一 上传

上传即将文件上传到服务器上，在客户端需要写相应的脚本，服务器端需要注册相应的 handle 接受客户端的请求。

原理：

  Rap 的上传和下载是通过普通的 web 的方式进行上传和下载的 , 但是和传统的 wen 还不相同

1、  rap 本身就单线程在跑 , 和上传下载的线程不能进行混淆

所以采用的方式如下：

上传：通过传统的方式上传到指定目录 ,rap 不能直接操作上传的文件流 , 如果想获得上传的数据必须要先上传到指定文件 , 然后让rap 去加载指定文件即可

下载： 先通过 rap 程序生成需要下载的文件到指定目录 , 然后通过 rap 加载成文件流的形式发送给客户端

1 在服务器端注册相应的 handler

 // 注册上传处理事件
  IServiceManager manager = RWT.getServiceManager ();
  IServiceHandler uploadHandler = new UploadServiceHandler();
manager.registerServiceHandler( "uploadServiceHandler" , uploadHandler); //$NON-NLS-1$

2 在客户端的脚本调用

目前的做法是创建上传的 dialog, 在 dialog 里面添加 browser 控件，然后 browser 里书写上传的 javaScript 脚本，脚本请求的 url 格式可以通过以下类似的代码创建：

  private String createUploadUrl(String uploadFileName) {
      StringBuffer url = new StringBuffer();
      url.append(RWT.getRequest ().getContextPath());
      url.append(RWT.getRequest ().getServletPath());
      url.append( "?" ); //$NON-NLS-1$
      url.append(IServiceHandler . REQUEST_PARAM );
      url.append( "=uploadServiceHandler" ); //$NON-NLS-1$
      url.append( "&fileName=" ); //$NON-NLS-1$
      url.append(uploadFileName);
      return url.toString();
   }

3 服务器端 handler 的写法

public class UploadServiceHandler implements IServiceHandler {
   public void service() throws IOException, ServletException {
      HttpServletRequest request = RWT.getRequest ();
      request.setCharacterEncoding( "UTF-8" );
      String fileName = request.getParameter( "fileName" );
      FileOutputStream o = null ;
      BufferedReader bufferReader = null ;
      InputStream in = null ;
      try {
         in = request.getInputStream();
         File f = null ;
         try {
          f = new File(FileUtil.getTempFilePathAndName (RWT.getRequest ()
            .getSession().getAttribute( "userName" ).toString(),
                   fileName));
         } catch (Exception e) {
            throw new IOException(e);
         }
         o = new FileOutputStream(f);
         bufferReader = new BufferedReader( new InputStreamReader(in));
         String line = null ;
         boolean beginWrite = false ;
         boolean endWrite = false ;
         while ((line = bufferReader.readLine()) != null ) {
            if (line.indexOf(PriceDomainBean. class .getName()) != -1) {
                if (!beginWrite) {
                   beginWrite = true ;
                } else {
                   endWrite = true ;
                }
            }
            if (beginWrite) {
                o.write((line + "\r\n" ).getBytes());
            }
            if (endWrite) {
                break ;
            }
         }
      } catch (IOException e) {
         throw e;
      } finally {
         if ( null != o) {
            o.close();
         }
         in.close();
         if ( null != bufferReader) {
            bufferReader.close();
         }
      }
      HttpServletResponse response = RWT.getResponse ();
      response.setContentType( "text/html;charset=UTF-8" );
      response.getWriter().write(
            "<br><br><br><DIV align=center><h2> 上传成功 !</h2>" );
   }
}

二 下载

下载和上传采用的方式基本相同，只不过是将服务器文件读取到本地，和上传是一个相反的过程。

1 在服务器端注册相应的 handler

  // 注册下载处理事件
  IServiceManager manager = RWT.getServiceManager ();
  IServiceHandler downloadHandler = new DownloadServiceHandler();
  manager.registerServiceHandler( "downloadServiceHandler" , downloadHandler);

2 在客户端节本的调用

在 bowser 控件中书写 js 请求脚本，脚本请求的 url 如下

private String createDownloadUrl(String fileName) {
        StringBuffer url = new StringBuffer();
        url.append (RWT.getRequest ().getContextPath());
        url.append (RWT.getRequest ().getServletPath());
        url.append ( "?" );
        url.append (IServiceHandler. REQUEST_PARAM );
        url.append ( "=downloadServiceHandler" );
        url.append ( "&fileName='+encodeURI('" );
        url.append (fileName);
        url.append ( "')" );
        return url.toString();
    }

3 服务器端 handler 的写法

public class DownloadServiceHandler implements IServiceHandler {
   public void service() throws IOException, ServletException {
      String fileName = URLDecoder.decode (
            RWT.getRequest ().getParameter( "fileName" ), "UTF-8" );
      String filePathAndName = null ;
      try {
         filePathAndName = FileUtil
         .getTempFilePathAndName (RWT.getRequest ().getSession()
                      .getAttribute( "userName" ).toString(), fileName);
      } catch (Exception e) {
         throw new IOException(e);
      }
      File file = new File(filePathAndName);
      if (!file.exists()) {
         return ;
      }
      HttpServletResponse response = RWT.getResponse ();
      response.setHeader( "pragma" , "no-cache" );
      response.setHeader( "cache-control" , "no-cache" );
      response.setDateHeader( "Expires" , 0);
      response.setCharacterEncoding( "UTF-8" );
      response.setContentType( "text/html;charset=UTF-8" );
      response.setHeader( "Content-Disposition" , "attachment;filename="
            + new String(fileName.getBytes( "gb2312" ), "ISO8859-1" ));
      try {
         BufferedInputStream in = new BufferedInputStream(
                new FileInputStream(filePathAndName));
         ByteArrayOutputStream out = new ByteArrayOutputStream(1024);
         byte [] temp = new byte [1024];
         int size = 0;
         while ((size = in.read(temp)) != -1) {
            out.write(temp, 0, size);
         }
         in.close();
         byte [] content = out.toByteArray();
         response.setContentLength(content. length );
         response.getOutputStream().write(content);
      } catch (IOException ioe) {
         throw new RuntimeException(ioe);
      } finally {
         try {
            FileUtil.deleteTempFile (RWT.getRequest ().getSession()
                   .getAttribute( "userName" ).toString(), fileName);
         } catch (Exception e) {
            throw new IOException(e);
         }
      }
   }
}