com.jenkov.mrpersister.itf
Interface IReadFilter

All Known Implementing Classes:

AcceptAllReadFilter, PageReadFilter

public interface IReadFilter

This interface represents the read filters that can be used in Mr. Persister. A read filter is used to limit the amount of records read, by having the filter not accept any records that are not desired to be read. This can be used to read pages of objects, for instance object 10-20 of a total ResultSet of 50 records.

It can also be used to just filter the ResultSet further than was possible (or hard to do) in the SQL generating the ResultSet in the first place. Also read filters can be combined, making it easier to have filters that can be switched on and off. Easier than having to generate the SQL for those kinds of on/off filterings.

Read filters are used when calling the functions of the object reader.

Author:

Jakob Jenkov, Jenkov Development

Method Summary

boolean	accept(java.sql.ResultSet result) Returns true if the filter can accept the record at the current position of the result set as part of the objects read.
void	acceptedByAllFilters(boolean wasAcceptedByAllFilters) If the filter is used in a combined filter, this filter can be told whether all other filters accepted this record, or not.
boolean	acceptMore() Returns true if the filter will accept anymore records at all.
void	clear() This method is called when all reading is done.
void	init(java.sql.ResultSet result) Called by the object reader before reading starts taking place.

Method Detail

init

void init(java.sql.ResultSet result)
          throws java.sql.SQLException,
                 PersistenceException

Called by the object reader before reading starts taking place. Can be used to manipulate the result set before the reading takes place, for instance, moving the result set forward to a certain record. This way paged reading can be implemented.

Parameters:

result - The ResultSet to initialize.

Throws:

java.sql.SQLException

PersistenceException

accept

boolean accept(java.sql.ResultSet result)
               throws java.sql.SQLException,
                      PersistenceException

Returns true if the filter can accept the record at the current position of the result set as part of the objects read. False if the filter doesn't want this record to be part of the list of objects read.

Parameters:

result - The ResultSet instance apply the filter filter to.

Returns:

True if the filter accepts the current record. False if not.

Throws:

java.sql.SQLException

PersistenceException

acceptMore

boolean acceptMore()

Returns true if the filter will accept anymore records at all. False if not. This can for instance be used to stop the reading after a certain amount of records has been accepted, for paged reading.

Returns:

True if the filter will accept anymore records at all. False if not.

acceptedByAllFilters

void acceptedByAllFilters(boolean wasAcceptedByAllFilters)

If the filter is used in a combined filter, this filter can be told whether all other filters accepted this record, or not. This may be useful for instance in a paged filter, that wants 10 records total, but only wants to count accepted records if other filters also accepts the records.

Parameters:

wasAcceptedByAllFilters - Will be set to true if all filters in a combined filter accepted the current record. Will be set to false if just one single filter do not accept the current record.

clear

void clear()

This method is called when all reading is done. This gives the filter a chance to clean up any objects instantiated during filtering.