ListShardSelector.java

/*
 * Copyright 2010 Outerthought bvba
 *
 * 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.lilyproject.indexer.model.sharding;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public class ListShardSelector extends BaseShardSelector {
    private Map<Object, String> valueToShard = new HashMap<Object, String>();

    public ListShardSelector(ShardingKey shardingKey) {
        super(shardingKey);
    }

    protected void addMapping(Comparable value, String shardName) throws ShardingConfigException {
        String existingShard = valueToShard.get(value);
        if (existingShard != null) {
            throw new ShardingConfigException("Same value maps to multiple shards. Value: " + value + ", shards: " +
                    existingShard + " and " + shardName);
        }
        valueToShard.put(value, shardName);
    }

    @Override
    public String getShard(Comparable key) throws ShardSelectorException {
        String shardName = valueToShard.get(key);
        if (shardName == null) {
            throw new ShardSelectorException("Shard value does not map to a shard: " + key);
        }
        return shardName;
    }

    @Override
    public Set<String> getShards() {
        return new HashSet<String>(valueToShard.values());
    }
}