并发编程之实现图片下载

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并发编程之实现图片下载

本文主要利用java中java.utils.concurrent包中的Future和Callable类来实现图片的下载。本文主要分为三步：

实现ImgUrl类，其主要作用是获取html文件中图片地址，利用Jsoup技术来实现html的解析，需要下载Jsoup的jar包，maven项目需要dependency下；
实现DownLoadImgUrl类，该类实现Callable类，根据图片的url把图片下载到本地；
实现测试类，测试代码的有效性，需要下载Junit的jar包，如果是maven项目需要dependency下。

首先，实现ImgUrl类。

import org.jsoup.Jsoup;import org.jsoup.nodes.Document;import java.io.IOException;import java.util.ArrayList;import java.util.List;import java.util.regex.Matcher;import java.util.regex.Pattern;/** * Created by lionel on 16/8/11. */public class ImgUrl {    /**     * 获取网页下所有图片的地址列表     * @param url 网页地址     * @return     */    public static List<String>  getImgUrl(String url){        Document document = null;        try {            document = Jsoup.connect(url).get();        } catch (IOException e) {            e.printStackTrace();        }        String html = document.html();        String img = "";        String regEx_img = "<img.*src=(.*?)[^>]*?>";        Pattern pattern = Pattern.compile(regEx_img,Pattern.CASE_INSENSITIVE);        Matcher matcher = pattern.matcher(html);        List<String> pics = new ArrayList<String>();        while (matcher.find()) {            img = img + "," + matcher.group();            Matcher m = Pattern.compile("src=\"?(.*?)(\"|>|\\s+)").matcher(img);            while (m.find()) {                pics.add(m.group(1));            }        }        return pics;    }}

其次，实现DownLoadImgUrl类

import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.MalformedURLException;import java.net.URL;import java.net.URLConnection;import java.util.concurrent.Callable;/** * Created by lionel on 16/8/12. */public class DownPicTask implements Callable<Boolean> {    String url;    String fileName;    public DownPicTask(String url, String fileName) {        this.url = url;        this.fileName = fileName;    }    @Override    public Boolean call() throws Exception {        return getImgFile(url, fileName);    }    /**     * 下载文件到本地     * @param url 图片地址     * @param fileName 下载到本地的文件地址     * @return     */    public static Boolean getImgFile(String url, String fileName) {        OutputStream os = null;        InputStream is = null;        try {            URL url1 = new URL(url);            URLConnection urlConnection = url1.openConnection();            is = urlConnection.getInputStream();            byte[] bs = new byte[1024];            int len;            os = new FileOutputStream(fileName);            while ((len = is.read(bs)) != -1) {                os.write(bs, 0, len);            }            return Boolean.TRUE;        } catch (MalformedURLException me) {            me.printStackTrace();        } catch (Exception e) {            e.printStackTrace();        } finally {            if (os != null) {                try {                    os.close();                } catch (IOException e) {                    e.printStackTrace();                }            }            if (is != null) {                try {                    is.close();                } catch (IOException e) {                    e.printStackTrace();                }            }        }        return Boolean.FALSE;    }}

最后，写一个测试类

import org.junit.Test;import java.util.List;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.TimeUnit;/** * Created by lionel on 16/8/11. */public class DownloadPictureTest {    @Test    public void test(){        ExecutorService executorService = Executors.newFixedThreadPool(5);        String pagehtml = "http://mp.weixin.qq.com/s?__biz=MzA4MTk3NTgyMQ==&mid=401795482&idx=1&sn=016237aa3979221741235214c1764c4c&scene=21#wechat_redirect";        List<String> imgUrlList = ImgUrl.getImgUrl(pagehtml);        int i=0;        for (String imgUrl:imgUrlList){            String filename="data/picture/"+i+".jpg";            DownPicTask downPicTask=new DownPicTask(imgUrl,filename);            executorService.submit(downPicTask1);            i++;        }        executorService.shutdown();        try {            executorService.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS);        } catch (InterruptedException e) {            e.printStackTrace();        }        System.out.println("all thread complete");    }}

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