第一次爬虫实验

这学期web编程课，第一个实验项目是新闻网站的爬虫。第一次接触，还很生疏，中间也有很多困难。

具体要求
1、选取3-5个代表性的新闻网站（比如新浪新闻、网易新闻等，或者某个垂直领域权威性的网站比如经济领域的雪球财经、东方财富等，或者体育领域的腾讯体育、虎扑体育等等）建立爬虫，针对不同网站的新闻页面进行分析，爬取出编码、标题、作者、时间、关键词、摘要、内容、来源等结构化信息，存储在数据库中。
2、建立网站提供对爬取内容的分项全文搜索，给出所查关键词的时间热度分析。
技术要求：
1、必须采用Node.JS实现网络爬虫
2、必须采用Node.JS实现查询网站后端，HTML+JS实现前端（尽量不要使用任何前后端框架）

前期准备
安装node.js和几个模块库
安装IDE：vscode

过程
1.爬虫
新闻网站选取了中国青年网的新闻版块http://news.youth.cn/

var source_name = "中国青年网";
var domain = 'http://www.news.youth.cn/';
var myEncoding = "GBK";
var seedURL = 'http://www.news.youth.cn/';

观察网页源代码得到

var seedURL_format = "$('a')";
var keywords_format = " $('meta[name=\"keywords\"]').eq(0).attr(\"content\")";
var title_format = "$('title').text()";
var date_format = "$('#publishdate').text()";
var author_format = "$('#author').text()";
var content_format = "$('page_text').text()";
var desc_format = " $('Meta[name=\"Description\"]').eq(0).attr(\"content\")";
var source_format = "$('#source').text()";
var url_reg = /\/(\d{6})\/t(\d{8})_(\d{8}).htm/;
var regExp = /((\d{4}|\d{2})(\-|\/|\.)\d{1,2}\3\d{1,2})|(\d{4}年\d{1,2}月\d{1,2}日)/

引用模块库

var fs = require('fs');
var myRequest = require('request');
var myCheerio = require('cheerio');
var myIconv = require('iconv-lite');
require('date-utils');

老师提供的防止网站屏蔽爬虫的代码

//防止网站屏蔽我们的爬虫
var headers = {
    'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.65 Safari/537.36'
}

后面借鉴了老师的代码

seedget();

function seedget() {
    request(seedURL, function(err, res, body) { //读取种子页面
        // try {
        //用iconv转换编码
        var html = myIconv.decode(body, myEncoding);
        //console.log(html);
        //准备用cheerio解析html
        var $ = myCheerio.load(html, { decodeEntities: true });
        // } catch (e) { console.log('读种子页面并转码出错：' + e) };
        var seedurl_news;
        try {
            seedurl_news = eval(seedURL_format);
        } catch (e) { console.log('url列表所处的html块识别出错：' + e) };
        seedurl_news.each(function(i, e) { //遍历种子页面里所有的a链接
            var myURL = "";
            try {
                //得到具体新闻url
                var href = "";
                href = $(e).attr("href");
                if (href == undefined) return;
                if (href.toLowerCase().indexOf('http://') >= 0) myURL = href; //http://开头的
                else if (href.startsWith('//')) myURL = 'http:' + href; ////开头的
                else myURL = seedURL.substr(0, seedURL.lastIndexOf('/') + 1) + href; //其他

            } catch (e) { console.log('识别种子页面中的新闻链接出错：' + e) }

            if (!url_reg.test(myURL)) return; //检验是否符合新闻url的正则表达式
            //console.log(myURL);

            var fetch_url_Sql = 'select url from fetches where url=?';
            var fetch_url_Sql_Params = [myURL];
            mysql.query(fetch_url_Sql, fetch_url_Sql_Params, function(qerr, vals, fields) {
                if (vals.length > 0) {
                    console.log('URL duplicate!')
                } else newsGet(myURL); //读取新闻页面
            });
        });
    });
};

function newsGet(myURL) { //读取新闻页面
    request(myURL, function(err, res, body) { //读取新闻页面
        //try {
        var html_news = myIconv.decode(body, myEncoding); //用iconv转换编码
        //console.log(html_news);
        //准备用cheerio解析html_news
        var $ = myCheerio.load(html_news, { decodeEntities: true });
        myhtml = html_news;
        //} catch (e) {    console.log('读新闻页面并转码出错：' + e);};

        console.log("转码读取成功:" + myURL);
        //动态执行format字符串，构建json对象准备写入文件或数据库
        var fetch = {};
        fetch.title = "";
        fetch.content = "";
        fetch.publish_date = (new Date()).toFormat("YYYY-MM-DD");
        //fetch.html = myhtml;
        fetch.url = myURL;
        fetch.source_name = source_name;
        fetch.source_encoding = myEncoding; //编码
        fetch.crawltime = new Date();

        if (keywords_format == "") fetch.keywords = source_name; // eval(keywords_format);  //没有关键词就用sourcename
        else fetch.keywords = eval(keywords_format);

        if (title_format == "") fetch.title = ""
        else fetch.title = eval(title_format); //标题

        if (date_format != "") fetch.publish_date = eval(date_format); //刊登日期   
        console.log('date: ' + fetch.publish_date);
        fetch.publish_date = regExp.exec(fetch.publish_date)[0];
        fetch.publish_date = fetch.publish_date.replace('年', '-')
        fetch.publish_date = fetch.publish_date.replace('月', '-')
        fetch.publish_date = fetch.publish_date.replace('日', '')
        fetch.publish_date = new Date(fetch.publish_date).toFormat("YYYY-MM-DD");

        if (author_format == "") fetch.author = source_name; //eval(author_format);  //作者
        else fetch.author = eval(author_format);

        if (content_format == "") fetch.content = "";
        else fetch.content = eval(content_format).replace("\r\n" + fetch.author, ""); //内容,是否要去掉作者信息自行决定

        if (source_format == "") fetch.source = fetch.source_name;
        else fetch.source = eval(source_format).replace("\r\n", ""); //来源

        if (desc_format == "") fetch.desc = fetch.title;
        else fetch.desc = eval(desc_format).replace("\r\n", ""); //摘要    

        // var filename = source_name + "_" + (new Date()).toFormat("YYYY-MM-DD") +
        //     "_" + myURL.substr(myURL.lastIndexOf('/') + 1) + ".json";
        // ////存储json
        // fs.writeFileSync(filename, JSON.stringify(fetch));

        var fetchAddSql = 'INSERT INTO fetches(url,source_name,source_encoding,title,' +
            'keywords,author,publish_date,crawltime,content) VALUES(?,?,?,?,?,?,?,?,?)';
        var fetchAddSql_Params = [fetch.url, fetch.source_name, fetch.source_encoding,
            fetch.title, fetch.keywords, fetch.author, fetch.publish_date,
            fetch.crawltime.toFormat("YYYY-MM-DD HH24:MI:SS"), fetch.content
        ];

        //执行sql，数据库中fetch表里的url属性是unique的，不会把重复的url内容写入数据库
        mysql.query(fetchAddSql, fetchAddSql_Params, function(qerr, vals, fields) {
            if (qerr) {
                console.log(qerr);
            }
        }); //mysql写入
    });
}

引入MySQL

var mysql = require("mysql");
var pool = mysql.createPool({
    host: '127.0.0.1',
    user: 'root',
    password: 'root',
    database: 'crawl'
});
var query = function(sql, sqlparam, callback) {
    pool.getConnection(function(err, conn) {
        if (err) {
            callback(err, null, null);
        } else {
            conn.query(sql, sqlparam, function(qerr, vals, fields) {
                conn.release(); //释放连接 
                callback(qerr, vals, fields); //事件驱动回调 
            });
        }
    });
};
var query_noparam = function(sql, callback) {
    pool.getConnection(function(err, conn) {
        if (err) {
            callback(err, null, null);
        } else {
            conn.query(sql, function(qerr, vals, fields) {
                conn.release(); //释放连接 
                callback(qerr, vals, fields); //事件驱动回调 
            });
        }
    });
};
exports.query = query;
exports.query_noparam = query_noparam;

建立mysql数据库

CREATE TABLE `fetches` (
  `id_fetches` int(11)  NOT NULL AUTO_INCREMENT,
  `url` varchar(200) DEFAULT NULL,
  `source_name` varchar(200) DEFAULT NULL,
  `source_encoding` varchar(45) DEFAULT NULL,
  `title` varchar(200) DEFAULT NULL,
  `keywords` varchar(200) DEFAULT NULL,
  `author` varchar(200) DEFAULT NULL,
  `publish_date` date DEFAULT NULL,
  `crawltime` datetime DEFAULT NULL,
  `content` longtext,
  `createtime` datetime DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id_fetches`),
  UNIQUE KEY `id_fetches_UNIQUE` (`id_fetches`),
  UNIQUE KEY `url_UNIQUE` (`url`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

2.建立网站
都借鉴了老师的代码

前段搭建

    
"http://127.0.0.1:8080/process_get" method="GET">
        
 标题："text" name="title">
        "submit" value="Submit">
    
    

后端搭建

var express = require('express');
var mysql = require('./mysql.js')
var app = express();
//app.use(express.static('public'));
app.get('/7.03.html', function(req, res) {
    res.sendFile(__dirname + "/" + "7.03.html");
})
app.get('/7.04.html', function(req, res) {
    res.sendFile(__dirname + "/" + "7.04.html");
})
app.get('/process_get', function(req, res) {
    res.writeHead(200, { 'Content-Type': 'text/html;charset=utf-8' }); //设置res编码为utf-8
    //sql字符串和参数
    var fetchSql = "select url,source_name,title,author,publish_date from fetches where title like '%" +
        req.query.title + "%'";
    mysql.query(fetchSql, function(err, result, fields) {
        console.log(result);
        res.end(JSON.stringify(result));
    });
})
var server = app.listen(8080, function() {
    console.log("访问地址为 http://127.0.0.1:8080/7.03.html")

})

第一次爬虫项目，觉得很难，很有挑战性，希望下一次能有所进步。