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
static int BEFORE_FIRST_ROW
           
 
Method Summary
 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