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 capabilities and features:

• 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.

The etree package is compatible with go versions 1.23 and later.

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-->
  <Person name="Jon"/>
  <Person name="Sally"/>
</People>

Reading an XML file

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

<bookstore xmlns:p="urn:schemas-books-com:prices">

  <book category="COOKING">
    <title lang="en">Everyday Italian</title>
    <author>Giada De Laurentiis</author>
    <year>2005</year>
    <p:price>30.00</p:price>
  </book>

  <book category="CHILDREN">
    <title lang="en">Harry Potter</title>
    <author>J K. Rowling</author>
    <year>2005</year>
    <p:price>29.99</p:price>
  </book>

  <book category="WEB">
    <title lang="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>

  <book category="WEB">
    <title lang="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()
if err := 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 := range root.SelectElementsSeq("book") {
    fmt.Println("CHILD element:", book.Tag)
    if title := book.SelectElement("title"); title != nil {
        lang := title.SelectAttrValue("lang", "unknown")
        fmt.Printf("  TITLE: %s (%s)\n", title.Text(), lang)
    }
    for _, attr := range book.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 := range doc.FindElementsSeq("//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 := range doc.FindElementsSeq("./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 := range doc.FindElementsPathSeq(path) {
    fmt.Println(e.Text())
}

Output:

XQuery Kick Start

Note that this example uses the FindElementsPathSeq 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!