Does golang have crawlers?

With the development of the Internet, network information has become more and more abundant, but how to efficiently capture data from some websites or applications has become a big challenge faced by many developers. In the past, many developers used languages ​​such as Python or Java for crawler development, but in recent years, more and more developers have begun to choose to use golang for crawler development.

So, does golang have crawlers? The answer is yes. The standard library of the Go language already has built-in support for HTTP requests and network protocols, and there are also a wealth of choices in third-party libraries. In this article, we will introduce several commonly used golang crawler libraries to help developers better understand the use of golang in crawler development.

1. goquery

goquery is an HTML parser based on jQuery syntax. It uses the selector syntax of the go language to query and parse HTML documents. The library is fully compatible with jQuery’s common selectors and methods, making it very developer-friendly.

Using goquery, we can easily parse the required data from HTML documents. For example, we can use the following code to get the title and URL from Baidu search results:

package main

import (
    "fmt"
    "github.com/PuerkitoBio/goquery"
    "log"
)

func main() {
    url := "https://www.baidu.com/s?wd=golang"
    doc, err := goquery.NewDocument(url)
    if err != nil {
        log.Fatal(err)
    }

    doc.Find("#content_left h3 a").Each(func(i int, s *goquery.Selection) {
        title := s.Text()
        link, _ := s.Attr("href")
        fmt.Printf("%d. %s - %s
", i+1, title, link)
    })
}

This code uses goquery to parse the Baidu search results page and extract the title and URL of each search result. It should be noted that the Find method in the goquery library can use CSS selectors or XPath expressions to locate elements.

2. colly

colly is a highly flexible and configurable golang crawler framework that supports asynchronous network requests, automated retries, data extraction, proxy settings and other features. With the help of colly, we can quickly write stable and efficient crawler programs.

The following is a simple example of crawling Baidu search results:

package main

import (
    "fmt"
    "github.com/gocolly/colly"
)

func main() {
    c := colly.NewCollector()

    c.OnHTML("#content_left h3 a", func(e *colly.HTMLElement) {
        title := e.Text
        link := e.Attr("href")
        fmt.Printf("%s - %s
", title, link)
    })

    c.Visit("https://www.baidu.com/s?wd=golang")
}

This code uses the colly framework to parse the Baidu search results page and extract the title and URL of each search result. It should be noted that the OnHTML method in the colly library can specify the selector of the HTML element and execute the callback function when the corresponding element is matched.

3. go_spider

go_spider is a high-concurrency crawler framework based on golang. It supports multiple data storage methods, distributed crawling, data deduplication, data filtering, etc. characteristic. With the help of go_spider, we can easily build high-performance crawler applications.

The following is an example of using the go_spider framework to crawl Baidu search results:

package main

import (
    "fmt"
    "github.com/hu17889/go_spider/core/common/page"
    "github.com/hu17889/go_spider/core/pipeline"
    "github.com/hu17889/go_spider/core/spider"
    "github.com/hu17889/go_spider/core/spider/parsers"
    "github.com/hu17889/go_spider/core/spider/parsers/common"
)

type BaiduResult struct {
    Title string `json:"title"`
    Link  string `json:"link"`
}

func main() {
    s := spider.NewSpider(nil)

    s.SetStartUrl("https://www.baidu.com/s?wd=golang")
    s.SetThreadnum(5)

    s.SetParseFunc(func(p *page.Page) {
        results := make([]*BaiduResult, 0)
        sel := parsers.Selector(p.GetBody())

        sel.Find("#content_left h3 a").Each(func(i int, s *common.Selection) {
            title := s.Text()
            link, ok := s.Attr("href")

            if ok && len(title) > 0 && len(link) > 0 {
                result := &BaiduResult{
                    Title: title,
                    Link:  link,
                }
                results = append(results, result)
            }
        })

        p.AddResultItem("results", results)
    })

    s.SetPipeline(pipeline.NewJsonWriterPipeline("results.json"))

    s.Run()
}

This code uses the go_spider framework to parse the Baidu search results page and extract the title and URL of each search result. , save the result in JSON format. It should be noted that go_spider provides a wealth of data parsing and storage methods, and you can choose different configuration methods according to needs.

Summary

This article introduces several commonly used crawler libraries and frameworks in golang, including goquery, colly and go_spider. It should be noted that when using these libraries and frameworks, you need to abide by the crawler conventions and laws and regulations of the website to avoid unnecessary disputes. In addition, golang has the advantages of simplicity, ease of use, high performance and high scalability in crawler development, and is worthy of in-depth study and use by developers.

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