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.text; import java.text.Format; import java.text.MessageFormat; import java.text.ParsePosition; import java.util.ArrayList; import java.util.Collection; import java.util.Iterator; import java.util.Locale; import java.util.Map; import java.util.Objects; /** * Extends <code>java.text.MessageFormat</code> to allow pluggable/additional formatting * options for embedded format elements. Client code should specify a registry * of <code>FormatFactory</code> instances associated with <code>String</code> * format names. This registry will be consulted when the format elements are * parsed from the message pattern. In this way custom patterns can be specified, * and the formats supported by <code>java.text.MessageFormat</code> can be overridden * at the format and/or format style level (see MessageFormat). A "format element" * embedded in the message pattern is specified (<b>()?</b> signifies optionality):<br> * <code>{</code><i>argument-number</i><b>(</b><code>,</code><i>format-name</i><b> * (</b><code>,</code><i>format-style</i><b>)?)?</b><code>}</code> * * <p> * <i>format-name</i> and <i>format-style</i> values are trimmed of surrounding whitespace * in the manner of <code>java.text.MessageFormat</code>. If <i>format-name</i> denotes * <code>FormatFactory formatFactoryInstance</code> in <code>registry</code>, a <code>Format</code> * matching <i>format-name</i> and <i>format-style</i> is requested from * <code>formatFactoryInstance</code>. If this is successful, the <code>Format</code> * found is used for this format element. * </p> * * <p><b>NOTICE:</b> The various subformat mutator methods are considered unnecessary; they exist on the parent * class to allow the type of customization which it is the job of this class to provide in * a configurable fashion. These methods have thus been disabled and will throw * <code>UnsupportedOperationException</code> if called. * </p> * * <p>Limitations inherited from <code>java.text.MessageFormat</code>:</p> * <ul> * <li>When using "choice" subformats, support for nested formatting instructions is limited * to that provided by the base class.</li> * <li>Thread-safety of <code>Format</code>s, including <code>MessageFormat</code> and thus * <code>ExtendedMessageFormat</code>, is not guaranteed.</li> * </ul> * * @since 1.0 */ public class ExtendedMessageFormat extends MessageFormat { private static final long serialVersionUID = -2362048321261811743L; private static final int HASH_SEED = 31; private static final String DUMMY_PATTERN = ""; private static final char START_FMT = ','; private static final char END_FE = '}'; private static final char START_FE = '{'; private static final char QUOTE = '\''; private String toPattern; private final Map<String, ? extends FormatFactory> registry; /** * Create a new ExtendedMessageFormat for the default locale. * * @param pattern the pattern to use, not null * @throws IllegalArgumentException in case of a bad pattern. */ public ExtendedMessageFormat(final String pattern) { this(pattern, Locale.getDefault()); } /** * Create a new ExtendedMessageFormat. * * @param pattern the pattern to use, not null * @param locale the locale to use, not null * @throws IllegalArgumentException in case of a bad pattern. */ public ExtendedMessageFormat(final String pattern, final Locale locale) { this(pattern, locale, null); } /** * Create a new ExtendedMessageFormat for the default locale. * * @param pattern the pattern to use, not null * @param registry the registry of format factories, may be null * @throws IllegalArgumentException in case of a bad pattern. */ public ExtendedMessageFormat(final String pattern, final Map<String, ? extends FormatFactory> registry) { this(pattern, Locale.getDefault(), registry); } /** * Create a new ExtendedMessageFormat. * * @param pattern the pattern to use, not null * @param locale the locale to use, not null * @param registry the registry of format factories, may be null * @throws IllegalArgumentException in case of a bad pattern. */ public ExtendedMessageFormat(final String pattern, final Locale locale, final Map<String, ? extends FormatFactory> registry) { super(DUMMY_PATTERN); setLocale(locale); this.registry = registry; applyPattern(pattern); } /** * {@inheritDoc} */ @Override public String toPattern() { return toPattern; } /** * Apply the specified pattern. * * @param pattern String */ @Override public final void applyPattern(final String pattern) { if (registry == null) { super.applyPattern(pattern); toPattern = super.toPattern(); return; } final ArrayList<Format> foundFormats = new ArrayList<>(); final ArrayList<String> foundDescriptions = new ArrayList<>(); final StringBuilder stripCustom = new StringBuilder(pattern.length()); final ParsePosition pos = new ParsePosition(0); final char[] c = pattern.toCharArray(); int fmtCount = 0; while (pos.getIndex() < pattern.length()) { switch (c[pos.getIndex()]) { case QUOTE: appendQuotedString(pattern, pos, stripCustom); break; case START_FE: fmtCount++; seekNonWs(pattern, pos); final int start = pos.getIndex(); final int index = readArgumentIndex(pattern, next(pos)); stripCustom.append(START_FE).append(index); seekNonWs(pattern, pos); Format format = null; String formatDescription = null; if (c[pos.getIndex()] == START_FMT) { formatDescription = parseFormatDescription(pattern, next(pos)); format = getFormat(formatDescription); if (format == null) { stripCustom.append(START_FMT).append(formatDescription); } } foundFormats.add(format); foundDescriptions.add(format == null ? null : formatDescription); if (foundFormats.size() != fmtCount) { throw new IllegalArgumentException("The validated expression is false"); } if (foundDescriptions.size() != fmtCount) { throw new IllegalArgumentException("The validated expression is false"); } if (c[pos.getIndex()] != END_FE) { throw new IllegalArgumentException("Unreadable format element at position " + start); } //$FALL-THROUGH$ default: stripCustom.append(c[pos.getIndex()]); next(pos); } } super.applyPattern(stripCustom.toString()); toPattern = insertFormats(super.toPattern(), foundDescriptions); if (containsElements(foundFormats)) { final Format[] origFormats = getFormats(); // only loop over what we know we have, as MessageFormat on Java 1.3 // seems to provide an extra format element: int i = 0; for (final Iterator<Format> it = foundFormats.iterator(); it.hasNext(); i++) { final Format f = it.next(); if (f != null) { origFormats[i] = f; } } super.setFormats(origFormats); } } /** * Throws UnsupportedOperationException - see class Javadoc for details. * * @param formatElementIndex format element index * @param newFormat the new format * @throws UnsupportedOperationException always thrown since this isn't supported by ExtendMessageFormat */ @Override public void setFormat(final int formatElementIndex, final Format newFormat) { throw new UnsupportedOperationException(); } /** * Throws UnsupportedOperationException - see class Javadoc for details. * * @param argumentIndex argument index * @param newFormat the new format * @throws UnsupportedOperationException always thrown since this isn't supported by ExtendMessageFormat */ @Override public void setFormatByArgumentIndex(final int argumentIndex, final Format newFormat) { throw new UnsupportedOperationException(); } /** * Throws UnsupportedOperationException - see class Javadoc for details. * * @param newFormats new formats * @throws UnsupportedOperationException always thrown since this isn't supported by ExtendMessageFormat */ @Override public void setFormats(final Format[] newFormats) { throw new UnsupportedOperationException(); } /** * Throws UnsupportedOperationException - see class Javadoc for details. * * @param newFormats new formats * @throws UnsupportedOperationException always thrown since this isn't supported by ExtendMessageFormat */ @Override public void setFormatsByArgumentIndex(final Format[] newFormats) { throw new UnsupportedOperationException(); } /** * Check if this extended message format is equal to another object. * * @param obj the object to compare to * @return true if this object equals the other, otherwise false */ @Override public boolean equals(final Object obj) { if (obj == this) { return true; } if (obj == null) { return false; } if (!super.equals(obj)) { return false; } if (!Objects.equals(getClass(), obj.getClass())) { return false; } final ExtendedMessageFormat rhs = (ExtendedMessageFormat) obj; if (!Objects.equals(toPattern, rhs.toPattern)) { return false; } if (!Objects.equals(registry, rhs.registry)) { return false; } return true; } /** * {@inheritDoc} */ @Override public int hashCode() { int result = super.hashCode(); result = HASH_SEED * result + Objects.hashCode(registry); result = HASH_SEED * result + Objects.hashCode(toPattern); return result; } /** * Get a custom format from a format description. * * @param desc String * @return Format */ private Format getFormat(final String desc) { if (registry != null) { String name = desc; String args = null; final int i = desc.indexOf(START_FMT); if (i > 0) { name = desc.substring(0, i).trim(); args = desc.substring(i + 1).trim(); } final FormatFactory factory = registry.get(name); if (factory != null) { return factory.getFormat(name, args, getLocale()); } } return null; } /** * Read the argument index from the current format element * * @param pattern pattern to parse * @param pos current parse position * @return argument index */ private int readArgumentIndex(final String pattern, final ParsePosition pos) { final int start = pos.getIndex(); seekNonWs(pattern, pos); final StringBuilder result = new StringBuilder(); boolean error = false; for (; !error && pos.getIndex() < pattern.length(); next(pos)) { char c = pattern.charAt(pos.getIndex()); if (Character.isWhitespace(c)) { seekNonWs(pattern, pos); c = pattern.charAt(pos.getIndex()); if (c != START_FMT && c != END_FE) { error = true; continue; } } if ((c == START_FMT || c == END_FE) && result.length() > 0) { try { return Integer.parseInt(result.toString()); } catch (final NumberFormatException e) { // NOPMD // we've already ensured only digits, so unless something // outlandishly large was specified we should be okay. } } error = !Character.isDigit(c); result.append(c); } if (error) { throw new IllegalArgumentException("Invalid format argument index at position " + start + ": " + pattern.substring(start, pos.getIndex())); } throw new IllegalArgumentException("Unterminated format element at position " + start); } /** * Parse the format component of a format element. * * @param pattern string to parse * @param pos current parse position * @return Format description String */ private String parseFormatDescription(final String pattern, final ParsePosition pos) { final int start = pos.getIndex(); seekNonWs(pattern, pos); final int text = pos.getIndex(); int depth = 1; for (; pos.getIndex() < pattern.length(); next(pos)) { switch (pattern.charAt(pos.getIndex())) { case START_FE: depth++; break; case END_FE: depth--; if (depth == 0) { return pattern.substring(text, pos.getIndex()); } break; case QUOTE: getQuotedString(pattern, pos); break; default: break; } } throw new IllegalArgumentException("Unterminated format element at position " + start); } /** * Insert formats back into the pattern for toPattern() support. * * @param pattern source * @param customPatterns The custom patterns to re-insert, if any * @return full pattern */ private String insertFormats(final String pattern, final ArrayList<String> customPatterns) { if (!containsElements(customPatterns)) { return pattern; } final StringBuilder sb = new StringBuilder(pattern.length() * 2); final ParsePosition pos = new ParsePosition(0); int fe = -1; int depth = 0; while (pos.getIndex() < pattern.length()) { final char c = pattern.charAt(pos.getIndex()); switch (c) { case QUOTE: appendQuotedString(pattern, pos, sb); break; case START_FE: depth++; sb.append(START_FE).append(readArgumentIndex(pattern, next(pos))); // do not look for custom patterns when they are embedded, e.g. in a choice if (depth == 1) { fe++; final String customPattern = customPatterns.get(fe); if (customPattern != null) { sb.append(START_FMT).append(customPattern); } } break; case END_FE: depth--; //$FALL-THROUGH$ default: sb.append(c); next(pos); } } return sb.toString(); } /** * Consume whitespace from the current parse position. * * @param pattern String to read * @param pos current position */ private void seekNonWs(final String pattern, final ParsePosition pos) { int len = 0; final char[] buffer = pattern.toCharArray(); do { len = StrMatcher.splitMatcher().isMatch(buffer, pos.getIndex()); pos.setIndex(pos.getIndex() + len); } while (len > 0 && pos.getIndex() < pattern.length()); } /** * Convenience method to advance parse position by 1 * * @param pos ParsePosition * @return <code>pos</code> */ private ParsePosition next(final ParsePosition pos) { pos.setIndex(pos.getIndex() + 1); return pos; } /** * Consume a quoted string, adding it to <code>appendTo</code> if * specified. * * @param pattern pattern to parse * @param pos current parse position * @param appendTo optional StringBuilder to append * @return <code>appendTo</code> */ private StringBuilder appendQuotedString(final String pattern, final ParsePosition pos, final StringBuilder appendTo) { assert pattern.toCharArray()[pos.getIndex()] == QUOTE : "Quoted string must start with quote character"; // handle quote character at the beginning of the string if (appendTo != null) { appendTo.append(QUOTE); } next(pos); final int start = pos.getIndex(); final char[] c = pattern.toCharArray(); final int lastHold = start; for (int i = pos.getIndex(); i < pattern.length(); i++) { switch (c[pos.getIndex()]) { case QUOTE: next(pos); return appendTo == null ? null : appendTo.append(c, lastHold, pos.getIndex() - lastHold); default: next(pos); } } throw new IllegalArgumentException("Unterminated quoted string at position " + start); } /** * Consume quoted string only * * @param pattern pattern to parse * @param pos current parse position */ private void getQuotedString(final String pattern, final ParsePosition pos) { appendQuotedString(pattern, pos, null); } /** * Learn whether the specified Collection contains non-null elements. * @param coll to check * @return <code>true</code> if some Object was found, <code>false</code> otherwise. */ private boolean containsElements(final Collection<?> coll) { if (coll == null || coll.isEmpty()) { return false; } for (final Object name : coll) { if (name != null) { return true; } } return false; } }