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 org.apache.sqoop.config; import java.io.IOException; import java.util.ArrayList; import java.util.List; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.JobContext; import org.apache.hadoop.util.GenericOptionsParser; import com.cloudera.sqoop.mapreduce.db.DBConfiguration; import org.apache.hadoop.util.ReflectionUtils; /** * This class provides static helper methods that allow access and manipulation * of job configuration. It is convenient to keep such access in one place in * order to allow easy modifications when some of these aspects change from * version to version of Hadoop. */ public final class ConfigurationHelper { /** * Set the (hinted) number of map tasks for a job. */ public static void setJobNumMaps(Job job, int numMapTasks) { job.getConfiguration().setInt(ConfigurationConstants.PROP_MAPRED_MAP_TASKS, numMapTasks); } /** * Get the (hinted) number of map tasks for a job. */ public static int getJobNumMaps(JobContext job) { return job.getConfiguration().getInt(ConfigurationConstants.PROP_MAPRED_MAP_TASKS, 1); } /** * @return the number of mapper output records from a job using its counters. */ public static long getNumMapOutputRecords(Job job) throws IOException, InterruptedException { return job.getCounters().findCounter(ConfigurationConstants.COUNTER_GROUP_MAPRED_TASK_COUNTERS, ConfigurationConstants.COUNTER_MAP_OUTPUT_RECORDS).getValue(); } /** * @return the number of mapper input records from a job using its counters. */ public static long getNumMapInputRecords(Job job) throws IOException, InterruptedException { return job.getCounters().findCounter(ConfigurationConstants.COUNTER_GROUP_MAPRED_TASK_COUNTERS, ConfigurationConstants.COUNTER_MAP_INPUT_RECORDS).getValue(); } /** * Get the (hinted) number of map tasks for a job. */ public static int getConfNumMaps(Configuration conf) { return conf.getInt(ConfigurationConstants.PROP_MAPRED_MAP_TASKS, 1); } /** * Set the mapper speculative execution property for a job. */ public static void setJobMapSpeculativeExecution(Job job, boolean isEnabled) { job.getConfiguration().setBoolean(ConfigurationConstants.PROP_MAPRED_MAP_TASKS_SPECULATIVE_EXEC, isEnabled); } /** * Set the reducer speculative execution property for a job. */ public static void setJobReduceSpeculativeExecution(Job job, boolean isEnabled) { job.getConfiguration().setBoolean(ConfigurationConstants.PROP_MAPRED_REDUCE_TASKS_SPECULATIVE_EXEC, isEnabled); } /** * Sets the Jobtracker address to use for a job. */ public static void setJobtrackerAddr(Configuration conf, String addr) { conf.set(ConfigurationConstants.PROP_MAPRED_JOB_TRACKER_ADDRESS, addr); } /** * @return the Configuration property identifying a DBWritable to use. */ public static String getDbInputClassProperty() { return DBConfiguration.INPUT_CLASS_PROPERTY; } /** * @return the Configuration property identifying the DB username. */ public static String getDbUsernameProperty() { return DBConfiguration.USERNAME_PROPERTY; } /** * @return the Configuration property identifying the DB password. */ public static String getDbPasswordProperty() { return DBConfiguration.PASSWORD_PROPERTY; } /** * @return the Configuration property identifying the DB connect string. */ public static String getDbUrlProperty() { return DBConfiguration.URL_PROPERTY; } /** * @return the Configuration property identifying the DB input table. */ public static String getDbInputTableNameProperty() { return DBConfiguration.INPUT_TABLE_NAME_PROPERTY; } /** * @return the Configuration property specifying WHERE conditions for the * db table. */ public static String getDbInputConditionsProperty() { return DBConfiguration.INPUT_CONDITIONS_PROPERTY; } /** * Parse arguments in 'args' via the GenericOptionsParser and * embed the results in the supplied configuration. * @param conf the configuration to populate with generic options. * @param args the arguments to process. * @return the unused args to be passed to the application itself. */ public static String[] parseGenericOptions(Configuration conf, String[] args) throws IOException { // This needs to be shimmed because in Apache Hadoop this can throw // an IOException, but it does not do so in CDH. We just mandate in // this method that an IOException is possible. GenericOptionsParser genericParser = new GenericOptionsParser(conf, args); return genericParser.getRemainingArgs(); } /** * Get the value of the <code>name</code> property as a <code>List</code> * of objects implementing the interface specified by <code>xface</code>. * * An exception is thrown if any of the classes does not exist, or if it does * not implement the named interface. * * @param name the property name. * @param xface the interface implemented by the classes named by * <code>name</code>. * @return a <code>List</code> of objects implementing <code>xface</code>. */ @SuppressWarnings("unchecked") public static <U> List<U> getInstances(Configuration conf, String name, Class<U> xface) { List<U> ret = new ArrayList<U>(); Class<?>[] classes = conf.getClasses(name); for (Class<?> cl : classes) { if (!xface.isAssignableFrom(cl)) { throw new RuntimeException(cl + " does not implement " + xface); } ret.add((U) ReflectionUtils.newInstance(cl, conf)); } return ret; } private ConfigurationHelper() { // Disable explicit object creation } }