1 | /*
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2 | * Copyright 2000-2004 The Apache Software Foundation
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3 | *
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4 | * Licensed under the Apache License, Version 2.0 (the "License");
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5 | * you may not use this file except in compliance with the License.
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6 | * You may obtain a copy of the License at
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7 | *
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8 | * http://www.apache.org/licenses/LICENSE-2.0
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9 | *
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10 | * Unless required by applicable law or agreed to in writing, software
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11 | * distributed under the License is distributed on an "AS IS" BASIS,
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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13 | * See the License for the specific language governing permissions and
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14 | * limitations under the License.
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15 | *
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16 | */
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17 |
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18 | package org.apache.tools.ant.util.regexp;
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19 |
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20 | import org.apache.tools.ant.BuildException;
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21 | import org.apache.tools.ant.Project;
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22 |
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23 | /**
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24 | * Simple Factory Class that produces an implementation of
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25 | * RegexpMatcher based on the system property
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26 | * <code>ant.regexp.matcherimpl</code> and the classes
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27 | * available.
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28 | *
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29 | * <p>In a more general framework this class would be abstract and
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30 | * have a static newInstance method.</p>
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31 | *
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32 | */
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33 | public class RegexpMatcherFactory {
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34 |
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35 | /** Constructor for RegexpMatcherFactory. */
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36 | public RegexpMatcherFactory() {
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37 | }
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38 |
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39 | /***
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40 | * Create a new regular expression instance.
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41 | * @return the matcher
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42 | * @throws BuildException on error
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43 | */
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44 | public RegexpMatcher newRegexpMatcher() throws BuildException {
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45 | return newRegexpMatcher(null);
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46 | }
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47 |
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48 | /***
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49 | * Create a new regular expression instance.
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50 | *
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51 | * @param p Project whose ant.regexp.regexpimpl property will be used.
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52 | * @return the matcher
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53 | * @throws BuildException on error
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54 | */
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55 | public RegexpMatcher newRegexpMatcher(Project p)
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56 | throws BuildException {
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57 | String systemDefault = null;
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58 | if (p == null) {
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59 | systemDefault = System.getProperty("ant.regexp.regexpimpl");
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60 | } else {
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61 | systemDefault = p.getProperty("ant.regexp.regexpimpl");
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62 | }
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63 |
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64 | if (systemDefault != null) {
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65 | return createInstance(systemDefault);
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66 | // XXX should we silently catch possible exceptions and try to
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67 | // load a different implementation?
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68 | }
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69 |
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70 | try {
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71 | testAvailability("java.util.regex.Matcher");
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72 | return createInstance("org.apache.tools.ant.util.regexp.Jdk14RegexpMatcher");
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73 | } catch (BuildException be) {
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74 | // ignore
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75 | }
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76 |
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77 | try {
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78 | testAvailability("org.apache.oro.text.regex.Pattern");
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79 | return createInstance("org.apache.tools.ant.util.regexp.JakartaOroMatcher");
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80 | } catch (BuildException be) {
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81 | // ignore
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82 | }
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83 |
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84 | try {
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85 | testAvailability("org.apache.regexp.RE");
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86 | return createInstance("org.apache.tools.ant.util.regexp.JakartaRegexpMatcher");
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87 | } catch (BuildException be) {
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88 | // ignore
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89 | }
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90 |
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91 | throw new BuildException("No supported regular expression matcher found");
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92 | }
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93 |
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94 | /**
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95 | * Create an instance of a matcher from a classname.
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96 | *
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97 | * @param className a <code>String</code> value
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98 | * @return a <code>RegexpMatcher</code> value
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99 | * @exception BuildException if an error occurs
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100 | */
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101 | protected RegexpMatcher createInstance(String className)
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102 | throws BuildException {
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103 | try {
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104 | Class implClass = Class.forName(className);
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105 | return (RegexpMatcher) implClass.newInstance();
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106 | } catch (Throwable t) {
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107 | throw new BuildException(t);
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108 | }
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109 | }
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110 |
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111 | /**
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112 | * Test if a particular class is available to be used.
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113 | *
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114 | * @param className a <code>String</code> value
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115 | * @exception BuildException if an error occurs
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116 | */
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117 | protected void testAvailability(String className) throws BuildException {
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118 | try {
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119 | Class.forName(className);
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120 | } catch (Throwable t) {
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121 | throw new BuildException(t);
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122 | }
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123 | }
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124 | }
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