问题描述
我正在尝试在 Go 中为大型 xml 文件(dblp.xml),摘录如下:
I'm trying to write a very simple parser in Go for a large xml file (the dblp.xml), an excerpt of which is below:
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE dblp SYSTEM "dblp.dtd">
<dblp>
<article key="journals/cacm/Gentry10" mdate="2010-04-26">
<author>Craig Gentry</author>
<title>Computing arbitrary functions of encrypted data.</title>
<pages>97-105</pages>
<year>2010</year>
<volume>53</volume>
<journal>Commun. ACM</journal>
<number>3</number>
<ee>http://doi.acm.org/10.1145/1666420.1666444</ee>
<url>db/journals/cacm/cacm53.html#Gentry10</url>
</article>
<article key="journals/cacm/Gentry10" mdate="2010-04-26">
<author>Craig Gentry Number2</author>
<title>Computing arbitrary functions of encrypted data.</title>
<pages>97-105</pages>
<year>2010</year>
<volume>53</volume>
<journal>Commun. ACM</journal>
<number>3</number>
<ee>http://doi.acm.org/10.1145/1666420.1666444</ee>
<url>db/journals/cacm/cacm53.html#Gentry10</url>
</article>
</dblp>
我的代码如下,看起来 xml.Unmarshal(byteValue, &articles)
发生了一些事情,因为我无法在输出中获取任何 xml 值.你能帮我解决我的代码有什么问题吗?
My code is as follows and it looks like there's something going on at xml.Unmarshal(byteValue, &articles)
, as I cannot get any of the xml's values in the output. Can you help me with what is wrong with my code?
package main
import (
"encoding/xml"
"fmt"
"io/ioutil"
"os"
)
// Contains the array of articles in the dblp xml
type Dblp struct {
XMLName xml.Name `xml:"dblp"`
Dblp []Article `xml:"article"`
}
// Contains the article element tags and attributes
type Article struct {
XMLName xml.Name `xml:"article"`
Key string `xml:"key,attr"`
Year string `xml:"year"`
}
func main() {
xmlFile, err := os.Open("TestDblp.xml")
if err != nil {
fmt.Println(err)
}
fmt.Println("Successfully Opened TestDblp.xml")
// defer the closing of our xmlFile so that we can parse it later on
defer xmlFile.Close()
// read our opened xmlFile as a byte array.
byteValue, _ := ioutil.ReadAll(xmlFile)
var articles Dblp
fmt.Println("Entered var")
// we unmarshal our byteArray which contains our
// xmlFiles content into 'users' which we defined above
xml.Unmarshal(byteValue, &articles)
for i := 0; i < len(articles.Dblp); i++ {
fmt.Println("Entered loop")
fmt.Println("get title: " + articles.Dblp[i].Key)
fmt.Println("get year: " + articles.Dblp[i].Year)
}
}
推荐答案
您的代码中有特定行返回错误
You have a specific line in your code that returns an error
xml.Unmarshal(byteValue, &articles)
如果你把它改成
err = xml.Unmarshal(byteValue, &articles)
if err != nil {
fmt.Println(err.Error())
}
您将看到一个错误报告:xml: encoding "ISO-8859-1" 声明但 Decoder.CharsetReader 为 nil
.作为最佳实践,您应该始终检查返回的错误.
You'll see an error being reported: xml: encoding "ISO-8859-1" declared but Decoder.CharsetReader is nil
. As a best practice, you should always check for errors being returned.
要解决此问题,您可以从 XML 中删除编码属性 (encoding="ISO-8859-1"
) 或稍微更改解组代码:
To fix that, you can either remove the encoding attribute (encoding="ISO-8859-1"
) from the XML or change the code of your unmarshalling a bit:
package main
import (
"encoding/xml"
"fmt"
"io"
"os"
"golang.org/x/text/encoding/charmap"
)
// Contains the array of articles in the dblp xml
type Dblp struct {
XMLName xml.Name `xml:"dblp"`
Dblp []Article `xml:"article"`
}
// Contains the article element tags and attributes
type Article struct {
XMLName xml.Name `xml:"article"`
Key string `xml:"key,attr"`
Year string `xml:"year"`
}
func main() {
xmlFile, err := os.Open("dblp.xml")
if err != nil {
fmt.Println(err)
}
fmt.Println("Successfully Opened TestDblp.xml")
// defer the closing of our xmlFile so that we can parse it later on
defer xmlFile.Close()
var articles Dblp
decoder := xml.NewDecoder(xmlFile)
decoder.CharsetReader = makeCharsetReader
err = decoder.Decode(&articles)
if err != nil {
fmt.Println(err)
}
for i := 0; i < len(articles.Dblp); i++ {
fmt.Println("Entered loop")
fmt.Println("get title: " + articles.Dblp[i].Key)
fmt.Println("get year: " + articles.Dblp[i].Year)
}
}
func makeCharsetReader(charset string, input io.Reader) (io.Reader, error) {
if charset == "ISO-8859-1" {
// Windows-1252 is a superset of ISO-8859-1, so should do here
return charmap.Windows1252.NewDecoder().Reader(input), nil
}
return nil, fmt.Errorf("Unknown charset: %s", charset)
}
运行上述程序会导致:
Successfully Opened TestDblp.xml
Entered var
Entered loop
get title: journals/cacm/Gentry10
get year: 2010
Entered loop
get title: journals/cacm/Gentry10
get year: 2010
这篇关于在 Golang 中解组一个简单的 xml 时出错的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!