    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
    018    package org.apache.commons.jexl2.introspection;
    019
    020    /**
    021     * Interface for getting values that appear to be properties.
    022     * Ex.
    023     * <code>
    024     * ${foo.bar}
    025     * </code>
    026     * @since 1.0
    027     */
    028    public interface JexlPropertyGet {
    029        /**
    030         * Method used to get the property value of an object.
    031         *
    032         * @param obj the object to get the property value from.
    033         * @return the property value.
    034         * @throws Exception on any error.
    035         */
    036        Object invoke(Object obj) throws Exception;
    037
    038        /**
    039         * Attempts to reuse this JexlPropertyGet, checking that it is compatible with
    040         * the actual set of arguments.
    041         * @param obj the object to invoke the property get upon
    042         * @param key the property key to get
    043         * @return the result of the method invocation that should be checked by tryFailed to determine if it succeeded
    044         * or failed.
    045         */
    046        Object tryInvoke(Object obj, Object key);
    047
    048        /**
    049         * Checks whether a tryInvoke failed or not.
    050         * @param rval the value returned by tryInvoke
    051         * @return true if tryInvoke failed, false otherwise
    052         */
    053        boolean tryFailed(Object rval);
    054
    055        /**
    056         * Specifies if this JexlPropertyGet is cacheable and able to be reused for
    057         * this class of object it was returned for.
    058         *
    059         * @return true if can be reused for this class, false if not
    060         */
    061        boolean isCacheable();
    062    }