com.hazelcast.query
Class PagingPredicate

java.lang.Object
  com.hazelcast.query.PagingPredicate

All Implemented Interfaces:

DataSerializable, IndexAwarePredicate, Predicate, Serializable

public class PagingPredicate
extends Object
implements IndexAwarePredicate, DataSerializable

This class is a special Predicate which helps to get a page-by-page result of a query. It can be constructed with a page-size, an inner predicate for filtering, and a comparator for sorting. This class is not thread-safe and stateless. To be able to reuse for another query, one should call reset()
Here is an example usage.

 Predicate lessEqualThanFour = Predicates.lessEqual("this", 4);

 // We are constructing our paging predicate with a predicate and page size. In this case query results fetched two
 by two.
 PagingPredicate predicate = new PagingPredicate(lessEqualThanFour, 2);

 // we are initializing our map with integers from 0 to 10 as keys and values.
 IMap map = hazelcastInstance.getMap(...);
 for (int i = 0; i < 10; i++) {
 map.put(i, i);
 }

 // invoking the query
 Collection values = map.values(predicate);
 System.out.println("values = " + values) // will print 'values = [0, 1]'
 predicate.nextPage(); // we are setting up paging predicate to fetch next page in the next call.
 values = map.values(predicate);
 System.out.println("values = " + values);// will print 'values = [2, 3]'
 Entry anchor = predicate.getAnchor();
 System.out.println("anchor -> " + anchor); // will print 'anchor -> 1=1',  since the anchor is the last entry of
 the previous page.
 predicate.previousPage(); // we are setting up paging predicate to fetch previous page in the next call
 values = map.values(predicate);
 System.out.println("values = " + values) // will print 'values = [0, 1]'
 

See Also:

Serialized Form

Constructor Summary

PagingPredicate()
Used for serialization internally

PagingPredicate(Comparator<Map.Entry> comparator, int pageSize)
Construct with a comparator and pageSize results will not be filtered results will be ordered via comparator throws IllegalArgumentException if pageSize is not greater than 0

PagingPredicate(int pageSize)
Construct with a pageSize results will not be filtered results will be natural ordered throws IllegalArgumentException if pageSize is not greater than 0

PagingPredicate(Predicate predicate, Comparator<Map.Entry> comparator, int pageSize)
Construct with an inner predicate, comparator and pageSize results will be filtered via inner predicate results will be ordered via comparator throws IllegalArgumentException if pageSize is not greater than 0 throws IllegalArgumentException if inner predicate is also PagingPredicate

PagingPredicate(Predicate predicate, int pageSize)
Construct with an inner predicate and pageSize results will be filtered via inner predicate results will be natural ordered throws IllegalArgumentException if pageSize is not greater than 0 throws IllegalArgumentException if inner predicate is also PagingPredicate

Method Summary

boolean	apply(Map.Entry mapEntry) Used for delegating filtering to inner predicate.
Set<QueryableEntry>	filter(QueryContext queryContext) Used if inner predicate is instanceof IndexAwarePredicate for filtering.
Map.Entry	getAnchor() Retrieve the anchor object which is the last value object on the previous page.
Comparator<Map.Entry>	getComparator()
IterationType	getIterationType()
int	getPage()
int	getPageSize()
Predicate	getPredicate()
boolean	isIndexed(QueryContext queryContext) Used if inner predicate is instanceof IndexAwarePredicate for checking if indexed.
void	nextPage() sets the page value to next page
void	previousPage() sets the page value to previous page
void	readData(ObjectDataInput in) Reads fields from the input stream
void	reset() resets for reuse
void	setIterationType(IterationType iterationType)
void	writeData(ObjectDataOutput out) Writes object fields to output stream

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PagingPredicate

public PagingPredicate()

Used for serialization internally

PagingPredicate

public PagingPredicate(int pageSize)

Construct with a pageSize results will not be filtered results will be natural ordered throws IllegalArgumentException if pageSize is not greater than 0

Parameters:

pageSize - page size

PagingPredicate

public PagingPredicate(Predicate predicate,
                       int pageSize)

Construct with an inner predicate and pageSize results will be filtered via inner predicate results will be natural ordered throws IllegalArgumentException if pageSize is not greater than 0 throws IllegalArgumentException if inner predicate is also PagingPredicate

Parameters:

predicate - the inner predicate through which results will be filtered

pageSize - the page size

PagingPredicate

public PagingPredicate(Comparator<Map.Entry> comparator,
                       int pageSize)

Construct with a comparator and pageSize results will not be filtered results will be ordered via comparator throws IllegalArgumentException if pageSize is not greater than 0

Parameters:

comparator - the comparator through which results will be ordered

pageSize - the page size

PagingPredicate

public PagingPredicate(Predicate predicate,
                       Comparator<Map.Entry> comparator,
                       int pageSize)

Construct with an inner predicate, comparator and pageSize results will be filtered via inner predicate results will be ordered via comparator throws IllegalArgumentException if pageSize is not greater than 0 throws IllegalArgumentException if inner predicate is also PagingPredicate

Parameters:

predicate - the inner predicate through which results will be filtered

comparator - the comparator through which results will be ordered

pageSize - the page size

Method Detail

filter

public Set<QueryableEntry> filter(QueryContext queryContext)

Used if inner predicate is instanceof IndexAwarePredicate for filtering.

Specified by:

filter in interface IndexAwarePredicate

Parameters:

queryContext -

Returns:

isIndexed

public boolean isIndexed(QueryContext queryContext)

Used if inner predicate is instanceof IndexAwarePredicate for checking if indexed.

Specified by:

isIndexed in interface IndexAwarePredicate

Parameters:

queryContext -

Returns:

apply

public boolean apply(Map.Entry mapEntry)

Used for delegating filtering to inner predicate.

Specified by:

apply in interface Predicate

Parameters:

mapEntry -

Returns:

reset

public void reset()

resets for reuse

nextPage

public void nextPage()

sets the page value to next page

previousPage

public void previousPage()

sets the page value to previous page

getIterationType

public IterationType getIterationType()

setIterationType

public void setIterationType(IterationType iterationType)

getPage

public int getPage()

getPageSize

public int getPageSize()

getPredicate

public Predicate getPredicate()

getComparator

public Comparator<Map.Entry> getComparator()

getAnchor

public Map.Entry getAnchor()

Retrieve the anchor object which is the last value object on the previous page. Note: This method will return `null` on the first page of the query result.

Returns:

Map.Entry the anchor object which is the last value object on the previous page

writeData

public void writeData(ObjectDataOutput out)
               throws IOException

Description copied from interface: DataSerializable

Writes object fields to output stream

Specified by:

writeData in interface DataSerializable

Parameters:

out - output

Throws:

IOException

readData

public void readData(ObjectDataInput in)
              throws IOException

Description copied from interface: DataSerializable

Reads fields from the input stream

Specified by:

readData in interface DataSerializable

Parameters:

in - input

Throws:

IOException