基於spark的網絡爬蟲實現

爬蟲是獲取網絡大數據的重要手段，爬蟲是一種非常成熟的技術了，然而想着在Spark環境下測試一下效果．

還是非常簡單的，利用JavaSparkContext來構建，就可以採用原來Java中的網頁獲取那一套來實現．

首先給定幾個初始種子，生成一個JavaRDD對象即可
JavaRDD<String> rdd = sc.parallelize("urllist");

JavaRDD<String> content = rdd.map(new Function<String, String>() {
            public String call(String url) throws Exception {
                System.out.println(url);
                CloseableHttpClient client = null;
                HttpGet get = null;
                CloseableHttpResponse response = null;
                try {
                   //## 創建默認連接
                    client = HttpClients.createDefault();
                    get = new HttpGet(url);
                    response = client.execute(get);
                    HttpEntity entity = response.getEntity();
                    //## 獲得輸出字節流
                    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
                    entity.writeTo(byteArrayOutputStream);
                    //## 轉化爲文檔
                    String html = new String(byteArrayOutputStream.toByteArray(), Charsets.UTF_8);
                    Document document = Jsoup.parse(html);
                    return html;
                } catch (Exception ex) {
                    ex.printStackTrace();
                    return "";
                } finally {
                    if (response != null) {
                        response.close();
                    }
                    if (client != null) {
                        client.close();
                    }
                }
            }
        });