图片爬虫工具，可以爬取指定网页的图片

public class Demo {

    public static void main(String[] args) throws IOException {

        //要抓取图片的网址连接

        String url = "https://image.baidu.com/search/index?tn=baiduimage&ct=201326592&lm=-1&cl=2&ie=gbk&word=%B6%AB%B7%BD%BD%F0%B9%DD%B3%A4&fr=ala&ala=1&alatpl=adress&pos=0&hs=2&xthttps=111111";

        //根据连接获取一个Connection对象

        InputStream is = getConnection(url,null).getInputStream();

        //调用commonsio工具包中IOUtils的方法，返回HTML内容；

        String html = IOUtils.toString(is, "GBK");

        //解析HTML内容，获取所有图片链接地址

        List<String> picPaths = parseHtml(html);

        //判断是否获取到图片链接

        if(picPaths.size() > 0) {

            //创建一个线程池，处理下载任务

            ExecutorService es = Executors.newFixedThreadPool(picPaths.size() < 50 ? picPaths.size() : 50);

            //循环处理资源

            for (final String picPath : picPaths) {

                //根据具体的资源，创建下载任务，提交到线程池中

                es.execute(()->{downLoad(pathHandle(picPath), "F:\\pic",url);});

            }

            //关闭线程池

            es.shutdown();

        }

    }

    /**

     * 获取唯一序列号，做为文件名

     * @return

     */

    private static String getUUID() {

        UUID uuid = UUID.randomUUID();

        return uuid.toString().replaceAll("-", "");

    }

    /**

     * 处理获取到的图片链接

     * @param picPath

     * @return

     */

    private static String pathHandle(String picPath) {

        if(!picPath.startsWith("http")) {

            picPath = "http:" + picPath;

        }

        //这个处理，是针对天猫的图片链接，用于下载大图;

        //天猫的商品图片链接示例如下：

        //http://img.alicdn.com/bao/uploaded/i4/TB19FGse7KWBuNjy1zjefkOypXa_032207.jpg_b.jpg

        //去掉最后一个_以后的内容，可以下载大图；否则就下载的是小图

        if(picPath.indexOf("_") != picPath.lastIndexOf("_")) {

            picPath = picPath.substring(0,picPath.lastIndexOf("_"));

        }

        return picPath;

    }

    /**

     * 下载图片

     * @param picPath

     * @param dir

     * @param referer

     */

    private static void downLoad(String picPath, String dir,String referer){

        try {

            //生成文件名

            String name = getUUID()+"."+FilenameUtils.getExtension(picPath);

            FileUtils.copyToFile(getConnection(picPath,referer).getInputStream(), new File(new File(dir),name));

            System.out.println(picPath + "下载完毕！");

        } catch (IOException e) {

            System.err.println(picPath+ "下载失败！");

        }

    }

    /**

     * 使用正则表达式解析html内容，获取图片链接

     * @param html

     * @return

     */

    private static List<String> parseHtml(String html) {

        String regex = "\"[^\"^(^)^}^>^<^{]+\\.(jpg|png|jpeg|gif)";

        List<String> list = new ArrayList<>();

        Pattern p = Pattern.compile(regex);

        Matcher m = p.matcher(html);

        while(m.find()) {

            list.add(m.group().substring(1));

        }

        return list;

    }

    /**

     * 根据url地址，获取一个连接对象，同时设置请求头，避免服务器防盗链，以及模拟浏览器请求

     * @param url

     * @param referer

     * @return

     */

    private static URLConnection getConnection(String url,String referer) {

        try {

            URLConnection uc = new URL(url).openConnection();

            //解决防盗链问题

            uc.setRequestProperty("referer", referer==null?"http://www.baidu.com/":referer);

            //模拟浏览器

            uc.setRequestProperty("user-agent", "Mozilla/5.0 (Windows NT 6.2; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36");

            return uc;

        } catch (IOException e) {

            e.printStackTrace();

            System.out.println(url);

            return null;

        }

    }

}