nesstar.api
Class PathIterator

java.lang.Object
  nesstar.api.PathIterator

public class PathIterator
extends Object

An iterator on a path. A path is a, possibly empty, sequence of path steps each one representing a property traversal. For example .children[1].variables[2] is a path composed by two steps. The first represent the traversal of the children property that returns a collection of elements followed by the extraction of the first element of the returned collection. In API terms this would translate to the expression: context.getChildren().get(1). The context is the object with respect to which the path is defined. If the path derives from a query then the context would be the queried object (e.g., a catalog)

Created:

26 April 2002

Constructor Summary

PathIterator(RDFObject obj)

PathIterator(String path)
Create a path iterator on the given path

Method Summary

static void	dbg(String msg) Method
static int	getIndex(String step)
String	getPath()
static PathIterator[]	getPathIterators(String paths)
static String	getProperty(String step)
Object	nextObj(Object context) Apply the current traversal element to the context object
String	nextStep()
Object	traversePath(Object context) Traverse the path starting from the given context and return the result object Useful for testing and as an example of path traversal

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PathIterator

public PathIterator(RDFObject obj)
             throws Exception

Parameters:

an - object with an iniatialised 'path' property

Throws:

Exception

PathIterator

public PathIterator(String path)

Create a path iterator on the given path

Parameters:

path -

Method Detail

getPathIterators

public static PathIterator[] getPathIterators(String paths)

Parameters:

paths - a ";" separate list of paths as returned by the PathsTo operations (e.g. Study2.PathsTo(nesstar.rdf.RDFObject)).

Returns:

an array of PathIterators, one per path

getProperty

public static String getProperty(String step)

Parameters:

step - the step, e.g.: children[3]

Returns:

the property part of the step, e.g.: children

getIndex

public static int getIndex(String step)

Parameters:

step - the step, e.g.: children[3]

Returns:

the index part of the step, e.g.: 3

dbg

public static void dbg(String msg)

Method

Parameters:

msg -

getPath

public String getPath()

nextStep

public String nextStep()

Returns:

the next step of the path or null if there are no more steps

nextObj

public Object nextObj(Object context)
               throws Exception

Apply the current traversal element to the context object

Parameters:

context - the object to which the traversal is to be applied

Returns:

the object that is obtained by traversing the current path property from the context

Throws:

Exception

traversePath

public Object traversePath(Object context)
                    throws Exception

Traverse the path starting from the given context and return the result object Useful for testing and as an example of path traversal

Parameters:

context -

Returns:

Throws:

Exception