hadoop FsUrlStreamHandlerFactory 源码

haddop FsUrlStreamHandlerFactory 代码

文件路径：/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FsUrlStreamHandlerFactory.java

/**
 * 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.hadoop.fs;

import java.io.IOException;
import java.net.URLStreamHandlerFactory;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;

/**
 * Factory for URL stream handlers.
 * 
 * There is only one handler whose job is to create UrlConnections. A
 * FsUrlConnection relies on FileSystem to choose the appropriate FS
 * implementation.
 * 
 * Before returning our handler, we make sure that FileSystem knows an
 * implementation for the requested scheme/protocol.
 */
@InterfaceAudience.Private
@InterfaceStability.Unstable
public class FsUrlStreamHandlerFactory implements
    URLStreamHandlerFactory {

  private static final Logger LOG =
      LoggerFactory.getLogger(FsUrlStreamHandlerFactory.class);

  /**
   * These are the protocols with MUST NOT be exported, as doing so
   * would conflict with the standard URL handlers registered by
   * the JVM. Many things will break.
   */
  public static final String[] UNEXPORTED_PROTOCOLS = {
      "http", "https"
  };

  // The configuration holds supported FS implementation class names.
  private Configuration conf;

  // This map stores whether a protocol is know or not by FileSystem
  private Map<String, Boolean> protocols =
      new ConcurrentHashMap<String, Boolean>();

  // The URL Stream handler
  private java.net.URLStreamHandler handler;

  public FsUrlStreamHandlerFactory() {
    this(new Configuration());
  }

  public FsUrlStreamHandlerFactory(Configuration conf) {
    this.conf = new Configuration(conf);
    // force init of FileSystem code to avoid HADOOP-9041
    try {
      FileSystem.getFileSystemClass("file", conf);
    } catch (IOException io) {
      throw new RuntimeException(io);
    }
    this.handler = new FsUrlStreamHandler(this.conf);
    for (String protocol : UNEXPORTED_PROTOCOLS) {
      protocols.put(protocol, false);
    }
  }

  @Override
  public java.net.URLStreamHandler createURLStreamHandler(String protocol) {
    LOG.debug("Creating handler for protocol {}", protocol);
    if (!protocols.containsKey(protocol)) {
      boolean known = true;
      try {
        Class<? extends FileSystem> impl
            = FileSystem.getFileSystemClass(protocol, conf);
        LOG.debug("Found implementation of {}: {}", protocol, impl);
      }
      catch (IOException ex) {
        known = false;
      }
      protocols.put(protocol, known);
    }
    if (protocols.get(protocol)) {
      LOG.debug("Using handler for protocol {}", protocol);
      return handler;
    } else {
      // FileSystem does not know the protocol, let the VM handle this
      LOG.debug("Unknown protocol {}, delegating to default implementation",
          protocol);
      return null;
    }
  }

}

相关信息

hadoop 源码目录

相关文章

hadoop Abortable 源码

hadoop AbstractFileSystem 源码

hadoop AvroFSInput 源码

hadoop BBPartHandle 源码

hadoop BBUploadHandle 源码

hadoop BatchListingOperations 源码

hadoop BatchedRemoteIterator 源码

hadoop BlockLocation 源码

hadoop BlockStoragePolicySpi 源码

hadoop BufferedFSInputStream 源码