| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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.apache.metamodel.membrane.app; |
| |
| import java.util.List; |
| import java.util.concurrent.TimeUnit; |
| |
| import org.apache.metamodel.DataContext; |
| import org.apache.metamodel.MetaModelException; |
| import org.apache.metamodel.factory.DataContextProperties; |
| import org.apache.metamodel.membrane.app.exceptions.DataSourceAlreadyExistException; |
| import org.apache.metamodel.membrane.app.exceptions.NoSuchDataSourceException; |
| import org.apache.metamodel.util.FileHelper; |
| |
| import com.google.common.cache.CacheBuilder; |
| import com.google.common.cache.CacheLoader; |
| import com.google.common.cache.LoadingCache; |
| import com.google.common.cache.RemovalListener; |
| import com.google.common.cache.RemovalNotification; |
| import com.google.common.util.concurrent.UncheckedExecutionException; |
| |
| /** |
| * A wrapper that adds a cache around a {@link DataSourceRegistry} in order to prevent re-connecting all the time to the |
| * same data source. |
| */ |
| public class CachedDataSourceRegistryWrapper implements DataSourceRegistry { |
| |
| /** |
| * The default timeout (in seconds) before the cache evicts and closes the created {@link DataContext}s. |
| */ |
| public static final int DEFAULT_TIMEOUT_SECONDS = 60; |
| |
| private final DataSourceRegistry delegate; |
| private final LoadingCache<String, DataContext> loadingCache; |
| |
| public CachedDataSourceRegistryWrapper(final DataSourceRegistry delegate) { |
| this(delegate, DEFAULT_TIMEOUT_SECONDS, TimeUnit.SECONDS); |
| } |
| |
| public CachedDataSourceRegistryWrapper(final DataSourceRegistry delegate, final long cacheTimeout, |
| final TimeUnit cacheTimeoutUnit) { |
| this.delegate = delegate; |
| this.loadingCache = CacheBuilder.newBuilder().expireAfterAccess(cacheTimeout, cacheTimeoutUnit) |
| .removalListener(createRemovalListener()).build(createCacheLoader()); |
| } |
| |
| private RemovalListener<String, DataContext> createRemovalListener() { |
| return new RemovalListener<String, DataContext>() { |
| @Override |
| public void onRemoval(final RemovalNotification<String, DataContext> notification) { |
| final DataContext dataContext = notification.getValue(); |
| // some DataContexts are closeable - attempt closing it here |
| FileHelper.safeClose(dataContext); |
| } |
| }; |
| } |
| |
| private CacheLoader<String, DataContext> createCacheLoader() { |
| return new CacheLoader<String, DataContext>() { |
| @Override |
| public DataContext load(final String key) throws Exception { |
| return delegate.openDataContext(key); |
| } |
| }; |
| } |
| |
| @Override |
| public List<String> getDataSourceNames() { |
| return delegate.getDataSourceNames(); |
| } |
| |
| @Override |
| public String registerDataSource(final String dataSourceName, final DataContextProperties dataContextProperties) |
| throws DataSourceAlreadyExistException { |
| loadingCache.invalidate(dataSourceName); |
| return delegate.registerDataSource(dataSourceName, dataContextProperties); |
| } |
| |
| @Override |
| public DataContext openDataContext(final String dataSourceName) throws NoSuchDataSourceException { |
| try { |
| return loadingCache.getUnchecked(dataSourceName); |
| } catch (UncheckedExecutionException e) { |
| final Throwable cause = e.getCause(); |
| if (cause instanceof RuntimeException) { |
| throw (RuntimeException) cause; |
| } |
| throw new MetaModelException( |
| "Unexpected error happened while getting DataContext '" + dataSourceName + "' from cache", e); |
| } |
| } |
| |
| @Override |
| public DataContext openDataContext(DataContextProperties properties) { |
| return delegate.openDataContext(properties); |
| } |
| |
| } |