org.jfree.report

Interface ReportData

All Superinterfaces:

DataSet

All Known Implementing Classes:

EmptyReportData, SQLReportData, TableReportData

public interface ReportData
extends DataSet

A report data source is a ordered set of rows. For a report, we assume that the report dataset does not change while the report is processed. Concurrent updates will invalidate the whole precomputed layout. A report dataset will be accessed in a linear fashion. On certain points, the cursor will be reset to the a previously read position, and processing the data will restart from there. It is guaranteed, that the cursor will never be set to a row that is beyond the last row that has been read with 'next()'. If the cursor is out of range, any call to get must return 'null'.

Author:

Thomas Morgner

Field Summary

Fields

Modifier and Type	Field and Description
static int	BEFORE_FIRST_ROW

Method Summary

Modifier and Type	Method and Description
void	close() Closes the datasource.
int	getCursorPosition()
boolean	isAdvanceable() This operation checks, whether a call to next will be likely to succeed.
boolean	isReadable() Checks, whether this report-data instance is currently readable.
boolean	next() This method produces the same result as 'setCursorPosition(getCursorPosition() + 1);'
boolean	setCursorPosition(int cursor) Moves the cursor back to an already visited position.

Methods inherited from interface org.jfree.report.DataSet

get, getColumnCount, getColumnName

Field Detail

BEFORE_FIRST_ROW

static final int BEFORE_FIRST_ROW

See Also:

Constant Field Values

Method Detail

getCursorPosition

int getCursorPosition()
               throws DataSourceException

Throws:

DataSourceException

setCursorPosition

boolean setCursorPosition(int cursor)
                   throws DataSourceException

Moves the cursor back to an already visited position. Calling this method for an row number that has not yet been read using 'next' is undefined, whether that call succeeds is implementation dependent. Calls to position zero (aka BEFORE_FIRST_ROW) will always succeeed (unless there is a physical error, which invalidated the whole report-data object).

Parameters:

cursor -

Returns:

true, if moving the cursor succeeded, false otherwise.

Throws:

DataSourceException

isAdvanceable

boolean isAdvanceable()
               throws DataSourceException

This operation checks, whether a call to next will be likely to succeed. If there is a next data row, this should return true.

Returns:

Throws:

DataSourceException

next

boolean next()
      throws DataSourceException

This method produces the same result as 'setCursorPosition(getCursorPosition() + 1);'

Returns:

Throws:

DataSourceException

close

void close()
    throws DataSourceException

Closes the datasource. This should be called at the end of each report processing run. Whether this closes the underlying data-source backend depends on the ReportDataFactory. Calling 'close()' on the ReportDataFactory *must* close all report data objects.

Throws:

DataSourceException

isReadable

boolean isReadable()
            throws DataSourceException

Checks, whether this report-data instance is currently readable. A report-data instance cannot be readable if it is positioned before the first row. (The look-ahead system of 'isAdvanceable()' will prevent that the datasource is positioned behind the last row.)

Returns:

true, if the datarow is valid, false otherwise.

Throws:

DataSourceException