Github user LosD commented on a diff in the pull request:
https://github.com/apache/metamodel-membrane/pull/1#discussion_r129260484
--- Diff:
core/src/main/java/org/apache/metamodel/membrane/app/CachedDataSourceRegistryWrapper.java
---
@@ -0,0 +1,109 @@
+/**
+ * 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.ExecutionException;
+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;
+
+/**
+ * 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(DataSourceRegistry delegate) {
+ this(delegate, DEFAULT_TIMEOUT_SECONDS, TimeUnit.SECONDS);
+ }
+
+ public CachedDataSourceRegistryWrapper(DataSourceRegistry delegate,
long cacheTimeout, 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(RemovalNotification<String, DataContext>
notification) {
--- End diff --
Arguments missing `final` (here and all other places).
Might be personal preference, but to me it's even more important than for
variables. Arguments are usually trusted to be stable. Let's force them.
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