/*
* Copyright 2014 the original author or authors.
*
* 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.springframework.data.hadoop.store.expression;
import org.springframework.expression.AccessException;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.MethodExecutor;
import org.springframework.expression.TypedValue;
/**
* A {@link MethodExecutor} using an first argument as an
* Object to get its hashcode and second argument expected to
* be an Integer to calculate a simple bucket name.
*
* <p>Spel expression "hash(region,2)" would create either key
* "0_hash" or "1_hash". Using a bucketsize 0 results
* an {@link AccessException}.
*
* @author Janne Valkealahti
*
*/
public class HashMethodExecutor implements MethodExecutor {
@Override
public TypedValue execute(EvaluationContext context, Object target, Object... arguments) throws AccessException {
if (arguments[1] instanceof Integer) {
try {
Integer buckets = ((Integer)arguments[1]);
return new TypedValue(Math.abs(arguments[0].hashCode()) % buckets + "_hash");
} catch (Exception e) {
throw new AccessException("Error creating hash", e);
}
}
throw new AccessException("Argument " + arguments[1] + " not an Integer");
}
}