Commons JXPath example source code file (PredicateContext.java)

This example Commons JXPath source code file (PredicateContext.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons JXPath tags/keywords

evalcontext, expression, expression, iterator, iterator, nameattributetest, nodepointer, nodepointer, object, object, predicatecontext, propertyownerpointer, propertypointer, string, util

The Commons JXPath PredicateContext.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.jxpath.ri.axes;

import java.util.Iterator;

import org.apache.commons.jxpath.ri.EvalContext;
import org.apache.commons.jxpath.ri.InfoSetUtil;
import org.apache.commons.jxpath.ri.compiler.Expression;
import org.apache.commons.jxpath.ri.compiler.NameAttributeTest;
import org.apache.commons.jxpath.ri.model.NodePointer;
import org.apache.commons.jxpath.ri.model.beans.PropertyOwnerPointer;
import org.apache.commons.jxpath.ri.model.beans.PropertyPointer;

/**
 * EvalContext that checks predicates.
 *
 * @author Dmitri Plotnikov
 * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
 */
public class PredicateContext extends EvalContext {
    private Expression expression;
    private boolean done = false;
    private Expression nameTestExpression;
    private PropertyPointer dynamicPropertyPointer;

    /**
     * Create a new PredicateContext.
     * @param parentContext parent context
     * @param expression compiled Expression
     */
    public PredicateContext(EvalContext parentContext, Expression expression) {
        super(parentContext);
        this.expression = expression;
        if (expression instanceof NameAttributeTest) {
            nameTestExpression =
                ((NameAttributeTest) expression).getNameTestExpression();
        }
    }

    public boolean nextNode() {
        if (done) {
            return false;
        }
        while (parentContext.nextNode()) {
            if (setupDynamicPropertyPointer()) {
                Object pred = nameTestExpression.computeValue(parentContext);
                String propertyName = InfoSetUtil.stringValue(pred);

                // At this point it would be nice to say:
                // dynamicPropertyPointer.setPropertyName(propertyName)
                // and then: dynamicPropertyPointer.isActual().
                // However some PropertyPointers, e.g. DynamicPropertyPointer
                // will declare that any property you ask for is actual.
                // That's not acceptable for us: we really need to know
                // if the property is currently declared. Thus,
                // we'll need to perform a search.
                boolean ok = false;
                String[] names = dynamicPropertyPointer.getPropertyNames();
                for (int i = 0; i < names.length; i++) {
                    if (names[i].equals(propertyName)) {
                        ok = true;
                        break;
                    }
                }
                if (ok) {
                    dynamicPropertyPointer.setPropertyName(propertyName);
                    position++;
                    return true;
                }
            }
            else {
                Object pred = expression.computeValue(parentContext);
                if (pred instanceof Iterator) {
                    if (!((Iterator) pred).hasNext()) {
                        return false;
                    }
                    pred = ((Iterator) pred).next();
                }

                if (pred instanceof NodePointer) {
                    pred = ((NodePointer) pred).getNode();
                }

                if (pred instanceof Number) {
                    int pos = (int) InfoSetUtil.doubleValue(pred);
                    position++;
                    done = true;
                    return parentContext.setPosition(pos);
                }
                if (InfoSetUtil.booleanValue(pred)) {
                    position++;
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Used for an optimized access to dynamic properties using the
     * "map[@name = 'name']" syntax
     * @return whether valid
     */
    private boolean setupDynamicPropertyPointer() {
        if (nameTestExpression == null) {
            return false;
        }

        NodePointer parent = parentContext.getCurrentNodePointer();
        if (parent == null) {
            return false;
        }
        parent = parent.getValuePointer();
        if (!(parent instanceof PropertyOwnerPointer)) {
            return false;
        }
        dynamicPropertyPointer =
            (PropertyPointer) ((PropertyOwnerPointer) parent)
                .getPropertyPointer()
                .clone();
        return true;
    }

    public boolean setPosition(int position) {
        if (nameTestExpression == null) {
            return setPositionStandard(position);
        }
        else {
            if (dynamicPropertyPointer == null && !setupDynamicPropertyPointer()) {
                return setPositionStandard(position);
            }
            if (position < 1
                || position > dynamicPropertyPointer.getLength()) {
                return false;
            }
            dynamicPropertyPointer.setIndex(position - 1);
            return true;
        }
    }

    public NodePointer getCurrentNodePointer() {
        if (position == 0 && !setPosition(1)) {
            return null;
        }
        if (dynamicPropertyPointer != null) {
            return dynamicPropertyPointer.getValuePointer();
        }
        return parentContext.getCurrentNodePointer();
    }

    public void reset() {
        super.reset();
        parentContext.reset();
        done = false;
    }

    public boolean nextSet() {
        reset();
        return parentContext.nextSet();
    }

    /**
     * Basic setPosition
     * @param position to set
     * @return whether valid
     */
    private boolean setPositionStandard(int position) {
        if (this.position > position) {
            reset();
        }

        while (this.position < position) {
            if (!nextNode()) {
                return false;
            }
        }
        return true;
    }
}