goProject/trunk/goutil/xmlUtil/gxpath/README.md

gxpath

gxpath is XPath packages for the Go, that lets you extract data from the custom documents using XPath expression.

XQuery : gxpath implemented, lets you extract data from HTML/XML documents using XPath.

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.

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.

• (expr) : Parenthesized expressions.

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

  • position()
  • last()
  • count(node-set)
  • name()
  • starts-with(string,string)
  • normalize-space(string)
  • substring(string,start[,length])
  • come more

• a or b : Boolean or.

• a and b : Boolean and.