Package com.healthmarketscience.jackcess

Interface Cursor

All Superinterfaces:

Iterable<Row>

All Known Subinterfaces:

IndexCursor

All Known Implementing Classes:

CursorImpl, IndexCursorImpl, TableScanCursor

public interface Cursor
extends Iterable<Row>

Manages iteration for a Table. Different cursors provide different methods of traversing a table. Cursors should be fairly robust in the face of table modification during traversal (although depending on how the table is traversed, row updates may or may not be seen). Multiple cursors may traverse the same table simultaneously.

Basic cursors will generally iterate table data in the order it appears in the database and searches will require scanning the entire table. Additional features are available when utilizing an Index backed IndexCursor.

The CursorBuilder provides a variety of static utility methods to construct cursors with given characteristics or easily search for specific values as well as friendly and flexible construction options.

A Cursor instance is not thread-safe (see Database for more thread-safety details).

Author:

James Ahlborn

Usage:

General: This class is general use.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	Cursor.Id	Identifier for a cursor.
static interface	Cursor.Position	Value object which maintains the current position of the cursor.
static interface	Cursor.Savepoint	Value object which represents a complete save state of the cursor.

Method Summary

Modifier and Type	Method	Description
void	afterLast()	Resets this cursor for reverse traversal (sets cursor to after the last row).
void	beforeFirst()	Resets this cursor for forward traversal (sets cursor to before the first row).
boolean	currentRowMatches(Column columnPattern, Object valuePattern)	Returns true if the current row matches the given pattern.
boolean	currentRowMatches(Map<String,?> rowPattern)	Returns true if the current row matches the given pattern.
void	deleteCurrentRow()	Delete the current row.
boolean	findFirstRow(Column columnPattern, Object valuePattern)	Moves to the first row (as defined by the cursor) where the given column has the given value.
boolean	findFirstRow(Map<String,?> rowPattern)	Moves to the first row (as defined by the cursor) where the given columns have the given values.
boolean	findNextRow(Column columnPattern, Object valuePattern)	Moves to the next row (as defined by the cursor) where the given column has the given value.
boolean	findNextRow(Map<String,?> rowPattern)	Moves to the next row (as defined by the cursor) where the given columns have the given values.
boolean	findRow(RowId rowId)	Moves to the row with the given rowId.
ColumnMatcher	getColumnMatcher()	Returns the currently configured ColumnMatcher, always non-null.
Row	getCurrentRow()	Returns the current row in this cursor (Column name -> Column value).
Row	getCurrentRow(Collection<String> columnNames)	Returns the current row in this cursor (Column name -> Column value).
Object	getCurrentRowValue(Column column)	Returns the given column from the current row.
ErrorHandler	getErrorHandler()	Gets the currently configured ErrorHandler (always non-null).
Cursor.Id	getId()
Row	getNextRow()	Moves to the next row in the table and returns it.
Row	getNextRow(Collection<String> columnNames)	Moves to the next row in the table and returns it.
Row	getPreviousRow()	Moves to the previous row in the table and returns it.
Row	getPreviousRow(Collection<String> columnNames)	Moves to the previous row in the table and returns it.
Cursor.Savepoint	getSavepoint()	Returns the current state of the cursor which can be restored at a future point in time by a call to restoreSavepoint(com.healthmarketscience.jackcess.Cursor.Savepoint).
Table	getTable()
boolean	isAfterLast()	Returns true if the cursor is currently positioned after the last row, false otherwise.
boolean	isBeforeFirst()	Returns true if the cursor is currently positioned before the first row, false otherwise.
boolean	isCurrentRowDeleted()	Returns true if the row at which the cursor is currently positioned is deleted, false otherwise (including invalid rows).
Iterator<Row>	iterator()	Calls beforeFirst() on this cursor and returns a modifiable Iterator which will iterate through all the rows of this table.
int	moveNextRows(int numRows)	Moves forward as many rows as possible up to the given number of rows.
int	movePreviousRows(int numRows)	Moves backward as many rows as possible up to the given number of rows.
boolean	moveToNextRow()	Moves to the next row as defined by this cursor.
boolean	moveToPreviousRow()	Moves to the previous row as defined by this cursor.
IterableBuilder	newIterable()	Convenience method for constructing a new IterableBuilder for this cursor.
void	reset()	Resets this cursor for forward traversal.
void	restoreSavepoint(Cursor.Savepoint savepoint)	Moves the cursor to a savepoint previously returned from getSavepoint().
void	setColumnMatcher(ColumnMatcher columnMatcher)	Sets a new ColumnMatcher.
void	setCurrentRowValue(Column column, Object value)	Updates a single value in the current row.
void	setErrorHandler(ErrorHandler newErrorHandler)	Sets a new ErrorHandler.
default Stream<Row>	stream()
Object[]	updateCurrentRow(Object... row)	Update the current row.
<M extends Map<String,Object>> M	updateCurrentRowFromMap(M row)	Update the current row.

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Method Detail

getId

Cursor.Id getId()

getTable

Table getTable()

getErrorHandler

ErrorHandler getErrorHandler()

Gets the currently configured ErrorHandler (always non-null). This will be used to handle all errors.

setErrorHandler

void setErrorHandler(ErrorHandler newErrorHandler)

Sets a new ErrorHandler. If null, resets to using the ErrorHandler configured at the Table level.

getColumnMatcher

ColumnMatcher getColumnMatcher()

Returns the currently configured ColumnMatcher, always non-null.

setColumnMatcher

void setColumnMatcher(ColumnMatcher columnMatcher)

Sets a new ColumnMatcher. If null, resets to using the default matcher (default depends on Cursor type).

getSavepoint

Cursor.Savepoint getSavepoint()

Returns the current state of the cursor which can be restored at a future point in time by a call to restoreSavepoint(com.healthmarketscience.jackcess.Cursor.Savepoint).

Savepoints may be used across different cursor instances for the same table, but they must have the same Cursor.Id.

restoreSavepoint

void restoreSavepoint(Cursor.Savepoint savepoint)
               throws IOException

Moves the cursor to a savepoint previously returned from getSavepoint().

Throws:

IllegalArgumentException - if the given savepoint does not have a cursorId equal to this cursor's id

IOException

reset

void reset()

Resets this cursor for forward traversal. Calls beforeFirst().

beforeFirst

void beforeFirst()

Resets this cursor for forward traversal (sets cursor to before the first row).

afterLast

void afterLast()

Resets this cursor for reverse traversal (sets cursor to after the last row).

isBeforeFirst

boolean isBeforeFirst()
               throws IOException

Returns true if the cursor is currently positioned before the first row, false otherwise.

Throws:

IOException

isAfterLast

boolean isAfterLast()
             throws IOException

Returns true if the cursor is currently positioned after the last row, false otherwise.

Throws:

IOException

isCurrentRowDeleted

boolean isCurrentRowDeleted()
                     throws IOException

Returns true if the row at which the cursor is currently positioned is deleted, false otherwise (including invalid rows).

Throws:

IOException

iterator

Iterator<Row> iterator()

Calls beforeFirst() on this cursor and returns a modifiable Iterator which will iterate through all the rows of this table. Use of the Iterator follows the same restrictions as a call to getNextRow().

For more flexible iteration see newIterable().

Specified by:

iterator in interface Iterable<Row>

Throws:

UncheckedIOException - if an IOException is thrown by one of the operations, the actual exception will be contained within

stream

default Stream<Row> stream()

Returns:

a Stream using the default Iterator.

newIterable

IterableBuilder newIterable()

Convenience method for constructing a new IterableBuilder for this cursor. An IterableBuilder provides a variety of options for more flexible iteration.

deleteCurrentRow

void deleteCurrentRow()
               throws IOException

Delete the current row.

Note, re-deleting an already deleted row is allowed (it does nothing).

Throws:

IllegalStateException - if the current row is not valid (at beginning or end of table)

IOException

updateCurrentRow

Object[] updateCurrentRow(Object... row)
                   throws IOException

Update the current row.

Returns:

the given row values if long enough, otherwise a new array, updated with the current row values

Throws:

IllegalStateException - if the current row is not valid (at beginning or end of table), or deleted.

IOException

updateCurrentRowFromMap

<M extends Map<String,Object>> M updateCurrentRowFromMap(M row)
                                                        throws IOException

Update the current row.

Returns:

the given row, updated with the current row values

Throws:

IllegalStateException - if the current row is not valid (at beginning or end of table), or deleted.

IOException

getNextRow

Row getNextRow()
        throws IOException

Moves to the next row in the table and returns it.

Returns:

The next row in this table (Column name -> Column value), or null if no next row is found

Throws:

IOException

getNextRow

Row getNextRow(Collection<String> columnNames)
        throws IOException

Moves to the next row in the table and returns it.

Parameters:

columnNames - Only column names in this collection will be returned

Returns:

The next row in this table (Column name -> Column value), or null if no next row is found

Throws:

IOException

getPreviousRow

Row getPreviousRow()
            throws IOException

Moves to the previous row in the table and returns it.

Returns:

The previous row in this table (Column name -> Column value), or null if no previous row is found

Throws:

IOException

getPreviousRow

Row getPreviousRow(Collection<String> columnNames)
            throws IOException

Moves to the previous row in the table and returns it.

Parameters:

columnNames - Only column names in this collection will be returned

Returns:

The previous row in this table (Column name -> Column value), or null if no previous row is found

Throws:

IOException

moveToNextRow

boolean moveToNextRow()
               throws IOException

Moves to the next row as defined by this cursor.

Returns:

true if a valid next row was found, false otherwise

Throws:

IOException

moveToPreviousRow

boolean moveToPreviousRow()
                   throws IOException

Moves to the previous row as defined by this cursor.

Returns:

true if a valid previous row was found, false otherwise

Throws:

IOException

findRow

boolean findRow(RowId rowId)
         throws IOException

Moves to the row with the given rowId. If the row is not found (or an exception is thrown), the cursor is restored to its previous state.

Returns:

true if a valid row was found with the given id, false if no row was found

Throws:

IOException

findFirstRow

boolean findFirstRow(Column columnPattern,
                     Object valuePattern)
              throws IOException

Moves to the first row (as defined by the cursor) where the given column has the given value. This may be more efficient on some cursors than others. If a match is not found (or an exception is thrown), the cursor is restored to its previous state.

Warning, this method always starts searching from the beginning of the Table (you cannot use it to find successive matches).

Parameters:

columnPattern - column from the table for this cursor which is being matched by the valuePattern

valuePattern - value which is equal to the corresponding value in the matched row. If this object is an instance of Predicate, it will be applied to the potential row value instead (overriding any configured ColumnMatcher)

Returns:

true if a valid row was found with the given value, false if no row was found

Throws:

IOException

findNextRow

boolean findNextRow(Column columnPattern,
                    Object valuePattern)
             throws IOException

Moves to the next row (as defined by the cursor) where the given column has the given value. This may be more efficient on some cursors than others. If a match is not found (or an exception is thrown), the cursor is restored to its previous state.

Parameters:

columnPattern - column from the table for this cursor which is being matched by the valuePattern

valuePattern - value which is equal to the corresponding value in the matched row. If this object is an instance of Predicate, it will be applied to the potential row value instead (overriding any configured ColumnMatcher)

Returns:

true if a valid row was found with the given value, false if no row was found

Throws:

IOException

findFirstRow

boolean findFirstRow(Map<String,?> rowPattern)
              throws IOException

Moves to the first row (as defined by the cursor) where the given columns have the given values. This may be more efficient on some cursors than others. If a match is not found (or an exception is thrown), the cursor is restored to its previous state.

Warning, this method always starts searching from the beginning of the Table (you cannot use it to find successive matches).

Parameters:

rowPattern - column names and values which must be equal to the corresponding values in the matched row. If a value is an instance of Predicate, it will be applied to the potential row value instead (overriding any configured ColumnMatcher)

Returns:

true if a valid row was found with the given values, false if no row was found

Throws:

IOException

findNextRow

boolean findNextRow(Map<String,?> rowPattern)
             throws IOException

Moves to the next row (as defined by the cursor) where the given columns have the given values. This may be more efficient on some cursors than others. If a match is not found (or an exception is thrown), the cursor is restored to its previous state.

Parameters:

rowPattern - column names and values which must be equal to the corresponding values in the matched row. If a value is an instance of Predicate, it will be applied to the potential row value instead (overriding any configured ColumnMatcher)

Returns:

true if a valid row was found with the given values, false if no row was found

Throws:

IOException

currentRowMatches

boolean currentRowMatches(Column columnPattern,
                          Object valuePattern)
                   throws IOException

Returns true if the current row matches the given pattern.

Parameters:

columnPattern - column from the table for this cursor which is being matched by the valuePattern

valuePattern - value which is equal to the corresponding value in the matched row. If this object is an instance of Predicate, it will be applied to the potential row value instead (overriding any configured ColumnMatcher)

Throws:

IOException

currentRowMatches

boolean currentRowMatches(Map<String,?> rowPattern)
                   throws IOException

Returns true if the current row matches the given pattern.

Parameters:

rowPattern - column names and values which must be equal to the corresponding values in the matched row. If a value is an instance of Predicate, it will be applied to the potential row value instead (overriding any configured ColumnMatcher)

Throws:

IOException

moveNextRows

int moveNextRows(int numRows)
          throws IOException

Moves forward as many rows as possible up to the given number of rows.

Returns:

the number of rows moved.

Throws:

IOException

movePreviousRows

int movePreviousRows(int numRows)
              throws IOException

Moves backward as many rows as possible up to the given number of rows.

Returns:

the number of rows moved.

Throws:

IOException

getCurrentRow

Row getCurrentRow()
           throws IOException

Returns the current row in this cursor (Column name -> Column value).

Throws:

IOException

getCurrentRow

Row getCurrentRow(Collection<String> columnNames)
           throws IOException

Returns the current row in this cursor (Column name -> Column value).

Parameters:

columnNames - Only column names in this collection will be returned

Throws:

IOException

getCurrentRowValue

Object getCurrentRowValue(Column column)
                   throws IOException

Returns the given column from the current row.

Throws:

IOException

setCurrentRowValue

void setCurrentRowValue(Column column,
                        Object value)
                 throws IOException

Updates a single value in the current row.

Throws:

IllegalStateException - if the current row is not valid (at beginning or end of table), or deleted.

IOException