| /** |
| * 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.lib.servlet; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.fs.FileSystem; |
| import org.apache.hadoop.lib.service.FileSystemAccess; |
| |
| import javax.servlet.Filter; |
| import javax.servlet.FilterChain; |
| import javax.servlet.FilterConfig; |
| import javax.servlet.ServletException; |
| import javax.servlet.ServletRequest; |
| import javax.servlet.ServletResponse; |
| import java.io.IOException; |
| |
| /** |
| * The <code>FileSystemReleaseFilter</code> releases back to the |
| * {@link FileSystemAccess} service a <code>FileSystem</code> instance. |
| * <p/> |
| * This filter is useful in situations where a servlet request |
| * is streaming out HDFS data and the corresponding filesystem |
| * instance have to be closed after the streaming completes. |
| */ |
| @InterfaceAudience.Private |
| public abstract class FileSystemReleaseFilter implements Filter { |
| private static final ThreadLocal<FileSystem> FILE_SYSTEM_TL = new ThreadLocal<FileSystem>(); |
| |
| /** |
| * Initializes the filter. |
| * <p/> |
| * This implementation is a NOP. |
| * |
| * @param filterConfig filter configuration. |
| * |
| * @throws ServletException thrown if the filter could not be initialized. |
| */ |
| @Override |
| public void init(FilterConfig filterConfig) throws ServletException { |
| } |
| |
| /** |
| * It delegates the incoming request to the <code>FilterChain</code>, and |
| * at its completion (in a finally block) releases the filesystem instance |
| * back to the {@link FileSystemAccess} service. |
| * |
| * @param servletRequest servlet request. |
| * @param servletResponse servlet response. |
| * @param filterChain filter chain. |
| * |
| * @throws IOException thrown if an IO error occurrs. |
| * @throws ServletException thrown if a servet error occurrs. |
| */ |
| @Override |
| public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) |
| throws IOException, ServletException { |
| try { |
| filterChain.doFilter(servletRequest, servletResponse); |
| } finally { |
| FileSystem fs = FILE_SYSTEM_TL.get(); |
| if (fs != null) { |
| FILE_SYSTEM_TL.remove(); |
| getFileSystemAccess().releaseFileSystem(fs); |
| } |
| } |
| } |
| |
| /** |
| * Destroys the filter. |
| * <p/> |
| * This implementation is a NOP. |
| */ |
| @Override |
| public void destroy() { |
| } |
| |
| /** |
| * Static method that sets the <code>FileSystem</code> to release back to |
| * the {@link FileSystemAccess} service on servlet request completion. |
| * |
| * @param fs fileystem instance. |
| */ |
| public static void setFileSystem(FileSystem fs) { |
| FILE_SYSTEM_TL.set(fs); |
| } |
| |
| /** |
| * Abstract method to be implemetned by concrete implementations of the |
| * filter that return the {@link FileSystemAccess} service to which the filesystem |
| * will be returned to. |
| * |
| * @return the FileSystemAccess service. |
| */ |
| protected abstract FileSystemAccess getFileSystemAccess(); |
| |
| } |