com.google.wave.api.Util.java Source code

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/**
 * 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 com.google.wave.api;

import org.apache.commons.codec.binary.Base64;

import java.net.URLEncoder;
import java.util.regex.Pattern;

import javax.annotation.Nullable;

/**
 * A class that contains various utility methods.
 */
public final class Util {

    /**
     * A regular expression that defines reserved {@code proxy_for} id.
     */
    private static final Pattern RESERVED_PROXY_FOR_CHARS_REGEX = Pattern.compile("[\\s\u0000-\u001F@,:<>\u007F]");

    /**
     * Checks if the given string is a valid proxy id, by asserting whether the
     * string contains reserved characters or not. This check is to ensure that
     * when we concatenate the robot id and the proxy id, it doesn't result in an
     * invalid participant id.
     *
     * The reserved characters are:
     * <ul>
     *   <li>whitespaces</li>
     *   <li>non-printing characters: decimal 0 - 31 (hex 00 - 1F), and decimal
     *       127 (hex 7F)</li>
     *   <li>{@code @}, {@code ,}, {@code :}, {@code <}, {@code >}</li>
     * </ul>
     *
     * If you need to pass in an arbitrary string as the proxy id, please consider
     * encoding the string with a Base64 encoder (for example, {@link Base64}) or
     * a URL encoder (for example, {@link URLEncoder}).
     *
     * @param string the string to be checked.
     * @return {@code true} if the string doesn't contain any reserved characters.
     */
    public static boolean isValidProxyForId(String string) {
        return !RESERVED_PROXY_FOR_CHARS_REGEX.matcher(string).find();
    }

    /**
     * Checks if the given string is a valid proxy id. Please see
     * {@link #isValidProxyForId(String)} for more details on the assertion. This
     * method throws an {@link IllegalArgumentException} if the input string is
     * not a valid proxy id.
     *
     * @param string the string to check.
     * @throws IllegalArgumentException if the input string is not a valid proxy
     *     id.
     */
    public static void checkIsValidProxyForId(String string) {
        if (string != null && !isValidProxyForId(string)) {
            throw new IllegalArgumentException("The input string \"" + string + "\" is not a valid "
                    + "proxy id. A valid proxy id may not contain whitespace characters, non-printing"
                    + "characters (decimal 0 - 31, and decimal 127), @, :, <, >, and comma.");
        }
    }

    /**
     * Returns {@code true} if the given string is null, empty, or comprises only
     * whitespace characters.
     * 
     * @param string the string reference to check
     * @return {@code true} if {@code string} is null, empty, or consists of
     *     whitespace characters only
     */
    public static boolean isEmptyOrWhitespace(@Nullable String string) {
        return string == null || string.matches("\\s*");
    }
}