(Java)网路路径文件下载

此篇时讲通过网路路径将文件以二进制流响应到浏览器，文件名称是前台所管控的。

下面是下载文件方法的主体：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

/**
 * 文件下载
 * Date: 2020/10/29
 * @author 时恰好那个i
 */
@Component
public class FileDownloadUtil {

    private static final Logger LOGGER = LoggerFactory.getLogger(FileDownloadUtil.class);


    /**
     * 从网络Url中下载文件
     * @param fileUrl   网路路径
     * @param fileName  文件名称
     */
    public void downLoadFromUrl(String fileUrl,String fileName, HttpServletResponse response) {
        ServletOutputStream outputStream = null;
        InputStream inputStream = null;
        try {
            URL url = new URL(fileUrl);
            HttpURLConnection conn = (HttpURLConnection)url.openConnection();
            //设置超时间为3秒
            conn.setConnectTimeout(3 * 1000);
            //防止屏蔽程序抓取而返回403错误
            conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");

            //得到输入流
            inputStream = conn.getInputStream();
            response.setContentType("application/json;charset=UTF-8");
            // response.setHeader("Content-Disposition", "attachment;fileName=" + URLEncoder.encode(fileName, "UTF-8") );
            response.setHeader("Cache-Control", "no-cache");
            outputStream = response.getOutputStream();
            byte[] b = new byte[1024];
            int len = 0;
            while((len = inputStream.read(b)) > 0) {
                outputStream.write(b, 0, len);
            }
            outputStream.flush();
        } catch (IOException e) {
            LOGGER.info("文件下载失败");
            e.printStackTrace();
        } finally {
            if (outputStream != null) {
                try {
                    outputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

}