com.vaadin.client.data

Class AbstractRemoteDataSource<T>

java.lang.Object

com.vaadin.client.data.AbstractRemoteDataSource<T>

Type Parameters:

T - the row type

All Implemented Interfaces:

DataSource<T>

Direct Known Subclasses:

DataCommunicatorConnector.VaadinDataSource

public abstract class AbstractRemoteDataSource<T>
extends Object
implements DataSource<T>

Base implementation for data sources that fetch data from a remote system. This class takes care of caching data and communicating with the data source user. An implementation of this class should override requestRows(int, int, RequestRowsCallback) to trigger asynchronously loading of data and then pass the loaded data into the provided callback.

Since:

7.4

Author:

Vaadin Ltd

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AbstractRemoteDataSource.RequestRowsCallback<T> Callback used by requestRows(int, int, RequestRowsCallback) to pass data to the underlying implementation when data has been fetched.
protected class	AbstractRemoteDataSource.RowHandleImpl

Nested classes/interfaces inherited from interface com.vaadin.client.data.DataSource

DataSource.RowHandle<T>

Constructor Summary

Constructors

Constructor and Description
AbstractRemoteDataSource()

Method Summary

Modifier and Type	Method and Description
Registration	addDataChangeHandler(DataChangeHandler dataChangeHandler) Sets a data change handler to inform when data is updated, added or removed.
protected boolean	canFetchData() Checks if it is possible to currently fetch data from the remote data source.
protected void	dropFromCache(Range range) Drop the given range of rows from this data source's cache.
void	ensureAvailability(int firstRowIndex, int numberOfRows) Informs the data source that data for the given range is needed.
Range	getCachedRange() Gets the current range of cached rows.
DataSource.RowHandle<T>	getHandle(T row) Gets a DataSource.RowHandle of a row object in the cache.
Range	getRequestedAvailability() Gets the row index range that was requested by the previous call to ensureAvailability(int, int).
T	getRow(int rowIndex) Retrieves the data for the row at the given index.
abstract Object	getRowKey(T row) Gets a stable key for the row object.
int	indexOf(T row) Retrieves the index for given row object.
protected int	indexOfKey(Object rowKey)
protected void	insertRowData(int firstRowIndex, int count) Informs this data source that new data has been inserted from the server.
protected boolean	isPinned(T row)
boolean	isWaitingForData() Checks whether this data source is currently waiting for more rows to become available.
protected void	onDropFromCache(int rowIndex) Deprecated. replaced by onDropFromCache(int, Object)
protected void	onDropFromCache(int rowIndex, T removed) A hook that can be overridden to do something whenever a row has been dropped from the cache.
protected void	pinHandle(AbstractRemoteDataSource.RowHandleImpl handle) Pins a row with given handle.
protected void	removeRowData(int firstRowIndex, int count) Informs this data source that the server has removed data.
protected abstract void	requestRows(int firstRowIndex, int numberOfRows, AbstractRemoteDataSource.RequestRowsCallback<T> callback) Triggers fetching rows from the remote data source.
protected void	resetDataAndSize(int newSize) Updates the size, discarding all cached data.
void	setCacheStrategy(CacheStrategy cacheStrategy) Sets the cache strategy that is used to determine how much data is fetched and cached.
protected void	setRowData(int firstRowIndex, List<T> rowData) Informs this data source that updated data has been sent from the server.
int	size() Returns the number of rows in the data source.
protected void	unpinHandle(AbstractRemoteDataSource.RowHandleImpl handle) Unpins a previously pinned row with given handle.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.vaadin.client.data.DataSource

addDataChangeHandler

Constructor Detail

AbstractRemoteDataSource

public AbstractRemoteDataSource()

Method Detail

pinHandle

protected void pinHandle(AbstractRemoteDataSource.RowHandleImpl handle)

Pins a row with given handle. This function can be overridden to do specific logic related to pinning rows.

Parameters:

handle - row handle to pin

unpinHandle

protected void unpinHandle(AbstractRemoteDataSource.RowHandleImpl handle)
                    throws IllegalStateException

Unpins a previously pinned row with given handle. This function can be overridden to do specific logic related to unpinning rows.

Parameters:

handle - row handle to unpin

Throws:

IllegalStateException - if given row handle has not been pinned before

ensureAvailability

public void ensureAvailability(int firstRowIndex,
                               int numberOfRows)

Description copied from interface: DataSource

Informs the data source that data for the given range is needed. A data source only has one active region at a time, so calling this method discards the previously set range.

This method triggers lazy loading of data if necessary. The change handler registered using DataSource.addDataChangeHandler(DataChangeHandler) is informed when new data has been loaded.

After any possible lazy loading and updates are done, the change handler is informed that new data is available.

Specified by:

ensureAvailability in interface DataSource<T>

Parameters:

firstRowIndex - the index of the first needed row

numberOfRows - the number of needed rows

getRequestedAvailability

public Range getRequestedAvailability()

Gets the row index range that was requested by the previous call to ensureAvailability(int, int).

Returns:

the requested availability range

isWaitingForData

public boolean isWaitingForData()

Checks whether this data source is currently waiting for more rows to become available.

Specified by:

isWaitingForData in interface DataSource<T>

Returns:

true if waiting for data; otherwise false

dropFromCache

protected void dropFromCache(Range range)

Drop the given range of rows from this data source's cache.

Parameters:

range - the range of rows to drop

onDropFromCache

@Deprecated
protected void onDropFromCache(int rowIndex)

Deprecated. replaced by onDropFromCache(int, Object)

A hook that can be overridden to do something whenever a row has been dropped from the cache. DataSource no longer has anything in the given index.

NOTE: This method has been replaced. Override onDropFromCache(int, Object) instead of this method.

Parameters:

rowIndex - the index of the dropped row

Since:

7.5.0

onDropFromCache

protected void onDropFromCache(int rowIndex,
                               T removed)

A hook that can be overridden to do something whenever a row has been dropped from the cache. DataSource no longer has anything in the given index.

Parameters:

rowIndex - the index of the dropped row

removed - the removed row object

Since:

7.6

requestRows

protected abstract void requestRows(int firstRowIndex,
                                    int numberOfRows,
                                    AbstractRemoteDataSource.RequestRowsCallback<T> callback)

Triggers fetching rows from the remote data source. The provided callback should be informed when the requested rows have been received.

Parameters:

firstRowIndex - the index of the first row to fetch

numberOfRows - the number of rows to fetch

callback - callback to inform when the requested rows are available

getRow

public T getRow(int rowIndex)

Description copied from interface: DataSource

Retrieves the data for the row at the given index. If the row data is not available, returns null.

This method does not trigger loading of unavailable data. DataSource.ensureAvailability(int, int) should be used to signal what data will be needed.

Specified by:

getRow in interface DataSource<T>

Parameters:

rowIndex - the index of the row to retrieve data for

Returns:

data for the row; or null if no data is available

indexOf

public int indexOf(T row)

Retrieves the index for given row object.

Note: This method does not verify that the given row object exists at all in this DataSource.

Parameters:

row - the row object

Returns:

index of the row; or -1 if row is not available

addDataChangeHandler

public Registration addDataChangeHandler(DataChangeHandler dataChangeHandler)

Description copied from interface: DataSource

Sets a data change handler to inform when data is updated, added or removed.

Specified by:

addDataChangeHandler in interface DataSource<T>

Parameters:

dataChangeHandler - the data change handler

Returns:

registration for removing the handler

setRowData

protected void setRowData(int firstRowIndex,
                          List<T> rowData)

Informs this data source that updated data has been sent from the server.

Parameters:

firstRowIndex - the index of the first received row

rowData - a list of rows, starting from firstRowIndex

removeRowData

protected void removeRowData(int firstRowIndex,
                             int count)

Informs this data source that the server has removed data.

Parameters:

firstRowIndex - the index of the first removed row

count - the number of removed rows, starting from firstRowIndex

insertRowData

protected void insertRowData(int firstRowIndex,
                             int count)

Informs this data source that new data has been inserted from the server.

Parameters:

firstRowIndex - the destination index of the new row data

count - the number of rows inserted

getCachedRange

public Range getCachedRange()

Gets the current range of cached rows.

Returns:

the range of currently cached rows

setCacheStrategy

public void setCacheStrategy(CacheStrategy cacheStrategy)

Sets the cache strategy that is used to determine how much data is fetched and cached.

The new strategy is immediately used to evaluate whether currently cached rows should be discarded or new rows should be fetched.

Parameters:

cacheStrategy - a cache strategy implementation, not null

getHandle

public DataSource.RowHandle<T> getHandle(T row)
                                  throws IllegalStateException

Description copied from interface: DataSource

Gets a DataSource.RowHandle of a row object in the cache.

Specified by:

getHandle in interface DataSource<T>

Parameters:

row - the row object for which to retrieve a row handle

Returns:

a non-null row handle of the given row object

Throws:

IllegalStateException

getRowKey

public abstract Object getRowKey(T row)

Gets a stable key for the row object.

This method is a workaround for the fact that there is no means to force proper implementations for Object.hashCode() and Object.equals(Object) methods.

Since the same row object will be created several times for the same logical data, the DataSource needs a mechanism to be able to compare two objects, and figure out whether or not they represent the same data. Even if all the fields of an entity would be changed, it still could represent the very same thing (say, a person changes all of her names.)

A very usual and simple example what this could be, is an unique ID for this object that would also be stored in a database.

Parameters:

row - the row object for which to get the key

Returns:

a non-null object that uniquely and consistently represents the row object

size

public int size()

Description copied from interface: DataSource

Returns the number of rows in the data source.

Specified by:

size in interface DataSource<T>

Returns:

the current size of the data source

resetDataAndSize

protected void resetDataAndSize(int newSize)

Updates the size, discarding all cached data. This method is used when the size of the container is changed without any information about the structure of the change. In this case, all cached data is discarded to avoid cache offset issues.

If you have information about the structure of the change, use insertRowData(int, int) or removeRowData(int, int) to indicate where the inserted or removed rows are located.

Parameters:

newSize - the new size of the container

indexOfKey

protected int indexOfKey(Object rowKey)

isPinned

protected boolean isPinned(T row)

canFetchData

protected boolean canFetchData()

Checks if it is possible to currently fetch data from the remote data source.

Returns:

true if it is ok to try to fetch data, false if it is known that fetching data will fail and should not be tried right now.

Since:

7.7.2