Java tutorial
/* * Copyright 2005 Joe Walker * * Licensed 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. */ import java.util.Arrays; import java.util.Locale; import java.util.SortedSet; import java.util.TreeSet; /** * Various Javascript code utilities. * The escape classes were taken from jakarta-commons-lang which in turn * borrowed from Turbine and other projects. The list of authors below is almost * certainly far too long, but I'm not sure who really wrote these methods. * @author Joe Walker [joe at getahead dot ltd dot uk] * @author Henri Yandell * @author Alexander Day Chaffee * @author Antony Riley * @author Helge Tesgaard * @author Sean Brown * @author Gary Gregory * @author Phil Steitz * @author Pete Gieser */ public class JavascriptUtil { /** * <p>Escapes the characters in a <code>String</code> using JavaScript String rules.</p> * <p>Escapes any values it finds into their JavaScript String form. * Deals correctly with quotes and control-chars (tab, backslash, cr, ff, etc.) </p> * * <p>So a tab becomes the characters <code>'\\'</code> and * <code>'t'</code>.</p> * * <p>The only difference between Java strings and JavaScript strings * is that in JavaScript, a single quote must be escaped.</p> * * <p>Example: * <pre> * input string: He didn't say, "Stop!" * output string: He didn\'t say, \"Stop!\" * </pre> * </p> * * @param str String to escape values in, may be null * @return String with escaped values, <code>null</code> if null string input */ public static String escapeJavaScript(String str) { if (str == null) { return null; } StringBuffer writer = new StringBuffer(str.length() * 2); int sz = str.length(); for (int i = 0; i < sz; i++) { char ch = str.charAt(i); // handle unicode if (ch > 0xfff) { writer.append("\\u"); writer.append(hex(ch)); } else if (ch > 0xff) { writer.append("\\u0"); writer.append(hex(ch)); } else if (ch > 0x7f) { writer.append("\\u00"); writer.append(hex(ch)); } else if (ch < 32) { switch (ch) { case '\b': writer.append('\\'); writer.append('b'); break; case '\n': writer.append('\\'); writer.append('n'); break; case '\t': writer.append('\\'); writer.append('t'); break; case '\f': writer.append('\\'); writer.append('f'); break; case '\r': writer.append('\\'); writer.append('r'); break; default: if (ch > 0xf) { writer.append("\\u00"); writer.append(hex(ch)); } else { writer.append("\\u000"); writer.append(hex(ch)); } break; } } else { switch (ch) { case '\'': // If we wanted to escape for Java strings then we would // not need this next line. writer.append('\\'); writer.append('\''); break; case '"': writer.append('\\'); writer.append('"'); break; case '\\': writer.append('\\'); writer.append('\\'); break; default: writer.append(ch); break; } } } return writer.toString(); } /** * <p>Returns an upper case hexadecimal <code>String</code> for the given * character.</p> * @param ch The character to convert. * @return An upper case hexadecimal <code>String</code> */ private static String hex(char ch) { return Integer.toHexString(ch).toUpperCase(Locale.ENGLISH); } /** * <p>Unescapes any JavaScript literals found in the <code>String</code>.</p> * <p>For example, it will turn a sequence of <code>'\'</code> and <code>'n'</code> * into a newline character, unless the <code>'\'</code> is preceded by another * <code>'\'</code>.</p> * @param str the <code>String</code> to unescape, may be null * @return A new unescaped <code>String</code>, <code>null</code> if null string input */ public static String unescapeJavaScript(String str) { if (str == null) { return null; } StringBuffer writer = new StringBuffer(str.length()); int sz = str.length(); StringBuffer unicode = new StringBuffer(4); boolean hadSlash = false; boolean inUnicode = false; for (int i = 0; i < sz; i++) { char ch = str.charAt(i); if (inUnicode) { // if in unicode, then we're reading unicode // values in somehow unicode.append(ch); if (unicode.length() == 4) { // unicode now contains the four hex digits // which represents our unicode character try { int value = Integer.parseInt(unicode.toString(), 16); writer.append((char) value); unicode.setLength(0); inUnicode = false; hadSlash = false; } catch (NumberFormatException nfe) { throw new IllegalArgumentException( "Unable to parse unicode value: " + unicode + " cause: " + nfe); } } continue; } if (hadSlash) { // handle an escaped value hadSlash = false; switch (ch) { case '\\': writer.append('\\'); break; case '\'': writer.append('\''); break; case '\"': writer.append('"'); break; case 'r': writer.append('\r'); break; case 'f': writer.append('\f'); break; case 't': writer.append('\t'); break; case 'n': writer.append('\n'); break; case 'b': writer.append('\b'); break; case 'u': // uh-oh, we're in unicode country.... inUnicode = true; break; default: writer.append(ch); break; } continue; } else if (ch == '\\') { hadSlash = true; continue; } writer.append(ch); } if (hadSlash) { // then we're in the weird case of a \ at the end of the // string, let's output it anyway. writer.append('\\'); } return writer.toString(); } /** * Check to see if the given word is reserved or a bad idea in any known * version of JavaScript. * @param name The word to check * @return false if the word is not reserved */ public static boolean isReservedWord(String name) { return reserved.contains(name); } /** * The array of javascript reserved words */ private static final String[] RESERVED_ARRAY = new String[] { // Reserved and used at ECMAScript 4 "as", "break", "case", "catch", "class", "const", "continue", "default", "delete", "do", "else", "export", "extends", "false", "finally", "for", "function", "if", "import", "in", "instanceof", "is", "namespace", "new", "null", "package", "private", "public", "return", "super", "switch", "this", "throw", "true", "try", "typeof", "use", "var", "void", "while", "with", // Reserved for future use at ECMAScript 4 "abstract", "debugger", "enum", "goto", "implements", "interface", "native", "protected", "synchronized", "throws", "transient", "volatile", // Reserved in ECMAScript 3, unreserved at 4 best to avoid anyway "boolean", "byte", "char", "double", "final", "float", "int", "long", "short", "static", // I have seen the following list as 'best avoided for function names' // but it seems way to all encompassing, so I'm not going to include it /* "alert", "anchor", "area", "arguments", "array", "assign", "blur", "boolean", "button", "callee", "caller", "captureevents", "checkbox", "clearinterval", "cleartimeout", "close", "closed", "confirm", "constructor", "date", "defaultstatus", "document", "element", "escape", "eval", "fileupload", "find", "focus", "form", "frame", "frames", "getclass", "hidden", "history", "home", "image", "infinity", "innerheight", "isfinite", "innerwidth", "isnan", "java", "javaarray", "javaclass", "javaobject", "javapackage", "length", "link", "location", "locationbar", "math", "menubar", "mimetype", "moveby", "moveto", "name", "nan", "navigate", "navigator", "netscape", "number", "object", "onblur", "onerror", "onfocus", "onload", "onunload", "open", "opener", "option", "outerheight", "outerwidth", "packages", "pagexoffset", "pageyoffset", "parent", "parsefloat", "parseint", "password", "personalbar", "plugin", "print", "prompt", "prototype", "radio", "ref", "regexp", "releaseevents", "reset", "resizeby", "resizeto", "routeevent", "scroll", "scrollbars", "scrollby", "scrollto", "select", "self", "setinterval", "settimeout", "status", "statusbar", "stop", "string", "submit", "sun", "taint", "text", "textarea", "toolbar", "top", "tostring", "unescape", "untaint", "unwatch", "valueof", "watch", "window", */ }; /** * The list of reserved words */ private static SortedSet<String> reserved = new TreeSet<String>(); /** * For easy access ... */ static { // The Javascript reserved words array so we don't generate illegal javascript reserved.addAll(Arrays.asList(RESERVED_ARRAY)); } }