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## com.caucho.xpath
Class XPath

    java.lang.Object
      |
      +--com.caucho.xpath.XPath

public class XPath
extends java.lang.Object

Public facade for selecting nodes and creating match patterns.

Applications can select nodes directly from the XPath facade. For example, ``

     Node verse = XPath.find("chapter/verse", node);

For greater efficiency, applications can also precompile the match patterns. ``

     Pattern pattern = XPath.parseSelect("chapter/verse");
     Node verse = pattern.find(node);

XPath can also return values based on XPath expressions, following the XPath expression syntax. Applications can use the expressions for the equivalent of xsl:value-of ``

     Expr expr = XPath.parseExpr("chapter/verse/@id + 1");
     double value = expr.evalNumber(node);

To support the XPath pattern variables, XPath uses an environment object. Most applications will not need to use it.

Method Summary
`static Env` | `createEnv()` Creates a new variable environment.
`static Env` | `createEnv(Env global)` Creates a new variable environment based on an old environment.
`static double` | `evalNumber(java.lang.String query, Node node)` Evaluates an XPath expression, returning a double.
`static java.lang.Object` | `evalObject(java.lang.String query, Node node)` Evaluates an XPath expression, returning an object
`static java.lang.String` | `evalString(java.lang.String query, Node node)` Evaluates an XPath expression, returning a string.
`static Node` | `find(java.lang.String query, Node node)` Finds a node based on an XPath pattern.
`static void` | `freeEnv(Env env)` Free an environment.
`static Expr` | `parseExpr(java.lang.String query)` Parses an XPath expression for later evaluation.
`static Expr` | `parseExpr(java.lang.String query, NamespaceContext namespace)` Parses an XPath expression for later evaluation.
`static Expr` | `parseExpr(java.lang.String query, NamespaceContext namespace, Pattern nodeList)` Parses an XPath expression for later evaluation.
`static Pattern` | `parseMatch(java.lang.String query)` Create a node match pattern.
`static Pattern` | `parseMatch(java.lang.String query, NamespaceContext namespace)` Create a node match pattern.
`static Pattern` | `parseSelect(java.lang.String query)` Create a node selection pattern.
`static Pattern` | `parseSelect(java.lang.String query, NamespaceContext namespace)` Create a node selection pattern.
`static java.util.Iterator` | `select(java.lang.String query, Node node)` Selects all node matching an XPath pattern

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Method Detail

### find

    public static Node find(java.lang.String query,
                            Node node)
                     throws XPathParseException

  Finds a node based on an XPath pattern. The pattern is relative to the node so `XPath.find("child", node)` will find children, not grandchildren.
  Parameters:
    `query` - XPath select pattern.
    `node` - XML node to start searching from.
  Returns:
    The first matching node in document order.

### select

    public static java.util.Iterator select(java.lang.String query,
                                            Node node)
                                     throws XPathParseException

  Selects all node matching an XPath pattern
  Parameters:
    `query` - XPath select pattern.
    `node` - XML node to start searching from.
  Returns:
    An iterator of nodes matching the pattern.

### parseSelect

    public static Pattern parseSelect(java.lang.String query,
                                      NamespaceContext namespace)
                               throws XPathParseException

  Create a node selection pattern. The pattern matches relative to the current node.

  XSLT uses this version of parseSelect for proper namespace matching.

  Parameters:
    `query` - XPath select pattern.
    `namespace` - the appropriate namespace mappings
  Returns:
    a pattern that can later select nodes.

### parseSelect

    public static Pattern parseSelect(java.lang.String query)
                               throws XPathParseException

  Create a node selection pattern. The pattern matches relative to the current node.
  Parameters:
    `query` - XPath select pattern.
  Returns:
    a pattern that can later select nodes.

### parseMatch

    public static Pattern parseMatch(java.lang.String query,
                                     NamespaceContext namespace)
                              throws XPathParseException

  Create a node match pattern. Match patterns are intended to test if a node matches the pattern. They do not work well for finding or selecting patterns. Essentially, a match pattern of 'foo[@bar]' is equivalent to a select pattern of '//foo[@bar]', but with less overhead.
  Parameters:
    `query` - XPath match pattern.
    `namespace` - the appropriate namespace mappings.
  Returns:
    a pattern that can later be used for isMatch.

### parseMatch

    public static Pattern parseMatch(java.lang.String query)
                              throws XPathParseException

  Create a node match pattern. Match patterns are intended to test if a node matches the pattern. They do not work well for finding or selecting patterns. Essentially, a match pattern of 'foo[@bar]' is equivalent to a select pattern of '//foo[@bar]', but with less overhead.
  Parameters:
    `query` - XPath match pattern.
  Returns:
    a pattern that can later be used for isMatch.

### evalString

    public static java.lang.String evalString(java.lang.String query,
                                              Node node)
                                       throws XPathParseException

  Evaluates an XPath expression, returning a string. evalString works like the XSL `value-of` element.

  For example, to get the value of an attribute use: ``

       String value = XPath.evalString("@id", node);

  Parameters:
    `query` - XPath expression
    `node` - the node context
  Returns:
    the string result of the expression.

### evalNumber

    public static double evalNumber(java.lang.String query,
                                    Node node)
                             throws XPathParseException

  Evaluates an XPath expression, returning a double.
  Parameters:
    `query` - XPath expression
    `node` - the node context
  Returns:
    the number result of the expression.

### evalObject

    public static java.lang.Object evalObject(java.lang.String query,
                                              Node node)
                                       throws XPathParseException

  Evaluates an XPath expression, returning an object
  Parameters:
    `query` - XPath expression
    `node` - the node context
  Returns:
    the result of the expression.

### parseExpr

    public static Expr parseExpr(java.lang.String query,
                                 NamespaceContext namespace,
                                 Pattern nodeList)
                          throws XPathParseException

  Parses an XPath expression for later evaluation.
  Parameters:
    `query` - XPath expression
    `namespace` - namespace context
    `nodeList` - containing nodeList pattern
  Returns:
    the compiled expression

### parseExpr

    public static Expr parseExpr(java.lang.String query,
                                 NamespaceContext namespace)
                          throws XPathParseException

  Parses an XPath expression for later evaluation.
  Parameters:
    `query` - XPath expression
    `namespace` - namespace context
  Returns:
    the compiled expression

### parseExpr

    public static Expr parseExpr(java.lang.String query)
                          throws XPathParseException

  Parses an XPath expression for later evaluation.
  Parameters:
    `query` - XPath expression
  Returns:
    the result of the expression.

### createEnv

    public static Env createEnv()

  Creates a new variable environment.

### createEnv

    public static Env createEnv(Env global)

  Creates a new variable environment based on an old environment.

  This lets environments share globals even through function calls.

### freeEnv

    public static void freeEnv(Env env)

  Free an environment.

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