Java tutorial
/* * QCRI, NADEEF LICENSE * NADEEF is an extensible, generalized and easy-to-deploy data cleaning platform built at QCRI. * NADEEF means "Clean" in Arabic * * Copyright (c) 2011-2013, Qatar Foundation for Education, Science and Community Development (on * behalf of Qatar Computing Research Institute) having its principle place of business in Doha, * Qatar with the registered address P.O box 5825 Doha, Qatar (hereinafter referred to as "QCRI") * * NADEEF has patent pending nevertheless the following is granted. * NADEEF is released under the terms of the MIT License, (http://opensource.org/licenses/MIT). */ package qa.qcri.nadeef.tools; import com.google.common.base.Preconditions; import com.google.common.base.Strings; import com.google.common.hash.Hashing; import javax.tools.*; import java.io.File; import java.io.FileNotFoundException; import java.io.IOException; import java.net.Socket; import java.net.URL; import java.net.URLClassLoader; import java.nio.charset.Charset; import java.util.Arrays; import java.util.List; /** * Common helper tools. */ public final class CommonTools { private static Tracer tracer = Tracer.getTracer(CommonTools.class); private static Process derbyProcess; public static char DOUBLE_QUOTE = '"'; public static char SINGLE_QUOTE = '\''; public static boolean isWindows() { String osName = System.getProperty("os.name"); return osName.indexOf("Win") >= 0; } public static boolean isMac() { String osName = System.getProperty("os.name"); return osName.indexOf("Mac") >= 0; } public static boolean isLinux() { String osName = System.getProperty("os.name"); return osName.indexOf("Linux") >= 0; } /** * Gets the file object given the full file name. * @param fileName full file name. * @return File object. */ public static File getFile(String fileName) throws FileNotFoundException { if (isWindows()) { fileName = fileName.replace("\\", "\\\\"); } else { fileName = fileName.replace("\\", "/"); } File file = new File(fileName); if (!file.exists()) { throw new FileNotFoundException(); } if (!file.isFile()) { throw new IllegalArgumentException("The given filename is not a file."); } return file; } /** * Loads a class in runtime using specified classpath. * @param className class name. * @param url classpath url. * @return Class type. */ public static Class loadClass(String className, URL url) throws ClassNotFoundException { URL[] urls = new URL[] { url }; URLClassLoader ucl = new URLClassLoader(urls); return ucl.loadClass(className); } /** * Loads a class in runtime using default classpath. * @param className class name. * @return Class type. */ public static Class loadClass(String className) throws ClassNotFoundException { ClassLoader classLoader = ClassLoader.getSystemClassLoader(); return classLoader.loadClass(className); } /** * Returns <code>True</code> when the given string is a numerical string. * @param string input string. * @return <code>True</code> when the given string is a numerical string. */ public static boolean isNumericalString(String string) { if (string == null) { return false; } return string.matches("-?\\d+(\\.\\d+)?"); } /** * Returns <code>True</code> when the given attribute name is a valid full column name. * @param attributeName Column name. * @return <code>True</code> when the column name is valid. */ public static boolean isValidColumnName(String attributeName) { String[] tokens = attributeName.split("\\."); // TODO: change to correct regexp. if (tokens.length != 2 || Strings.isNullOrEmpty(tokens[0]) || Strings.isNullOrEmpty(tokens[1])) { return false; } return true; } /** * Compiles the input file and generates the output class file. * @param fullFilePath input .java file path. * @return class file path. */ public static String compileFile(File fullFilePath) throws IOException { Preconditions.checkArgument(fullFilePath != null && fullFilePath.isFile()); JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); Preconditions.checkNotNull(compiler); DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<JavaFileObject>(); StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, null, null); Iterable<? extends JavaFileObject> compilationUnit = fileManager .getJavaFileObjectsFromFiles(Arrays.asList(fullFilePath)); List<String> args = Arrays.asList("-Xlint:none"); boolean result = compiler.getTask(null, fileManager, diagnostics, args, null, compilationUnit).call(); String msg = ""; if (!result) { for (Diagnostic diagnostic : diagnostics.getDiagnostics()) { msg += String.format("Error on line %d in %s%n", diagnostic.getLineNumber(), diagnostic.getMessage(null)); } tracer.err(msg); } fileManager.close(); return msg; } /** * Converts a string into an integer hashcode. * @param value string value. * @return integer hashcode. */ public static int toHashCode(String value) { return Math.abs(Hashing.md5().newHasher().putString(value, Charset.forName("UTF8")).hash().asInt()); } public static boolean isPortOccupied(int port) { try (Socket ignored = new Socket("localhost", port)) { return true; } catch (IOException ignored) { return false; } } public static boolean waitForService(int port) { final int MAX_TRY_COUNT = 10; int tryCount = 0; while (true) { if (isPortOccupied(port)) { return true; } if (tryCount == MAX_TRY_COUNT) { System.err.println("Waiting for port " + port + " time out."); return false; } try { Thread.sleep(1000); } catch (InterruptedException e) { // ignore } tryCount++; } } public static void startDerby(int port) throws IOException { Runtime runtime = Runtime.getRuntime(); runtime.addShutdownHook(new Thread() { public void run() { if (derbyProcess != null) derbyProcess.destroy(); } }); System.out.print("Start embedded database..."); String cmd = String.format( "java -Dderby.drda.portNumber=%d -jar out/bin/derbyrun.jar server start -noSecurityManager", port); derbyProcess = runtime.exec(cmd); if (!CommonTools.waitForService(port)) { System.out.println("FAILED"); System.exit(1); } System.out.println("OK"); } public static String escapeString(String s, char enclosed) { StringBuilder builder = new StringBuilder(); builder.append(enclosed); for (char c : s.toCharArray()) { if (c == enclosed) builder.append("\\").append(enclosed); else builder.append(c); } builder.append(enclosed); return builder.toString(); } public static String unescapeString(String s, char enclosed) { // return unchanged when the string is not enclosed. if (s.charAt(0) != enclosed) return s; String reg = "\\\\" + enclosed; String replaced = s.replaceAll(reg, Character.toString(enclosed)); return replaced.substring(1, replaced.length() - 1); } }