在GWT中将文件从服务器发送到客户端

我正在使用GWT

我必须从服务器下载一个文件到客户端

文档位于外部存储库中

客户机通过Servlet发送文档的id

在服务器端：检索使用此ID的文档：

Document document = (Document)session.getObject(docId);
ContentStream contentStream = document.getContentStream();

ByteArrayInputStream inputStream = (ByteArrayInputStream) contentStream.getStream();

int c;
while ((c = inputStream.read()) != -1) {
    System.out.print((char) c); 
}
String mime = contentStream.getMimeType();
String name = contentStream.getFileName();
InputStream strm = contentStream.getStream();

在这里我可以阅读文件

我想把这个发给客户。 如何将其设置为文件并发送回客户端？

在Servlet中：

Document document =(Document)session.getObject(docId);
ContentStream contentStream = document.getContentStream();
String name = contentStream.getFileName();
response.setHeader("Content-Type", "application/octet-stream;");
response.setHeader("Content-Disposition", "attachment;filename=\"" + name + "\"");
OutputStream os = response.getOutputStream();
InputStream is = 
  (ByteArrayInputStream) contentStream.getStream();
BufferedInputStream buf = new BufferedInputStream(is);
int readBytes=0;
while((readBytes=buf.read())!=-1) {
      os.write(readBytes);
}   
os.flush();
os.close();// *important*
return; 

在Servlet中：

Document document =(Document)session.getObject(docId);
ContentStream contentStream = document.getContentStream();
String name = contentStream.getFileName();
response.setHeader("Content-Type", "application/octet-stream;");
response.setHeader("Content-Disposition", "attachment;filename=\"" + name + "\"");
OutputStream os = response.getOutputStream();
InputStream is = 
  (ByteArrayInputStream) contentStream.getStream();
BufferedInputStream buf = new BufferedInputStream(is);
int readBytes=0;
while((readBytes=buf.read())!=-1) {
      os.write(readBytes);
}   
os.flush();
os.close();// *important*
return; 

---

您可以在服务器端创建一个标准servlet（它扩展了

HttpServlet

，而不是

RemoteServiceServlet

），并有机会在客户端将id作为servlet参数提交

现在，您需要在收到请求后创建excel文件并将其发送到客户端。浏览器显示自动弹出的下载对话框。 但是您应该确保设置了正确的内容类型响应头。此标题将指示浏览器它是哪种类型的文件

protected void doGet(HttpServletRequest request, HttpServletResponse response) 
                                              throws ServletException, IOException { 

String fileId = reguest.getParameter("fileId"); // value of file id from request
File file = CreatorExel.getFile(fileId); // your method to create file from helper class

// setting response headers
response.setHeader("Content-Type", getServletContext().getMimeType(file.getName())); 
response.setHeader("Content-Length", file.length()); 
response.setHeader("Content-Disposition", "inline; filename=\"" + file.getName() + "\""); 

BufferedInputStream input = null; 
BufferedOutputStream output = null; 

try { 
    InputStream inputStream = new FileInputStream(file);
    ServletOutputStream outputStream = response.getOutputStream();

    input = new BufferedInputStream(fileInput); 
    output = new BufferedOutputStream(outputStream); 

    int count;
    byte[] buffer = new byte[8192]; //  buffer size is 512*16
    while ((count = input.read(buffer)) > 0) {
         output.write(buffer, 0, count);
    }

} finally { 
    if (output != null) {
       try { 
          output.close(); 
       } catch (IOException ex) {
       } 
    }
    if (input != null) {
       try { 
          input.close(); 
       } catch (IOException ex) {
       } 
    } 
} 

---

您可以在服务器端创建一个标准servlet（它扩展了

HttpServlet

，而不是

RemoteServiceServlet

），并有机会在客户端将id作为servlet参数提交

现在，您需要在收到请求后创建excel文件并将其发送到客户端。浏览器显示自动弹出的下载对话框。 但是您应该确保设置了正确的内容类型响应头。此标题将指示浏览器它是哪种类型的文件

protected void doGet(HttpServletRequest request, HttpServletResponse response) 
                                              throws ServletException, IOException { 

String fileId = reguest.getParameter("fileId"); // value of file id from request
File file = CreatorExel.getFile(fileId); // your method to create file from helper class

// setting response headers
response.setHeader("Content-Type", getServletContext().getMimeType(file.getName())); 
response.setHeader("Content-Length", file.length()); 
response.setHeader("Content-Disposition", "inline; filename=\"" + file.getName() + "\""); 

BufferedInputStream input = null; 
BufferedOutputStream output = null; 

try { 
    InputStream inputStream = new FileInputStream(file);
    ServletOutputStream outputStream = response.getOutputStream();

    input = new BufferedInputStream(fileInput); 
    output = new BufferedOutputStream(outputStream); 

    int count;
    byte[] buffer = new byte[8192]; //  buffer size is 512*16
    while ((count = input.read(buffer)) > 0) {
         output.write(buffer, 0, count);
    }

} finally { 
    if (output != null) {
       try { 
          output.close(); 
       } catch (IOException ex) {
       } 
    }
    if (input != null) {
       try { 
          input.close(); 
       } catch (IOException ex) {
       } 
    } 
} 

---

：从服务器下载到客户端的所有文件都是空的，但这些文件不是空的。我已经编辑了答案。现在请尝试检查您正在

contentStream.getStream（）中获取的数据，这是您的代码。：What is input<代码>新的BufferedInputStream（输入）对不起，输入错误：应该是“is”：
字节[]buf=new BufferedInputStream（inputStream）此行给我错误类型不匹配：无法从BufferedInputStream转换为byte[]将类型更改为buf BufferInputStream：从服务器到客户端的所有文件都是空的，但文件不是空的。我已编辑了答案。现在请尝试检查您正在
contentStream.getStream（）中获取的数据，这是您的代码。：What is input<代码>新的BufferedInputStream（输入）对不起，输入错误：应该是“is”：
字节[]buf=new BufferedInputStream（inputStream）此行给我错误类型不匹配：无法从BufferedInputStream转换为byte[]将类型更改为buf BufferInputStream