alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Commons JXPath example source code file (CoreOperationCompare.java)

This example Commons JXPath source code file (CoreOperationCompare.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

collection, collection, coreoperationcompare, evalcontext, expression, expression, iterator, iterator, number, object, object, pointer, selfcontext, string, util

The Commons JXPath CoreOperationCompare.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.compiler;

import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;

import org.apache.commons.jxpath.Pointer;
import org.apache.commons.jxpath.ri.EvalContext;
import org.apache.commons.jxpath.ri.InfoSetUtil;
import org.apache.commons.jxpath.ri.axes.InitialContext;
import org.apache.commons.jxpath.ri.axes.SelfContext;

/**
 * Common superclass for the implementations of Expression for the operations
 * "=" and "!=".
 *
 * @author Dmitri Plotnikov
 * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
 */
public abstract class CoreOperationCompare extends CoreOperation {
    private boolean invert;

    /**
     * Create a new CoreOperationCompare.
     * @param arg1 left operand
     * @param arg2 right operand
     */
    public CoreOperationCompare(Expression arg1, Expression arg2) {
        this(arg1, arg2, false);
    }

    /**
     * Create a new CoreOperationCompare.
     * @param arg1 left operand
     * @param arg2 right operand
     * @param invert whether to invert (not) the comparison
     */
    protected CoreOperationCompare(Expression arg1, Expression arg2, boolean invert) {
        super(new Expression[] { arg1, arg2 });
        this.invert = invert;
    }

    public Object computeValue(EvalContext context) {
        return equal(context, args[0], args[1]) ? Boolean.TRUE : Boolean.FALSE;
    }

    protected int getPrecedence() {
        return COMPARE_PRECEDENCE;
    }

    protected boolean isSymmetric() {
        return true;
    }

    /**
     * Compares two values.
     * @param context evaluation context
     * @param left operand
     * @param right operand
     * @return whether left = right in XPath terms
     */
    protected boolean equal(EvalContext context, Expression left,
            Expression right) {
        Object l = left.compute(context);
        Object r = right.compute(context);

        if (l instanceof InitialContext) {
            ((EvalContext) l).reset();
        }

        if (l instanceof SelfContext) {
            l = ((EvalContext) l).getSingleNodePointer();
        }

        if (r instanceof InitialContext) {
            ((EvalContext) r).reset();
        }

        if (r instanceof SelfContext) {
            r = ((EvalContext) r).getSingleNodePointer();
        }

        if (l instanceof Collection) {
            l = ((Collection) l).iterator();
        }

        if (r instanceof Collection) {
            r = ((Collection) r).iterator();
        }

        if (l instanceof Iterator && r instanceof Iterator) {
            return findMatch((Iterator) l, (Iterator) r);
        }
        if (l instanceof Iterator) {
            return contains((Iterator) l, r);
        }
        if (r instanceof Iterator) {
            return contains((Iterator) r, l);
        }
        return equal(l, r);
    }

    /**
     * Learn whether it contains value.
     * @param it Iterator to check
     * @param value for which to look
     * @return whether value was found
     */
    protected boolean contains(Iterator it, Object value) {
        while (it.hasNext()) {
            Object element = it.next();
            if (equal(element, value)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Learn whether lit intersects rit.
     * @param lit left Iterator
     * @param rit right Iterator
     * @return boolean
     */
    protected boolean findMatch(Iterator lit, Iterator rit) {
        HashSet left = new HashSet();
        while (lit.hasNext()) {
            left.add(lit.next());
        }
        while (rit.hasNext()) {
            if (contains(left.iterator(), rit.next())) {
                return true;
            }
        }
        return false;
    }

    /**
     * Learn whether l equals r in XPath terms.
     * @param l left operand
     * @param r right operand
     * @return whether l = r
     */
    protected boolean equal(Object l, Object r) {
        if (l instanceof Pointer) {
            l = ((Pointer) l).getValue();
        }

        if (r instanceof Pointer) {
            r = ((Pointer) r).getValue();
        }

        boolean result;
        if (l instanceof Boolean || r instanceof Boolean) {
            result = l == r || InfoSetUtil.booleanValue(l) == InfoSetUtil.booleanValue(r);
        }
        else if (l instanceof Number || r instanceof Number) {
            //if either side is NaN, no comparison returns true:
            double ld = InfoSetUtil.doubleValue(l);
            if (Double.isNaN(ld)) {
                return false;
            }
            double rd = InfoSetUtil.doubleValue(r);
            if (Double.isNaN(rd)) {
                return false;
            }
            result = ld == rd;
        }
        else {
            if (l instanceof String || r instanceof String) {
                l = InfoSetUtil.stringValue(l);
                r = InfoSetUtil.stringValue(r);
            }
            result = l == r || l != null && l.equals(r);
        }
        return result ^ invert;
    }

}

Other Commons JXPath examples (source code examples)

Here is a short list of links related to this Commons JXPath CoreOperationCompare.java source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.