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 ;

         }

     }

}