从GWT调用servlet,使用servlet生成的post数据和下载文件

RequestBuilder builder = new RequestBuilder(RequestBuilder.POST, "http://localhost:8080/myapp/MyServlet");
builder.setHeader("Content-Type", "application/x-www-form-urlencoded");
builder.setRequestData(new JSONObject().put("key", "value").toString());
builder.setCallback(new RequestCallback() {
    @Override
    public void onResponseReceived(Request request, Response response) {
        // 处理响应数据
    }

    @Override
    public void onError(Request request, Throwable exception) {
        // 处理错误
    }
});
builder.send();

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // 读取post数据
    String key = request.getParameter("key");

    // 生成下载文件
    String filename = "myfile.txt";
    String content = "This is the content of the file.";
    byte[] contentBytes = content.getBytes("UTF-8");
    ByteArrayInputStream bais = new ByteArrayInputStream(contentBytes);

    // 设置响应头以实现文件下载
    response.setHeader("Content-Disposition", "attachment; filename=" + filename);
    response.setContentType("application/octet-stream");
    response.setContentLength(contentBytes.length);

    // 将下载文件的输入流写入到HttpServletResponse的输出流中
    try (ServletOutputStream out = response.getOutputStream()) {
        byte[] buffer = new byte[1024];
        int bytesRead;
        while ((bytesRead = bais.read(buffer)) != -1) {
            out.write(buffer, 0, bytesRead);
        }
    }
}