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.jexl2.internal;
019import java.lang.reflect.InvocationTargetException;
020
021/**
022 * Specialized executor to get a property from an object.
023 * @since 2.0
024 */
025public final class PropertyGetExecutor extends AbstractExecutor.Get {
026    /** A static signature for method(). */
027    private static final Object[] EMPTY_PARAMS = {};
028    /** The property. */
029    private final String property;
030    
031    /**
032     * Creates an instance by attempting discovery of the get method.
033     * @param is the introspector
034     * @param clazz the class to introspect
035     * @param identifier the property to get
036     */
037    public PropertyGetExecutor(Introspector is, Class<?> clazz, String identifier) {
038        super(clazz, discover(is, clazz, identifier));
039        property = identifier;
040    }
041
042    /** {@inheritDoc} */
043    @Override
044    public Object getTargetProperty() {
045        return property;
046    }
047    
048    /** {@inheritDoc} */
049    @Override
050    public Object execute(Object o)
051        throws IllegalAccessException, InvocationTargetException {
052        return method == null ? null : method.invoke(o, (Object[]) null);
053    }
054
055    /** {@inheritDoc} */
056    @Override
057    public Object tryExecute(Object o, Object identifier) {
058        if (o != null && method !=  null
059            && property.equals(identifier)
060            && objectClass.equals(o.getClass())) {
061            try {
062                return method.invoke(o, (Object[]) null);
063            } catch (InvocationTargetException xinvoke) {
064                return TRY_FAILED; // fail
065            } catch (IllegalAccessException xill) {
066                return TRY_FAILED;// fail
067            }
068        }
069        return TRY_FAILED;
070    }
071
072    /**
073     * Discovers the method for a {@link PropertyGet}.
074     * <p>The method to be found should be named "get{P,p}property.</p>
075     *@param is the introspector
076     *@param clazz the class to find the get method from
077     *@param property the property name to find
078     *@return the method if found, null otherwise
079     */
080    static java.lang.reflect.Method discover(Introspector is,
081            final Class<?> clazz, String property) {
082        return discoverGet(is, "get", clazz, property);
083    }
084
085
086    /**
087     * Base method for boolean & object property get.
088     * @param is the introspector
089     * @param which "is" or "get" for boolean or object
090     * @param clazz The class being examined.
091     * @param property The property being addressed.
092     * @return The {get,is}{p,P}roperty method if one exists, null otherwise.
093     */
094    static java.lang.reflect.Method discoverGet(Introspector is,
095            String which, Class<?> clazz, String property) {
096        //  this is gross and linear, but it keeps it straightforward.
097        java.lang.reflect.Method method = null;
098        final int start = which.length(); // "get" or "is" so 3 or 2 for char case switch
099        // start with get<Property>
100        StringBuilder sb = new StringBuilder(which);
101        sb.append(property);
102        // uppercase nth char
103        char c = sb.charAt(start);
104        sb.setCharAt(start, Character.toUpperCase(c));
105        method = is.getMethod(clazz, sb.toString(), EMPTY_PARAMS);
106        //lowercase nth char
107        if (method == null) {
108            sb.setCharAt(start, Character.toLowerCase(c));
109            method = is.getMethod(clazz, sb.toString(), EMPTY_PARAMS);
110        }
111        return method;
112    }
113}
114