xpath

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Version: v1.2.0 Latest Latest
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Published: Jun 3, 2021 License: MIT Imports: 11 Imported by: 73

README

XPath

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XPath is Go package provides selecting nodes from XML, HTML or other documents using XPath expression.

Implementation

  • htmlquery - an XPath query package for HTML document

  • xmlquery - an XPath query package for XML document.

  • jsonquery - an XPath query package for JSON document

Supported Features

The basic XPath patterns.

The basic XPath patterns cover 90% of the cases that most stylesheets will need.

  • node : Selects all child elements with nodeName of node.

  • * : Selects all child elements.

  • @attr : Selects the attribute attr.

  • @* : Selects all attributes.

  • node() : Matches an org.w3c.dom.Node.

  • text() : Matches a org.w3c.dom.Text node.

  • comment() : Matches a comment.

  • . : Selects the current node.

  • .. : Selects the parent of current node.

  • / : Selects the document node.

  • a[expr] : Select only those nodes matching a which also satisfy the expression expr.

  • a[n] : Selects the nth matching node matching a When a filter's expression is a number, XPath selects based on position.

  • a/b : For each node matching a, add the nodes matching b to the result.

  • a//b : For each node matching a, add the descendant nodes matching b to the result.

  • //b : Returns elements in the entire document matching b.

  • a|b : All nodes matching a or b, union operation(not boolean or).

  • (a, b, c) : Evaluates each of its operands and concatenates the resulting sequences, in order, into a single result sequence

Node Axes
  • child::* : The child axis selects children of the current node.

  • descendant::* : The descendant axis selects descendants of the current node. It is equivalent to '//'.

  • descendant-or-self::* : Selects descendants including the current node.

  • attribute::* : Selects attributes of the current element. It is equivalent to @*

  • following-sibling::* : Selects nodes after the current node.

  • preceding-sibling::* : Selects nodes before the current node.

  • following::* : Selects the first matching node following in document order, excluding descendants.

  • preceding::* : Selects the first matching node preceding in document order, excluding ancestors.

  • parent::* : Selects the parent if it matches. The '..' pattern from the core is equivalent to 'parent::node()'.

  • ancestor::* : Selects matching ancestors.

  • ancestor-or-self::* : Selects ancestors including the current node.

  • self::* : Selects the current node. '.' is equivalent to 'self::node()'.

Expressions

The gxpath supported three types: number, boolean, string.

  • path : Selects nodes based on the path.

  • a = b : Standard comparisons.

    • a = b True if a equals b.
    • a != b True if a is not equal to b.
    • a < b True if a is less than b.
    • a <= b True if a is less than or equal to b.
    • a > b True if a is greater than b.
    • a >= b True if a is greater than or equal to b.
  • a + b : Arithmetic expressions.

    • - a Unary minus
    • a + b Add
    • a - b Substract
    • a * b Multiply
    • a div b Divide
    • a mod b Floating point mod, like Java.
  • a or b : Boolean or operation.

  • a and b : Boolean and operation.

  • (expr) : Parenthesized expressions.

  • fun(arg1, ..., argn) : Function calls:

Function Supported
boolean()
ceiling()
choose()
concat()
contains()
count()
current()
document()
element-available()
ends-with()
false()
floor()
format-number()
function-available()
generate-id()
id()
key()
lang()
last()
local-name()
matches()
name()
namespace-uri()
normalize-space()
not()
number()
position()
replace()
reverse()
round()
starts-with()
string()
string-length()
substring()
substring-after()
substring-before()
sum()
system-property()
translate()
true()
unparsed-entity-url()

Changelogs

2019-03-19

  • optimize XPath | operation performance. #33. Tips: suggest split into multiple subquery if you have a lot of | operations.

2019-01-29

  • improvement normalize-space function. #32

2018-12-07

  • supports XPath 2.0 Sequence expressions. #30 by @minherz.

Documentation

Overview

Example

XPath package example.

package main

import (
	"fmt"

	"github.com/antchfx/xpath"
)

func main() {
	expr, err := xpath.Compile("count(//book)")
	if err != nil {
		panic(err)
	}
	var root xpath.NodeNavigator
	// using Evaluate() method
	val := expr.Evaluate(root) // it returns float64 type
	fmt.Println(val.(float64))

	// using Evaluate() method
	expr = xpath.MustCompile("//book")
	val = expr.Evaluate(root) // it returns NodeIterator type.
	iter := val.(*xpath.NodeIterator)
	for iter.MoveNext() {
		fmt.Println(iter.Current().Value())
	}

	// using Select() method
	iter = expr.Select(root) // it always returns NodeIterator object.
	for iter.MoveNext() {
		fmt.Println(iter.Current().Value())
	}
}
Output:

Index

Examples

Constants

This section is empty.

Variables

View Source
var (
	// RegexpCache is a loading cache for string -> *regexp.Regexp mapping. It is exported so that in rare cases
	// client can customize load func and/or capacity.
	RegexpCache = defaultRegexpCache()
)

Functions

func NewLoadingCache added in v1.1.11

func NewLoadingCache(load loadFunc, capacity int) *loadingCache

NewLoadingCache creates a new instance of a loading cache with capacity. Capacity must be >= 0, or it will panic. Capacity == 0 means the cache growth is unbounded.

Types

type Expr

type Expr struct {
	// contains filtered or unexported fields
}

Expr is an XPath expression for query.

func Compile

func Compile(expr string) (*Expr, error)

Compile compiles an XPath expression string.

func MustCompile

func MustCompile(expr string) *Expr

MustCompile compiles an XPath expression string and ignored error.

func (*Expr) Evaluate

func (expr *Expr) Evaluate(root NodeNavigator) interface{}

Evaluate returns the result of the expression. The result type of the expression is one of the follow: bool,float64,string,NodeIterator).

func (*Expr) Select

func (expr *Expr) Select(root NodeNavigator) *NodeIterator

Select selects a node set using the specified XPath expression.

func (*Expr) String

func (expr *Expr) String() string

String returns XPath expression string.

type NodeIterator

type NodeIterator struct {
	// contains filtered or unexported fields
}

NodeIterator holds all matched Node object.

func Select

func Select(root NodeNavigator, expr string) *NodeIterator

Select selects a node set using the specified XPath expression. This method is deprecated, recommend using Expr.Select() method instead.

func (*NodeIterator) Current

func (t *NodeIterator) Current() NodeNavigator

Current returns current node which matched.

func (*NodeIterator) MoveNext

func (t *NodeIterator) MoveNext() bool

MoveNext moves Navigator to the next match node.

type NodeNavigator

type NodeNavigator interface {
	// NodeType returns the XPathNodeType of the current node.
	NodeType() NodeType

	// LocalName gets the Name of the current node.
	LocalName() string

	// Prefix returns namespace prefix associated with the current node.
	Prefix() string

	// Value gets the value of current node.
	Value() string

	// Copy does a deep copy of the NodeNavigator and all its components.
	Copy() NodeNavigator

	// MoveToRoot moves the NodeNavigator to the root node of the current node.
	MoveToRoot()

	// MoveToParent moves the NodeNavigator to the parent node of the current node.
	MoveToParent() bool

	// MoveToNextAttribute moves the NodeNavigator to the next attribute on current node.
	MoveToNextAttribute() bool

	// MoveToChild moves the NodeNavigator to the first child node of the current node.
	MoveToChild() bool

	// MoveToFirst moves the NodeNavigator to the first sibling node of the current node.
	MoveToFirst() bool

	// MoveToNext moves the NodeNavigator to the next sibling node of the current node.
	MoveToNext() bool

	// MoveToPrevious moves the NodeNavigator to the previous sibling node of the current node.
	MoveToPrevious() bool

	// MoveTo moves the NodeNavigator to the same position as the specified NodeNavigator.
	MoveTo(NodeNavigator) bool
}

NodeNavigator provides cursor model for navigating XML data.

type NodeType

type NodeType int

NodeType represents a type of XPath node.

const (
	// RootNode is a root node of the XML document or node tree.
	RootNode NodeType = iota

	// ElementNode is an element, such as <element>.
	ElementNode

	// AttributeNode is an attribute, such as id='123'.
	AttributeNode

	// TextNode is the text content of a node.
	TextNode

	// CommentNode is a comment node, such as <!-- my comment -->
	CommentNode
)

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