SpringMVC把后台文件打印到前台

实现效果如下：

代码为：

@RequestMapping(value = "/tools/printContract")
public void cell(HttpServletResponse response,HttpServletRequest request,String outName) {
    //根据outName获取到保存在服务器上的文件
    String filePath = request.getSession().getServletContext().getRealPath(ImgUtil.TOOLS_PATH+ImgUtil.TOOLS_TXT)+'/'+outName+".txt";
    try(OutputStream out = response.getOutputStream()) {
        Date currentTime = new Date();
        SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMdd_HHmmss");
        String dateString = formatter.format(currentTime);
        //fileName是输出的文件的名字（不支持中文），包括了后缀
        String fileName = "EncryptFile_" + dateString + ".txt";
        byte[] bytes = FileEcodeUtil.file2byte(filePath);
        response.setContentType("application/x-msdownload");
        response.setHeader("Content-Disposition","attachment;filename=" + fileName);
        response.setContentLength(bytes.length);
        out.write(bytes);
        out.flush();
    } catch (IOException e) {
    //e.printStackTrace();
    }
}

//上面用到的file2byte方法为：
public static byte[] file2byte(String filePath) {
    byte[] buffer = null;
    File file = new File(filePath);
    try (FileInputStream fis = new FileInputStream(file);
         ByteArrayOutputStream bos = new ByteArrayOutputStream()) {
        byte[] b = new byte[1024];
        int n;
        while ((n = fis.read(b)) != -1) {
            bos.write(b, 0, n);
        }
        buffer = bos.toByteArray();
    } catch (Exception e) {
        // e.printStackTrace();
    }
    return buffer;
}

 

需要注意：返回值的类型是void 而不是String，不能返回到某一个页面，否则服务器会抛出IllegalStateException异常，虽然在页面上表现不出来。

　　java.lang.IllegalStateException: Cannot create a session after the response has been committed

 

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