    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.jxpath.ri.compiler;
    019
    020import org.apache.commons.jxpath.ri.EvalContext;
    021import org.apache.commons.jxpath.ri.axes.InitialContext;
    022import org.apache.commons.jxpath.ri.axes.NodeSetContext;
    023import org.apache.commons.jxpath.ri.axes.PredicateContext;
    024import org.apache.commons.jxpath.ri.axes.SimplePathInterpreter;
    025import org.apache.commons.jxpath.ri.axes.UnionContext;
    026import org.apache.commons.jxpath.ri.model.NodePointer;
    027
    028/**
    029 * An element of the parse tree that represents an expression path, which is a path that starts with an expression like a function call: {@code getFoo(.)
    030 * /bar}.
    031 */
    032public class ExpressionPath extends Path {
    033
    034    private final Expression expression;
    035    private final Expression[] predicates;
    036    private boolean basicKnown;
    037    private boolean basic;
    038
    039    /**
    040     * Constructs a new ExpressionPath.
    041     *
    042     * @param expression Expression
    043     * @param predicates to execute
    044     * @param steps      navigation
    045     */
    046    public ExpressionPath(final Expression expression, final Expression[] predicates, final Step[] steps) {
    047        super(steps);
    048        this.expression = expression;
    049        this.predicates = predicates;
    050    }
    051
    052    @Override
    053    public Object compute(final EvalContext context) {
    054        return expressionPath(context, false);
    055    }
    056
    057    /**
    058     * Returns true if the root expression or any of the predicates or the path steps are context dependent.
    059     *
    060     * @return boolean
    061     */
    062    @Override
    063    public boolean computeContextDependent() {
    064        if (expression.isContextDependent()) {
    065            return true;
    066        }
    067        if (predicates != null) {
    068            for (final Expression predicate : predicates) {
    069                if (predicate.isContextDependent()) {
    070                    return true;
    071                }
    072            }
    073        }
    074        return super.computeContextDependent();
    075    }
    076
    077    @Override
    078    public Object computeValue(final EvalContext context) {
    079        return expressionPath(context, true);
    080    }
    081
    082    /**
    083     * Walks an expression path (a path that starts with an expression)
    084     *
    085     * @param evalContext base context
    086     * @param firstMatch  whether to return the first match found
    087     * @return Object found
    088     */
    089    protected Object expressionPath(final EvalContext evalContext, final boolean firstMatch) {
    090        final Object value = expression.compute(evalContext);
    091        EvalContext context;
    092        if (value instanceof InitialContext) {
    093            // This is an optimization. We can avoid iterating through a
    094            // collection if the context bean is in fact one.
    095            context = (InitialContext) value;
    096        } else if (value instanceof EvalContext) {
    097            // UnionContext will collect all values from the "value" context
    098            // and treat the whole thing as a big collection.
    099            context = new UnionContext(evalContext, new EvalContext[] { (EvalContext) value });
    100        } else {
    101            context = evalContext.getRootContext().getConstantContext(value);
    102        }
    103        if (firstMatch && isSimpleExpressionPath() && !(context instanceof NodeSetContext)) {
    104            final EvalContext ctx = context;
    105            final NodePointer ptr = (NodePointer) ctx.getSingleNodePointer();
    106            if (ptr != null && (ptr.getIndex() == NodePointer.WHOLE_COLLECTION || predicates == null || predicates.length == 0)) {
    107                return SimplePathInterpreter.interpretSimpleExpressionPath(evalContext, ptr, predicates, getSteps());
    108            }
    109        }
    110        if (predicates != null) {
    111            for (int j = 0; j < predicates.length; j++) {
    112                if (j != 0) {
    113                    context = new UnionContext(context, new EvalContext[] { context });
    114                }
    115                context = new PredicateContext(context, predicates[j]);
    116            }
    117        }
    118        return firstMatch ? (Object) getSingleNodePointerForSteps(context) : evalSteps(context);
    119    }
    120
    121    /**
    122     * Gets the expression.
    123     *
    124     * @return Expression
    125     */
    126    public Expression getExpression() {
    127        return expression;
    128    }
    129
    130    /**
    131     * Predicates are the expressions in brackets that may follow the root expression of the path.
    132     *
    133     * @return Expression[]
    134     */
    135    public Expression[] getPredicates() {
    136        return predicates;
    137    }
    138
    139    /**
    140     * Recognized paths formatted as {@code $x[3]/foo[2]}. The evaluation of such "simple" paths is optimized and streamlined.
    141     *
    142     * @return boolean
    143     */
    144    public synchronized boolean isSimpleExpressionPath() {
    145        if (!basicKnown) {
    146            basicKnown = true;
    147            basic = isSimplePath() && areBasicPredicates(getPredicates());
    148        }
    149        return basic;
    150    }
    151
    152    @Override
    153    public String toString() {
    154        final StringBuilder buffer = new StringBuilder();
    155        if (expression instanceof CoreOperation || expression instanceof ExpressionPath || expression instanceof LocationPath) {
    156            buffer.append('(');
    157            buffer.append(expression);
    158            buffer.append(')');
    159        } else {
    160            buffer.append(expression);
    161        }
    162        if (predicates != null) {
    163            for (final Expression predicate : predicates) {
    164                buffer.append('[');
    165                buffer.append(predicate);
    166                buffer.append(']');
    167            }
    168        }
    169        final Step[] steps = getSteps();
    170        if (steps != null) {
    171            for (final Step step : steps) {
    172                buffer.append("/");
    173                buffer.append(step);
    174            }
    175        }
    176        return buffer.toString();
    177    }
    178}