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.jexl3.internal.introspection;
019import java.lang.reflect.InvocationTargetException;
020import org.apache.commons.jexl3.JexlException;
021
022/**
023 * Specialized executor to get a property from an object.
024 * @since 2.0
025 */
026public final class PropertyGetExecutor extends AbstractExecutor.Get {
027    /** A static signature for method(). */
028    private static final Object[] EMPTY_PARAMS = {};
029    /** The property. */
030    private final String property;
031
032    /**
033     * Discovers a PropertyGetExecutor.
034     * <p>The method to be found should be named "get{P,p}property.</p>
035     *
036     * @param is the introspector
037     * @param clazz the class to find the get method from
038     * @param property the property name to find
039     * @return the executor if found, null otherwise
040     */
041    public static PropertyGetExecutor discover(final Introspector is, final Class<?> clazz, final String property) {
042        final java.lang.reflect.Method method = discoverGet(is, "get", clazz, property);
043        return method == null? null : new PropertyGetExecutor(clazz, method, property);
044    }
045
046    /**
047     * Creates an instance.
048     * @param clazz he class the get method applies to
049     * @param method the method held by this executor
050     * @param identifier the property to get
051     */
052    private PropertyGetExecutor(final Class<?> clazz, final java.lang.reflect.Method method, final String identifier) {
053        super(clazz, method);
054        property = identifier;
055    }
056
057    @Override
058    public Object getTargetProperty() {
059        return property;
060    }
061
062    @Override
063    public Object invoke(final Object o) throws IllegalAccessException, InvocationTargetException {
064        return method == null ? null : method.invoke(o, (Object[]) null);
065    }
066
067    @Override
068    public Object tryInvoke(final Object o, final Object identifier) {
069        if (o != null && method != null
070            && property.equals(castString(identifier))
071            && objectClass.equals(o.getClass())) {
072            try {
073                return method.invoke(o, (Object[]) null);
074            } catch (IllegalAccessException | IllegalArgumentException xill) {
075                return TRY_FAILED;// fail
076            } catch (final InvocationTargetException xinvoke) {
077                throw JexlException.tryFailed(xinvoke); // throw
078            }
079        }
080        return TRY_FAILED;
081    }
082
083    /**
084     * Base method for boolean and object property get.
085     * @param is the introspector
086     * @param which "is" or "get" for boolean or object
087     * @param clazz The class being examined.
088     * @param property The property being addressed.
089     * @return The {get,is}{p,P}roperty method if one exists, null otherwise.
090     */
091    static java.lang.reflect.Method discoverGet(final Introspector is,
092                                                final String which,
093                                                final Class<?> clazz,
094                                                final String property) {
095        if (property == null || property.isEmpty()) {
096            return null;
097        }
098        //  this is gross and linear, but it keeps it straightforward.
099        java.lang.reflect.Method method;
100        final int start = which.length(); // "get" or "is" so 3 or 2 for char case switch
101        // start with get<Property>
102        final StringBuilder sb = new StringBuilder(which);
103        sb.append(property);
104        // uppercase nth char
105        final char c = sb.charAt(start);
106        sb.setCharAt(start, Character.toUpperCase(c));
107        method = is.getMethod(clazz, sb.toString(), EMPTY_PARAMS);
108        //lowercase nth char
109        if (method == null) {
110            sb.setCharAt(start, Character.toLowerCase(c));
111            method = is.getMethod(clazz, sb.toString(), EMPTY_PARAMS);
112        }
113        return method;
114    }
115}
116