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