网络资源url转化为file对象下载文件

注：只测试过网络图片资源。

一、使用org.apache.commons.io.FileUtils

二、

三、httpURLConnection.disconnect();

四、

import org.apache.commons.io.FileUtils;
import org.apache.commons.lang3.StringUtils;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.UUID;

/**
 * URLConnection的连接、超时、关闭用法总结 : https://www.cnblogs.com/achengmu/p/10057243.html
 * RandomAccessFile简介与使用 : https://blog.csdn.net/qq_31615049/article/details/88562892
 */
public class Test {

    private static String dirPath = "F:\\\\upload2222";
    public static void main(String[] args) throws IOException {

        String url = "http://imgsrc.baidu.com/forum/pic/item/a701a18b87d6277fff058e4125381f30e924fcb0.jpg";
        //方式1
//        copyByUrl(url, rewriteFileName(url), dirPath);
        //方式2
//        urlOpenStreamWrite(url, "antStorm_100171553219414047v.jpg", dirPath);
        //方式3
//        downLoadByUrl(url, "antStorm_100171553219414047m3v.jpg", dirPath);
        //方式4
        randomAccessWrite(url);
    }

    /**
     * import org.apache.commons.io.FileUtils;
     */
    public static void copyByUrl(String urlStr,String fileName,String savePath)throws IOException {
        URL url = new URL(urlStr);
        FileUtils.copyURLToFile(url, new File(savePath+ File.separator+fileName));
    }

    /**
     * urlOpenStreamWrite file
     */
    public static void urlOpenStreamWrite(String urlStr,String fileName,String savePath) throws IOException {
        URL url =new URL(urlStr);
        InputStream is = url.openStream();
//        int available = is.available();
//        System.out.println(available);

        File file = new File(savePath + File.separatorChar + fileName);
        //不存在,创建必要的(多层)目录
        File parentDir = file.getParentFile();
        if(!parentDir.exists())
            parentDir.mkdirs();

        FileOutputStream fos = new FileOutputStream(file);

        byte[] buffer = new byte[2048];
        int len;
        while ((len = is.read(buffer)) != -1) {
            fos.write(buffer, 0, len);
        }

        if(fos!=null) fos.close();
        if(is!=null) is.close();
    }

    /**
     * (HttpURLConnection)url.openConnection()
     * httpURLConnection.getInputStream()
     */
    public static void downLoadByUrl(String urlStr,String fileName,String savePath)throws IOException{

        URL url =new URL(urlStr);

        /**
         * 此处的urlConnection对象实际上是根据URL的
         * 请求协议(此处是http)生成的URLConnection类
         * 的子类HttpURLConnection,故此处最好将其转化
         * 为HttpURLConnection类型的对象,以便用到
         * HttpURLConnection更多的API.
         */
        HttpURLConnection conn = (HttpURLConnection)url.openConnection();

        //设置超时间为3秒
//        conn.setConnectTimeout(5*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 is = conn.getInputStream();
        //偷看有效长度
//        int available = is.available();

        //文件保存位置
        File saveDir =new File(savePath);
        if(!saveDir.exists()) saveDir.mkdirs();

        File file =new File(saveDir + File.separator + fileName);
        FileOutputStream fos =new FileOutputStream(file);
        //获取缓存内容的byte数组，可以转化成其他流
        byte[] cachedBytes =readInputStream(is);
        fos.write(cachedBytes);

        if(fos!=null) fos.close();
        if(is!=null) is.close();

        System.out.println("info:"+url+" download success");
　　　　　//断开
　　　　　conn.disconnect();　
        //删除文件
//        file.delete();
    }

    /**
     * 获取缓存内容的byte数组，可以转化成其他流
     */
    public static byte[] readInputStream(InputStream inputStream) throws IOException {

        byte[] buffer =new byte[1024];
        int len =0;
        ByteArrayOutputStream bos =new ByteArrayOutputStream();
        while((len = inputStream.read(buffer)) != -1) {
            bos.write(buffer,0, len);
        }
        bos.close();
        return bos.toByteArray();

    }

    /**
     * rewriteFileName重命名，UUIU
     */
    public static String rewriteFileName(String oleFileName) {
        oleFileName = getOriginalFileName(oleFileName);
        if (StringUtils.isEmpty(oleFileName)) {
            return oleFileName;
        }
        //得到后缀
        if (oleFileName.indexOf(".") == -1) {
            //对于没有后缀的文件，直接返回重命名
            return UUID.randomUUID().toString();
        }
        String[] arr = oleFileName.split("\\.");
        // 根据uuid重命名图片
        String fileName = UUID.randomUUID().toString() + "." + arr[arr.length - 1];

        return fileName;
    }

    /**
     * 把带路径的文件地址解析为真实文件名 /25h/upload/hc/1448089199416_06cc07bf-7606-4a81-9844-87d847f8740f.mp4 解析为 1448089199416_06cc07bf-7606-4a81-9844-87d847f8740f.mp4
     * @param url
     */
    public static String getOriginalFileName(final String url) {
        if (StringUtils.isEmpty(url)) {
            return url;
        }
        String newUrl = url;
        newUrl = newUrl.split("[?]")[0];
        String[] bb = newUrl.split("/");
        String fileName = bb[bb.length - 1];
        return fileName;
    }

    /**
     * RandomAccessFile 读写文件
     * https://blog.csdn.net/qq_31615049/article/details/88562892
     */
    private static void writeFile(InputStream is, File storeFile){

        RandomAccessFile raf = null;
        int buffer_len = 1024;
        byte[] buffer = new byte[buffer_len];
        int readLen = 0;

        try{
            raf = new RandomAccessFile(storeFile, "rw");
            raf.seek(raf.length());//设置光标位置。从此处开始写（插）入文件内容。
            while(-1 != (readLen = is.read(buffer, 0, buffer_len))){
                raf.write(buffer, 0, readLen);
            }

        } catch (Exception e){
            e.printStackTrace();
        } finally {

            try {
                if(raf != null)
                    raf.close();
                if(is != null)
                    is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     *
     * @param funnyUrl
     * @throws IOException
     */
    public static void randomAccessWrite(String funnyUrl) throws IOException {
//        String newFIleName = rewriteFileName(funnyUrl).replace("-", "");
        //创建tempfile取用后缀就够了
        String newFIleName = getOriginalFileName(funnyUrl);

        String suffix = newFIleName.substring(newFIleName.lastIndexOf("."));
        //指定路径，否则存储在默认路径中
        File tempFile = File.createTempFile("url_dwn", suffix, new File(dirPath));
        //File tempFile = File.createTempFile("url_dwn", suffix);
        URL url = new URL(funnyUrl);
        InputStream is = url.openStream();
        writeFile(is, tempFile);
    }

}

java通过url得到文件对象(支持http和https)：

https://blog.csdn.net/qq_21235239/article/details/99415421

五、trash

    /**
     * 后台验证：以后缀名称检查图片格式
     * @param files
     * @return 不容许的文件名称，以“ , ”隔开
     */
    public static String checkFileType(MultipartFile[] files) {

        StringBuilder rejectFileNames = new StringBuilder();

        for (MultipartFile file : files) {
            String originalFilename = file.getOriginalFilename();
            String suffix = originalFilename.substring(originalFilename.lastIndexOf(".") + 1);
            //枚举中可以上传的文件类型
            List<String> fileTypes = FileType.getFileTypes();
            //可以上传的文件类型检查
            if(!fileTypes.contains(suffix)) {
                rejectFileNames.append(originalFilename).append(" , ");
            }
        }

        if(rejectFileNames.length() > 0) {
            int idx = rejectFileNames.lastIndexOf(",");
            //删除末尾的自定义分隔符
            rejectFileNames.delete(idx - 1, rejectFileNames.length());
        }

        return rejectFileNames.toString();
    }

    /**
     * 图片格式后缀名称枚举
     */
    enum FileType {
        PEG("peg"),
        JPG("jpg"),
        BMP("bmp"),
        PNG("png");

        private String type;

        FileType(String type) {
            this.type = type;
        }

        public String getType() {
            return type;
        }

        public static List<String> getFileTypes() {
            FileType[] fileTypes = FileType.values();
            List<String> types = Arrays.stream(fileTypes).map(FileType::getType).collect(Collectors.toList());
            return types;
        }
    }