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.falcon.util; import org.apache.commons.io.IOUtils; import org.apache.commons.lang3.StringUtils; import org.apache.falcon.FalconException; import org.apache.falcon.expression.ExpressionHelper; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.net.URL; import java.util.HashSet; import java.util.Properties; import java.util.Set; /** * Base class for reading application properties. */ public abstract class ApplicationProperties extends Properties { private static final Logger LOG = LoggerFactory.getLogger(ApplicationProperties.class); protected abstract String getPropertyFile(); private String domain; protected ApplicationProperties() throws FalconException { init(); } protected void init() throws FalconException { setDomain(System.getProperty("falcon.domain", System.getenv("FALCON_DOMAIN"))); loadProperties(); } protected void setDomain(String domain) { this.domain = domain; } public String getDomain() { return domain; } protected void loadProperties() throws FalconException { String propertyFileName = getPropertyFile(); String confDir = System.getProperty("config.location"); loadProperties(propertyFileName, confDir); } /** * This method reads the given properties file in the following order: * config.location & classpath. It falls back in that specific order. * * @throws FalconException */ protected void loadProperties(String propertyFileName, String confDir) throws FalconException { try { InputStream resourceAsStream = checkConfigLocation(propertyFileName, confDir); //Fallback to classpath if (resourceAsStream == null) { resourceAsStream = checkClassPath(propertyFileName); } if (resourceAsStream != null) { try { doLoadProperties(resourceAsStream); return; } finally { IOUtils.closeQuietly(resourceAsStream); } } throw new FileNotFoundException("Unable to find: " + propertyFileName); } catch (IOException e) { throw new FalconException("Error loading properties file: " + getPropertyFile(), e); } } private InputStream checkConfigLocation(String propertyFileName, String confDir) throws FileNotFoundException { InputStream resourceAsStream = null; if (confDir != null) { File fileToLoad = new File(confDir, propertyFileName); if (fileToLoad.exists() && fileToLoad.isFile() && fileToLoad.canRead()) { LOG.info("config.location is set, using: {}/{}", confDir, propertyFileName); resourceAsStream = new FileInputStream(fileToLoad); } } return resourceAsStream; } private InputStream checkClassPath(String propertyFileName) { InputStream resourceAsStream = null; Class clazz = ApplicationProperties.class; URL resource = clazz.getResource("/" + propertyFileName); if (resource != null) { LOG.info("Fallback to classpath for: {}", resource); resourceAsStream = clazz.getResourceAsStream("/" + propertyFileName); } else { resource = clazz.getResource(propertyFileName); if (resource != null) { LOG.info("Fallback to classpath for: {}", resource); resourceAsStream = clazz.getResourceAsStream(propertyFileName); } } return resourceAsStream; } private void doLoadProperties(InputStream resourceAsStream) throws IOException, FalconException { Properties origProps = new Properties(); origProps.load(resourceAsStream); if (domain == null) { domain = origProps.getProperty("*.domain"); if (domain == null) { throw new FalconException("Domain is not set!"); } else { domain = ExpressionHelper.substitute(domain); } } LOG.info("Initializing {} properties with domain {}", this.getClass().getName(), domain); Set<String> keys = getKeys(origProps.keySet()); for (String key : keys) { String value = origProps.getProperty(domain + "." + key, origProps.getProperty("*." + key)); if (value != null) { value = ExpressionHelper.substitute(value); LOG.debug("{}={}", key, value); put(key, value); } } } private Set<String> getKeys(Set<Object> keySet) { Set<String> keys = new HashSet<String>(); for (Object keyObj : keySet) { String key = (String) keyObj; keys.add(key.substring(key.indexOf('.') + 1)); } return keys; } @Override public String getProperty(String key) { return StringUtils.trim(super.getProperty(key)); } @Override public String getProperty(String key, String defaultValue) { return StringUtils.trim(super.getProperty(key, defaultValue)); } }