Package com.puppycrawl.tools.checkstyle.utils

Class XpathUtil

java.lang.Object
com.puppycrawl.tools.checkstyle.utils.XpathUtil
public final class XpathUtil extends Object
Contains utility methods for xpath.

  • Field Details

    • TOKEN_TYPES_WITH_TEXT_ATTRIBUTE

      private static final BitSet TOKEN_TYPES_WITH_TEXT_ATTRIBUTE
      Token types which support text attribute. These token types were selected based on analysis that all others do not match required criteria - text attribute of the token must be useful and help to retrieve more precise results. There are three types of AST tokens: 1. Tokens for which the texts are equal to the name of the token. Or in other words, nodes for which the following expression is always true: 
           detailAst.getText().equals(TokenUtil.getTokenName(detailAst.getType()))
      For example: 
           //MODIFIERS[@text='MODIFIERS']
     //OBJBLOCK[@text='OBJBLOCK']
      These tokens do not match required criteria because their texts do not carry any additional information, they do not affect the xpath requests and do not help to get more accurate results. The texts of these nodes are useless. No matter what code you analyze, these texts are always the same. In addition, they make xpath queries more complex, less readable and verbose. 2. Tokens for which the texts differ from token names, but texts are always constant. For example: 
           //LITERAL_VOID[@text='void']
     //RCURLY[@text='}']
      These tokens are not used for the same reasons as were described in the previous part. 3. Tokens for which texts are not constant. The texts of these nodes are closely related to a concrete class, method, variable and so on. For example: 
           String greeting = "HelloWorld";
     //STRING_LITERAL[@text='HelloWorld']
 
           int year = 2017;
     //NUM_INT[@text=2017]
 
           int age = 23;
     //NUM_INT[@text=23]
      As you can see same NUM_INT token type can have different texts, depending on context. 
           public class MyClass {}
     //IDENT[@text='MyClass']
      Only these tokens support text attribute because they make our xpath queries more accurate. These token types are listed below.

    • NEWLINE_TO_TAG

      private static final Pattern NEWLINE_TO_TAG
      This regexp is used to convert new line to newline tag.

    • CARRIAGE_RETURN_TO_TAG

      private static final Pattern CARRIAGE_RETURN_TO_TAG
      This regexp is used to convert carriage return to carriage-return tag.

    • DELIMITER

      private static final String DELIMITER
      Delimiter to separate xpath results.

  • Constructor Details

    • XpathUtil

      private XpathUtil()
      Stop instances being created.

  • Method Details

    • createChildren

      public static List<AbstractNode> createChildren(AbstractNode root, AbstractNode parent, DetailAST firstChild)
      Iterates siblings of the given node and creates new Xpath-nodes.
      Parameters:
      root - the root node
      parent - the parent node
      firstChild - the first DetailAST
      Returns:
      children list

    • supportsTextAttribute

      public static boolean supportsTextAttribute(DetailAST ast)
      Checks, if specified node can have @text attribute.
      Parameters:
      ast - DetailAst element
      Returns:
      true if element supports @text attribute, false otherwise

    • getTextAttributeValue

      public static String getTextAttributeValue(DetailAST ast)
      Returns content of the text attribute of the ast element.
      Parameters:
      ast - DetailAst element
      Returns:
      text attribute of the ast element

    • printXpathBranch

      public static String printXpathBranch(String xpath, File file) throws CheckstyleException, IOException
      Returns xpath query results on file as string.
      Parameters:
      xpath - query to evaluate
      file - file to run on
      Returns:
      all results as string separated by delimiter
      Throws:
      CheckstyleException - if some parsing error happens
      IOException - if an error occurs

    • getXpathItems

      public static List<net.sf.saxon.om.NodeInfo> getXpathItems(String xpath, AbstractNode rootNode) throws net.sf.saxon.trans.XPathException
      Returns list of nodes matching xpath expression given node context.
      Parameters:
      xpath - Xpath expression
      rootNode - NodeInfo node context
      Returns:
      list of nodes matching xpath expression given node context
      Throws:
      net.sf.saxon.trans.XPathException - if Xpath cannot be parsed