Java tutorial
/* * 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 gobblin.source.extractor.hadoop; import java.io.IOException; import java.io.InputStream; import java.net.URI; import java.net.URISyntaxException; import java.util.ArrayList; import java.util.List; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileStatus; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.compress.CompressionCodec; import org.apache.hadoop.io.compress.CompressionCodecFactory; import com.google.common.base.Strings; import gobblin.configuration.ConfigurationKeys; import gobblin.configuration.State; import gobblin.source.extractor.filebased.FileBasedHelper; import gobblin.source.extractor.filebased.FileBasedHelperException; import gobblin.source.extractor.filebased.TimestampAwareFileBasedHelper; import gobblin.util.HadoopUtils; import gobblin.util.ProxiedFileSystemWrapper; /** * A common helper that extends {@link FileBasedHelper} and provides access to a files via a {@link FileSystem}. */ public class HadoopFsHelper implements TimestampAwareFileBasedHelper { private final State state; private final Configuration configuration; private FileSystem fs; public HadoopFsHelper(State state) { this(state, HadoopUtils.getConfFromState(state)); } public HadoopFsHelper(State state, Configuration configuration) { this.state = state; this.configuration = configuration; } protected State getState() { return this.state; } public FileSystem getFileSystem() { return this.fs; } @Override public void connect() throws FileBasedHelperException { String uri = this.state.getProp(ConfigurationKeys.SOURCE_FILEBASED_FS_URI); try { if (Strings.isNullOrEmpty(uri)) { throw new FileBasedHelperException( ConfigurationKeys.SOURCE_FILEBASED_FS_URI + " has not been configured"); } this.createFileSystem(uri); } catch (IOException e) { throw new FileBasedHelperException("Cannot connect to given URI " + uri + " due to " + e.getMessage(), e); } catch (URISyntaxException e) { throw new FileBasedHelperException("Malformed uri " + uri + " due to " + e.getMessage(), e); } catch (InterruptedException e) { throw new FileBasedHelperException("Interrupted exception is caught when getting the proxy file system", e); } } @Override public List<String> ls(String path) throws FileBasedHelperException { List<String> results = new ArrayList<>(); try { lsr(new Path(path), results); } catch (IOException e) { throw new FileBasedHelperException("Cannot do ls on path " + path + " due to " + e.getMessage(), e); } return results; } public void lsr(Path p, List<String> results) throws IOException { if (!this.fs.getFileStatus(p).isDirectory()) { results.add(p.toString()); } Path qualifiedPath = this.fs.makeQualified(p); for (FileStatus status : this.fs.listStatus(p)) { if (status.isDirectory()) { // Fix for hadoop issue: https://issues.apache.org/jira/browse/HADOOP-12169 if (!qualifiedPath.equals(status.getPath())) { lsr(status.getPath(), results); } } else { results.add(status.getPath().toString()); } } } private void createFileSystem(String uri) throws IOException, InterruptedException, URISyntaxException { if (this.state.getPropAsBoolean(ConfigurationKeys.SHOULD_FS_PROXY_AS_USER, ConfigurationKeys.DEFAULT_SHOULD_FS_PROXY_AS_USER)) { // Initialize file system as a proxy user. this.fs = new ProxiedFileSystemWrapper().getProxiedFileSystem(this.state, ProxiedFileSystemWrapper.AuthType.TOKEN, this.state.getProp(ConfigurationKeys.FS_PROXY_AS_USER_TOKEN_FILE), uri, configuration); } else { // Initialize file system as the current user. this.fs = FileSystem.newInstance(URI.create(uri), this.configuration); } } @Override public long getFileMTime(String filePath) throws FileBasedHelperException { try { return this.getFileSystem().getFileStatus(new Path(filePath)).getModificationTime(); } catch (IOException e) { throw new FileBasedHelperException( String.format("Failed to get last modified time for file at path %s due to error %s", filePath, e.getMessage()), e); } } @Override public long getFileSize(String filePath) throws FileBasedHelperException { try { return this.getFileSystem().getFileStatus(new Path(filePath)).getLen(); } catch (IOException e) { throw new FileBasedHelperException(String .format("Failed to get size for file at path %s due to error %s", filePath, e.getMessage()), e); } } /** * Returns an {@link InputStream} to the specified file. * <p> * Note: It is the caller's responsibility to close the returned {@link InputStream}. * </p> * * @param path The path to the file to open. * @return An {@link InputStream} for the specified file. * @throws FileBasedHelperException if there is a problem opening the {@link InputStream} for the specified file. */ @Override public InputStream getFileStream(String path) throws FileBasedHelperException { try { Path p = new Path(path); InputStream in = this.getFileSystem().open(p); // Account for compressed files (e.g. gzip). // https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/input/WholeTextFileRecordReader.scala CompressionCodecFactory factory = new CompressionCodecFactory(this.getFileSystem().getConf()); CompressionCodec codec = factory.getCodec(p); return (codec == null) ? in : codec.createInputStream(in); } catch (IOException e) { throw new FileBasedHelperException("Cannot open file " + path + " due to " + e.getMessage(), e); } } @Override public void close() throws IOException { this.getFileSystem().close(); } }