What is the reason why golang crawler is garbled? How to deal with it?

In the process of using golang to crawl web pages, many developers will encounter one of the very troublesome problems - garbled characters. Because the content on the Internet is encoded, and some websites are encoded in a special way, this may cause garbled characters when we crawl the data.

This article will introduce in detail the garbled code problems that often occur in golang crawlers and their solutions from the following aspects:

1. Causes of garbled codes
2. Get the response How to process data
3. Encoding format conversion method
4. Encoding detection and automatic conversion
5. Cause of garbled characters

The so-called encoding refers to It is the way computers process characters during storage, transmission, display, etc. During the crawling process, the response data we receive will be encoded by the server and then transmitted to us, which means we may get very messy data. This is the reason for the garbled code.

On the Web, there are various ways to encode characters. For example, GBK, UTF-8, ISO-8859-1, GB2312, Big5, etc. These encoding methods have different character sets, character set ranges, representation methods and other characteristics. If our web crawler does not handle the encoding problem well, it will trigger a series of garbled code problems.

2. Processing method when obtaining response data

In the golang crawler, we usually use the http.Get() method when obtaining response data. The obtained data is passed through the Response.Body property. Therefore, the first step in solving the garbled problem is to correctly handle the original data in the Response.Body property.

First, we need to use the ReadAll() method in the ioutil package to obtain the response data and decode it accordingly. For example:

resp, err := http.Get(url)
if err != nil {
   // 处理错误
}
defer resp.Body.Close()
bodyBytes, err := ioutil.ReadAll(resp.Body)
if err != nil {
   // 处理错误
}
bodyString := string(bodyBytes)

In the above code, we use the ReadAll() method in the ioutil package to read the data in Response.Body into a byte array, and then use Go's built-in string() method to Decode it and get a correct string.

3. Encoding format conversion method

In the previous step, we have decoded the original data obtained from Response.Body. If we find that the resulting string is garbled, then we need to process it further.

Usually, Unicode/UTF-8 related APIs can be used to convert strings to the target encoding format. Go's built-in strings package provides methods for converting Unicode/UTF-8 to other encoding formats.

For example, we can use the ToUpper() method in the strings package to convert a string from the original encoding format (such as GBK) to the target encoding format (such as UTF-8). Likewise, the strings package also provides methods to convert strings from the target encoding format to Unicode/UTF-8.

For example, to convert a string from GBK format to UTF-8 format, you can use the following code:

gbkString := "你好，世界"
decoder := simplifiedchinese.GBK.NewDecoder()
utf8String, err := decoder.String(gbkString)
if err != nil {
   // 处理错误
}

It should be noted that in the above code, we use Go’s built-in The GBK.NewDecoder() method in the simplified Chinese library converts GBK format strings into Unicode/UTF-8 format strings. If you need to replace it with another encoding format, just change the parameters of the NewDecoder() method.

4. Encoding detection and automatic conversion

Usually, we are not sure what the encoding format of the target website is. At this time, we can first detect whether the response header of the target website contains encoding format information. If so, use the encoding format in the response header for decoding instead of using the default UTF-8 encoding format. In this way, we can avoid garbled characters caused by encoding problems.

In addition, we can also use third-party libraries to automatically detect and convert encoding formats. For example, GoDoc recommends the go-charset package for encoding problems in golang crawlers. This library can implement encoding format conversion based on automatic detection. We can directly pass the Response.Body property to the go-charset package and let it automatically detect the encoding format and convert accordingly.

For example, to use the go-charset package to convert the encoding format, you can use the following code:

import "github.com/djimenez/iconv-go"

// 默认使用 GBK 编码格式
resp, err := http.Get(url)
if err != nil {
   // 处理错误
}
defer resp.Body.Close()

// 自动检测编码格式并转换
bodyReader, err := iconv.NewReader(resp.Body, iconv.DetectEncoding(resp.Body), "utf-8")
if err != nil {
   // 处理错误
}
bodyBytes, err := ioutil.ReadAll(bodyReader)
if err != nil {
   // 处理错误
}
bodyString := string(bodyBytes)

In the above code, we use the NewReader() method in the go-charset package to convert the response data Decode and convert to UTF-8 encoded format. It should be noted that we use the DetectEncoding() method to automatically detect the encoding format, which can work well in multi-encoding websites.

Summary

Whenever, encoding issues are one of the headaches in golang crawlers. However, through the methods introduced above, we can avoid problems such as garbled characters when crawling data. Correctly handling coding issues can make our golang web crawler more stable and reliable in practical applications.

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