Util.java

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/*******************************************************************************
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use these files 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.
 *
 * Copyright 2014 - Juan Pino, Aurelien Waite, William Byrne
 *******************************************************************************/
package uk.ac.cam.eng.extraction.hadoop.util;

import java.lang.reflect.Field;

import org.apache.hadoop.conf.Configuration;

import com.beust.jcommander.JCommander;
import com.beust.jcommander.Parameter;
import com.beust.jcommander.ParameterException;
import com.beust.jcommander.ParametersDelegate;

public final class Util {

        private Util() {

        }

        private static void setProps(Object params, Configuration conf)
                        throws IllegalArgumentException, IllegalAccessException {
                for (Field field : params.getClass().getDeclaredFields()) {
                        Parameter paramAnnotation = field.getAnnotation(Parameter.class);
                        if (paramAnnotation != null) {
                                // Use the first name only in annotation
                                String name = paramAnnotation.names()[0];
                                Object val = field.get(params);
                                if(val == null){
                                        throw new RuntimeException("Null value for " + name);
                                }
                                Class<?> clazz = val.getClass();
                                if (Integer.class == clazz) {
                                        conf.setInt(name, (Integer) val);
                                }else if (Double.class == clazz) {
                                        conf.set(name, val.toString()); 
                                }else if (Boolean.class == clazz) {
                                        conf.setBoolean(name, (Boolean) val);
                                } else if (String.class == clazz) {
                                        conf.set(name, (String) val);
                                }
                        } else if (field.getAnnotation(ParametersDelegate.class) != null) {
                                setProps(field.get(params), conf);
                        }
                }
        }

        public static void ApplyConf(Object params, Configuration conf)
                        throws IllegalArgumentException, IllegalAccessException {
                setProps(params, conf);
        }

        public static JCommander parseCommandLine(String[] args, Object params) {
                JCommander cmd = new JCommander();
                cmd.setAcceptUnknownOptions(true);
                cmd.addObject(params);
                try {
                        cmd.parse(args);
                } catch (ParameterException e) {
                        System.err.println(e.getMessage());
                        cmd.usage();
                        throw e;
                }
                return cmd;
        }

}