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.introspection;
019
020/**
021 * Interface used for regular method invocation.
022 * Ex.
023 * <code>
024 * ${foo.bar()}
025 * </code>
026 * 
027 * @since 1.0
028 */
029public interface JexlMethod {
030    /**
031     * Invocation method, called when the method invocation should be performed
032     * and a value returned.
033
034     * @param obj the object
035     * @param params method parameters.
036     * @return the result
037     * @throws Exception on any error.
038     */
039    Object invoke(Object obj, Object[] params) throws Exception;
040
041    /**
042     * Attempts to reuse this JexlMethod, checking that it is compatible with
043     * the actual set of arguments.
044     * Related to isCacheable since this method is often used with cached JexlMethod instances.
045     * @param obj the object to invoke the method upon
046     * @param name the method name
047     * @param params the method arguments
048     * @return the result of the method invocation that should be checked by tryFailed to determine if it succeeded
049     * or failed.
050     */
051    Object tryInvoke(String name, Object obj, Object[] params);
052
053    /**
054     * Checks whether a tryInvoke failed or not.
055     * @param rval the value returned by tryInvoke
056     * @return true if tryInvoke failed, false otherwise
057     */
058    boolean tryFailed(Object rval);
059
060    /**
061     * Specifies if this JexlMethod is cacheable and able to be reused for this
062     * class of object it was returned for.
063     * 
064     * @return true if can be reused for this class, false if not
065     */
066    boolean isCacheable();
067
068    /**
069     * returns the return type of the method invoked.
070     * @return return type
071     */
072    Class<?> getReturnType();
073}