View Javadoc

1   /************************************************************************
2    * Copyright (c) 2000-2004 The Apache Software Foundation.             *
3    * All rights reserved.                                                *
4    * ------------------------------------------------------------------- *
5    * Licensed under the Apache License, Version 2.0 (the "License"); you *
6    * may not use this file except in compliance with the License. You    *
7    * 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     *
14   * implied.  See the License for the specific language governing       *
15   * permissions and limitations under the License.                      *
16   ***********************************************************************/
17  
18  package org.codehaus.ivory.util;
19  
20  import org.apache.avalon.framework.context.Context;
21  import org.apache.avalon.framework.context.ContextException;
22  
23  import java.io.File;
24  import java.io.IOException;
25  
26  /***
27   * This class is essentially a set of static functions for
28   * extracting information from the Avalon context.  This class
29   * should never be instantiated.  Each function takes the context
30   * as a first argument.
31   */
32  public class AvalonContextUtilities {
33  
34      /***
35       * The file URL prefix
36       */
37      private static String filePrefix = "file://";
38  
39      /***
40       * The file URL prefix length
41       */
42      private static int filePrefixLength = filePrefix.length();
43  
44      public static final String APPLICATION_HOME = "app.home";
45      
46      /***
47       * Gets the file or directory described by the argument file URL.
48       *
49       * @param context the Avalon context
50       * @param fileURL an appropriately formatted URL describing a file on
51       *                the filesystem on which the server is running.  The
52       *                URL is evaluated as a location relative to the
53       *                application home, unless it begins with a slash.  In
54       *                the latter case the file location is evaluated relative
55       *                to the underlying file system root.
56       *
57       * @throws IllegalArgumentException if the arguments are null or the file
58       *                                  URL is not appropriately formatted.
59       * @throws ContextException if the underlying context generates a
60       *                          ContextException, if the application home is
61       *                          not correct, or if an IOException is generated
62       *                          while accessing the file.
63       */
64      public static File getFile(Context context, String fileURL)
65              throws Exception {
66          if ((context == null) || (fileURL == null)) {
67              throw new IllegalArgumentException("The getFile method doesn't allow null arguments.");
68          }
69          String internalFileURL = fileURL.trim();
70          if (!(internalFileURL.startsWith(filePrefix))) {
71              throw new IllegalArgumentException("The fileURL argument to getFile doesn't start with the required file prefix - "  + filePrefix);
72          }
73  
74          String fileName = fileURL.substring(filePrefixLength);
75          if (!(fileName.startsWith("/"))) {
76              String baseDirectory = "";
77              try {
78                  File applicationHome =
79                      (File)context.get(APPLICATION_HOME);
80                  baseDirectory = applicationHome.toString();
81              } catch (ContextException ce) {
82                  throw new ContextException("Encountered exception when resolving application home in Avalon context.", ce);
83              } catch (ClassCastException cce) {
84                  throw new ContextException("Application home object stored in Avalon context was not of type java.io.File.", cce);
85              }
86              StringBuffer fileNameBuffer =
87                  new StringBuffer(128)
88                      .append(baseDirectory)
89                      .append(File.separator)
90                              .append(fileName);
91              fileName = fileNameBuffer.toString();
92          }
93          try {
94              File returnValue = (new File(fileName)).getCanonicalFile();
95              return returnValue;
96          } catch (IOException ioe) {
97              throw new ContextException("Encountered an unexpected exception while retrieving file.", ioe);
98          }
99      }
100 
101     /***
102      * Private constructor to ensure that instances of this class aren't
103      * instantiated.
104      */
105     private AvalonContextUtilities() {}
106 }