core/src/main/java/org/apache/oozie/util/StringUtils.java

/**
 * 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.oozie.util;

/**
 * Utility methods for working with {@link String} objects.
 */
public class StringUtils {
    /**
     * Trims leading and trailing whitespaces of a {@link String} object. Also replaces new lines characters and tab characters by
     * empty Strings.
     *
     * @param str the {@link String} to trim
     * @return the trimmed {@link String}
     */
    public static String trim(String str) {
        if (str != null) {
            str = str.replaceAll("\\n", "");
            str = str.replaceAll("\\t", "");
            str = str.trim();
        }
        return str;
    }

    /**
     * Return the internalized string, or null if the given string is null.
     * @param str The string to intern
     * @return The identical string cached in the JVM string pool.
     */
    public static String intern(String str) {
        if (str == null) {
            return null;
        }
        return str.intern();
    }

    /**
     * Check if the input expression contains sequence statically. for example
     * identify if "," is present outside of a function invocation in the given
     * expression. Ex "${func('abc')},${func('def'}",
     *
     * @param expr - Expression string
     * @param sequence - char sequence to check in the input expression
     * @return true if present
     * @throws ELEvaluationException if evaluation of expression fails
     */
    public static boolean checkStaticExistence(String expr, String sequence) throws ELEvaluationException {
        int curlyBracketDept = 0;
        int functionDepth = 0;
        int index = 0;
        boolean foundSequence = false;
        while (index < expr.length()) {
            String substring = expr.substring(index);
            if (substring.startsWith("${")) {
                ++curlyBracketDept;
            }
            else if (substring.startsWith("}")) {
                --curlyBracketDept;
                if (curlyBracketDept < 0) {
                    throw new ELEvaluationException("Invalid curly bracket closing");
                }
            }
            if (curlyBracketDept > 0) {
                if (substring.startsWith("(")) {
                    ++functionDepth;
                }
                else if (substring.startsWith(")")) {
                    --functionDepth;
                    if (functionDepth < 0) {
                        throw new ELEvaluationException("Invalid function closing");
                    }
                }
            }
            if (curlyBracketDept == 0 && substring.startsWith(sequence)) {
                foundSequence = true;
            }
            if (curlyBracketDept > 0 && functionDepth == 0 && substring.startsWith(sequence)) {
                foundSequence = true;
            }
            ++index;
        }
        if (curlyBracketDept != 0) {
            throw new ELEvaluationException("Unclosed curly brackets");
        }
        if (functionDepth != 0) {
            throw new ELEvaluationException("Unfinished function calling");
        }
        return foundSequence;
    }
}