文件下载+保存本地服务器

```package com.oristand.starcloud.common.utils;

import com.oristand.starcloud.common.constants.KeyboardSpecialCharConstants;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;

import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;


/**
 * 文件下载
 *
 * @author peiyuxiang
 * @date 2021/05/04
 */
@Slf4j
public class FileDownloadUtil {

    /**
     * pdf下载流
     */
    public static final String APPLICATION_PDF = "application/pdf";
    /**
     * pdf下载流
     */
    public static final String APPLICATION_TEXT_PLAIN = "text/plain";

    /**
     * http 传输文件
     *
     * @param response servlet响应
     * @param filePath 文件全路径名
     * @param fileName 附件文件名
     */
    public static void download(HttpServletResponse response,
                                String filePath,
                                String fileName,
                                String contentType
    ) throws IOException {

        if (StringUtils.isBlank(contentType)) {
            response.setContentType("application/octet-stream");
        } else {
            response.setContentType(contentType);
        }

        try {
            response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "utf-8"));
        } catch (Exception e) {
            // pass
        }

        byte[] buff = new byte[1024];

        //创建缓冲输入流
        BufferedInputStream bis = null;
        OutputStream outputStream = null;

        try {
            outputStream = response.getOutputStream();

            //这个路径为待下载文件的路径
            bis = new BufferedInputStream(new FileInputStream(new File(filePath)));
            int read = bis.read(buff);

            //通过while循环写入到指定了的文件夹中
            while (read != -1) {
                outputStream.write(buff, 0, read);
                outputStream.flush();
                read = bis.read(buff);
            }
        } finally {
            if (null != bis) {
                try {
                    bis.close();
                } catch (IOException e) {
                    // 忽略
                }
            }
            if (null != outputStream) {
                try {
                    outputStream.flush();
                    outputStream.close();
                } catch (IOException e) {
                    // 忽略
                }
            }
        }
    }


    /**
     * 用http请求将url文件保存到本地
     *
     * @param url      请求文件的url
     * @param filePath 需要保存的路径
     * @return 是否保存文件成功, 成功返回true, 失败返回false
     */
    public static boolean saveFileByUrl(URL url, String filePath) {
        try {
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setConnectTimeout(10000);
            connection.setReadTimeout(10000);
            DataInputStream inputStream = new DataInputStream(connection.getInputStream());
            DataOutputStream outputStream = new DataOutputStream(new FileOutputStream(filePath));
            byte[] buffer = new byte[1024];
            int count;
            while ((count = inputStream.read(buffer)) > 0) {
                outputStream.write(buffer, 0, count);
            }
            outputStream.close();
            inputStream.close();
            log.info("this is connection success");
            return true;
        } catch (Exception e) {
            log.error("FileDownloadUtil#saveFileByUrl error url:{},filePath:{}", url, filePath);
            return false;
        }
    }

    /**
     * 将数据保存到path路径
     *
     * @param inputStream 文件流
     * @param savePath    路径："D:\\testFile\\"
     * @param fileName    文件名：text.pdf
     */
    public static Boolean saveFileToPath(InputStream inputStream, String savePath, String fileName) {
        if (null == inputStream || StringUtils.isBlank(savePath) || StringUtils.isBlank(fileName)) {
            return false;
        }
        FileOutputStream fileOutputStream = null;
        DataOutputStream dataOutputStream = null;
        try {
            //输出的文件流保存到本地文件
            File file = new File(savePath);
            boolean flag = file.exists();
            if (!flag) {
                flag = file.mkdirs();
            }
            if (!flag) {
                return false;
            }
            String finalPath;
            if (savePath.endsWith(KeyboardSpecialCharConstants.SLASH) ||
                    savePath.endsWith(KeyboardSpecialCharConstants.BACKSLASH)) {
                finalPath = savePath + fileName;
            } else {
                finalPath = savePath + KeyboardSpecialCharConstants.SLASH + fileName;
            }

            fileOutputStream = new FileOutputStream(finalPath);
            dataOutputStream = new DataOutputStream(fileOutputStream);
            //保存到临时文件
            byte[] bs = new byte[1024];
            //读取到的数据长度
            int len;
            while ((len = inputStream.read(bs)) != -1) {
                dataOutputStream.write(bs, 0, len);
                dataOutputStream.flush();
            }
        } catch (IOException e) {
            log.error("saveFileToPath#error", e);
            return false;
        } finally {
            //完毕，关闭所有链接
            try {
                inputStream.close();
            } catch (IOException e) {
                // 忽略
            }
            if (null != fileOutputStream) {
                try {
                    fileOutputStream.close();
                } catch (IOException e) {
                    // 忽略
                }
            }
            if (null != dataOutputStream) {
                try {
                    dataOutputStream.close();
                } catch (IOException e) {
                    // 忽略
                }
            }
        }
        return true;
    }


    /**
     * 创建目录
     *
     * @param filePath 文件路径
     * @return true/false
     */
    public static Boolean createDirectory(String filePath) {
        if (StringUtils.isBlank(filePath)) {
            return false;
        }
        File file = new File(filePath);
        boolean flag = file.exists();
        if (!flag) {
            flag = file.mkdirs();
        }
        if (flag) {
            return true;
        }
        log.info("createDirectory Failed#filePath:{}", filePath);
        return false;
    }
}