org.apache.directory.api.ldap.model.filter
Class BranchNormalizedVisitor

java.lang.Object
  org.apache.directory.api.ldap.model.filter.BranchNormalizedVisitor

All Implemented Interfaces:

FilterVisitor

public class BranchNormalizedVisitor
extends Object
implements FilterVisitor

Visitor which traverses a filter tree while normalizing the branch node order. Filter expressions can change the order of expressions in branch nodes without effecting the logical meaning of the expression. This visitor orders the children of expression tree branch nodes consistantly. It is really useful for comparing expression trees which may be altered for performance or altered because of codec idiosyncracies: for example the SNACC4J codec uses a hashmap to store expressions in a sequence which rearranges the order of children based on object hashcodes. We need this visitor to remove such inconsitancies in order hence normalizing the branch node's child order.

Author:

Apache Directory Project

Constructor Summary

BranchNormalizedVisitor()

Method Summary

boolean	canVisit(ExprNode node) Checks to see if a node can be visited.
static String	getNormalizedFilter(ExprNode filter) Normalizes a filter expression to a canonical representation while retaining logical meaning of the expression.
static String	getNormalizedFilter(SchemaManager schemaManager, String filter) Normalizes a filter expression to a canonical representation while retaining logical meaning of the expression.
List<ExprNode>	getOrder(BranchNode node, List<ExprNode> children) Get the array of children to visit sequentially to determine the order of child visitations.
boolean	isPrefix() Determines whether the visitation order is prefix or postfix.
Object	visit(ExprNode node) Visits a filter expression AST using a specific visitation order.

Methods inherited from class java.lang.Object

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

Constructor Detail

BranchNormalizedVisitor

public BranchNormalizedVisitor()

Method Detail

visit

public Object visit(ExprNode node)

Description copied from interface: FilterVisitor

Visits a filter expression AST using a specific visitation order.

Specified by:

visit in interface FilterVisitor

Parameters:

node - the node to visit

Returns:

node the resulting modified node

canVisit

public boolean canVisit(ExprNode node)

Description copied from interface: FilterVisitor

Checks to see if a node can be visited.

Specified by:

canVisit in interface FilterVisitor

Parameters:

node - the node to be visited

Returns:

whether or node the node should be visited

isPrefix

public boolean isPrefix()

Description copied from interface: FilterVisitor

Determines whether the visitation order is prefix or postfix.

Specified by:

isPrefix in interface FilterVisitor

Returns:

true if the visitation is in prefix order, false otherwise.

getOrder

public List<ExprNode> getOrder(BranchNode node,
                               List<ExprNode> children)

Description copied from interface: FilterVisitor

Get the array of children to visit sequentially to determine the order of child visitations. Some children may not be returned at all if canVisit() returns false on them.

Specified by:

getOrder in interface FilterVisitor

Parameters:

node - the parent branch node

children - the child node array

Returns:

the new reordered array of children

getNormalizedFilter

public static String getNormalizedFilter(SchemaManager schemaManager,
                                         String filter)
                                  throws ParseException

Normalizes a filter expression to a canonical representation while retaining logical meaning of the expression.

Parameters:

filter - the filter to normalize

Returns:

the normalized version of the filter

Throws:

ParseException - if the filter is malformed

getNormalizedFilter

public static String getNormalizedFilter(ExprNode filter)

Normalizes a filter expression to a canonical representation while retaining logical meaning of the expression.

Parameters:

filter - the filter to normalize

Returns:

the normalized String version of the filter