Question

我正在研究GWT RPC。我在从SQL检索图像时遇到问题。这是我的代码：

 Base64 bas = new Base64();

 // sun.misc.BASE64Encoder enc = new sun.misc.BASE64Encoder(); 
 UploadfileJpaController up = new UploadfileJpaController();

 // this function returns the value in blob field in the form of byte array
 byte[] b = up.findUploadfile(n);

 String base64Contents = enc.encode(b).replaceAll("\\s+", ""); 
 //String base64 = Base64Utils.toBase64(b); 
 base64Contents = "data:image/gif;base64,"+base64Contents;
 return base64Contents;

但这不起作用..图像不显示。请帮忙:(

Answer 1

您应该让常规servlet负责返回图像数据，而不是使用GWT-RPC。 servlet应设置正确的image / gif头并将二进制数据写入响应输出流。编辑这应该看起来像这样

公共类FileDownloadServlet扩展了HttpServletv {

// This method is called by the servlet container to process a GET request.
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {

    // Set content type
    resp.setContentType("image/gif");               

    //Up to you!
    byte[] binaryData = getDataFromDbase();

    ByteArrayInputStream bis = new ByteArrayInputStream(binaryData);
    OutputStream out = resp.getOutputStream();

    // Copy the contents of the file to the output stream
    byte[] buf = new byte[1024];
    int count = 0;
    while ((count = bis.read(buf)) >= 0) {
        out.write(buf, 0, count);
    }
    bis.close();
    out.close();
}

}

你的网址会像

http://server/application/image_servlet?id=123545您在servlet中使用id参数来查找图像。当然，将servlet添加到web.xml中。祝你好运。

在GWT中从我的sql中检索图像

1 个答案: