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This nifi-utils module should be a general purpose place to store widely and generally useful functions that any component might want to leverage. NO DEPENDENCIES should be added. This module is likely to be leveraged by every extension and should not bring along any other dependencies. The only dependency intended is the nifi-api and even this is expected to be already provided in any case where it would be used. The typical place this util would be found is within a nar and all nars already have nifi-api as a parent dependency. The nifi-api can be thought of as a NiFi Application Container level dependency.

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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 org.apache.nifi.util.text;

/**
 * 
 * A utility class that can be used to determine whether or not a String matches a given date/time format, as specified
 * by the Time Format used in {@link java.time.format.DateTimeFormatter}. It is not uncommon to see code written along the lines of:
 * 
 *
 *  * final String format = "yyyy/MM/dd HH:mm:ss.SSS";
 * try {
 *     DateTimeFormatter.ofPattern(format).parse(text);
 *     return true;
 * } catch (Exception e) {
 *     return false;
 * }
 * 
 *
 * 
 *     This approach, however, is frowned upon for two important reasons. Firstly, the performance is poor. A micro-benchmark that involves executing
 *     the above code o evaluate whether or not text is a timestamp took approximately 125-130 seconds
 *     to iterate 1,000,000 times (after discarding the first 1,000,000 iterations as a 'warmup'). As a comparison, this utility takes about 8-11 seconds against
 *     the same data and on the same machine.
 * 
 *
 * 
 *     Secondly, the above snippet has a very expensive side effect of throwing an Exception if the text does not match the format. This Exception is silently ignored,
 *     but can have devastating effects on the JVM as a whole, as creating the Exception object can result in requiring a Safepoint, which means that all threads in the JVM
 *     may be forced to pause.
 * 
 *
 * 
 *     Note, however, that this class is not intended to replace DateTimeFormatter, as it does not perform the actual parsing but instead only determines whether or not
 *     a given input text matches the pattern, so that if it does, a DateTimeFormatter can be used parse the input.
 * 
 */
public interface DateTimeMatcher {
    /**
     * Determines whether or not the text matches the pattern
     * @param text the text to evaluate
     * @return true if the text matches the pattern, false otherwise
     */
    boolean matches(String text);

    static DateTimeMatcher compile(String format) {
        if (format == null) {
            return t -> false;
        }

        return new DateTimeMatcherCompiler().compile(format);
    }
}