1 /***
2 * Copyright 2003-2010 Terracotta, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package net.sf.ehcache.search.aggregator;
18
19 import net.sf.ehcache.search.Attribute;
20
21 /***
22 * An AggregatorInstance takes input objects and computes an aggregate function from them.
23 *
24 * @author Greg Luck
25 * @param <T>
26 * the runtime type of aggregation result
27 */
28 public interface AggregatorInstance<T> {
29
30 /***
31 * Add the given value to the aggregator function
32 *
33 * @param input a single input value
34 * @throws AggregatorException if the function cannot be computed, possibly due to unsupported types
35 */
36 void accept(Object input) throws AggregatorException;
37
38 /***
39 * Retrieve the final result
40 *
41 * @return aggregate result
42 */
43 Object aggregateResult();
44
45 /***
46 * Get the attribute to pass to aggregator
47 *
48 * @return attribute to aggregate (null if no attribute is applicable to function)
49 */
50 Attribute<?> getAttribute();
51 }