网络爬虫开发(四)-爬虫基础——环境准备、定义options接口、抽取公共部分代码、定义抽象方法、实现TeacherPhotos类、实现NewsList类及总结
封装爬虫基础库
以上代码重复的地方非常多，可以考虑以面向对象的思想进行封装，进一步的提高代码复用率，为了方便开发，保证代码规范，建议使用TypeScript进行封装
以下知识点为扩展内容，需要对面向对象和TypeScript有一定了解！
执行tsc --init初始化项目，生成ts配置文件
TS配置：
{
"compilerOptions": {
/* Basic Options */
"target": "es2015",
"module": "commonjs",
"outDir": "./bin",
"rootDir": "./src",
"strict": true,
"esModuleInterop": true
},
"include": [
"src/**/*"
],
"exclude": [
"node_modules",
"**/*.spec.ts"
]
}
Spider抽象类：定义options接口、抽取公共部分代码
// 引入http模块
const http = require('http')
import SpiderOptions from './interfaces/SpiderOptions'
export default abstract class Spider {
options: SpiderOptions;
constructor(options: SpiderOptions = {
url: '', method: 'get' }) {
this.options = options
this.start()
}
start(): void {
// 创建请求对象 (此时未发送http请求)
let req = http.request(this.options.url, {
headers: this.options.headers,
method: this.options.method
}, (res: any) => {
// 异步的响应
// console.log(res)
let chunks: any[] = []
// 监听data事件,获取传递过来的数据片段
// 拼接数据片段
res.on('data', (c: any) => chunks.push(c))
// 监听end事件,获取数据完毕时触发
res.on('end', () => {
// 拼接所有的chunk,并转换成字符串 ==> html字符串
let htmlStr = Buffer.concat(chunks).toString('utf-8')
this.onCatchHTML(htmlStr)
})
})
// 将请求发出去
req.end()
}
abstract onCatchHTML(result: string): any
}
export default Spider
SpiderOptions接口：
export default interface SpiderOptions {
url: string,
method?: string,
headers?: object
}
PhotoListSpider类：
import Spider from './Spider'
const cheerio = require('cheerio')
const download = require('download')
export default class PhotoListSpider extends Spider {
onCatchHTML(result: string) {
// console.log(result)
let $ = cheerio.load(result)
let imgs = Array.prototype.map.call($('.tea_main .tea_con .li_img > img'), item => 'http://web.itheima.com/' + encodeURI($(item).attr('src')))
Promise.all(imgs.map(x => download(x, 'dist'))).then(() => {
console.log('files downloaded!');
});
}
}
NewsListSpider类：
import Spider from "./Spider";
export default class NewsListSpider extends Spider {
onCatchHTML(result: string) {
console.log(JSON.parse(result))
}
}
测试类：
import Spider from './Spider'
import PhotoListSpider from './PhotoListSpider'
import NewsListSpider from './NewsListSpider'
let spider1: Spider = new PhotoListSpider({
url: 'http://web.itheima.com/teacher.html'
})
let spider2: Spider = new NewsListSpider({
url: 'http://www.itcast.cn/news/json/f1f5ccee-1158-49a6-b7c4-f0bf40d5161a.json',
method: 'post',
headers: {
"Host": "www.itcast.cn",
"Connection": "keep-alive",
"Content-Length": "0",
"Accept": "*/*",
"Origin": "http://www.itcast.cn",
"X-Requested-With": "XMLHttpRequest",
"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.100 Safari/537.36",
"DNT": "1",
"Referer": "http://www.itcast.cn/newsvideo/newslist.html",
"Accept-Encoding": "gzip, deflate",
"Accept-Language": "zh-CN,zh;q=0.9,en;q=0.8",
"Cookie": "UM_distinctid=16b8a0c1ea534c-0c311b256ffee7-e343166-240000-16b8a0c1ea689c; bad_idb2f10070-624e-11e8-917f-9fb8db4dc43c=8e1dcca1-9692-11e9-97fb-e5908bcaecf8; parent_qimo_sid_b2f10070-624e-11e8-917f-9fb8db4dc43c=921b3900-9692-11e9-9a47-855e632e21e7; CNZZDATA1277769855=1043056636-1562825067-null%7C1562825067; cid_litiancheng_itcast.cn=TUd3emFUWjBNV2syWVRCdU5XTTRhREZs; PHPSESSID=j3ppafq1dgh2jfg6roc8eeljg2; CNZZDATA4617777=cnzz_eid%3D926291424-1561388898-http%253A%252F%252Fmail.itcast.cn%252F%26ntime%3D1563262791; Hm_lvt_0cb375a2e834821b74efffa6c71ee607=1561389179,1563266246; qimo_seosource_22bdcd10-6250-11e8-917f-9fb8db4dc43c=%E7%AB%99%E5%86%85; qimo_seokeywords_22bdcd10-6250-11e8-917f-9fb8db4dc43c=; href=http%3A%2F%2Fwww.itcast.cn%2F; bad_id22bdcd10-6250-11e8-917f-9fb8db4dc43c=f2f41b71-a7a4-11e9-93cc-9b702389a8cb; nice_id22bdcd10-6250-11e8-917f-9fb8db4dc43c=f2f41b72-a7a4-11e9-93cc-9b702389a8cb; openChat22bdcd10-6250-11e8-917f-9fb8db4dc43c=true; parent_qimo_sid_22bdcd10-6250-11e8-917f-9fb8db4dc43c=fc61e520-a7a4-11e9-94a8-01dabdc2ed41; qimo_seosource_b2f10070-624e-11e8-917f-9fb8db4dc43c=%E7%AB%99%E5%86%85; qimo_seokeywords_b2f10070-624e-11e8-917f-9fb8db4dc43c=; accessId=b2f10070-624e-11e8-917f-9fb8db4dc43c; pageViewNum=2; nice_idb2f10070-624e-11e8-917f-9fb8db4dc43c=20d2a1d1-a7a8-11e9-bc20-e71d1b8e4bb6; openChatb2f10070-624e-11e8-917f-9fb8db4dc43c=true; Hm_lpvt_0cb375a2e834821b74efffa6c71ee607=1563267937"
}
})
封装后，如果需要写新的爬虫，则可以直接继承Spider类后，在测试类中进行测试即可，仅需实现具体的爬虫类onCatchHTML方法，测试时传入url和headers即可。
而且全部爬虫的父类均为Spider，后期管理起来也非常方便！
实例1
目录
第一步：执行tsc --init初始化项目，生成ts配置文件
tsconfig.json
{
"compilerOptions": {
/* Basic Options */
// "incremental": true, /* Enable incremental compilation */
"target": "ES2015", /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019' or 'ESNEXT'. */
"module": "commonjs", /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'. */
// "lib": [], /* Specify library files to be included in the compilation. */
// "allowJs": true, /* Allow javascript files to be compiled. */
// "checkJs": true, /* Report errors in .js files. */
// "jsx": "preserve", /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
// "declaration": true, /* Generates corresponding '.d.ts' file. */
// "declarationMap": true, /* Generates a sourcemap for each corresponding '.d.ts' file. */
// "sourceMap": true, /* Generates corresponding '.map' file. */
// "outFile": "./", /* Concatenate and emit output to single file. */
"outDir": "./bin", /* Redirect output structure to the directory. */
"rootDir": "./src", /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
// "composite": true, /* Enable project compilation */
// "tsBuildInfoFile": "./", /* Specify file to store incremental compilation information */
// "removeComments": true, /* Do not emit comments to output. */
// "noEmit": true, /* Do not emit outputs. */
// "importHelpers": true, /* Import emit helpers from 'tslib'. */
// "downlevelIteration": true, /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
// "isolatedModules": true, /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
/* Strict Type-Checking Options */
"strict": true, /* Enable all strict type-checking options. */
// "noImplicitAny": true, /* Raise error on expressions and declarations with an implied 'any' type. */
// "strictNullChecks": true, /* Enable strict null checks. */
// "strictFunctionTypes": true, /* Enable strict checking of function types. */
// "strictBindCallApply": true, /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
// "strictPropertyInitialization": true, /* Enable strict checking of property initialization in classes. */
// "noImplicitThis": true, /* Raise error on 'this' expressions with an implied 'any' type. */
// "alwaysStrict": true, /* Parse in strict mode and emit "use strict" for each source file. */
/* Additional Checks */
// "noUnusedLocals": true, /* Report errors on unused locals. */
// "noUnusedParameters": true, /* Report errors on unused parameters. */
// "noImplicitReturns": true, /* Report error when not all code paths in function return a value. */
// "noFallthroughCasesInSwitch": true, /* Report errors for fallthrough cases in switch statement. */
/* Module Resolution Options */
// "moduleResolution": "node", /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
// "baseUrl": "./", /* Base directory to resolve non-absolute module names. */
// "paths": {}, /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
// "rootDirs": [], /* List of root folders whose combined content represents the structure of the project at runtime. */
// "typeRoots": [], /* List of folders to include type definitions from. */
// "types": [], /* Type declaration files to be included in compilation. */
// "allowSyntheticDefaultImports": true, /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
"esModuleInterop": true /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
// "preserveSymlinks": true, /* Do not resolve the real path of symlinks. */
// "allowUmdGlobalAccess": true, /* Allow accessing UMD globals from modules. */
/* Source Map Options */
// "sourceRoot": "", /* Specify the location where debugger should locate TypeScript files instead of source locations. */
// "mapRoot": "", /* Specify the location where debugger should locate map files instead of generated locations. */
// "inlineSourceMap": true, /* Emit a single file with source maps instead of having a separate file. */
// "inlineSources": true, /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
/* Experimental Options */
// "experimentalDecorators": true, /* Enables experimental support for ES7 decorators. */
// "emitDecoratorMetadata": true, /* Enables experimental support for emitting type metadata for decorators. */
},
"include": [
"src/**/*"
],
"exclude": [
"node_modules",
"**/*.spec.ts"
]
}
第二步：在src文件夹下新建一个Spider类，定义抽象方法
src/Spider.ts
// 目标: 希望将来写爬虫的时候, 来一个类继承祖宗类
// 然后, 在子类中处理得到的结果即可
// 爬虫用法: 创建爬虫对象, 传入URL自动开爬
const http = require('http')
import SpiderOptions from './interfaces/SpiderOptions'
export default abstract class Spider {
// 定义成员
options: SpiderOptions
// 使用接口定义options的成员
constructor(options: SpiderOptions = {
url: '', method: 'get' }) {
// 初始化
this.options = options
this.start()
}
start() {
// 创建请求对象
let req = http.request(this.options.url, {
headers: this.options.headers,
method: this.options.method
}, (res: any) => {
let chunks: any[] = []
res.on('data', (c: any) => chunks.push(c))
res.on('end', () => {
let result = Buffer.concat(chunks).toString('utf-8')
// console.log(result)
// 抽象方法调用 子子孙孙干的事儿 他都不知道 他只管调用一下抽象方法
// 具体的实现由子子孙孙继承时实现即可
this.onCatchHTML(result)
})
})
// 发送请求
req.end()
}
abstract onCatchHTML(result: string): any
}
第三步：新建文件夹interfaces，并在其中新建接口文件SpiderOptions.ts，对外定义Options接口
src/interfaces/SpiderOptions.ts
export default interface SpiderOptions {
url: string,
method?: string,
headers?: object
}
第四步：在src文件夹下新建爬虫文件TeacherPhotos.ts
src/TeacherPhotos.ts
// 封装完毕后,如果需要做爬虫,只需要以下几步:
// 1. 写一个爬虫类, 继承Spider
// 2. 实现onCatchHTML方法(爬虫获取资源后需要做的事情)
// 3. 使用: 创建该爬虫对象,传入URL即可
const cheerio = require('cheerio')
const download = require('download')
import Spider from './Spider'
export default class TeacherPhotos extends Spider {
onCatchHTML(result: string) {
// 获取到html之后的操作 由子类具体实现
// console.log(result)
// 根据html的img标签src属性来下载图片
let $ = cheerio.load(result)
let imgs = Array.prototype.map.call($('.tea_main .tea_con .li_img > img'), (item: any) => 'http://web.itheima.com/' + encodeURI($(item).attr('src')))
Promise.all(imgs.map(x => download(x, 'dist'))).then(() => {
console.log('files downloaded!');
});
}
}
第五步：在src文件夹下新建测试接口文件test.ts
src/test.ts
import TeacherPhotos from './TeacherPhotos'
new TeacherPhotos({
url: 'http://web.itheima.com/teacher.html'
})
编译成tes.js文件后，运行文件
node .\bin\test.js
此时，就爬取了http://web.itheima.com/teacher.html的html文件信息
实例2
前四步同上，
第五步：在src文件夹下新建测试接口文件test.ts
src/test.ts
import NewsList from './NewsList'
new NewsList({
url: 'http://www.itcast.cn/news/json/f1f5ccee-1158-49a6-b7c4-f0bf40d5161a.json'
})
也可以配置请求头
src/test.ts
// import Spider from './Spider'
// new Spider({
// url: 'http://www.itcast.cn/newsvideo/newslist.html'
// })
// new Spider({
// url: 'http://web.itheima.com/teacher.html'
// })
// import TeacherPhotos from './TeacherPhotos'
// new TeacherPhotos({
// url: 'http://web.itheima.com/teacher.html'
// })
import NewsList from './NewsList'
new NewsList({
url: 'http://www.itcast.cn/news/json/f1f5ccee-1158-49a6-b7c4-f0bf40d5161a.json',
method: 'post',
headers: {
"Host": "www.itcast.cn",
"Connection": "keep-alive",
"Content-Length": "0",
"Accept": "*/*",
"Origin": "http://www.itcast.cn",
"X-Requested-With": "XMLHttpRequest",
"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.100 Safari/537.36",
"DNT": "1",
"Referer": "http://www.itcast.cn/newsvideo/newslist.html",
"Accept-Encoding": "gzip, deflate",
"Accept-Language": "zh-CN,zh;q=0.9,en;q=0.8",
"Cookie": "UM_distinctid=16b8a0c1ea534c-0c311b256ffee7-e343166-240000-16b8a0c1ea689c; bad_idb2f10070-624e-11e8-917f-9fb8db4dc43c=8e1dcca1-9692-11e9-97fb-e5908bcaecf8; parent_qimo_sid_b2f10070-624e-11e8-917f-9fb8db4dc43c=921b3900-9692-11e9-9a47-855e632e21e7; CNZZDATA1277769855=1043056636-1562825067-null%7C1562825067; cid_litiancheng_itcast.cn=TUd3emFUWjBNV2syWVRCdU5XTTRhREZs; PHPSESSID=j3ppafq1dgh2jfg6roc8eeljg2; CNZZDATA4617777=cnzz_eid%3D926291424-1561388898-http%253A%252F%252Fmail.itcast.cn%252F%26ntime%3D1563262791; Hm_lvt_0cb375a2e834821b74efffa6c71ee607=1561389179,1563266246; qimo_seosource_22bdcd10-6250-11e8-917f-9fb8db4dc43c=%E7%AB%99%E5%86%85; qimo_seokeywords_22bdcd10-6250-11e8-917f-9fb8db4dc43c=; href=http%3A%2F%2Fwww.itcast.cn%2F; bad_id22bdcd10-6250-11e8-917f-9fb8db4dc43c=f2f41b71-a7a4-11e9-93cc-9b702389a8cb; nice_id22bdcd10-6250-11e8-917f-9fb8db4dc43c=f2f41b72-a7a4-11e9-93cc-9b702389a8cb; openChat22bdcd10-6250-11e8-917f-9fb8db4dc43c=true; parent_qimo_sid_22bdcd10-6250-11e8-917f-9fb8db4dc43c=fc61e520-a7a4-11e9-94a8-01dabdc2ed41; qimo_seosource_b2f10070-624e-11e8-917f-9fb8db4dc43c=%E7%AB%99%E5%86%85; qimo_seokeywords_b2f10070-624e-11e8-917f-9fb8db4dc43c=; accessId=b2f10070-624e-11e8-917f-9fb8db4dc43c; pageViewNum=2; nice_idb2f10070-624e-11e8-917f-9fb8db4dc43c=20d2a1d1-a7a8-11e9-bc20-e71d1b8e4bb6; openChatb2f10070-624e-11e8-917f-9fb8db4dc43c=true; Hm_lpvt_0cb375a2e834821b74efffa6c71ee607=1563267937"
}
})
编译成tes.js文件后，运行文件
node .\bin\test.js
此时，就爬取了接口的文件信息