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java用Jsoup来做爬虫

环境

jdk 1.8

依赖

        <dependency>
            <groupId>org.jsoup</groupId>
            <artifactId>jsoup</artifactId>
            <version>1.10.2</version>
        </dependency>

demo例子

1.创建线程池

    /**
     * 爬取数据线程池
     */
    public static ExecutorService exec = Executors.newFixedThreadPool(10);

2.从数据库查询待爬取的url

        log.info("从数据库获取爬取url列表");
        Example example = new Example(DemoPO.class);
        example.createCriteria().andEqualTo("type",NUMONE);
        List<DemoPO> poList = DemoMapper.selectByExample(example);

3. 用CompletionService 来异步获取执行结果

 CompletionService<List<DemoPO>> everyWeekCs = new ExecutorCompletionService<>(exec);

4.向线程池提交任务

不同的url 具体怎么解析有差别

 for (DemoPOpo : poList) {
            if("test1".equals(po.getSource())){
                everyWeekCs.submit(()->getEveryWeekPoFromDocument(po,NUMONE,day));
            }
            if("test2".equals(po.getSource())){
                everyWeekCs.submit(()->getEveryWeekPoFromDocument(po,NUMTWO,day));
            }
            if("test3".equals(po.getSource())){
                everyWeekCs.submit(()->getEveryWeekPoFromDocument(po,NUMTHREE,day));
            }
        }

5.简单爬数据

用Jsoup的api，根据页面标签来解析获取数据

        List<DemoPO> list = new ArrayList<>();
        String url = po.getUrl();
        Connection connection = Jsoup.connect(url);
        Connection.Response response = connection.execute();
        if(response.statusCode() == 200) {
           Document doc = connection.get();
           List<Element> elements = doc.getElementsByClass("xlayer02 yh ohd clear");
           for (Element element : elements) {
               DemoPO demoPo = new DemoPO();
               String title = element.select("a").text();
               po.setTitle(title);
               String contentUrl = element.select("a").attr("href");
               Connection con = Jsoup.connect("http:" + contentUrl);
               Connection.Response res = con.execute();
               if (res.statusCode() == 200) {
                    Document contentDoc = con.get();
                    String content = contentDoc.getElementsByClass("xcc font14 yh ohd clear").get(0).getElementsByTag("p").toString();
                    po.setContent(content);
                    list.add(po);
               }
           }
        }
        return list;       

6.获取各子线程执行后得到的结果

        List<DemoPO> list = new ArrayList<>();
 //按任务完成顺序获取值，减少阻塞获取值的所需时间
        for (int i = 0;i<poList.size();i++){
            list.addAll(everyWeekCs.take().get());
        }

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