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.commons.configuration; import java.awt.Color; import java.lang.reflect.Array; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.math.BigDecimal; import java.math.BigInteger; import java.net.InetAddress; import java.net.MalformedURLException; import java.net.URL; import java.net.UnknownHostException; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Calendar; import java.util.Collection; import java.util.Date; import java.util.Iterator; import java.util.List; import java.util.Locale; import org.apache.commons.collections.IteratorUtils; import org.apache.commons.collections.iterators.IteratorChain; import org.apache.commons.collections.iterators.SingletonIterator; import org.apache.commons.lang.BooleanUtils; import org.apache.commons.lang.StringUtils; import org.apache.commons.lang.SystemUtils; /** * A utility class to convert the configuration properties into any type. * * @author Emmanuel Bourg * @version $Revision: 662269 $, $Date: 2008-06-01 21:30:02 +0200 (So, 01 Jun 2008) $ * @since 1.1 */ public final class PropertyConverter { /** Constant for the list delimiter as char.*/ static final char LIST_ESC_CHAR = '\\'; /** Constant for the list delimiter escaping character as string.*/ static final String LIST_ESCAPE = String.valueOf(LIST_ESC_CHAR); /** Constant for the prefix of hex numbers.*/ private static final String HEX_PREFIX = "0x"; /** Constant for the radix of hex numbers.*/ private static final int HEX_RADIX = 16; /** Constant for the Java version 1.5.*/ private static final float JAVA_VERSION_1_5 = 1.5f; /** Constant for the argument classes of the Number constructor that takes a String. */ private static final Class[] CONSTR_ARGS = { String.class }; /** The fully qualified name of {@link javax.mail.internet.InternetAddress} */ private static final String INTERNET_ADDRESS_CLASSNAME = "javax.mail.internet.InternetAddress"; /** * Private constructor prevents instances from being created. */ private PropertyConverter() { // to prevent instanciation... } /** * Converts the specified value to the target class. If the class is a * primitive type (Integer.TYPE, Boolean.TYPE, etc) the value returned * will use the wrapper type (Integer.class, Boolean.class, etc). * * @param cls the target class of the converted value * @param value the value to convert * @param params optional parameters used for the conversion * @return the converted value * @throws ConversionException if the value is not compatible with the requested type * * @since 1.5 */ static Object to(Class cls, Object value, Object[] params) throws ConversionException { if (Boolean.class.equals(cls) || Boolean.TYPE.equals(cls)) { return toBoolean(value); } else if (Number.class.isAssignableFrom(cls) || cls.isPrimitive()) { if (Integer.class.equals(cls) || Integer.TYPE.equals(cls)) { return toInteger(value); } else if (Long.class.equals(cls) || Long.TYPE.equals(cls)) { return toLong(value); } else if (Byte.class.equals(cls) || Byte.TYPE.equals(cls)) { return toByte(value); } else if (Short.class.equals(cls) || Short.TYPE.equals(cls)) { return toShort(value); } else if (Float.class.equals(cls) || Float.TYPE.equals(cls)) { return toFloat(value); } else if (Double.class.equals(cls) || Double.TYPE.equals(cls)) { return toDouble(value); } else if (BigInteger.class.equals(cls)) { return toBigInteger(value); } else if (BigDecimal.class.equals(cls)) { return toBigDecimal(value); } } else if (Date.class.equals(cls)) { return toDate(value, (String) params[0]); } else if (Calendar.class.equals(cls)) { return toCalendar(value, (String) params[0]); } else if (URL.class.equals(cls)) { return toURL(value); } else if (Locale.class.equals(cls)) { return toLocale(value); } else if (isEnum(cls)) { return toEnum(value, cls); } else if (Color.class.equals(cls)) { return toColor(value); } else if (cls.getName().equals(INTERNET_ADDRESS_CLASSNAME)) { return toInternetAddress(value); } else if (InetAddress.class.isAssignableFrom(cls)) { return toInetAddress(value); } throw new ConversionException("The value '" + value + "' (" + value.getClass() + ")" + " can't be converted to a " + cls.getName() + " object"); } /** * Convert the specified object into a Boolean. Internally the * <code>org.apache.commons.lang.BooleanUtils</code> class from the * <a href="http://commons.apache.org/lang/">Commons Lang</a> * project is used to perform this conversion. This class accepts some more * tokens for the boolean value of <b>true</b>, e.g. <code>yes</code> and * <code>on</code>. Please refer to the documentation of this class for more * details. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a boolean */ public static Boolean toBoolean(Object value) throws ConversionException { if (value instanceof Boolean) { return (Boolean) value; } else if (value instanceof String) { Boolean b = BooleanUtils.toBooleanObject((String) value); if (b == null) { throw new ConversionException("The value " + value + " can't be converted to a Boolean object"); } return b; } else { throw new ConversionException("The value " + value + " can't be converted to a Boolean object"); } } /** * Convert the specified object into a Byte. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a byte */ public static Byte toByte(Object value) throws ConversionException { Number n = toNumber(value, Byte.class); if (n instanceof Byte) { return (Byte) n; } else { return new Byte(n.byteValue()); } } /** * Convert the specified object into a Short. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a short */ public static Short toShort(Object value) throws ConversionException { Number n = toNumber(value, Short.class); if (n instanceof Short) { return (Short) n; } else { return new Short(n.shortValue()); } } /** * Convert the specified object into an Integer. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to an integer */ public static Integer toInteger(Object value) throws ConversionException { Number n = toNumber(value, Integer.class); if (n instanceof Integer) { return (Integer) n; } else { return new Integer(n.intValue()); } } /** * Convert the specified object into a Long. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a Long */ public static Long toLong(Object value) throws ConversionException { Number n = toNumber(value, Long.class); if (n instanceof Long) { return (Long) n; } else { return new Long(n.longValue()); } } /** * Convert the specified object into a Float. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a Float */ public static Float toFloat(Object value) throws ConversionException { Number n = toNumber(value, Float.class); if (n instanceof Float) { return (Float) n; } else { return new Float(n.floatValue()); } } /** * Convert the specified object into a Double. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a Double */ public static Double toDouble(Object value) throws ConversionException { Number n = toNumber(value, Double.class); if (n instanceof Double) { return (Double) n; } else { return new Double(n.doubleValue()); } } /** * Convert the specified object into a BigInteger. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a BigInteger */ public static BigInteger toBigInteger(Object value) throws ConversionException { Number n = toNumber(value, BigInteger.class); if (n instanceof BigInteger) { return (BigInteger) n; } else { return BigInteger.valueOf(n.longValue()); } } /** * Convert the specified object into a BigDecimal. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a BigDecimal */ public static BigDecimal toBigDecimal(Object value) throws ConversionException { Number n = toNumber(value, BigDecimal.class); if (n instanceof BigDecimal) { return (BigDecimal) n; } else { return new BigDecimal(n.doubleValue()); } } /** * Tries to convert the specified object into a number object. This method * is used by the conversion methods for number types. Note that the return * value is not in always of the specified target class, but only if a new * object has to be created. * * @param value the value to be converted (must not be <b>null</b>) * @param targetClass the target class of the conversion (must be derived * from <code>java.lang.Number</code>) * @return the converted number * @throws ConversionException if the object cannot be converted */ static Number toNumber(Object value, Class targetClass) throws ConversionException { if (value instanceof Number) { return (Number) value; } else { String str = value.toString(); if (str.startsWith(HEX_PREFIX)) { try { return new BigInteger(str.substring(HEX_PREFIX.length()), HEX_RADIX); } catch (NumberFormatException nex) { throw new ConversionException( "Could not convert " + str + " to " + targetClass.getName() + "! Invalid hex number.", nex); } } try { Constructor constr = targetClass.getConstructor(CONSTR_ARGS); return (Number) constr.newInstance(new Object[] { str }); } catch (InvocationTargetException itex) { throw new ConversionException("Could not convert " + str + " to " + targetClass.getName(), itex.getTargetException()); } catch (Exception ex) { // Treat all possible exceptions the same way throw new ConversionException( "Conversion error when trying to convert " + str + " to " + targetClass.getName(), ex); } } } /** * Convert the specified object into an URL. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to an URL */ public static URL toURL(Object value) throws ConversionException { if (value instanceof URL) { return (URL) value; } else if (value instanceof String) { try { return new URL((String) value); } catch (MalformedURLException e) { throw new ConversionException("The value " + value + " can't be converted to an URL", e); } } else { throw new ConversionException("The value " + value + " can't be converted to an URL"); } } /** * Convert the specified object into a Locale. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a Locale */ public static Locale toLocale(Object value) throws ConversionException { if (value instanceof Locale) { return (Locale) value; } else if (value instanceof String) { List elements = split((String) value, '_'); int size = elements.size(); if (size >= 1 && (((String) elements.get(0)).length() == 2 || ((String) elements.get(0)).length() == 0)) { String language = (String) elements.get(0); String country = (String) ((size >= 2) ? elements.get(1) : ""); String variant = (String) ((size >= 3) ? elements.get(2) : ""); return new Locale(language, country, variant); } else { throw new ConversionException("The value " + value + " can't be converted to a Locale"); } } else { throw new ConversionException("The value " + value + " can't be converted to a Locale"); } } /** * Split a string on the specified delimiter. To be removed when * commons-lang has a better replacement available (Tokenizer?). * * todo: replace with a commons-lang equivalent * * @param s the string to split * @param delimiter the delimiter * @param trim a flag whether the single elements should be trimmed * @return a list with the single tokens */ public static List split(String s, char delimiter, boolean trim) { if (s == null) { return new ArrayList(); } List list = new ArrayList(); StringBuffer token = new StringBuffer(); int begin = 0; boolean inEscape = false; while (begin < s.length()) { char c = s.charAt(begin); if (inEscape) { // last character was the escape marker // can current character be escaped? if (c != delimiter && c != LIST_ESC_CHAR) { // no, also add escape character token.append(LIST_ESC_CHAR); } token.append(c); inEscape = false; } else { if (c == delimiter) { // found a list delimiter -> add token and reset buffer String t = token.toString(); if (trim) { t = t.trim(); } list.add(t); token = new StringBuffer(); } else if (c == LIST_ESC_CHAR) { // eventually escape next character inEscape = true; } else { token.append(c); } } begin++; } // Trailing delimiter? if (inEscape) { token.append(LIST_ESC_CHAR); } // Add last token String t = token.toString(); if (trim) { t = t.trim(); } list.add(t); return list; } /** * Split a string on the specified delimiter always trimming the elements. * This is a shortcut for <code>split(s, delimiter, true)</code>. * * @param s the string to split * @param delimiter the delimiter * @return a list with the single tokens */ public static List split(String s, char delimiter) { return split(s, delimiter, true); } /** * Escapes the delimiters that might be contained in the given string. This * method ensures that list delimiter characters that are part of a * property's value are correctly escaped when a configuration is saved to a * file. Otherwise when loaded again the property will be treated as a list * property. A single backslash will also be escaped. * * @param s the string with the value * @param delimiter the list delimiter to use * @return the correctly esaped string */ public static String escapeDelimiters(String s, char delimiter) { String s1 = StringUtils.replace(s, LIST_ESCAPE, LIST_ESCAPE + LIST_ESCAPE); return StringUtils.replace(s1, String.valueOf(delimiter), LIST_ESCAPE + delimiter); } /** * Convert the specified object into a Color. If the value is a String, * the format allowed is (#)?[0-9A-F]{6}([0-9A-F]{2})?. Examples: * <ul> * <li>FF0000 (red)</li> * <li>0000FFA0 (semi transparent blue)</li> * <li>#CCCCCC (gray)</li> * <li>#00FF00A0 (semi transparent green)</li> * </ul> * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a Color */ public static Color toColor(Object value) throws ConversionException { if (value instanceof Color) { return (Color) value; } else if (value instanceof String && !StringUtils.isBlank((String) value)) { String color = ((String) value).trim(); int[] components = new int[3]; // check the size of the string int minlength = components.length * 2; if (color.length() < minlength) { throw new ConversionException("The value " + value + " can't be converted to a Color"); } // remove the leading # if (color.startsWith("#")) { color = color.substring(1); } try { // parse the components for (int i = 0; i < components.length; i++) { components[i] = Integer.parseInt(color.substring(2 * i, 2 * i + 2), HEX_RADIX); } // parse the transparency int alpha; if (color.length() >= minlength + 2) { alpha = Integer.parseInt(color.substring(minlength, minlength + 2), HEX_RADIX); } else { alpha = Color.black.getAlpha(); } return new Color(components[0], components[1], components[2], alpha); } catch (Exception e) { throw new ConversionException("The value " + value + " can't be converted to a Color", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a Color"); } } /** * Convert the specified value into an internet address. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a InetAddress * * @since 1.5 */ static InetAddress toInetAddress(Object value) throws ConversionException { if (value instanceof InetAddress) { return (InetAddress) value; } else if (value instanceof String) { try { return InetAddress.getByName((String) value); } catch (UnknownHostException e) { throw new ConversionException("The value " + value + " can't be converted to a InetAddress", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a InetAddress"); } } /** * Convert the specified value into an email address. * * @param value the value to convert * @return the converted value * @throws ConversionException thrown if the value cannot be converted to an email address * * @since 1.5 */ static Object toInternetAddress(Object value) throws ConversionException { if (value.getClass().getName().equals(INTERNET_ADDRESS_CLASSNAME)) { return value; } else if (value instanceof String) { try { Constructor ctor = Class.forName(INTERNET_ADDRESS_CLASSNAME) .getConstructor(new Class[] { String.class }); return ctor.newInstance(new Object[] { value }); } catch (Exception e) { throw new ConversionException("The value " + value + " can't be converted to a InternetAddress", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a InternetAddress"); } } /** * Calls Class.isEnum() on Java 5, returns false on older JRE. */ static boolean isEnum(Class cls) { if (!SystemUtils.isJavaVersionAtLeast(JAVA_VERSION_1_5)) { return false; } try { Method isEnumMethod = Class.class.getMethod("isEnum", new Class[] {}); return ((Boolean) isEnumMethod.invoke(cls, new Object[] {})).booleanValue(); } catch (Exception e) { // impossible throw new RuntimeException(e.getMessage()); } } /** * Convert the specified value into a Java 5 enum. * * @param value the value to convert * @param cls the type of the enumeration * @return the converted value * @throws ConversionException thrown if the value cannot be converted to an enumeration * * @since 1.5 */ static Object toEnum(Object value, Class cls) throws ConversionException { if (value.getClass().equals(cls)) { return value; } else if (value instanceof String) { try { Method valueOfMethod = cls.getMethod("valueOf", new Class[] { String.class }); return valueOfMethod.invoke(null, new Object[] { value }); } catch (Exception e) { throw new ConversionException("The value " + value + " can't be converted to a " + cls.getName()); } } else if (value instanceof Number) { try { Method valuesMethod = cls.getMethod("values", new Class[] {}); Object valuesArray = valuesMethod.invoke(null, new Object[] {}); return Array.get(valuesArray, ((Number) value).intValue()); } catch (Exception e) { throw new ConversionException("The value " + value + " can't be converted to a " + cls.getName()); } } else { throw new ConversionException("The value " + value + " can't be converted to a " + cls.getName()); } } /** * Convert the specified object into a Date. * * @param value the value to convert * @param format the DateFormat pattern to parse String values * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a Calendar */ public static Date toDate(Object value, String format) throws ConversionException { if (value instanceof Date) { return (Date) value; } else if (value instanceof Calendar) { return ((Calendar) value).getTime(); } else if (value instanceof String) { try { return new SimpleDateFormat(format).parse((String) value); } catch (ParseException e) { throw new ConversionException("The value " + value + " can't be converted to a Date", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a Date"); } } /** * Convert the specified object into a Calendar. * * @param value the value to convert * @param format the DateFormat pattern to parse String values * @return the converted value * @throws ConversionException thrown if the value cannot be converted to a Calendar */ public static Calendar toCalendar(Object value, String format) throws ConversionException { if (value instanceof Calendar) { return (Calendar) value; } else if (value instanceof Date) { Calendar calendar = Calendar.getInstance(); calendar.setTime((Date) value); return calendar; } else if (value instanceof String) { try { Calendar calendar = Calendar.getInstance(); calendar.setTime(new SimpleDateFormat(format).parse((String) value)); return calendar; } catch (ParseException e) { throw new ConversionException("The value " + value + " can't be converted to a Calendar", e); } } else { throw new ConversionException("The value " + value + " can't be converted to a Calendar"); } } /** * Return an iterator over the simple values of a composite value. The value * specified is handled depending on its type: * <ul> * <li>Strings are checked for delimiter characters and splitted if necessary.</li> * <li>For collections the single elements are checked.</li> * <li>Arrays are treated like collections.</li> * <li>All other types are directly inserted.</li> * <li>Recursive combinations are supported, e.g. a collection containing array that contain strings.</li> * </ul> * * @param value the value to "split" * @param delimiter the delimiter for String values * @return an iterator for accessing the single values */ public static Iterator toIterator(Object value, char delimiter) { if (value == null) { return IteratorUtils.emptyIterator(); } if (value instanceof String) { String s = (String) value; if (s.indexOf(delimiter) > 0) { return split((String) value, delimiter).iterator(); } else { return new SingletonIterator(value); } } else if (value instanceof Collection) { return toIterator(((Collection) value).iterator(), delimiter); } else if (value.getClass().isArray()) { return toIterator(IteratorUtils.arrayIterator(value), delimiter); } else if (value instanceof Iterator) { Iterator iterator = (Iterator) value; IteratorChain chain = new IteratorChain(); while (iterator.hasNext()) { chain.addIterator(toIterator(iterator.next(), delimiter)); } return chain; } else { return new SingletonIterator(value); } } /** * Performs interpolation of the specified value. This method checks if the * given value contains variables of the form <code>${...}</code>. If * this is the case, all occurrances will be substituted by their current * values. * * @param value the value to be interpolated * @param config the current configuration object * @return the interpolated value */ public static Object interpolate(Object value, AbstractConfiguration config) { if (value instanceof String) { return config.getSubstitutor().replace((String) value); } else { return value; } } }