java/src/main/com/google/appengine/spi/ServicesFile.java

   1 // Copyright 2008 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.spi;
   4
   5 import java.io.BufferedReader;
   6 import java.io.BufferedWriter;
   7 import java.io.IOException;
   8 import java.io.InputStream;
   9 import java.io.InputStreamReader;
  10 import java.io.OutputStream;
  11 import java.io.OutputStreamWriter;
  12 import java.util.Collection;
  13 import java.util.HashSet;
  14 import java.util.Set;
  15
  16 /**
  17  * A helper class for reading and writing Services files.
  18  *
  19  * @see java.util.ServiceLoader
  20  *
  21  */
  22 public class ServicesFile {
  23
  24   public static final String SERVICES_PATH = "META-INF/services";
  25
  26   private ServicesFile() {}
  27
  28   /**
  29    * Returns an absolute path to a service file given the class name of the service.
  30    *
  31    * @param serviceName not {@code null}
  32    * @return SERVICES_PATH + serviceName
  33    */
  34   public static String getPath(String serviceName) {
  35     return SERVICES_PATH + "/" + serviceName;
  36   }
  37
  38   /**
  39    * Reads the set of service classes from a service file.
  40    *
  41    * @param input not {@code null}. Closed after use.
  42    * @return a not {@code null Set} of service class names.
  43    * @throws IOException
  44    */
  45   public static Set<String> readServiceFile(InputStream input) throws IOException {
  46     BufferedReader r = null;
  47     HashSet<String> serviceClasses = new HashSet<String>();
  48     try {
  49       r = new BufferedReader(new InputStreamReader(input, "UTF-8"));
  50       String line;
  51       while ((line = r.readLine()) != null) {
  52         int commentStart = line.indexOf('#');
  53         if (commentStart >= 0) {
  54           line = line.substring(0, commentStart);
  55         }
  56         line = line.trim();
  57         if (!line.equals("")) {
  58           serviceClasses.add(line);
  59         }
  60       }
  61     } finally {
  62       try {
  63         if (r != null) {
  64           r.close();
  65         }
  66       } catch (IOException e) {
  67       }
  68     }
  69     return serviceClasses;
  70   }
  71
  72   /**
  73    * Writes the set of service class names to a service file.
  74    *
  75    * @param output not {@code null}. Not closed after use.
  76    * @param services a not {@code null Collection} of service class names.
  77    * @throws IOException
  78    */
  79   public static void writeServiceFile(Collection<String> services, OutputStream output)
  80       throws IOException {
  81     BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(output, "UTF-8"));
  82     for (String service : services) {
  83       writer.write(service);
  84       writer.newLine();
  85     }
  86     writer.flush();
  87   }
  88 }