/*
* Copyright © 2014 Cask Data, 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 co.cask.tigon.internal.app.runtime.flow;
import co.cask.tigon.internal.io.Schema;
import co.cask.tigon.internal.io.SchemaHash;
import com.google.common.base.Preconditions;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.Maps;
import java.nio.ByteBuffer;
import java.util.Map;
import java.util.concurrent.ExecutionException;
/**
* Dynamic loading of schema from classloader and caching of known schemas.
*/
public final class SchemaCache {
private final LoadingCache<SchemaHash, Schema> cache;
/**
* Creates the schema cache with a set of know schemas.
*
* @param schemas Set of known schemas
*/
public SchemaCache(Iterable<Schema> schemas, ClassLoader classLoader) {
// TODO: Later on we should use ClassLoader.getResource
final Map<SchemaHash, Schema> schemaMap = Maps.newHashMap();
for (Schema schema : schemas) {
schemaMap.put(schema.getSchemaHash(), schema);
}
cache = CacheBuilder.newBuilder().build(new CacheLoader<SchemaHash, Schema>() {
@Override
public Schema load(SchemaHash key) throws Exception {
Schema schema = schemaMap.get(key);
Preconditions.checkNotNull(schema);
// TODO: Load from classloader
return schema;
}
}
);
}
/**
* Reads a {@link SchemaHash} from the given buffer and returns a {@link Schema} associated
* with the hash.
*
* @param buffer {@link java.nio.ByteBuffer} for reading in schema hash
* @return A {@link Schema} or {@code null} if the schema is not found.
*/
public Schema get(ByteBuffer buffer) {
return get(new SchemaHash(buffer));
}
public Schema get(SchemaHash hash) {
try {
return cache.get(hash);
} catch (ExecutionException e) {
return null;
}
}
}