peridot/vendor/github.com/antchfx/xmlquery/README.md
2022-07-07 22:13:21 +02:00

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xmlquery
====
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Overview
===
`xmlquery` is an XPath query package for XML documents, allowing you to extract
data or evaluate from XML documents with an XPath expression.
`xmlquery` has a built-in query object caching feature that caches recently used
XPATH query strings. Enabling caching can avoid recompile XPath expression for
each query.
Change Logs
===
2020-08-??
- Add XML stream loading and parsing support.
2019-11-11
- Add XPath query caching.
2019-10-05
- Add new methods compatible with invalid XPath expression error: `QueryAll` and `Query`.
- Add `QuerySelector` and `QuerySelectorAll` methods, support for reused query objects.
- PR [#12](https://github.com/antchfx/xmlquery/pull/12) (Thanks @FrancescoIlario)
- PR [#11](https://github.com/antchfx/xmlquery/pull/11) (Thanks @gjvnq)
2018-12-23
- Added XML output including comment nodes. [#9](https://github.com/antchfx/xmlquery/issues/9)
2018-12-03
- Added support to attribute name with namespace prefix and XML output. [#6](https://github.com/antchfx/xmlquery/issues/6)
Installation
====
```
$ go get github.com/antchfx/xmlquery
```
Getting Started
===
### Find specified XPath query.
```go
list, err := xmlquery.QueryAll(doc, "a")
if err != nil {
panic(err)
}
```
#### Parse an XML from URL.
```go
doc, err := xmlquery.LoadURL("http://www.example.com/sitemap.xml")
```
#### Parse an XML from string.
```go
s := `<?xml version="1.0" encoding="utf-8"?><rss version="2.0"></rss>`
doc, err := xmlquery.Parse(strings.NewReader(s))
```
#### Parse an XML from io.Reader.
```go
f, err := os.Open("../books.xml")
doc, err := xmlquery.Parse(f)
```
#### Parse an XML in a stream fashion (simple case without elements filtering).
```go
f, err := os.Open("../books.xml")
p, err := xmlquery.CreateStreamParser(f, "/bookstore/book")
for {
n, err := p.Read()
if err == io.EOF {
break
}
if err != nil {
...
}
}
```
#### Parse an XML in a stream fashion (simple case advanced element filtering).
```go
f, err := os.Open("../books.xml")
p, err := xmlquery.CreateStreamParser(f, "/bookstore/book", "/bookstore/book[price>=10]")
for {
n, err := p.Read()
if err == io.EOF {
break
}
if err != nil {
...
}
}
```
#### Find authors of all books in the bookstore.
```go
list := xmlquery.Find(doc, "//book//author")
// or
list := xmlquery.Find(doc, "//author")
```
#### Find the second book.
```go
book := xmlquery.FindOne(doc, "//book[2]")
```
#### Find all book elements and only get `id` attribute. (New Feature)
```go
list := xmlquery.Find(doc,"//book/@id")
```
#### Find all books with id `bk104`.
```go
list := xmlquery.Find(doc, "//book[@id='bk104']")
```
#### Find all books with price less than 5.
```go
list := xmlquery.Find(doc, "//book[price<5]")
```
#### Evaluate total price of all books.
```go
expr, err := xpath.Compile("sum(//book/price)")
price := expr.Evaluate(xmlquery.CreateXPathNavigator(doc)).(float64)
fmt.Printf("total price: %f\n", price)
```
#### Evaluate number of all book elements.
```go
expr, err := xpath.Compile("count(//book)")
price := expr.Evaluate(xmlquery.CreateXPathNavigator(doc)).(float64)
```
FAQ
====
#### `Find()` vs `QueryAll()`, which is better?
`Find` and `QueryAll` both do the same thing: searches all of matched XML nodes.
`Find` panics if provided with an invalid XPath query, while `QueryAll` returns
an error.
#### Can I save my query expression object for the next query?
Yes, you can. We provide `QuerySelector` and `QuerySelectorAll` methods; they
accept your query expression object.
Caching a query expression object avoids recompiling the XPath query
expression, improving query performance.
#### Create XML document.
```go
doc := &xmlquery.Node{
Type: xmlquery.DeclarationNode,
Data: "xml",
Attr: []xml.Attr{
xml.Attr{Name: xml.Name{Local: "version"}, Value: "1.0"},
},
}
root := &xmlquery.Node{
Data: "rss",
Type: xmlquery.ElementNode,
}
doc.FirstChild = root
channel := &xmlquery.Node{
Data: "channel",
Type: xmlquery.ElementNode,
}
root.FirstChild = channel
title := &xmlquery.Node{
Data: "title",
Type: xmlquery.ElementNode,
}
title_text := &xmlquery.Node{
Data: "W3Schools Home Page",
Type: xmlquery.TextNode,
}
title.FirstChild = title_text
channel.FirstChild = title
fmt.Println(doc.OutputXML(true))
// <?xml version="1.0"?><rss><channel><title>W3Schools Home Page</title></channel></rss>
```
Quick Tutorial
===
```go
import (
"github.com/antchfx/xmlquery"
)
func main(){
s := `<?xml version="1.0" encoding="UTF-8" ?>
<rss version="2.0">
<channel>
<title>W3Schools Home Page</title>
<link>https://www.w3schools.com</link>
<description>Free web building tutorials</description>
<item>
<title>RSS Tutorial</title>
<link>https://www.w3schools.com/xml/xml_rss.asp</link>
<description>New RSS tutorial on W3Schools</description>
</item>
<item>
<title>XML Tutorial</title>
<link>https://www.w3schools.com/xml</link>
<description>New XML tutorial on W3Schools</description>
</item>
</channel>
</rss>`
doc, err := xmlquery.Parse(strings.NewReader(s))
if err != nil {
panic(err)
}
channel := xmlquery.FindOne(doc, "//channel")
if n := channel.SelectElement("title"); n != nil {
fmt.Printf("title: %s\n", n.InnerText())
}
if n := channel.SelectElement("link"); n != nil {
fmt.Printf("link: %s\n", n.InnerText())
}
for i, n := range xmlquery.Find(doc, "//item/title") {
fmt.Printf("#%d %s\n", i, n.InnerText())
}
}
```
List of supported XPath query packages
===
| Name | Description |
| ------------------------------------------------- | ----------------------------------------- |
| [htmlquery](https://github.com/antchfx/htmlquery) | XPath query package for HTML documents |
| [xmlquery](https://github.com/antchfx/xmlquery) | XPath query package for XML documents |
| [jsonquery](https://github.com/antchfx/jsonquery) | XPath query package for JSON documents |
Questions
===
Please let me know if you have any questions