将文件从Java服务器发送到Javascript客户端-问题处理文件客户端

Question

我有一个运行码头的Java服务器，该码头将发送base64编码的excel文件作为对客户端请求的响应。 在客户端上收到响应后，我可以访问/解码响应，但是，下载导致文件无法由excel打开。

在文本编辑器中打开生成的客户端文件看起来就像一个有效的excel文件（16进制束）。我还有什么遗漏？

Java代码（使用spark）：

get("/file", (request, response) -> {
   File file = new File(".\\file.xlsx");
   InputStream is = new FileInputStream(file);
   byte[] buff = new byte[(int)file.length()];
   int bytesRead = 0;
   ByteArrayOutputStream bao = new ByteArrayOutputStream();

   while((bytesRead = is.read(buff)) != -1){
    bao.write(buff, 0, bytesRead);
   }
   is.close();
   byte[data] = bao.toByteArray();

   response.header("Content-Type", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
   //creates an encoded string as intended   
   response.body(new String(Base64.encodeBase64(data)));
   return response.body();

});

JavaScript代码（原始）：

function download(window) {
    let text;
    let blob;
    let reader = new FileReader();
    reader.onloadend = function(e) {
        //decodes base64 encoded response (file) from server
        text = window.atob(e.srcElement.result);
        blob = new Blob([text], {type: "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"})

        let url = window.URL.createObjectURL(blob);
        let downloadLink = document.createElement('a');
        downloadLink.href = url;
        downloadLink.download = "excelFile.xlsx";
        downloadLink.click();
        downloadLink.remove();
    }

    fetch("http://javaServer.com/file")
    .then(response => response.blob())
    .then(blob => {
        this.blob = blob;
        //triggers 'onloadend' event handler
        reader.readAsText(blob);
    });
}
download(window);