core/src/main/java/com/twitter/elephantbird/util/HadoopUtils.java
public static void writeStringListToConfAsBase64(String key, List<String> list, Configuration
    conf) {
    Preconditions.checkNotNull(list);
    Iterator<String> iter = list.iterator();
    StringBuilder sb = new StringBuilder();
    while(iter.hasNext()) {
      byte[] bytes = Base64.encodeBase64(iter.next().getBytes(Charsets.UTF_8), false);
      sb.append(new String(bytes, Charsets.UTF_8));
      if (iter.hasNext()) {
        sb.append(',');
      }
    }
    conf.set(key, sb.toString());
  }
public static void writeStringListToConfAsBase64(String key, List<String> list, Configuration
    conf) {
    Preconditions.checkNotNull(list);
    Iterator<String> iter = list.iterator();
    StringBuilder sb = new StringBuilder();
    while(iter.hasNext()) {
      byte[] bytes = Base64.encodeBase64(iter.next().getBytes(Charsets.UTF_8), false);
      sb.append(new String(bytes, Charsets.UTF_8));
      if (iter.hasNext()) {
        sb.append(',');
      }
    }
    conf.set(key, sb.toString());
  }
Writes a list of strings into a configuration by base64 encoding them and separating
them with commas

@param key for the configuration
@param list to write
@param conf to write to