按钮从primefaces的galleria组件下载图像

<p:galleria value="#{bean.images}" var="image" panelWidth="500" panelHeight="300">
    <p:graphicImage name="#{image}" />
</p:galleria>

<p:commandButton value="下载图像" action="#{bean.downloadImage}" ajax="false" />

public void downloadImage() throws IOException {
    FacesContext facesContext = FacesContext.getCurrentInstance();
    ExternalContext externalContext = facesContext.getExternalContext();
    
    // 获取用户选择的图像路径
    String selectedImage = "path/to/selected/image.jpg";
    
    // 设置响应头，告诉浏览器下载文件
    externalContext.setResponseContentType("application/octet-stream");
    externalContext.setResponseHeader("Content-Disposition", "attachment;filename=image.jpg");
    
    // 读取图像文件并写入响应流
    try (InputStream inputStream = externalContext.getResourceAsStream(selectedImage);
         OutputStream outputStream = externalContext.getResponseOutputStream()) {
        byte[] buffer = new byte[1024];
        int length;
        while ((length = inputStream.read(buffer)) > 0) {
            outputStream.write(buffer, 0, length);
        }
    }
    
    facesContext.responseComplete();
}