ConditionInfo


1   /*
2    * $Header: /cvshome/build/org.osgi.service.condpermadmin/src/org/osgi/service/condpermadmin/ConditionInfo.java,v 1.13 2006/06/16 16:31:37 hargrave Exp $
3    *
4    * Copyright (c) OSGi Alliance (2004, 2006). All Rights Reserved.
5    * 
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * You may obtain a copy of the License at
9    *
10   *      http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.osgi.service.condpermadmin;
20  
21  import java.util.ArrayList  ;
22  
23  /**
24   * Condition representation used by the Conditional Permission Admin service.
25   * 
26   * <p>
27   * This class encapsulates two pieces of information: a Condition <i>type</i>
28   * (class name), which must implement <code>Condition</code>, and the
29   * arguments passed to its constructor.
30   * 
31   * <p>
32   * In order for a Condition represented by a <code>ConditionInfo</code> to be
33   * instantiated and considered during a permission check, its Condition class
34   * must be available from the system classpath.
35   * 
36   * <p>
37   * The Condition class must either:
38   * <ul>
39   * <li>Declare a public static <code>getCondition</code> method that takes a
40   * <code>Bundle</code> object and a <code>ConditionInfo</code> object as
41   * arguments. That method must return an object that implements the
42   * <code>Condition</code> interface.</li>
43   * <li>Implement the <code>Condition</code> interface and define a public
44   * constructor that takes a <code>Bundle</code> object and a
45   * <code>ConditionInfo</code> object as arguments.
46   * </ul>
47   * 
48   * @version $Revision: 1.13 $
49   */
50  public class ConditionInfo {
51      private String        type;
52      private String  []    args;
53  
54      /**
55       * Constructs a <code>ConditionInfo</code> from the specified type and
56       * args.
57       * 
58       * @param type The fully qualified class name of the Condition represented
59       *        by this <code>ConditionInfo</code>.
60       * @param args The arguments for the Condition. These arguments are
61       *        available to the newly created Condition by calling the
62       *        {@link #getArgs()} method.
63       * @throws java.lang.NullPointerException If <code>type</code> is
64       *         <code>null</code>.
65       */
66      public ConditionInfo(String   type, String  [] args) {
67          this.type = type;
68          this.args = args != null ? args : new String  [0];
69          if (type == null) {
70              throw new NullPointerException  ("type is null");
71          }
72      }
73  
74      /**
75       * Constructs a <code>ConditionInfo</code> object from the specified
76       * encoded <code>ConditionInfo</code> string. White space in the encoded
77       * <code>ConditionInfo</code> string is ignored.
78       * 
79       * @param encodedCondition The encoded <code>ConditionInfo</code>.
80       * @see #getEncoded
81       * @throws java.lang.IllegalArgumentException If the
82       *         <code>encodedCondition</code> is not properly formatted.
83       */
84      public ConditionInfo(String   encodedCondition) {
85          if (encodedCondition == null) {
86              throw new NullPointerException  ("missing encoded condition");
87          }
88          if (encodedCondition.length() == 0) {
89              throw new IllegalArgumentException  ("empty encoded condition");
90          }
91          try {
92              char[] encoded = encodedCondition.toCharArray();
93              int length = encoded.length;
94              int pos = 0;
95  
96              /* skip whitespace */
97              while (Character.isWhitespace(encoded[pos])) {
98                  pos++;
99              }
100 
101             /* the first character must be '[' */
102             if (encoded[pos] != '[') {
103                 throw new IllegalArgumentException  ("expecting open bracket");
104             }
105             pos++;
106 
107             /* skip whitespace */
108             while (Character.isWhitespace(encoded[pos])) {
109                 pos++;
110             }
111 
112             /* type is not quoted or encoded */
113             int begin = pos;
114             while (!Character.isWhitespace(encoded[pos])
115                     && (encoded[pos] != ']')) {
116                 pos++;
117             }
118             if (pos == begin || encoded[begin] == '"') {
119                 throw new IllegalArgumentException  ("expecting type");
120             }
121             this.type = new String  (encoded, begin, pos - begin);
122 
123             /* skip whitespace */
124             while (Character.isWhitespace(encoded[pos])) {
125                 pos++;
126             }
127 
128             /* type may be followed by args which are quoted and encoded */
129             ArrayList   argsList = new ArrayList  ();
130             while (encoded[pos] == '"') {
131                 pos++;
132                 begin = pos;
133                 while (encoded[pos] != '"') {
134                     if (encoded[pos] == '\\') {
135                         pos++;
136                     }
137                     pos++;
138                 }
139                 argsList.add(unescapeString(encoded, begin, pos));
140                 pos++;
141 
142                 if (Character.isWhitespace(encoded[pos])) {
143                     /* skip whitespace */
144                     while (Character.isWhitespace(encoded[pos])) {
145                         pos++;
146                     }
147                 }
148             }
149             this.args = (String  []) argsList
150                     .toArray(new String  [argsList.size()]);
151 
152             /* the final character must be ']' */
153             char c = encoded[pos];
154             pos++;
155             while ((pos < length) && Character.isWhitespace(encoded[pos])) {
156                 pos++;
157             }
158             if ((c != ']') || (pos != length)) {
159                 throw new IllegalArgumentException  ("expecting close bracket");
160             }
161         }
162         catch (ArrayIndexOutOfBoundsException   e) {
163             throw new IllegalArgumentException  ("parsing terminated abruptly");
164         }
165     }
166 
167     /**
168      * Returns the string encoding of this <code>ConditionInfo</code> in a
169      * form suitable for restoring this <code>ConditionInfo</code>.
170      * 
171      * <p>
172      * The encoding format is:
173      * 
174      * <pre>
175      *   [type &quot;arg0&quot; &quot;arg1&quot; ...]
176      * </pre>
177      * 
178      * where <i>argN</i> are strings that are encoded for proper parsing.
179      * Specifically, the <code>"</code>, <code>\</code>, carriage return,
180      * and linefeed characters are escaped using <code>\"</code>,
181      * <code>\\</code>, <code>\r</code>, and <code>\n</code>,
182      * respectively.
183      * 
184      * <p>
185      * The encoded string contains no leading or trailing whitespace characters.
186      * A single space character is used between type and "<i>arg0</i>" and
187      * between the arguments.
188      * 
189      * @return The string encoding of this <code>ConditionInfo</code>.
190      */
191     public final String   getEncoded() {
192         StringBuffer   output = new StringBuffer  ();
193         output.append('[');
194         output.append(type);
195 
196         for (int i = 0; i < args.length; i++) {
197             output.append(" \"");
198             escapeString(args[i], output);
199             output.append('\"');
200         }
201 
202         output.append(']');
203 
204         return output.toString();
205     }
206 
207     /**
208      * Returns the string representation of this <code>ConditionInfo</code>.
209      * The string is created by calling the <code>getEncoded</code> method on
210      * this <code>ConditionInfo</code>.
211      * 
212      * @return The string representation of this <code>ConditionInfo</code>.
213      */
214     public String   toString() {
215         return getEncoded();
216     }
217 
218     /**
219      * Returns the fully qualified class name of the condition represented by
220      * this <code>ConditionInfo</code>.
221      * 
222      * @return The fully qualified class name of the condition represented by
223      *         this <code>ConditionInfo</code>.
224      */
225     public final String   getType() {
226         return type;
227     }
228 
229     /**
230      * Returns arguments of this <code>ConditionInfo</code>.
231      * 
232      * @return The arguments of this <code>ConditionInfo</code>. An empty
233      *         array is returned if the <code>ConditionInfo</code> has no
234      *         arguments.
235      */
236     public final String  [] getArgs() {
237         return args;
238     }
239 
240     /**
241      * Determines the equality of two <code>ConditionInfo</code> objects.
242      * 
243      * This method checks that specified object has the same type and args as
244      * this <code>ConditionInfo</code> object.
245      * 
246      * @param obj The object to test for equality with this
247      *        <code>ConditionInfo</code> object.
248      * @return <code>true</code> if <code>obj</code> is a
249      *         <code>ConditionInfo</code>, and has the same type and args as
250      *         this <code>ConditionInfo</code> object; <code>false</code>
251      *         otherwise.
252      */
253     public boolean equals(Object   obj) {
254         if (obj == this) {
255             return true;
256         }
257 
258         if (!(obj instanceof ConditionInfo)) {
259             return false;
260         }
261 
262         ConditionInfo other = (ConditionInfo) obj;
263 
264         if (!type.equals(other.type) || args.length != other.args.length)
265             return false;
266 
267         for (int i = 0; i < args.length; i++) {
268             if (!args[i].equals(other.args[i]))
269                 return false;
270         }
271         return true;
272     }
273 
274     /**
275      * Returns the hash code value for this object.
276      * 
277      * @return A hash code value for this object.
278      */
279 
280     public int hashCode() {
281         int hash = type.hashCode();
282 
283         for (int i = 0; i < args.length; i++) {
284             hash ^= args[i].hashCode();
285         }
286         return hash;
287     }
288 
289     /**
290      * This escapes the quotes, backslashes, \n, and \r in the string using a
291      * backslash and appends the newly escaped string to a StringBuffer.
292      */
293     private static void escapeString(String   str, StringBuffer   output) {
294         int len = str.length();
295         for (int i = 0; i < len; i++) {
296             char c = str.charAt(i);
297             switch (c) {
298                 case '"' :
299                 case '\\' :
300                     output.append('\\');
301                     output.append(c);
302                     break;
303                 case '\r' :
304                     output.append("\\r");
305                     break;
306                 case '\n' :
307                     output.append("\\n");
308                     break;
309                 default :
310                     output.append(c);
311                     break;
312             }
313         }
314     }
315 
316     /**
317      * Takes an encoded character array and decodes it into a new String.
318      */
319     private static String   unescapeString(char[] str, int begin, int end) {
320         StringBuffer   output = new StringBuffer  (end - begin);
321         for (int i = begin; i < end; i++) {
322             char c = str[i];
323             if (c == '\\') {
324                 i++;
325                 if (i < end) {
326                     c = str[i];
327                     switch (c) {
328                         case '"' :
329                         case '\\' :
330                             break;
331                         case 'r' :
332                             c = '\r';
333                             break;
334                         case 'n' :
335                             c = '\n';
336                             break;
337                         default :
338                             c = '\\';
339                             i--;
340                             break;
341                     }
342                 }
343             }
344             output.append(c);
345         }
346 
347         return output.toString();
348     }
349 }
350
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