import com.sun.org.apache.xpath.internal.compiler.XPathParser; //导入依赖的package包/类
/**
 * Construct an XPath object.
 *
 * (Needs review -sc) This method initializes an XPathParser/
 * Compiler and compiles the expression.
 * @param exprString The XPath expression.
 * @param locator The location of the expression, may be null.
 * @param prefixResolver A prefix resolver to use to resolve prefixes to
 *                       namespace URIs.
 * @param type one of {@link #SELECT} or {@link #MATCH}.
 * @param errorListener The error listener, or null if default should be used.
 *
 * @throws javax.xml.transform.TransformerException if syntax or other error.
 */
public XPath(
        String exprString, SourceLocator locator, PrefixResolver prefixResolver, int type,
        ErrorListener errorListener)
          throws javax.xml.transform.TransformerException
{
  initFunctionTable();
  if(null == errorListener)
    errorListener = new com.sun.org.apache.xml.internal.utils.DefaultErrorHandler();

  m_patternString = exprString;

  XPathParser parser = new XPathParser(errorListener, locator);
  Compiler compiler = new Compiler(errorListener, locator, m_funcTable);

  if (SELECT == type)
    parser.initXPath(compiler, exprString, prefixResolver);
  else if (MATCH == type)
    parser.initMatchPattern(compiler, exprString, prefixResolver);
  else
    throw new RuntimeException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_CANNOT_DEAL_XPATH_TYPE, new Object[]{Integer.toString(type)})); //"Can not deal with XPath type: " + type);

  // System.out.println("----------------");
  Expression expr = compiler.compile(0);

  // System.out.println("expr: "+expr);
  this.setExpression(expr);

  if((null != locator) && locator instanceof ExpressionNode)
  {
      expr.exprSetParent((ExpressionNode)locator);
  }

}