MapGetExecutor.java

/*
* Copyright 2016 Nabarun Mondal
* Licensed 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 com.noga.njexl.lang.internal;

import java.util.Map;

 /**
 * Specialized executor to get a property from a Map.
  * @since 2.0
 */
public final class MapGetExecutor extends AbstractExecutor.Get {
    /** The java.util.map.get method used as an active marker in MapGet. */
    private static final java.lang.reflect.Method MAP_GET =
            initMarker(Map.class, "get", Object.class);
    /** The property. */
    private final Object property;

    /**
     * Creates an instance checking for the Map interface.
     * @param is the introspector
     * @param clazz the class that might implement the map interface
     * @param key the key to use in map.get(key)
     */
    public MapGetExecutor(Introspector is, Class<?> clazz, Object key) {
        super(clazz, discover(clazz));
        property = key;
    }

    /** {@inheritDoc} */
    @Override
    public Object getTargetProperty() {
        return property;
    }
    
    /**
     * Get the property from the map.
     * @param obj the map.
     * @return map.get(property)
     */
    @Override
    public Object execute(final Object obj) {
        @SuppressWarnings("unchecked") // ctor only allows Map instances - see discover() method
        final Map<Object,?> map = (Map<Object, ?>) obj;
        return map.get(property);
    }

    /** {@inheritDoc} */
    @Override
    public Object tryExecute(final Object obj, Object key) {
        if (obj != null &&  method != null
            && objectClass.equals(obj.getClass())
            && (key == null || property.getClass().equals(key.getClass()))) {
            @SuppressWarnings("unchecked") // ctor only allows Map instances - see discover() method
            final Map<Object,?> map = (Map<Object, ?>) obj;
            return map.get(key);
        }
        return TRY_FAILED;
    }

    /**
     * Finds the method to perform 'get' on a map.
     * @param clazz the class to introspect
     * @return a marker method, map.get
     */
    static java.lang.reflect.Method discover(Class<?> clazz) {
        return (Map.class.isAssignableFrom(clazz))? MAP_GET : null;
    }
}