解析XPath表达式验证 [英] Parse XPath Expressions

问题描述

我想创建一个AET（摘要表达式树）用于XPath（当我写一个所见即所得的编辑器，XSL）。我一直在打我的头靠在与XPath的BNF墙在过去三到四个小时。

I am trying to create a 'AET' (Abstract Expression Tree) for XPath (as I am writing a WYSIWYG XSL editor). I have been hitting my head against the wall with the XPath BNF for the past three to four hours.

我也曾想过另一种解决方案。我想我可以写一个实现IXPathNavigable，它返回我自己的一个XPathNavigator的时候CreateNavigator称为类。这XPathNavigator的总会上的任何方法调用成功，将保持这些电话的轨迹 - 例如我们搬到客户的节点，然后用户节点。然后我可以使用该信息（希望）以创建AET（所以我们有顾客/客户的对象模型现在）

I have thought of another solution. I thought I could write a class that implements IXPathNavigable, which returns a XPathNavigator of my own when CreateNavigator is called. This XPathNavigator would always succeed on any method calls, and would keep track of those calls - e.g. we moved to the customers node and then the customer node. I could then use this information (hopefully) to create the 'AET' (so we would have customers/customer in a object model now).

唯一的问题是：如何上的地球的做我通过XPathExpression运行IXPathNavigable？

Only question is: how on earth do I run a IXPathNavigable through an XPathExpression?

我知道这是过于懒惰。但是有其他人通过努力去和编写的XPath表达式解析器？我还没有POC'd我可能的解决方案，因为我不能测试它（因为我不能运行针对IXPathNavigable的XPathExpression），所以我甚至不知道我的解决方案，甚至会工作。

I know this is excessively lazy. But has anyone else gone through the effort and written a XPath expression parser? I haven't yet POC'd my possible solution, because I can't test it (because I can't run the XPathExpression against a IXPathNavigable), so I don't even know if my solution will even work.

推荐答案

有一个ANTLR的XPath语法的此处。由于它的许可证允许，我在这里复制了整个语法，以避免在未来的链接腐

There is an antlr xpath grammar here. Since its license permits, I copied the whole grammar here to avoid link rot in the future.

grammar xpath;

/*
XPath 1.0 grammar. Should conform to the official spec at
http://www.w3.org/TR/1999/REC-xpath-19991116. The grammar
rules have been kept as close as possible to those in the
spec, but some adjustmewnts were unavoidable. These were
mainly removing left recursion (spec seems to be based on
LR), and to deal with the double nature of the '*' token
(node wildcard and multiplication operator). See also
section 3.7 in the spec. These rule changes should make
no difference to the strings accepted by the grammar.
Written by Jan-Willem van den Broek
Version 1.0
Do with this code as you will.
*/
/*
    Ported to Antlr4 by Tom Everett <[e-mail]>
*/


main  :  expr
  ;

locationPath 
  :  relativeLocationPath
  |  absoluteLocationPathNoroot
  ;

absoluteLocationPathNoroot
  :  '/' relativeLocationPath
  |  '//' relativeLocationPath
  ;

relativeLocationPath
  :  step (('/'|'//') step)*
  ;

step  :  axisSpecifier nodeTest predicate*
  |  abbreviatedStep
  ;

axisSpecifier
  :  AxisName '::'
  |  '@'?
  ;

nodeTest:  nameTest
  |  NodeType '(' ')'
  |  'processing-instruction' '(' Literal ')'
  ;

predicate
  :  '[' expr ']'
  ;

abbreviatedStep
  :  '.'
  |  '..'
  ;

expr  :  orExpr
  ;

primaryExpr
  :  variableReference
  |  '(' expr ')'
  |  Literal
  |  Number  
  |  functionCall
  ;

functionCall
  :  functionName '(' ( expr ( ',' expr )* )? ')'
  ;

unionExprNoRoot
  :  pathExprNoRoot ('|' unionExprNoRoot)?
  |  '/' '|' unionExprNoRoot
  ;

pathExprNoRoot
  :  locationPath
  |  filterExpr (('/'|'//') relativeLocationPath)?
  ;

filterExpr
  :  primaryExpr predicate*
  ;

orExpr  :  andExpr ('or' andExpr)*
  ;

andExpr  :  equalityExpr ('and' equalityExpr)*
  ;

equalityExpr
  :  relationalExpr (('='|'!=') relationalExpr)*
  ;

relationalExpr
  :  additiveExpr (('<'|'>'|'<='|'>=') additiveExpr)*
  ;

additiveExpr
  :  multiplicativeExpr (('+'|'-') multiplicativeExpr)*
  ;

multiplicativeExpr
  :  unaryExprNoRoot (('*'|'div'|'mod') multiplicativeExpr)?
  |  '/' (('div'|'mod') multiplicativeExpr)?
  ;

unaryExprNoRoot
  :  '-'* unionExprNoRoot
  ;

qName  :  nCName (':' nCName)?
  ;

functionName
  :  qName  // Does not match nodeType, as per spec.
  ;

variableReference
  :  '$' qName
  ;

nameTest:  '*'
  |  nCName ':' '*'
  |  qName
  ;

nCName  :  NCName
  |  AxisName
  ;

NodeType:  'comment'
  |  'text'
  |  'processing-instruction'
  |  'node'
  ;

Number  :  Digits ('.' Digits?)?
  |  '.' Digits
  ;

fragment
Digits  :  ('0'..'9')+
  ;

AxisName:  'ancestor'
  |  'ancestor-or-self'
  |  'attribute'
  |  'child'
  |  'descendant'
  |  'descendant-or-self'
  |  'following'
  |  'following-sibling'
  |  'namespace'
  |  'parent'
  |  'preceding'
  |  'preceding-sibling'
  |  'self'
  ;


  PATHSEP 
       :'/';
  ABRPATH   
       : '//';
  LPAR   
       : '(';
  RPAR   
       : ')';
  LBRAC   
       :  '[';
  RBRAC   
       :  ']';
  MINUS   
       :  '-';
  PLUS   
       :  '+';
  DOT   
       :  '.';
  MUL   
       : '*';
  DOTDOT   
       :  '..';
  AT   
       : '@';
  COMMA  
       : ',';
  PIPE   
       :  '|';
  LESS   
       :  '<';
  MORE_ 
       :  '>';
  LE   
       :  '<=';
  GE   
       :  '>=';
  COLON   
       :  ':';
  CC   
       :  '::';
  APOS   
       :  '\'';
  QUOT   
       :  '\"';

Literal  :  '"' ~'"'* '"'
  |  '\'' ~'\''* '\''
  ;

Whitespace
  :  (' '|'\t'|'\n'|'\r')+ ->skip
  ;

NCName  :  NCNameStartChar NCNameChar*
  ;

fragment
NCNameStartChar
  :  'A'..'Z'
  |   '_'
  |  'a'..'z'
  |  '\u00C0'..'\u00D6'
  |  '\u00D8'..'\u00F6'
  |  '\u00F8'..'\u02FF'
  |  '\u0370'..'\u037D'
  |  '\u037F'..'\u1FFF'
  |  '\u200C'..'\u200D'
  |  '\u2070'..'\u218F'
  |  '\u2C00'..'\u2FEF'
  |  '\u3001'..'\uD7FF'
  |  '\uF900'..'\uFDCF'
  |  '\uFDF0'..'\uFFFD'
// Unfortunately, java escapes can't handle this conveniently,
// as they're limited to 4 hex digits. TODO.
//  |  '\U010000'..'\U0EFFFF'
  ;

fragment
NCNameChar
  :  NCNameStartChar | '-' | '.' | '0'..'9'
  |  '\u00B7' | '\u0300'..'\u036F'
  |  '\u203F'..'\u2040'
  ;

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