com.moz.fiji.hadoop.configurator.ConfigurationVariable.java Source code

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Here is the source code for com.moz.fiji.hadoop.configurator.ConfigurationVariable.java

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/**
 * (c) Copyright 2015 WibiData, Inc.
 *
 * See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * Licensed 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 com.moz.fiji.hadoop.configurator;

import java.lang.reflect.Field;
import java.util.Collection;

import org.apache.hadoop.conf.Configuration;

/**
 * This class encapsulates everything there is to know about a Hadoop
 * configuration variable declaration.
 */
public class ConfigurationVariable {
    private Field mField;
    private HadoopConf mAnnotation;

    /**
     * Constructs a ConfigurationVariable instance.
     *
     * @param field The variable that has the annotation on it.
     * @param annotation The annotation on the field.
     */
    public ConfigurationVariable(Field field, HadoopConf annotation) {
        mField = field;
        mAnnotation = annotation;
    }

    /**
     * Gets the configuration key that should be used to populate the field.
     *
     * @return The key that was specified in the HadoopConf annotation.
     */
    public String getKey() {
        return mAnnotation.key();
    }

    /**
     * Populates an object's field with the value read from a Configuration instance.
     *
     * @param instance The object to populate.
     * @param conf The configuration to read from.
     * @throws IllegalAccessException If the field cannot be set on the object.
     * @throws HadoopConfigurationException If there is a problem with the annotation definition.
     */
    public void setValue(Object instance, Configuration conf) throws IllegalAccessException {
        final String key = getKey();
        if (null == key) {
            throw new HadoopConfigurationException("Missing 'key' attribute of @HadoopConf on "
                    + instance.getClass().getName() + "." + mField.getName());
        }
        if (null == conf.get(key) && mAnnotation.defaultValue().isEmpty()) {
            // Nothing set in the configuration, and no default value
            // specified. Just leave the field alone.
            return;
        }

        if (!mField.isAccessible()) {
            mField.setAccessible(true);
        }

        try {
            if (boolean.class == mField.getType()) {
                mField.setBoolean(instance, conf.getBoolean(key, getDefaultBoolean(instance)));
            } else if (float.class == mField.getType()) {
                mField.setFloat(instance, conf.getFloat(key, getDefaultFloat(instance)));
            } else if (double.class == mField.getType()) {
                mField.setDouble(instance, conf.getFloat(key, getDefaultDouble(instance)));
            } else if (int.class == mField.getType()) {
                mField.setInt(instance, conf.getInt(key, getDefaultInt(instance)));
            } else if (long.class == mField.getType()) {
                mField.setLong(instance, conf.getLong(key, getDefaultLong(instance)));
            } else if (mField.getType().isAssignableFrom(String.class)) {
                mField.set(instance, conf.get(key, getDefaultString(instance)));
            } else if (mField.getType().isAssignableFrom(Collection.class)) {
                mField.set(instance, conf.getStringCollection(key));
            } else if (String[].class == mField.getType()) {
                mField.set(instance, conf.getStrings(key));
            } else {
                throw new HadoopConfigurationException("Unsupported field type annotated by @HadoopConf: "
                        + instance.getClass().getName() + "." + mField.getName());
            }
        } catch (NumberFormatException e) {
            // That's okay. The default value for the field will be kept.
        }
    }

    /**
     * Gets the default value as a boolean.
     *
     * @param instance The object instance.
     * @return The default boolean value.
     * @throws IllegalAccessException If the field cannot be read.
     */
    private boolean getDefaultBoolean(Object instance) throws IllegalAccessException {
        String defaultValue = mAnnotation.defaultValue();
        if (defaultValue.isEmpty()) {
            return mField.getBoolean(instance);
        }
        return Boolean.parseBoolean(defaultValue);
    }

    /**
     * Gets the default value as a float.
     *
     * @param instance The object instance.
     * @return The default float value.
     * @throws IllegalAccessException If the field cannot be read.
     */
    private float getDefaultFloat(Object instance) throws IllegalAccessException {
        String defaultValue = mAnnotation.defaultValue();
        if (defaultValue.isEmpty()) {
            return mField.getFloat(instance);
        }
        return Float.parseFloat(defaultValue);
    }

    /**
     * Gets the default value as a double.
     *
     * @param instance The object instance.
     * @return The default double value.
     * @throws IllegalAccessException If the field cannot be read.
     */
    private float getDefaultDouble(Object instance) throws IllegalAccessException {
        String defaultValue = mAnnotation.defaultValue();
        if (defaultValue.isEmpty()) {
            return (float) mField.getDouble(instance);
        }
        return Float.parseFloat(defaultValue);
    }

    /**
     * Gets the default value as an int.
     *
     * @param instance The object instance.
     * @return The default int value.
     * @throws IllegalAccessException If the field cannot be read.
     */
    private int getDefaultInt(Object instance) throws IllegalAccessException {
        String defaultValue = mAnnotation.defaultValue();
        if (defaultValue.isEmpty()) {
            return mField.getInt(instance);
        }
        return Integer.parseInt(defaultValue);
    }

    /**
     * Gets the default value as a long.
     *
     * @param instance The object instance.
     * @return The default long value.
     * @throws IllegalAccessException If the field cannot be read.
     */
    private long getDefaultLong(Object instance) throws IllegalAccessException {
        String defaultValue = mAnnotation.defaultValue();
        if (defaultValue.isEmpty()) {
            return mField.getLong(instance);
        }
        return Long.parseLong(defaultValue);
    }

    /**
     * Gets the default value as a string.
     *
     * @param instance The object instance.
     * @return The default string value.
     * @throws IllegalAccessException If the field cannot be read.
     */
    private String getDefaultString(Object instance) throws IllegalAccessException {
        String defaultValue = mAnnotation.defaultValue();
        if (defaultValue.isEmpty()) {
            return (String) mField.get(instance);
        }
        return defaultValue;
    }
}