| 1 | package com.hammurapi.common; |
| 2 | |
| 3 | import java.util.HashSet; |
| 4 | import java.util.Set; |
| 5 | import java.util.StringTokenizer; |
| 6 | |
| 7 | /** |
| 8 | * Expands tokens like $[myToken] to token values. |
| 9 | * Nested tokens are supported, i.e. if myToken value contains $[someOtherToken] |
| 10 | * then it will also be expanded. $[ can be escaped by adding extra $, e.g. $$[ will be replaced with $[. |
| 11 | * Token can contain default value separated from the token name by pipe, e.g. $[myToken|tokenDefaultValue]. |
| 12 | * @author Pavel Vlasov |
| 13 | */ |
| 14 | public class TokenExpander { |
| 15 | |
| 16 | /** |
| 17 | * Source of tokens. |
| 18 | * @author Pavel Vlasov |
| 19 | */ |
| 20 | public interface TokenSource { |
| 21 | |
| 22 | /** |
| 23 | * @param name Token name. |
| 24 | * @return Token value or null. |
| 25 | */ |
| 26 | String getToken(String name); |
| 27 | |
| 28 | } |
| 29 | |
| 30 | public static final String TOKEN_CLOSING_CHAR = "}"; |
| 31 | public static final String TOKEN_SECOND_OPENING_CHAR = "{"; |
| 32 | public static final String TOKEN_FIRST_OPENING_CHAR = "$"; |
| 33 | |
| 34 | private String tokenClosingChar = TOKEN_CLOSING_CHAR; |
| 35 | private String tokenSecondOpeningChar = TOKEN_SECOND_OPENING_CHAR; |
| 36 | private String tokenFirstOpeningChar = TOKEN_FIRST_OPENING_CHAR; |
| 37 | |
| 38 | private TokenSource tokens; |
| 39 | |
| 40 | /** |
| 41 | * Creates a new instance of PropertyParser |
| 42 | * @param properties Properties |
| 43 | * @param useNameAsDefault If true then property name will be used |
| 44 | * as property default value. |
| 45 | */ |
| 46 | public TokenExpander(TokenSource tokens) { |
| 47 | if (tokens==null) { |
| 48 | throw new NullPointerException("Tokens map is null"); |
| 49 | } |
| 50 | this.tokens=tokens; |
| 51 | } |
| 52 | |
| 53 | /** |
| 54 | * Creates a new instance of TokenExpander. |
| 55 | * @param tokens |
| 56 | * @param tokenFirstOpeningChar Token first opening char. Default is $. |
| 57 | * @param tokenSecondOpeningChar Token second opening char. Default is {. |
| 58 | * @param tokenClosingChar Token closing char. Default is }. |
| 59 | */ |
| 60 | public TokenExpander(TokenSource tokens, char tokenFirstOpeningChar, char tokenSecondOpeningChar, char tokenClosingChar) { |
| 61 | this(tokens); |
| 62 | this.tokenClosingChar=String.valueOf(tokenClosingChar); |
| 63 | this.tokenFirstOpeningChar=String.valueOf(tokenFirstOpeningChar); |
| 64 | this.tokenSecondOpeningChar=String.valueOf(tokenSecondOpeningChar); |
| 65 | } |
| 66 | |
| 67 | /** |
| 68 | * Property parsing. |
| 69 | * Replaces string ${<property name>} with property value. |
| 70 | * If property value contains ${<other property name>} it |
| 71 | * will be parsed. |
| 72 | */ |
| 73 | public String expandToken(String token, String defaultValue) throws TokenExpansionException { |
| 74 | return expandToken(token, defaultValue, new HashSet<String>()); |
| 75 | } |
| 76 | |
| 77 | /** |
| 78 | * Parses a string by replacing occurences of ${<property name>} |
| 79 | * with property values. |
| 80 | * If property value contains ${<other property name>} it |
| 81 | * will be parsed. |
| 82 | */ |
| 83 | public String expand(String str) throws TokenExpansionException { |
| 84 | return parse(str, null); |
| 85 | } |
| 86 | |
| 87 | private String expandToken(String token, String defaultValue, Set<String> stack) throws TokenExpansionException { |
| 88 | String value = tokens.getToken(token); |
| 89 | if (value==null) { |
| 90 | if (defaultValue==null) { |
| 91 | throw new TokenExpansionException("Token not found: "+token); |
| 92 | } |
| 93 | value = defaultValue; |
| 94 | } |
| 95 | |
| 96 | if (stack.contains(token)) { |
| 97 | throw new TokenExpansionException("Circular reference in token substitution, token: "+token); |
| 98 | } |
| 99 | |
| 100 | stack.add(token); |
| 101 | |
| 102 | return parse(value, stack); |
| 103 | } |
| 104 | |
| 105 | private String parse(String str, Set<String> stack) throws TokenExpansionException { |
| 106 | if (str==null) { |
| 107 | return null; |
| 108 | } |
| 109 | |
| 110 | StringTokenizer st=new StringTokenizer(str,tokenFirstOpeningChar+tokenSecondOpeningChar+tokenClosingChar,true); |
| 111 | |
| 112 | StringBuilder ret=new StringBuilder(); |
| 113 | |
| 114 | /** |
| 115 | * Parser state: |
| 116 | * 0: Text |
| 117 | * 1: $ |
| 118 | * 2: ${ |
| 119 | */ |
| 120 | final int TEXT = 0; |
| 121 | final int OPEN_FIRST = 1; |
| 122 | final int OPEN_SECOND = 2; |
| 123 | |
| 124 | int state=0; |
| 125 | |
| 126 | String propTxt=null; |
| 127 | while (st.hasMoreTokens()) { |
| 128 | String tkn=st.nextToken(); |
| 129 | switch (state) { |
| 130 | case TEXT: |
| 131 | if (tokenFirstOpeningChar.equals(tkn)) |
| 132 | state=OPEN_FIRST; |
| 133 | else |
| 134 | ret.append(tkn); |
| 135 | break; |
| 136 | case OPEN_FIRST: |
| 137 | if (tokenSecondOpeningChar.equals(tkn)) |
| 138 | state=OPEN_SECOND; |
| 139 | else { |
| 140 | state=TEXT; |
| 141 | ret.append(tokenFirstOpeningChar); |
| 142 | if (tkn.equals(tokenFirstOpeningChar)) { |
| 143 | String next = st.hasMoreTokens() ? st.nextToken() : null; |
| 144 | if (next==null) { |
| 145 | ret.append(tkn); |
| 146 | } else { |
| 147 | if (!next.equals(tokenSecondOpeningChar)) { |
| 148 | ret.append(tkn); |
| 149 | } |
| 150 | ret.append(next); |
| 151 | } |
| 152 | } else { |
| 153 | ret.append(tkn); |
| 154 | } |
| 155 | } |
| 156 | break; |
| 157 | case OPEN_SECOND: |
| 158 | if (tokenClosingChar.equals(tkn)) { |
| 159 | int pipeIdx = propTxt==null ? -1 : propTxt.indexOf('|'); |
| 160 | String propVal=expandToken(pipeIdx==-1 ? propTxt : propTxt.substring(0, pipeIdx), pipeIdx==-1 ? null : propTxt.substring(pipeIdx+1), stack==null ? new HashSet<String>() : stack); |
| 161 | ret.append(propVal); |
| 162 | propTxt=null; |
| 163 | state=0; |
| 164 | } else { |
| 165 | if (propTxt==null) { |
| 166 | propTxt=tkn; |
| 167 | } else { |
| 168 | propTxt+=tkn; |
| 169 | } |
| 170 | } |
| 171 | break; |
| 172 | default: |
| 173 | throw new IllegalStateException("Illegal parser state: "+state); |
| 174 | } |
| 175 | } |
| 176 | |
| 177 | if (state==OPEN_SECOND) { |
| 178 | ret.append(tokenFirstOpeningChar+tokenSecondOpeningChar+propTxt); |
| 179 | } |
| 180 | |
| 181 | return ret.toString(); |
| 182 | } |
| 183 | } |