org.apache.ambari.server.controller.internal

Class SimplifyingPredicateVisitor

java.lang.Object

org.apache.ambari.server.controller.internal.SimplifyingPredicateVisitor

All Implemented Interfaces:

PredicateVisitor

public class SimplifyingPredicateVisitor
extends Object
implements PredicateVisitor

A predicate visitor used to simplify by doing the following ... 1) distribute across OR (e.g. A && ( B || C ) becomes ( A && B ) || ( A && C )). This is done because an individual back end request object can not handle OR. Instead we need to break up the predicate to form multiple requests and take the union of all the responses. 2) convert predicates based on unsupported properties to AlwaysPredicate. Unsupported properties are those not returned by the resource provider. For these properties we need to wait until the property provider that handles the property has been called. 3) convert predicates based on any operator other than == to AlwaysPredicate. The back end requests can not handle any operator other than equals. The complete predicate will get applied further down the line if necessary. After visiting a predicate, the visitor should be able to supply a list of predicates that can be used to generate requests to the backend, working around the restrictions above. Note that the results acquired using the generated predicates may be a super set of what is actually desired given the original predicate, but the original predicate will be applied at a suitable time down the line if required.

Constructor Summary

Constructors

Constructor and Description
SimplifyingPredicateVisitor(ResourceProvider provider) Constructor.

Method Summary

Modifier and Type	Method and Description
void	acceptAlwaysPredicate(AlwaysPredicate predicate)
void	acceptArrayPredicate(ArrayPredicate arrayPredicate)
void	acceptCategoryPredicate(CategoryPredicate predicate)
void	acceptComparisonPredicate(ComparisonPredicate predicate)
void	acceptUnaryPredicate(UnaryPredicate predicate)
List<Predicate>	getSimplifiedPredicates() Obtain a list of simplified predicates based on the rules described in the class documentation.

Methods inherited from class java.lang.Object

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

Constructor Detail

SimplifyingPredicateVisitor

public SimplifyingPredicateVisitor(ResourceProvider provider)

Constructor.

Parameters:

provider - associated resource provider

Method Detail

getSimplifiedPredicates

public List<Predicate> getSimplifiedPredicates()

Obtain a list of simplified predicates based on the rules described in the class documentation.

Returns:

a list of simplified predicates

acceptComparisonPredicate

public void acceptComparisonPredicate(ComparisonPredicate predicate)

Specified by:

acceptComparisonPredicate in interface PredicateVisitor

acceptArrayPredicate

public void acceptArrayPredicate(ArrayPredicate arrayPredicate)

Specified by:

acceptArrayPredicate in interface PredicateVisitor

acceptUnaryPredicate

public void acceptUnaryPredicate(UnaryPredicate predicate)

Specified by:

acceptUnaryPredicate in interface PredicateVisitor

acceptAlwaysPredicate

public void acceptAlwaysPredicate(AlwaysPredicate predicate)

Specified by:

acceptAlwaysPredicate in interface PredicateVisitor

acceptCategoryPredicate

public void acceptCategoryPredicate(CategoryPredicate predicate)

Specified by:

acceptCategoryPredicate in interface PredicateVisitor