Java tutorial
/* * Copyright (c) 2011, Cloudera, Inc. All Rights Reserved. * * Cloudera, Inc. 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 * * This software 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.cloudera.lib.util; import org.apache.hadoop.conf.Configuration; import org.w3c.dom.DOMException; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.w3c.dom.Text; import org.xml.sax.ErrorHandler; import org.xml.sax.InputSource; import org.xml.sax.SAXException; import org.xml.sax.SAXParseException; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.Reader; import java.util.Map; import java.util.Properties; /** * Extends Hadoop Configuration providing a new constructor which reads an XML configuration from an InputStream. * <p/> * OConfiguration(InputStream is). */ public class XConfiguration extends Configuration { /** * Create an empty configuration. * <p/> * Default values are not loaded. */ public XConfiguration() { super(false); } /** * Create a configuration from an InputStream. * <p/> * ERROR canibalized from <code>Configuration.loadResource()</code>. * * @param is inputstream to read the configuration from. * * @throws IOException thrown if the configuration could not be read. */ public XConfiguration(InputStream is) throws IOException { this(); parse(is); } /** * Create a configuration from an Reader. * <p/> * ERROR canibalized from <code>Configuration.loadResource()</code>. * * @param reader reader to read the configuration from. * * @throws IOException thrown if the configuration could not be read. */ public XConfiguration(Reader reader) throws IOException { this(); Check.notNull(reader, "reader"); parse(reader); } /** * Create an configuration from a Properties instance. * * @param props Properties instance to get all properties from. */ public XConfiguration(Properties props) { this(); Check.notNull(props, "props)"); for (Map.Entry entry : props.entrySet()) { set((String) entry.getKey(), (String) entry.getValue()); } } /** * This is a stop gap fix for <link href="https://issues.apache.org/jira/browse/HADOOP-4416">HADOOP-4416</link>. */ public Class<?> getClassByName(String name) throws ClassNotFoundException { Check.notEmpty(name, "name"); return super.getClassByName(name.trim()); } /** * Copy configuration key/value pairs from one configuration to another if a property exists in the target, it gets * replaced. * * @param source source configuration. * @param target target configuration. */ public static void copy(Configuration source, Configuration target) { Check.notNull(source, "source"); Check.notNull(target, "target"); for (Map.Entry<String, String> entry : source) { target.set(entry.getKey(), entry.getValue()); } } /** * Injects configuration key/value pairs from one configuration to another if the key does not exist in the target * configuration. * * @param source source configuration. * @param target target configuration. */ public static void injectDefaults(Configuration source, Configuration target) { Check.notNull(source, "source"); Check.notNull(target, "target"); for (Map.Entry<String, String> entry : source) { if (target.get(entry.getKey()) == null) { target.set(entry.getKey(), entry.getValue()); } } } /** * Returns a new XConfiguration with all values trimmed. * * @return a new XConfiguration with all values trimmed. */ public XConfiguration trim() { XConfiguration trimmed = new XConfiguration(); for (Map.Entry<String, String> entry : this) { trimmed.set(entry.getKey(), entry.getValue().trim()); } return trimmed; } /** * Returns a new XConfiguration instance with all inline values resolved. * * @return a new XConfiguration instance with all inline values resolved. */ public XConfiguration resolve() { XConfiguration resolved = new XConfiguration(); for (Map.Entry<String, String> entry : this) { resolved.set(entry.getKey(), get(entry.getKey())); } return resolved; } // Canibalized from Hadoop <code>Configuration.loadResource()</code>. private void parse(InputStream is) throws IOException { try { DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance(); // ignore all comments inside the xml file docBuilderFactory.setIgnoringComments(true); DocumentBuilder builder = docBuilderFactory.newDocumentBuilder(); Document doc = builder.parse(is); parseDocument(doc); } catch (SAXException e) { throw new IOException(e); } catch (ParserConfigurationException e) { throw new IOException(e); } } // Canibalized from Hadoop <code>Configuration.loadResource()</code>. private void parse(Reader reader) throws IOException { try { DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance(); // ignore all comments inside the xml file docBuilderFactory.setIgnoringComments(true); DocumentBuilder builder = docBuilderFactory.newDocumentBuilder(); builder.setErrorHandler(new ErrorHandler() { @Override public void warning(SAXParseException exception) throws SAXException { throw exception; } @Override public void error(SAXParseException exception) throws SAXException { throw exception; } @Override public void fatalError(SAXParseException exception) throws SAXException { throw exception; } }); Document doc = builder.parse(new InputSource(reader)); parseDocument(doc); } catch (SAXException e) { throw new IOException(e); } catch (ParserConfigurationException e) { throw new IOException(e); } } // Canibalized from Hadoop <code>Configuration.loadResource()</code>. private void parseDocument(Document doc) throws IOException { try { Element root = doc.getDocumentElement(); if (!"configuration".equals(root.getTagName())) { throw new IOException("bad conf file: top-level element not <configuration>"); } NodeList props = root.getChildNodes(); for (int i = 0; i < props.getLength(); i++) { Node propNode = props.item(i); if (!(propNode instanceof Element)) { continue; } Element prop = (Element) propNode; if (!"property".equals(prop.getTagName())) { throw new IOException("bad conf file: element not <property>"); } NodeList fields = prop.getChildNodes(); String attr = null; String value = null; for (int j = 0; j < fields.getLength(); j++) { Node fieldNode = fields.item(j); if (!(fieldNode instanceof Element)) { continue; } Element field = (Element) fieldNode; if ("name".equals(field.getTagName()) && field.hasChildNodes()) { attr = ((Text) field.getFirstChild()).getData().trim(); } if ("value".equals(field.getTagName()) && field.hasChildNodes()) { value = ((Text) field.getFirstChild()).getData(); } } if (attr != null && value != null) { set(attr, value); } } } catch (DOMException e) { throw new IOException(e); } } /** * Return a string with the configuration in XML format. * * @return a string with the configuration in XML format. */ public String toXmlString() { return toXmlString(true); } public String toXmlString(boolean prolog) { String xml; try { ByteArrayOutputStream baos = new ByteArrayOutputStream(); this.writeXml(baos); baos.close(); xml = new String(baos.toByteArray()); } catch (IOException ex) { throw new RuntimeException("It should not happen, " + ex.getMessage(), ex); } if (!prolog) { xml = xml.substring(xml.indexOf("<configuration>")); } return xml; } /** * Return a Properties instance with the configuration properties. * * @return a Properties instance with the configuration properties. */ public Properties toProperties() { Properties props = new Properties(); for (Map.Entry<String, String> entry : this) { props.setProperty(entry.getKey(), entry.getValue()); } return props; } }