Class Substring

All Implemented Interfaces:
Serializable, SourceLocator, LocationProvider, SaxonLocator, InstructionInfo, Locator

public class Substring extends SystemFunction
This class implements the XPath substring() function
See Also:
  • Constructor Details

    • Substring

      public Substring()
  • Method Details

    • typeCheck

      public Expression typeCheck(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) throws XPathException
      Type-check the expression. This also calls preEvaluate() to evaluate the function if all the arguments are constant; functions that do not require this behavior can override the preEvaluate method.
      Overrides:
      typeCheck in class FunctionCall
      Parameters:
      visitor - an expression visitor
      contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE
      Returns:
      the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
      Throws:
      XPathException - if an error is discovered during this phase (typically a type error)
    • evaluateItem

      public Item evaluateItem(XPathContext context) throws XPathException
      Evaluate the function
      Overrides:
      evaluateItem in class Expression
      Parameters:
      context - The context in which the expression is to be evaluated
      Returns:
      the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence
      Throws:
      XPathException - if any dynamic error occurs evaluating the expression
    • substring

      public static CharSequence substring(StringValue sv, NumericValue start)
      Implement the substring function with two arguments.
      Parameters:
      sv - the string value
      start - the numeric offset (1-based) of the first character to be included in the result (if not an integer, the XPath rules apply)
      Returns:
      the substring starting at this position.
    • substring

      public static CharSequence substring(StringValue sv, NumericValue start, NumericValue len, XPathContext context)
      Implement the substring function with three arguments.
      Parameters:
      sv - the string value
      start - the numeric offset (1-based) of the first character to be included in the result (if not an integer, the XPath rules apply)
      len - the length of the required substring (again, XPath rules apply)
      context - the XPath dynamic context. Provided because some arithmetic computations require it
      Returns:
      the substring starting at this position.