io.github.microcks.util.el.function.RandomStringELFunction Maven / Gradle / Ivy

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/*
 * Licensed to Laurent Broudoux (the "Author") under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Author 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 io.github.microcks.util.el.function;

import io.github.microcks.util.el.EvaluationContext;

import java.util.Random;

/**
 * This is an implementation of ELFunction that generates random Alphanumeric string.
 * You may specify string length as first argument. Default length is 32.
 * @author laurent
 */
public class RandomStringELFunction implements ELFunction {

   public static final int DEFAULT_LENGTH = 32;

   private static final int leftLimit = 48; // numeral '0'
   private static final int rightLimit = 122; // letter 'z'

   @Override
   public String evaluate(EvaluationContext evaluationContext, String... args) {
      Random generator = new Random();

      if (args != null) {
         switch (args.length) {
            case 1:
               int maxLength = DEFAULT_LENGTH;
               try {
                  maxLength = Integer.parseInt(args[0]);
               } catch (NumberFormatException nfe) {
                  // Ignore, we'll stick to the default.
               }
               return generateString(generator, maxLength);
         }
      }
      return generateString(generator, DEFAULT_LENGTH);
   }

   private String generateString(Random random, int length) {
      // See https://www.baeldung.com/java-random-string for reference.
      return random.ints(leftLimit, rightLimit + 1)
            .filter(i -> (i <= 57 || i >= 65) && (i <= 90 || i >= 97))
            .limit(length)
            .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
            .toString();
   }
}