etree

The etree package is a lightweight, pure go package that expresses XML in the form of an element tree. Its design was inspired by the Python ElementTree module. Some of the package's features include:

• Represents XML documents as trees of elements for easy traversal.
• Imports, serializes, modifies or creates XML documents from scratch.
• Writes and reads XML to/from files, byte slices, strings and io interfaces.
• Performs simple or complex searches with lightweight XPath-like query APIs.
• Auto-indents XML using spaces or tabs for better readability.
• Implemented in pure go; depends only on standard go libraries.
• Built on top of the go encoding/xml package.

Creating an XML document

The following example creates an XML document from scratch using the etree package and outputs its indented contents to stdout.

doc:=etree.NewDocument()
doc.CreateProcInst("xml", `version="1.0" encoding="UTF-8"`)
doc.CreateProcInst("xml-stylesheet", `type="text/xsl" href="style.xsl"`)
people:=doc.CreateElement("People")
people.CreateComment("These are all known people")
jon:=people.CreateElement("Person")
jon.CreateAttr("name", "Jon")
sally:=people.CreateElement("Person")
sally.CreateAttr("name", "Sally")
doc.Indent(2)
doc.WriteTo(os.Stdout)

Output:

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="style.xsl"?>
<People>
<!--These are all known people-->
<Personname="Jon"/>
<Personname="Sally"/>
</People>

Reading an XML file

Suppose you have a file on disk called bookstore.xml containing the following data:

<bookstorexmlns:p="urn:schemas-books-com:prices">
<bookcategory="COOKING">
<titlelang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<p:price>30.00</p:price>
</book>
<bookcategory="CHILDREN">
<titlelang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<p:price>29.99</p:price>
</book>
<bookcategory="WEB">
<titlelang="en">XQuery Kick Start</title>
<author>James McGovern</author>
<author>Per Bothner</author>
<author>Kurt Cagle</author>
<author>James Linn</author>
<author>Vaidyanathan Nagarajan</author>
<year>2003</year>
<p:price>49.99</p:price>
</book>
<bookcategory="WEB">
<titlelang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<p:price>39.95</p:price>
</book>
</bookstore>

This code reads the file's contents into an etree document.

doc:=etree.NewDocument()
iferr:=doc.ReadFromFile("bookstore.xml"); err!=nil {
panic(err)
}

You can also read XML from a string, a byte slice, or an io.Reader.

Processing elements and attributes

This example illustrates several ways to access elements and attributes using etree selection queries.

root:=doc.SelectElement("bookstore")
fmt.Println("ROOT element:", root.Tag)
for_, book:=rangeroot.SelectElements("book") {
fmt.Println("CHILD element:", book.Tag)
iftitle:=book.SelectElement("title"); title!=nil {
lang:=title.SelectAttrValue("lang", "unknown")
fmt.Printf(" TITLE: %s (%s)\n", title.Text(), lang)
}
for_, attr:=rangebook.Attr {
fmt.Printf(" ATTR: %s=%s\n", attr.Key, attr.Value)
}
}

Output:

ROOT element: bookstore
CHILD element: book
TITLE: Everyday Italian (en)
ATTR: category=COOKING
CHILD element: book
TITLE: Harry Potter (en)
ATTR: category=CHILDREN
CHILD element: book
TITLE: XQuery Kick Start (en)
ATTR: category=WEB
CHILD element: book
TITLE: Learning XML (en)
ATTR: category=WEB

Path queries

This example uses etree's path functions to select all book titles that fall into the category of 'WEB'. The double-slash prefix in the path causes the search for book elements to occur recursively; book elements may appear at any level of the XML hierarchy.

for_, t:=rangedoc.FindElements("//book[@category='WEB']/title") {
fmt.Println("Title:", t.Text())
}

Output:

Title: XQuery Kick Start
Title: Learning XML

This example finds the first book element under the root bookstore element and outputs the tag and text of each of its child elements.

for_, e:=rangedoc.FindElements("./bookstore/book[1]/*") {
fmt.Printf("%s: %s\n", e.Tag, e.Text())
}

Output:

title: Everyday Italian
author: Giada De Laurentiis
year: 2005
price: 30.00

This example finds all books with a price of 49.99 and outputs their titles.

path:=etree.MustCompilePath("./bookstore/book[p:price='49.99']/title")
for_, e:=rangedoc.FindElementsPath(path) {
fmt.Println(e.Text())
}

Output:

XQuery Kick Start

Note that this example uses the FindElementsPath function, which takes as an argument a pre-compiled path object. Use precompiled paths when you plan to search with the same path more than once.

###Other features

These are just a few examples of the things the etree package can do. See the documentation for a complete description of its capabilities.

###Contributing

This project accepts contributions. Just fork the repo and submit a pull request!