuilder with the given select clause that we can add fetch clauses to.

We chain select() with one or more fetch() clauses to define the object graph to load.

 FetchGroup<Customer> fetchGroup = FetchGroup.of(Customer.class)
   .select("name, status")
   .fetch("contacts", "firstName, lastName, email")
   .build();

 Customer.query()
   .select(fetchGroup)
   .findList();

 

Returns:

The FetchGroupBuilder with the given select clause which we will add fetch clauses to

queryFor

static <T> SpiFetchGroupQuery<T> queryFor(Class<T> beanType)

Return a query to be used by query beans for constructing FetchGroup.