/*
* @(#)OnlyOneApplicablePolicyAlg.java
*
* Copyright 2003-2005 Sun Microsystems, Inc. All Rights Reserved.
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package com.sun.xacml.combine;
import java.net.URI;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import com.sun.xacml.AbstractPolicy;
import com.sun.xacml.EvaluationCtx;
import com.sun.xacml.MatchResult;
import com.sun.xacml.ctx.Result;
import com.sun.xacml.ctx.Status;
/**
* This is the standard Only One Applicable Policy combining algorithm. This is a special algorithm
* used at the root of a policy/pdp to make sure that pdp only selects one policy per request.
*
* @since 1.0
* @author Seth Proctor
*
* Adding generic type support by Christian Mueller (geotools)
*/
public class OnlyOneApplicablePolicyAlg extends PolicyCombiningAlgorithm {
/**
* The standard URN used to identify this algorithm
*/
public static final String algId = "urn:oasis:names:tc:xacml:1.0:policy-combining-algorithm:"
+ "only-one-applicable";
// a URI form of the identifier
private static final URI identifierURI = URI.create(algId);
/**
* Standard constructor.
*/
public OnlyOneApplicablePolicyAlg() {
super(identifierURI);
}
/**
* Applies the combining rule to the set of policies based on the evaluation context.
*
* @param context
* the context from the request
* @param parameters
* a (possibly empty) non-null <code>List</code> of <code>CombinerParameter<code>s
* @param policyElements
* the policies to combine
*
* @return the result of running the combining algorithm
*/
public Result combine(EvaluationCtx context, List<CombinerParameter> parameters,
List<? extends CombinerElement> policyElements) {
boolean atLeastOne = false;
AbstractPolicy selectedPolicy = null;
Iterator<? extends CombinerElement> it = policyElements.iterator();
while (it.hasNext()) {
AbstractPolicy policy = ((PolicyCombinerElement) (it.next())).getPolicy();
// see if the policy matches the context
MatchResult match = policy.match(context);
int result = match.getResult();
// if there is an error in trying to match any of the targets,
// we always return INDETERMINATE immediately
if (result == MatchResult.INDETERMINATE)
return new Result(Result.DECISION_INDETERMINATE, match.getStatus(), context
.getResourceId().encode());
if (result == MatchResult.MATCH) {
// if this isn't the first match, then this is an error
if (atLeastOne) {
List<String> code = new ArrayList<String>();
code.add(Status.STATUS_PROCESSING_ERROR);
String message = "Too many applicable policies";
return new Result(Result.DECISION_INDETERMINATE, new Status(code, message),
context.getResourceId().encode());
}
// if this was the first applicable policy in the set, then
// remember it for later
atLeastOne = true;
selectedPolicy = policy;
}
}
// if we got through the loop and found exactly one match, then
// we return the evaluation result of that policy
if (atLeastOne)
return selectedPolicy.evaluate(context);
// if we didn't find a matching policy, then we don't apply
return new Result(Result.DECISION_NOT_APPLICABLE, context.getResourceId().encode());
}
}