0.需要的知识点
- 正则表达式
- java多线程线程池池知识
- httpclient网络库及json和html结构
1.获取主话题
在知乎中一共有33个主话题，在33个主话题下又有15776个子话题，因此我们首先要获取到33个主话题
(ps:一开始打算用HttpURLConnection进行网络请求，由于后面需要以post形式访问并且提交form因此后面的代码改用了httpclient进行网络请求)
图中的data-id就是主话题的id
public static void getTopicId(){
new Thread(new Runnable() {
@Override
public void run() {
Connection connection;
int id = 1;
try {
URL url = new URL("https://www.zhihu.com/topics");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.connect();
BufferedReader bfr = new BufferedReader(new InputStreamReader(conn.getInputStream(),"UTF-8"));
String line = null;
StringBuilder sb = new StringBuilder();
while ((line = (bfr.readLine())) != null){
sb.append(line);
}
String result = sb.toString();
String regex = "data-id=\"[0-9]{0,6}\"";
Pattern pattern = Pattern.compile(regex);
Matcher m = pattern.matcher(result);
String regx = "href=\"#.*?\"";
Pattern p = Pattern.compile(regx);
Matcher mn = p.matcher(result);
while (m.find() && mn.find()){
String s = m.group();
s = s.substring(9,s.length() - 1);
String sn = mn.group();
sn = sn.substring(7,sn.length() - 1);
System.out.println(s + " " + sn);
connection = JDBCUtil.getConn();
PreparedStatement state = (PreparedStatement) connection.prepareStatement("insert into main_topic values(?,?,?)");
state.setInt(1, id++);
state.setInt(2, Integer.valueOf(s));
state.setString(3, sn);
state.execute();
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}).start();
}
2.获取各个主话题下的分话题
通过抓包我们可以发现在分话题页面通过post请求访问到服务器来加载分话题，没一次下拉到底部会多加载20个分话题，通过offset来控制，因此我们可以通过post请求服务器来获得json数据
post请求结构
通过postman模拟post请求得到返回数据
由于返回的json数据中的中文为unicode编码，因此运用了Utils类中的方法来转换为中文以便储存到数据库中
public static void getChildTopics(int topic_id,Connection conn) throws Exception{
int offset = 0;;
while (true){
PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
CloseableHttpClient httpClient = HttpClients.custom()
.setRetryHandler(new DefaultHttpRequestRetryHandler())
.setConnectionManager(cm)
.build();
HttpPost req = new HttpPost("https://www.zhihu.com/node/TopicsPlazzaListV2");
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("method", "next"));
params.add(new BasicNameValuePair("params", "{\"topic_id\":" + topic_id + ",\"offset\":" + offset +",\"hash_id\":\"37492588249aa9b50ee49d1797e9af81\"}"));
req.setEntity(new UrlEncodedFormEntity(params,Consts.UTF_8));
HttpResponse resp = httpClient.execute(req);
String sb = EntityUtils.toString(resp.getEntity());
if (sb.length() < 25) break;
String regex = "<strong>.*?<\\\\/strong>";
Pattern p = Pattern.compile(regex);
Matcher m = p.matcher(sb);
String regx = "href=\\\\\"\\\\/topic\\\\/[0-9]+\\\\\"";
Pattern p1 = Pattern.compile(regx);
Matcher m1 = p1.matcher(sb);
while (m.find() && m1.find()){
String temp = m.group().substring(8, m.group().length() - 10);
String sql = "insert into child_topic values(null,?,?,?)";
PreparedStatement state = (PreparedStatement) conn.prepareStatement(sql);
state.setInt(1,topic_id);
state.setString(2,m1.group().substring(16, m1.group().length() - 2));
state.setString(3,Utils.decodeUnicode(temp));
state.execute();
}
offset += 20;
}
}
通过主话题id来获取下面的子话题id
3.通过分话题id来获取热门问答
public static void loadOneTopicHotQA(int child_topic_id) throws Exception{
PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
CloseableHttpClient httpClient = HttpClients.custom()
.setRetryHandler(new DefaultHttpRequestRetryHandler())
.setConnectionManager(cm)
.build();
HttpGet req = new HttpGet("https://www.zhihu.com/topic/" + child_topic_id + "/hot");
HttpResponse resp = httpClient.execute(req);
String result = EntityUtils.toString(resp.getEntity());
//正则匹配打不出来，后面以截图形式给出
Pattern p_qa_id = Pattern.compile(regex_qa_id);
Pattern p_qa_name = Pattern.compile(regex_qa_name);
Pattern p_qa_username = Pattern.compile(regex_qa_username);
Matcher m_qa_id = p_qa_id.matcher(result);
Matcher m_qa_name = p_qa_name.matcher(result);
Matcher m_qa_username = p_qa_username.matcher(result);
while (m_qa_id.find() && m_qa_name.find() && m_qa_username.find()){
String[] qanda_id = m_qa_id.group().split("/");
String q_id = qanda_id[2];
String a_id = qanda_id[4].substring(0, qanda_id[4].length() - 2);
String q_name = m_qa_name.group().split("\n")[1];
String temp = m_qa_username.group();
String q_username = null;
if (temp.contains("匿名用户")) q_username = "匿名用户";
else if (temp.contains("知乎用户")) q_username = "知乎用户";
else q_username = temp.substring(30, temp.length() - 1);
HotQA qa = new HotQA(child_topic_id,Integer.valueOf(q_id), q_name, Integer.valueOf(a_id), q_username);
DaoImpl daoimpl = new DaoImpl();
daoimpl.save(qa, child_topic_id);
}
}
正则匹配
由于未登陆情况下可能会出现答主名字被替换为知乎用户，因此要考虑答主名字为知乎用户这种情况
4.爬到的数据能做什么
数据
- 通过child_topic_id可知道问题属于哪个话题
- 通过question_id可以通过拼接url:https://www.zhihu.com/question/{question_id}来访问问题
- 同理可得url:https://www.zhihu.com/question/{question_id}/answer/{answer_id}来访问回答
- 同理:https://www.zhihu.com/people/{username}/answers
5.扩展
在DAO层中提供了返回指定话题最新动态的方法，同时也包含了通过answer_id获取指定回答的方法，将来可能还会加入爬取用户信息的功能。
6.感谢
感谢看到这里，如果不嫌弃的话给gayhub项目一个star呗，关注一下我也是最最最最吼的
gayhub项目 可以直接点哟
另外大家可以也可以通过微博联系我哟：关耳金名
如何使用及编程过程中踩过的坑
