281 lines
9.3 KiB
Java
281 lines
9.3 KiB
Java
/**
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*
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* Copyright 2003-2007 Jive Software.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.jivesoftware.smack.util;
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import java.io.UnsupportedEncodingException;
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import java.util.Collection;
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import java.util.Random;
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/**
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* A collection of utility methods for String objects.
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*/
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public class StringUtils {
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public static final String MD5 = "MD5";
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public static final String SHA1 = "SHA-1";
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public static final String UTF8 = "UTF-8";
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public static final String USASCII = "US-ASCII";
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public static final String QUOTE_ENCODE = """;
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public static final String APOS_ENCODE = "'";
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public static final String AMP_ENCODE = "&";
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public static final String LT_ENCODE = "<";
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public static final String GT_ENCODE = ">";
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public static final char[] HEX_CHARS = "0123456789abcdef".toCharArray();
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/**
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* Escapes all necessary characters in the String so that it can be used
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* in an XML doc.
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*
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* @param string the string to escape.
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* @return the string with appropriate characters escaped.
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*/
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public static CharSequence escapeForXML(final String string) {
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if (string == null) {
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return null;
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}
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final char[] input = string.toCharArray();
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final int len = input.length;
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final StringBuilder out = new StringBuilder((int)(len*1.3));
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CharSequence toAppend;
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char ch;
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int last = 0;
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int i = 0;
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while (i < len) {
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toAppend = null;
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ch = input[i];
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switch(ch) {
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case '<':
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toAppend = LT_ENCODE;
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break;
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case '>':
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toAppend = GT_ENCODE;
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break;
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case '&':
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toAppend = AMP_ENCODE;
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break;
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case '"':
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toAppend = QUOTE_ENCODE;
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break;
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case '\'':
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toAppend = APOS_ENCODE;
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break;
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default:
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break;
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}
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if (toAppend != null) {
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if (i > last) {
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out.append(input, last, i - last);
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}
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out.append(toAppend);
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last = ++i;
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} else {
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i++;
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}
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}
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if (last == 0) {
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return string;
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}
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if (i > last) {
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out.append(input, last, i - last);
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}
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return out;
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}
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/**
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* Hashes a String using the SHA-1 algorithm and returns the result as a
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* String of hexadecimal numbers. This method is synchronized to avoid
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* excessive MessageDigest object creation. If calling this method becomes
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* a bottleneck in your code, you may wish to maintain a pool of
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* MessageDigest objects instead of using this method.
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* <p>
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* A hash is a one-way function -- that is, given an
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* input, an output is easily computed. However, given the output, the
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* input is almost impossible to compute. This is useful for passwords
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* since we can store the hash and a hacker will then have a very hard time
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* determining the original password.
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*
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* @param data the String to compute the hash of.
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* @return a hashed version of the passed-in String
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* @deprecated use {@link org.jivesoftware.smack.util.SHA1#hex(String)} instead.
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*/
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@Deprecated
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public synchronized static String hash(String data) {
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return org.jivesoftware.smack.util.SHA1.hex(data);
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}
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/**
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* Encodes an array of bytes as String representation of hexadecimal.
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*
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* @param bytes an array of bytes to convert to a hex string.
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* @return generated hex string.
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*/
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public static String encodeHex(byte[] bytes) {
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char[] hexChars = new char[bytes.length * 2];
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for ( int j = 0; j < bytes.length; j++ ) {
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int v = bytes[j] & 0xFF;
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hexChars[j * 2] = HEX_CHARS[v >>> 4];
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hexChars[j * 2 + 1] = HEX_CHARS[v & 0x0F];
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}
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return new String(hexChars);
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}
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public static byte[] toBytes(String string) {
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try {
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return string.getBytes(StringUtils.UTF8);
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}
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catch (UnsupportedEncodingException e) {
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throw new IllegalStateException("UTF-8 encoding not supported by platform", e);
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}
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}
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/**
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* Pseudo-random number generator object for use with randomString().
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* The Random class is not considered to be cryptographically secure, so
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* only use these random Strings for low to medium security applications.
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*/
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private static Random randGen = new Random();
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/**
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* Array of numbers and letters of mixed case. Numbers appear in the list
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* twice so that there is a more equal chance that a number will be picked.
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* We can use the array to get a random number or letter by picking a random
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* array index.
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*/
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private static char[] numbersAndLetters = ("0123456789abcdefghijklmnopqrstuvwxyz" +
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"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
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/**
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* Returns a random String of numbers and letters (lower and upper case)
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* of the specified length. The method uses the Random class that is
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* built-in to Java which is suitable for low to medium grade security uses.
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* This means that the output is only pseudo random, i.e., each number is
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* mathematically generated so is not truly random.<p>
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*
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* The specified length must be at least one. If not, the method will return
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* null.
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*
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* @param length the desired length of the random String to return.
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* @return a random String of numbers and letters of the specified length.
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*/
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public static String randomString(int length) {
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if (length < 1) {
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return null;
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}
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// Create a char buffer to put random letters and numbers in.
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char [] randBuffer = new char[length];
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for (int i=0; i<randBuffer.length; i++) {
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randBuffer[i] = numbersAndLetters[randGen.nextInt(numbersAndLetters.length)];
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}
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return new String(randBuffer);
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}
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/**
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* Returns true if CharSequence is not null and is not empty, false otherwise.
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* Examples:
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* isNotEmpty(null) - false
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* isNotEmpty("") - false
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* isNotEmpty(" ") - true
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* isNotEmpty("empty") - true
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*
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* @param cs checked CharSequence
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* @return true if string is not null and is not empty, false otherwise
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*/
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public static boolean isNotEmpty(CharSequence cs) {
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return !isNullOrEmpty(cs);
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}
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/**
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* Returns true if the given CharSequence is null or empty.
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*
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* @param cs
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* @return true if the given CharSequence is null or empty
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*/
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public static boolean isNullOrEmpty(CharSequence cs) {
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return cs == null || isEmpty(cs);
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}
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/**
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* Returns true if the given CharSequence is empty.
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*
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* @param cs
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* @return true if the given CharSequence is empty
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*/
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public static boolean isEmpty(CharSequence cs) {
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return cs.length() == 0;
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}
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public static String collectionToString(Collection<String> collection) {
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StringBuilder sb = new StringBuilder();
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for (String s : collection) {
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sb.append(s);
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sb.append(" ");
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}
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String res = sb.toString();
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// Remove the trailing whitespace
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res = res.substring(0, res.length() - 1);
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return res;
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}
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public static String returnIfNotEmptyTrimmed(String string) {
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if (string == null)
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return null;
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String trimmedString = string.trim();
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if (trimmedString.length() > 0) {
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return trimmedString;
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} else {
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return null;
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}
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}
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public static boolean nullSafeCharSequenceEquals(CharSequence csOne, CharSequence csTwo) {
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return nullSafeCharSequenceComperator(csOne, csTwo) == 0;
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}
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public static int nullSafeCharSequenceComperator(CharSequence csOne, CharSequence csTwo) {
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if (csOne == null ^ csTwo == null) {
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return (csOne == null) ? -1 : 1;
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}
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if (csOne == null && csTwo == null) {
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return 0;
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}
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return csOne.toString().compareTo(csTwo.toString());
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}
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public static <CS extends CharSequence> CS requireNotNullOrEmpty(CS cs, String message) {
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if (isNullOrEmpty(cs)) {
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throw new IllegalArgumentException(message);
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}
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return cs;
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}
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/**
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* Return the String representation of the given char sequence if it is not null.
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*
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* @param cs the char sequence or null.
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* @return the String representation of <code>cs</code> or null.
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*/
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public static String maybeToString(CharSequence cs) {
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if (cs == null) {
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return null;
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}
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return cs.toString();
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}
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}
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