ctubbsii commented on code in PR #48:
URL:
https://github.com/apache/accumulo-classloaders/pull/48#discussion_r2699961399
##########
modules/local-caching-classloader/src/main/java/org/apache/accumulo/classloader/lcc/LocalCachingContextClassLoaderFactory.java:
##########
@@ -90,6 +92,14 @@
*/
public class LocalCachingContextClassLoaderFactory implements
ContextClassLoaderFactory {
+ // Configure the URL class to know about the "hdfs://" protocol. This can
only be
+ // called once in the JVM, so it has to be in a static initializer vs the
init
+ // method. We are not using org.apache.hadoop.fs.FsUrlStreamHandlerFactory
+ // because it overrides the handling of the "file" protocol.
+ static {
+ URL.setURLStreamHandlerFactory(new HdfsUrlStreamHandlerFactory(new
Configuration()));
Review Comment:
Apparently, in Java 9+, there's a better way to do this, that avoids the
problem of needing to call this only once in the JVM. Instead of setting the
factory, you can register a
[URLStreamHandlerProvider](https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/net/spi/URLStreamHandlerProvider.html)
to handle the hdfs URLs. We can use `@AutoService` to generate the appropriate
`META-INF/services` file.
##########
modules/local-caching-classloader/src/main/java/org/apache/accumulo/classloader/lcc/util/HdfsUrlStreamHandlerFactory.java:
##########
@@ -0,0 +1,115 @@
+/*
+ * 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
+ *
+ * https://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.accumulo.classloader.lcc.util;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.net.URLConnection;
+import java.net.URLStreamHandler;
+import java.net.URLStreamHandlerFactory;
+import java.util.Objects;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.base.Preconditions;
+
+public class HdfsUrlStreamHandlerFactory implements URLStreamHandlerFactory {
+
+ private static final Logger LOG =
LoggerFactory.getLogger(HdfsUrlStreamHandlerFactory.class);
+
+ private class HdfsUrlConnection extends URLConnection {
+
+ private final Configuration conf;
+
+ private InputStream is;
+
+ public HdfsUrlConnection(Configuration conf, URL url) {
+ super(url);
+ Objects.requireNonNull(conf, "null conf argument");
+ Objects.requireNonNull(url, "null url argument");
+ this.conf = conf;
+ }
+
+ @Override
+ public void connect() throws IOException {
+ Preconditions.checkState(is == null, "Already connected");
+ try {
+ LOG.debug("Connecting to {}", url);
+ URI uri = url.toURI();
+ FileSystem fs = FileSystem.get(uri, conf);
+ // URI#getPath returns null value if path contains relative path
+ // i.e file:root/dir1/file1
+ // So path can not be constructed from URI.
+ // We can only use schema specific part in URI.
+ // Uri#isOpaque return true if path is relative.
Review Comment:
This comment seems to be addressing the fact that a URI could contain a
relative path. However, that is not possible if it came from a file: URL,
because URLs, by definition, are absolute paths. While it is possible to have a
URI that represents a relative file: path, it is not possible for a URL to do
that, and this URI came from a URL, so the relative Path situation is not
possible here.
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