org.jfree.report

Interface ReportData

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
static intBEFORE_FIRST_ROW
Method Summary
voidclose()
Closes the datasource.
intgetCursorPosition()
booleanisAdvanceable()
This operation checks, whether a call to next will be likely to succeed.
booleanisReadable()
Checks, whether this report-data instance is currently readable.
booleannext()
This method produces the same result as 'setCursorPosition(getCursorPosition() + 1);'
booleansetCursorPosition(int cursor)
Moves the cursor back to an already visited position.

Field Detail

BEFORE_FIRST_ROW

public static final int BEFORE_FIRST_ROW

Method Detail

close

public void close()
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

getCursorPosition

public int getCursorPosition()

isAdvanceable

public boolean isAdvanceable()
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

isReadable

public boolean isReadable()
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

next

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

Returns:

Throws: DataSourceException

setCursorPosition

public boolean setCursorPosition(int cursor)
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