com.goldencode.p2j.persist

Class ResultsAdapter

java.lang.Object

com.goldencode.p2j.persist.ResultsAdapter

All Implemented Interfaces:

Results

final class ResultsAdapter
extends java.lang.Object
implements Results

An implementation of the Results interface which delegates all work to another Results implementation. A worker can be connected at any time using setResults(com.goldencode.p2j.persist.Results), or disconnected by passing a null parameter to this method.

Client code may expire the current delegate worker by invoking the prepareDelegateChange() method. This will cause the adapter to replace the delegate at the next safe opportunity. This is accomplished by requesting a new Results object from a ResultsProvider which is registered at construction time.

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	delegateNeeded State flag indicating a new delegate worker must be installed
private ResultsProvider	provider Object which provides results to this adapter upon request
private Results	results Delegate worker object

Fields inherited from interface com.goldencode.p2j.persist.Results

LOG

Constructor Summary

Constructors

Constructor and Description
ResultsAdapter(ResultsProvider provider) Default constructor.

Method Summary

Modifier and Type	Method and Description
private void	checkDelegate() Check whether a new delegate worker is needed and if so, request the ResultsProvider registered with this object to create a new one and to attach it to this adapter.
void	cleanup() Delegate cleanup to the underlying worker.
boolean	first() Move cursor to the first result row.
java.lang.Object[]	get() Get the array of objects at the current result row.
java.lang.Object	get(int column) Get the object at the current result row, at the specified column.
java.lang.Long	getID(int column) Get the primary key ID at the current result row, at the specified column.
(package private) Results	getResults() Get the underlying Results worker object for this adapter.
int	getRowNumber() Get the row number currently under the cursor.
boolean	isAutoFetch() Is the result delegate responsible for fetching? This is usually true when using query delegates which handle the fetching process already.
(package private) boolean	isConnected() Report whether this adapter currently is connected to a delegate worker.
boolean	isFirst() Is the cursor on the first row in the result set?
boolean	isLast() Is the cursor on the last row in the result set?
boolean	isResultSetCached() Indicate whether the full result set is cached in this object.
boolean	last() Move cursor to the last result row.
boolean	next() Move cursor to the next result row.
(package private) void	prepareDelegateChange() Prepare for a disconnect and for a request for new delegate results from the results provider.
boolean	previous() Move cursor to the previous result row.
void	reset() Reset the cursor to its natural starting position, before the first result row.
boolean	scroll(int rows) Scroll the cursor ahead by the specified number of rows.
void	sessionClosing() Give the underlying worker a chance to respond to a session closing event.
(package private) void	setResults(Results results) Set the underlying Results worker object for this adapter.
boolean	setRowNumber(int row) Set the row number currently under the cursor.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.goldencode.p2j.persist.Results

addRow, deleteRow, get, getNumberOfLoadedRows

Field Detail

provider

private final ResultsProvider provider

Object which provides results to this adapter upon request

results

private Results results

Delegate worker object

delegateNeeded

private boolean delegateNeeded

State flag indicating a new delegate worker must be installed

Constructor Detail

ResultsAdapter

ResultsAdapter(ResultsProvider provider)

Default constructor.

Parameters:

provider - Object which provides results to this adapter upon request.

Method Detail

first

public boolean first()

Move cursor to the first result row.

Specified by:

first in interface Results

Returns:

true if there are any results.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

last

public boolean last()

Move cursor to the last result row.

Specified by:

last in interface Results

Returns:

true if there are any results.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

next

public boolean next()

Move cursor to the next result row.

Specified by:

next in interface Results

Returns:

true if there is a result under the cursor after the move.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

previous

public boolean previous()

Move cursor to the previous result row.

Specified by:

previous in interface Results

Returns:

true if there is a result under the cursor after the move.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

isFirst

public boolean isFirst()

Is the cursor on the first row in the result set?

Specified by:

isFirst in interface Results

Returns:

true if the cursor is on the first row.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

isLast

public boolean isLast()

Is the cursor on the last row in the result set?

Specified by:

isLast in interface Results

Returns:

true if the cursor is on the first row.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

isAutoFetch

public boolean isAutoFetch()

Is the result delegate responsible for fetching? This is usually true when using query delegates which handle the fetching process already.

Specified by:

isAutoFetch in interface Results

Returns:

true for complex results which also do the fetching.

get

public java.lang.Object[] get()

Get the array of objects at the current result row.

Specified by:

get in interface Results

Returns:

Object array or null.

get

public java.lang.Object get(int column)

Get the object at the current result row, at the specified column.

Specified by:

get in interface Results

Parameters:

column - Zero-based index column of the desired object.

Returns:

Object at column or null.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

getID

public java.lang.Long getID(int column)

Get the primary key ID at the current result row, at the specified column.

Specified by:

getID in interface Results

Parameters:

column - Zero-based index column of the desired ID.

Returns:

ID of the record or null.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

getRowNumber

public int getRowNumber()

Get the row number currently under the cursor.

Specified by:

getRowNumber in interface Results

Returns:

Zero-based index of the current row, or -1 if the cursor is not currently on a result.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

setRowNumber

public boolean setRowNumber(int row)

Set the row number currently under the cursor.

Specified by:

setRowNumber in interface Results

Parameters:

row - Zero-based index of the row to be set as the current row.

Returns:

true if there is a row at the specified row number, else false.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

scroll

public boolean scroll(int rows)

Scroll the cursor ahead by the specified number of rows. If the number is negative, the cursor is moved backward. This may put the cursor off the end (either end) of the query's results.

Specified by:

scroll in interface Results

Parameters:

rows - Number of rows to jump ahead or back.

Returns:

true if there is a row at the new location, else false.

Throws:

java.lang.NullPointerException - if the adapter is not connected.

reset

public void reset()

Reset the cursor to its natural starting position, before the first result row.

Specified by:

reset in interface Results

Throws:

java.lang.NullPointerException - if the adapter is not connected.

sessionClosing

public void sessionClosing()

Give the underlying worker a chance to respond to a session closing event.

Specified by:

sessionClosing in interface Results

See Also:

Results.sessionClosing()

cleanup

public void cleanup()

Delegate cleanup to the underlying worker.

Specified by:

cleanup in interface Results

isResultSetCached

public boolean isResultSetCached()

Indicate whether the full result set is cached in this object.

Specified by:

isResultSetCached in interface Results

Returns:

true if all results are contained this object; false if not or if unknown (such as for a scrolling or cursored result set. This implementation passes on the invocation to the delegate results object, if any. If none, it returns false.

prepareDelegateChange

void prepareDelegateChange()

Prepare for a disconnect and for a request for new delegate results from the results provider. The current delegate will be disconnected, and a request for new results made, on the next call to any method which would change the current position within the result set.

getResults

Results getResults()

Get the underlying Results worker object for this adapter.

Returns:

Underlying delegate worker.

setResults

void setResults(Results results)

Set the underlying Results worker object for this adapter.

Parameters:

results - Underlying delegate worker.

isConnected

boolean isConnected()

Report whether this adapter currently is connected to a delegate worker.

Returns:

true if there is a delegate Results object connected to this adapter, else false.

checkDelegate

private void checkDelegate()

Check whether a new delegate worker is needed and if so, request the ResultsProvider registered with this object to create a new one and to attach it to this adapter.