public RespBean downloadThirdFileHttpServletResponse response throws UnsupportedEncodingException String thirdUrl = httpsdppttianjinchinataxgovcn8443kpfwfpjfzzv1exportDzfpwjEwmWjgs=PDF&Jym=728E

要使此方法可用，您需要进行以下更改：

1. 添加所需的导入语句：

import cn.hutool.core.date.DateUtil;
import cn.hutool.core.util.StrUtil;

import javax.servlet.http.HttpServletResponse;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.io.UnsupportedEncodingException;
import java.util.Date;

2. 将方法签名中的返回类型更改为void，因为不需要将RespBean返回给调用者。

public void downloadThirdFile(HttpServletResponse response) throws UnsupportedEncodingException {

3. 删除最后的return语句，因为不再返回RespBean。

4. 将HttpServletResponse的response对象的getOutputStream()方法更改为response.getOutputStream()，以便在方法结束时自动关闭流。

最终的代码如下：

public void downloadThirdFile(HttpServletResponse response) throws UnsupportedEncodingException {
    String thirdUrl = "https://dppt.tianjin.chinatax.gov.cn:8443/kpfw/fpjfzz/v1/exportDzfpwjEwmWjgs=PDF&Jym=728E&Fphm=23122000000008542853&Kprq=20230905145917&Czsj=1693897158216";
    response.setContentType("application/x-msdownload");
    response.setHeader("Content-Disposition", "attachment;filename=" + new String((DateUtil.format(new Date(), "yyyyMMddHHmmss") + ".pdf").getBytes(), "ISO-8859-1"));
    if (StrUtil.isBlank(thirdUrl)) {
        // 下载失败的处理逻辑
        return;
    }
    if (!thirdUrl.toLowerCase().contains("http")) {
        thirdUrl = "http://" + thirdUrl;
    }
    HttpURLConnection httpUrl = null;
    BufferedInputStream in = null;
    try {
        URL url = new URL(thirdUrl);
        httpUrl = (HttpURLConnection) url.openConnection();
        httpUrl.connect();
        if (httpUrl.getResponseCode() != 200) {
            // 下载地址错误的处理逻辑
            return;
        }
        in = new BufferedInputStream(httpUrl.getInputStream());
        int len = 2048;
        byte[] bytes = new byte[len];
        while ((len = in.read(bytes)) != -1) {
            response.getOutputStream().write(bytes, 0, len);
        }
    } catch (Exception e) {
        e.printStackTrace();
        // 下载文件失败的处理逻辑
    } finally {
        if (httpUrl != null) {
            httpUrl.disconnect();
        }
        try {
            if (in != null) {
                in.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            response.getOutputStream().close();
            response.getOutputStream().flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
``