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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache license, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License. You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the license for the specific language governing permissions and
15   * limitations under the license.
16   */
17  
18  package org.apache.commons.text.lookup;
19  
20  import java.util.Objects;
21  
22  import javax.script.ScriptEngine;
23  import javax.script.ScriptEngineManager;
24  
25  import org.apache.commons.text.StringSubstitutor;
26  
27  /**
28   * Executes the script with the given engine name.
29   * <p>
30   * Execute the script with the engine name in the format "EngineName:Script".
31   * </p>
32   * <p>
33   * For example: {@code "javascript:3 + 4"}.
34   * </p>
35   * <p>
36   * Using a {@link StringSubstitutor}:
37   * </p>
38   *
39   * <pre>
40   * StringSubstitutor.createInterpolator().replace("${script:javascript:3 + 4}"));
41   * </pre>
42   *
43   * @since 1.5
44   */
45  final class ScriptStringLookup extends AbstractStringLookup {
46  
47      /**
48       * Defines the singleton for this class.
49       */
50      static final ScriptStringLookup INSTANCE = new ScriptStringLookup();
51  
52      /**
53       * No need to build instances for now.
54       */
55      private ScriptStringLookup() {
56          // empty
57      }
58  
59      /**
60       * Execute the script with the engine name in the format "EngineName:Script". Extra colons will be ignored.
61       * <p>
62       * For example: {@code "javascript:3 + 4"}.
63       * </p>
64       *
65       * @param key the engine:script to execute, may be null
66       * @return The value returned by the execution.
67       */
68      @Override
69      public String lookup(final String key) {
70          if (key == null) {
71              return null;
72          }
73          final String[] keys = key.split(SPLIT_STR, 2);
74          final int keyLen = keys.length;
75          if (keyLen != 2) {
76              throw IllegalArgumentExceptions.format("Bad script key format [%s]; expected format is EngineName:Script.",
77                  key);
78          }
79          final String engineName = keys[0];
80          final String script = keys[1];
81          try {
82              final ScriptEngine scriptEngine = new ScriptEngineManager().getEngineByName(engineName);
83              if (scriptEngine == null) {
84                  throw new IllegalArgumentException("No script engine named " + engineName);
85              }
86              return Objects.toString(scriptEngine.eval(script), null);
87          } catch (final Exception e) {
88              throw IllegalArgumentExceptions.format(e, "Error in script engine [%s] evaluating script [%s].", engineName,
89                  script);
90          }
91      }
92  
93  }