us.daveread.basicquery.queries

Class QueryHistory

java.lang.Object

us.daveread.basicquery.queries.QueryHistory

public class QueryHistory
extends java.lang.Object

Maintain the query history and current location in that history.

Author:

David Read

Field Summary

Fields

Modifier and Type	Field and Description
private int	currentPosition Current position in the history list
private static QueryHistory	instance Singleton instance
private static org.apache.log4j.Logger	LOGGER Logger
private static int	MAXIMUM_HISTORY_ENTRIES Maximum size of the query history list
private java.util.List<QueryInfo>	queryHistoryList Collection of historical queries

Constructor Summary

Constructors

Modifier	Constructor and Description
private	QueryHistory() Private constructor for Singleton

Method Summary

Methods

Modifier and Type	Method and Description
void	addQuery(QueryInfo query) Places the query at end of list and changes current position to point to that query.
private void	appendQuery(QueryInfo query) Append a query at the end of the history list.
void	clearAllQueries() Remove all queries from history
void	deleteQueryAtIndex(int index) Delete the query at the SQL index position given.
private void	enforceSize() Ensure that the size of the history list does not go beyond the defined maximum size
QueryInfo	getCurrentQueryInfo() Get the query info for the current query position in the history list.
private int	getHistoryPosition() Get the position of the current query in the history list
static QueryHistory	getInstance() Get the instance
int	getNumberOfQueries() Get the number of queries in the history list
boolean	hasNext() Check whether there is a query in the history list after to the current history position.
boolean	hasPrevious() Check whether there is a query in the history list prior to the current history position.
void	moveBackward() Move back one position in the history list.
void	moveForward() Move forward on position in the history list.
private void	setHistoryPosition(int position) Set the current history position
private void	truncateQueryHistory() Remove queries that follow the currently selected query in the history list.

Methods inherited from class java.lang.Object

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

Field Detail

LOGGER

private static final org.apache.log4j.Logger LOGGER

Logger

MAXIMUM_HISTORY_ENTRIES

private static final int MAXIMUM_HISTORY_ENTRIES

Maximum size of the query history list

See Also:

Constant Field Values

instance

private static QueryHistory instance

Singleton instance

queryHistoryList

private final java.util.List<QueryInfo> queryHistoryList

Collection of historical queries

currentPosition

private int currentPosition

Current position in the history list

Constructor Detail

QueryHistory

private QueryHistory()

Private constructor for Singleton

Method Detail

getInstance

public static final QueryHistory getInstance()

Get the instance

Returns:

The instance

addQuery

public void addQuery(QueryInfo query)

Places the query at end of list and changes current position to point to that query. If the query is at the same position as the current query in the history, then only the result set and connection URL are replaced.

Parameters:

query - The query that is to be added to the history list

deleteQueryAtIndex

public void deleteQueryAtIndex(int index)

Delete the query at the SQL index position given. This is NOT the position in the history list, it is the SQL index position. Any queries in the history list with a matching SQL index will be removed and SQL indexes beyond the removed index will be decremented by one so that they point to the correct position in the SQL list.

Parameters:

index - The SQL index of the query being deleted

truncateQueryHistory

private void truncateQueryHistory()

Remove queries that follow the currently selected query in the history list.

appendQuery

private void appendQuery(QueryInfo query)

Append a query at the end of the history list. If the SQL index matches the current history position's query's SQL index then only the results and connection URL are updated in the query history.

Parameters:

query - The query to be inserted at the end of the query history list

enforceSize

private void enforceSize()

Ensure that the size of the history list does not go beyond the defined maximum size

setHistoryPosition

private void setHistoryPosition(int position)

Set the current history position

Parameters:

position - The current history position

getNumberOfQueries

public int getNumberOfQueries()

Get the number of queries in the history list

Returns:

The number of queries in the history list

getHistoryPosition

private int getHistoryPosition()

Get the position of the current query in the history list

Returns:

The position of the current query in the history list

getCurrentQueryInfo

public QueryInfo getCurrentQueryInfo()

Get the query info for the current query position in the history list. If there is no query history and exception is thrown.

Returns:

The current query info from the history list

moveBackward

public void moveBackward()

Move back one position in the history list. If the list is empty or already at the beginning an exception is thrown

See Also:

hasPrevious()

moveForward

public void moveForward()

Move forward on position in the history list. If the list is empty of already at the end an exception is thrown

See Also:

hasNext()

hasPrevious

public boolean hasPrevious()

Check whether there is a query in the history list prior to the current history position.

Returns:

True if there is a query prior to the current history position

See Also:

moveBackward()

hasNext

public boolean hasNext()

Check whether there is a query in the history list after to the current history position.

Returns:

True if there is a query after the current history position

See Also:

moveForward()

clearAllQueries

public void clearAllQueries()

Remove all queries from history