功能

提供异步图片的下载功能，实时返回替换的链接。

import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Date;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

import org.apache.commons.io.IOUtils;
import org.apache.log4j.Logger;
import org.jsoup.Connection.Response;
import org.jsoup.Jsoup;
import org.mall.spider.cont.SpiderConstant;
import org.mall.utils.DateUtil;
import org.mall.utils.gson.GsonHelper;

/**
 * @description Http协议下载工具（不支持断点续传），每个图片会重试10次
 * @author <a href="mailto:fengwuze@kk.com">fengwuze</a>
 * @since 2016年9月19日
 * @version 1.0.0
 */
public final class HttpDownloadUtils {

    private static final Logger logger = Logger.getLogger(HttpDownloadUtils.class);

    /**
     * 图片命名计数器（保证不重复）
     */
    private static AtomicLong imgNameCounter = new AtomicLong(Long.valueOf(DateUtil.format(new Date(), "yyyyMMddHHmmss")));

    /**
     * 线程池
     */
    private static ExecutorService exec = new ThreadPoolExecutor(10, 100, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>(),
            Executors.defaultThreadFactory());

    /**
     * 提交下载任务
     * 
     * @param targetUrl
     * @param saveDir
     * @return String
     */
    public static String submitTask(final String targetUrl, final String saveDir, final String subSaveDir) {
        final HttpTask task = new HttpTask(targetUrl, saveDir, subSaveDir);

        exec.submit(new HttpDownTask(task));

        return task.getSubSaveDir();
    }

    static class HttpDownTask implements Runnable {

        private HttpTask task;

        public HttpDownTask(HttpTask task) {
            this.task = task;
        }

        @Override
        public void run() {
            FileOutputStream out = null;
            try {
                Response rsp = Jsoup.connect(task.getTargetUrl()).timeout(10 * 1000).header("User-Agent", SpiderConstant.UA)
                    .ignoreContentType(true).execute();

                out = new FileOutputStream(task.getSavePath());
                IOUtils.write(rsp.bodyAsBytes(), out);
                out.flush();
                logger.info("down succ, task: " + GsonHelper.toJson(task));
            } catch (Exception e) {
                if (task.getRetry() <= 10) {
                    task.setRetry(task.getRetry() + 1);
                    exec.submit(new HttpDownTask(task));
                } else {
                    logger.error("down fail, task: " + GsonHelper.toJson(task), e);
                }
            } finally {
                if (out != null) {
                    try {
                        out.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

    static class HttpTask {

        private String targetUrl;
        private String saveDir;
        private String subSaveDir;
        private String savePath;

        private Integer retry = 0;

        public HttpTask(String targetUrl, String saveDir, String subSaveDir) {
            this.targetUrl = targetUrl;
            this.saveDir = saveDir;
            this.subSaveDir = subSaveDir;

            String suffix = targetUrl.substring(targetUrl.lastIndexOf("."), targetUrl.length());
            this.subSaveDir = this.subSaveDir + "/" + imgNameCounter.addAndGet(1) + suffix;
            this.savePath = saveDir + this.subSaveDir;
        }

        public String getSavePath() {
            return savePath;
        }

        public String getTargetUrl() {
            return targetUrl;
        }

        public String getSaveDir() {
            return saveDir;
        }

        public Integer getRetry() {
            return retry;
        }

        public void setRetry(Integer retry) {
            this.retry = retry;
        }

        public String getSubSaveDir() {
            return subSaveDir;
        }

        public void setSubSaveDir(String subSaveDir) {
            this.subSaveDir = subSaveDir;
        }
    }

    public static void main(String[] args) {
        String subDir = HttpDownloadUtils.submitTask("http://img.zcool.cn/community/03377fb554c721200000158fc8ac222.jpg", "D:\\", "/imgs");
        System.out.println(subDir);
    }
}