1 /**
2 * Copyright (C) 2008-2010 Matt Gumbley, DevZendo.org <http://devzendo.org>;
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 /**
18 *
19 */
20 package org.devzendo.xplp;
21
22 import java.util.HashSet;
23 import java.util.Properties;
24 import java.util.regex.Matcher;
25 import java.util.regex.Pattern;
26
27 /**
28 * Interpolation of name=value pairs from a
29 * Properties object into a String, using Ant-style references
30 * to names - e.g ${name}.
31 * @author matt
32 *
33 */
34 public final class PropertiesInterpolator {
35 private final Properties mProps;
36 private final Matcher variableReferenceMatcher =
37 Pattern.compile("^(.*?)\\$\\{([^}]+?)\\}(.*?)$", Pattern.DOTALL).matcher("");
38 private final HashSet<String> verbatimVariables = new HashSet<>();
39
40 /**
41 * Create an interpolator, given a set of properties to
42 * interpolate inside incoming string data.
43 * @param props the name=value pairs.
44 *
45 */
46 public PropertiesInterpolator(final Properties props) {
47 mProps = props;
48 }
49
50 /**
51 * Replace any ${names} with their ${values}, except in # lines
52 * @param input the input string, can be null
53 * @return the output, null iff input == null
54 */
55 public String interpolate(final String input) {
56 //System.out.println("Interpolating '" + input + "'");
57 if (input == null || input.length() == 0) {
58 return input;
59 }
60 if (input.matches("^\\s*#.*$")) {
61 return input;
62 }
63 String s = input;
64 final StringBuilder sb = new StringBuilder();
65 while (true) {
66 variableReferenceMatcher.reset(s);
67 // System.out.println("Finding variables in '" + s + "'");
68 if (variableReferenceMatcher.find()) {
69 // System.out.println("Found variable");
70 final String before = variableReferenceMatcher.group(1);
71 final String variableName = variableReferenceMatcher.group(2);
72 final String after = variableReferenceMatcher.group(3);
73 // System.out.println("Variable '" + variableName + "'");
74 if (verbatimVariables.contains(variableName)) {
75 // System.out.println("Verbatim variable '" + variableName + "'");
76 sb.append(before);
77 sb.append("${");
78 sb.append(variableName);
79 sb.append("}");
80 } else {
81 if (mProps.containsKey(variableName)) {
82 final String variableValue = mProps.getProperty(variableName);
83 // System.out.println("Replacement is '" + variableValue + "'");
84 sb.append(before);
85 sb.append(variableValue);
86 } else {
87 //System.out.println("Got no value for variable");
88 throw new IllegalStateException("The name '" + variableName + "' is not defined");
89 }
90 }
91 s = after;
92 } else {
93 // System.out.println("No more variables");
94 sb.append(s);
95 break;
96 }
97 }
98 // System.out.println("Output is '" + sb.toString() + "'");
99 return sb.toString();
100 }
101
102 /**
103 * Mark ${verbatimVariable} as a variable name that should not be interpolated
104 * @param verbatimVariable a variable not to be interpolated; should be passed through as ${verbatimVariable}
105 */
106 public void doNotInterpolate(final String verbatimVariable) {
107 verbatimVariables.add(verbatimVariable);
108 }
109 }