GWTShellServlet.java

private void doGetPublicFile(HttpServletRequest request,
      HttpServletResponse response, TreeLogger logger, String partialPath,
      String moduleName) throws IOException {

    // Create a logger branch for this request.
    String msg = "The development shell servlet received a request for '"
        + partialPath + "' in module '" + moduleName + "' ";
    logger = logger.branch(TreeLogger.TRACE, msg, null);
    // ...
    URL foundResource;
    try {
      // Look for the requested file on the public path.
      //
      ModuleDef moduleDef = getModuleDef(logger, moduleName);
      foundResource = moduleDef.findPublicFile(partialPath);

      if (foundResource == null) {
        // Look in the place where we write compiled output.
        File moduleDir = new File(getOutputDir(), moduleName);
        File requestedFile = new File(moduleDir, partialPath);
        if (requestedFile.exists()) {
          try {
            foundResource = requestedFile.toURI().toURL();
          } catch (MalformedURLException e) {
            // ignore since it was speculative anyway
          }
        }

        if (foundResource == null) {
          msg = "Resource not found: " + partialPath;
          logger.log(TreeLogger.WARN, msg, null);
          throw new UnableToCompleteException();
        }
      }
    } catch (UnableToCompleteException e) {
      sendErrorResponse(response, HttpServletResponse.SC_NOT_FOUND,
          "Cannot find resource '" + partialPath
              + "' in the public path of module '" + moduleName + "'");
      return;
    }
    // ... omitted 
}