Package com.vaadin.flow.data.provider

Class CallbackDataProvider<T,F>

java.lang.Object

com.vaadin.flow.data.provider.AbstractDataProvider<T,F>

com.vaadin.flow.data.provider.AbstractBackEndDataProvider<T,F>

com.vaadin.flow.data.provider.CallbackDataProvider<T,F>

Type Parameters:

T - data provider data type

F - data provider filter type

All Implemented Interfaces:

BackEndDataProvider<T,F>, DataProvider<T,F>, Serializable

public class CallbackDataProvider<T,F>
extends AbstractBackEndDataProvider<T,F>

Data provider that uses one callback for fetching items from a back end and another callback for counting the number of available items.

Since:

1.0

Author:

Vaadin Ltd

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	CallbackDataProvider.CountCallback<T,F>	Callback interface for counting the number of items in a backend based on a query.
static interface	CallbackDataProvider.FetchCallback<T,F>	Callback interface for fetching a stream of items from a backend based on a query.

Constructor Summary

Constructors

Constructor	Description
CallbackDataProvider(CallbackDataProvider.FetchCallback<T,F> fetchCallback, CallbackDataProvider.CountCallback<T,F> countCallback)	Constructs a new DataProvider to request data using callbacks for fetching and counting items in the back end.
CallbackDataProvider(CallbackDataProvider.FetchCallback<T,F> fetchCallBack, CallbackDataProvider.CountCallback<T,F> countCallback, ValueProvider<T,Object> identifierGetter)	Constructs a new DataProvider to request data using callbacks for fetching and counting items in the back end.

Method Summary

Modifier and Type	Method	Description
Stream<T>	fetchFromBackEnd(Query<T,F> query)	Fetches data from the back end using the given query.
Object	getId(T item)	Gets an identifier for the given item.
protected int	sizeInBackEnd(Query<T,F> query)	Counts the number of items available in the back end.

Methods inherited from class com.vaadin.flow.data.provider.AbstractBackEndDataProvider

fetch, setSortOrders, size

Methods inherited from class com.vaadin.flow.data.provider.AbstractDataProvider

addDataProviderListener, addListener, fireEvent, refreshAll, refreshItem, refreshItem

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.vaadin.flow.data.provider.BackEndDataProvider

isInMemory, setSortOrder, setSortOrders

Methods inherited from interface com.vaadin.flow.data.provider.DataProvider

addDataProviderListener, refreshAll, refreshItem, refreshItem, withConfigurableFilter, withConfigurableFilter, withConvertedFilter

Constructor Details

CallbackDataProvider

public CallbackDataProvider(CallbackDataProvider.FetchCallback<T,F> fetchCallback,
 CallbackDataProvider.CountCallback<T,F> countCallback)

Constructs a new DataProvider to request data using callbacks for fetching and counting items in the back end.

Parameters:

fetchCallback - function that returns a stream of items from the back end for a query

countCallback - function that return the number of items in the back end for a query

See Also:

• CallbackDataProvider(FetchCallback, CountCallback, ValueProvider)

CallbackDataProvider

public CallbackDataProvider(CallbackDataProvider.FetchCallback<T,F> fetchCallBack,
 CallbackDataProvider.CountCallback<T,F> countCallback,
 ValueProvider<T,Object> identifierGetter)

Constructs a new DataProvider to request data using callbacks for fetching and counting items in the back end.

Parameters:

fetchCallBack - function that requests data from back end based on query

countCallback - function that returns the amount of data in back end for query

identifierGetter - function that returns the identifier for a given item

Method Details

fetchFromBackEnd

public Stream<T> fetchFromBackEnd(Query<T,F> query)

Description copied from class: AbstractBackEndDataProvider

Fetches data from the back end using the given query.

Specified by:

fetchFromBackEnd in class AbstractBackEndDataProvider<T,F>

Parameters:

query - the query that defines sorting, filtering and paging for fetching the data

Returns:

a stream of items matching the query

sizeInBackEnd

protected int sizeInBackEnd(Query<T,F> query)

Description copied from class: AbstractBackEndDataProvider

Counts the number of items available in the back end.

Specified by:

sizeInBackEnd in class AbstractBackEndDataProvider<T,F>

Parameters:

query - the query that defines filtering to be used for counting the number of items

Returns:

the number of available items

getId

public Object getId(T item)

Description copied from interface: DataProvider

Gets an identifier for the given item. This identifier is used by the framework to determine equality between two items.

Default is to use item itself as its own identifier. If the item has Object.equals(Object) and Object.hashCode() implemented in a way that it can be compared to other items, no changes are required.

Note: This method will be called often by the Framework. It should not do any expensive operations.

Parameters:

item - the item to get identifier for; not null

Returns:

the identifier for given item; not null