org.drools.core.base.accumulators.CollectSetAccumulateFunction Maven / Gradle / Ivy
/*
* Copyright 2010 Red Hat, Inc. and/or its affiliates.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.drools.core.base.accumulators;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.io.Serializable;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
/**
* An implementation of an accumulator capable of collecting sets of values.
* This is similar to the "collect" CE, but allows us to collect any value, not
* only facts.
*
* Example:
*
* rule "Set of unique employee names"
* when
* $names : Set() from accumulate(
* Employee( $n : firstName, $l : lastName ),
* collectSet( $n + " " + $l ) )
* then
* // do something
* end
*
*
* The set obviously does not computes duplications and the order of the elements in the set is not
* guaranteed.
*/
public class CollectSetAccumulateFunction extends AbstractAccumulateFunction {
public void readExternal(ObjectInput in) throws IOException,
ClassNotFoundException {
// functions are stateless, so nothing to serialize
}
public void writeExternal(ObjectOutput out) throws IOException {
// functions are stateless, so nothing to serialize
}
public static class CollectListData
implements
Externalizable {
public Map< Object, MutableInt > map = new HashMap();
public CollectListData() {
}
@SuppressWarnings("unchecked")
public void readExternal(ObjectInput in) throws IOException,
ClassNotFoundException {
map = (Map< Object, MutableInt >) in.readObject();
}
public void writeExternal(ObjectOutput out) throws IOException {
out.writeObject( map );
}
public static class MutableInt implements Serializable {
private static final long serialVersionUID = 510l;
public int value = 0;
}
}
/* (non-Javadoc)
* @see org.kie.base.accumulators.AccumulateFunction#createContext()
*/
public CollectListData createContext() {
return new CollectListData();
}
/* (non-Javadoc)
* @see org.kie.base.accumulators.AccumulateFunction#init(java.lang.Object)
*/
public void init(CollectListData data) {
data.map.clear();
}
/* (non-Javadoc)
* @see org.kie.base.accumulators.AccumulateFunction#accumulate(java.lang.Object, java.lang.Object)
*/
public void accumulate(CollectListData data,
Object value) {
CollectListData.MutableInt counter = data.map.get( value );
if( counter == null ) {
counter = new CollectListData.MutableInt();
data.map.put( value, counter );
}
counter.value++;
}
/* (non-Javadoc)
* @see org.kie.base.accumulators.AccumulateFunction#reverse(java.lang.Object, java.lang.Object)
*/
public void reverse(CollectListData data,
Object value) {
CollectListData.MutableInt counter = data.map.get( value );
if( (--counter.value) == 0 ) {
data.map.remove( value );
}
}
/* (non-Javadoc)
* @see org.kie.base.accumulators.AccumulateFunction#getResult(java.lang.Object)
*/
public Object getResult(CollectListData data) {
return Collections.unmodifiableSet( data.map.keySet() );
}
/* (non-Javadoc)
* @see org.kie.base.accumulators.AccumulateFunction#supportsReverse()
*/
public boolean supportsReverse() {
return true;
}
/**
* {@inheritDoc}
*/
public Class< ? > getResultType() {
return Set.class;
}
}