/**
* Copyright 2010 JBoss Inc
*
* 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.base.evaluators;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import org.drools.RuntimeDroolsException;
public class Operator
implements
Externalizable, org.drools.runtime.rule.Operator {
private static final long serialVersionUID = 510l;
// a static private cache so that pluggable operator can register their implementations
// it is automatically initialized with common operator implementations
private static final Map<String, Operator> CACHE = Collections.synchronizedMap( new HashMap<String, Operator>() );
// these static operator constants are kept here just to make it easier for the engine
// to reference common used operators. The addition of new constants here is not
// advisable though.
public static final Operator EQUAL = addOperatorToRegistry( "==",
false );
public static final Operator NOT_EQUAL = addOperatorToRegistry( "!=",
false );
public static final Operator LESS = addOperatorToRegistry( "<",
false );
public static final Operator LESS_OR_EQUAL = addOperatorToRegistry( "<=",
false );
public static final Operator GREATER = addOperatorToRegistry( ">",
false );
public static final Operator GREATER_OR_EQUAL = addOperatorToRegistry( ">=",
false );
/**
* Creates a new Operator instance for the given parameters,
* adds it to the registry and return it
*
* @param operatorId the identification symbol of the operator
* @param isNegated true if it is negated
*
* @return the newly created operator
*/
public static Operator addOperatorToRegistry(final String operatorId,
final boolean isNegated) {
Operator op = new Operator( operatorId,
isNegated );
CACHE.put( getKey( operatorId,
isNegated ),
op );
return op;
}
/**
* Returns the operator instance for the given parameters
*
* @param operatorId the identification symbol of the operator
* @param isNegated true if it is negated
*
* @return the operator in case it exists
*/
public static Operator determineOperator(final String operatorId,
final boolean isNegated) {
Operator op = CACHE.get( getKey( operatorId,
isNegated ) );
if ( op == null ) {
throw new RuntimeDroolsException( "unable to determine operator for symbol [" + (isNegated ? "not " : "") + operatorId + "]" );
}
return op;
}
private static String getKey(final String string,
final boolean isNegated) {
return isNegated + ":" + string;
}
// This class attributes
private String operator;
private boolean isNegated;
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
operator = (String)in.readObject();
isNegated = in.readBoolean();
}
public void writeExternal(ObjectOutput out) throws IOException {
out.writeObject(operator);
out.writeBoolean(isNegated);
}
public Operator() {
}
private Operator(final String operator,
final boolean isNegated) {
this.operator = operator;
this.isNegated = isNegated;
}
private Object readResolve() throws java.io.ObjectStreamException {
return determineOperator( this.operator,
this.isNegated );
}
public String toString() {
return "Operator = '" + this.operator + "'";
}
/* (non-Javadoc)
* @see org.drools.base.evaluators.OperatorInterface#getOperatorString()
*/
public String getOperatorString() {
return this.operator;
}
/* (non-Javadoc)
* @see org.drools.base.evaluators.OperatorInterface#isNegated()
*/
public boolean isNegated() {
return this.isNegated;
}
@Override
public int hashCode() {
final int PRIME = 31;
int result = super.hashCode();
result = PRIME * result + (isNegated ? 1231 : 1237);
result = PRIME * result + ((operator == null) ? 0 : operator.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if ( this == obj ) return true;
if ( obj == null ) return false;
if ( getClass() != obj.getClass() ) return false;
final Operator other = (Operator) obj;
if ( isNegated != other.isNegated ) return false;
if ( operator == null ) {
if ( other.operator != null ) return false;
} else if ( !operator.equals( other.operator ) ) return false;
return true;
}
}