    001// Copyright 2011 The Apache Software Foundation
    002//
    003// Licensed under the Apache License, Version 2.0 (the "License");
    004// you may not use this file except in compliance with the License.
    005// You may obtain a copy of the License at
    006//
    007// http://www.apache.org/licenses/LICENSE-2.0
    008//
    009// Unless required by applicable law or agreed to in writing, software
    010// distributed under the License is distributed on an "AS IS" BASIS,
    011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012// See the License for the specific language governing permissions and
    013// limitations under the License.
    014
    015package org.apache.tapestry5.plastic;
    016
    017import java.lang.reflect.Method;
    018
    019/**
    020 * A representation of the invocation of a method that allows the behavior of the method to be advised: either by
    021 * changing parameter values, or by changing the return value, or by catch or throwing different exceptions. Provides
    022 * access to annotations on the advised method.
    023 *
    024 * @see MethodAdvice
    025 */
    026public interface MethodInvocation extends MethodInvocationResult, AnnotationAccess
    027{
    028    /** The instance on which the method was originally invoked. */
    029    Object getInstance();
    030
    031    InstanceContext getInstanceContext();
    032
    033    /**
    034     * Proceed with the method invocation, either chaining into the next {@link MethodAdvice} added to the method, or
    035     * ultimately into the actual method implementation. The method may throw a checked exception, which will be caught
    036     * and be reported as {@link #didThrowCheckedException()}.
    037     *
    038     * @return this method invocation, for a fluent API
    039     */
    040    MethodInvocation proceed();
    041
    042    /**
    043     * Overrides the return value of the method. The value provided will be cast to the actual return type
    044     * (or, if the return type is a primitive value, the value will be cast to the corresponding wrapper type and then
    045     * converted to a primitive).
    046     * <p>
    047     * Overriding the return value clears any checked exception.
    048     *
    049     * @param returnValue
    050     * @return this method invocation, for a fluent API
    051     * @throws NullPointerException
    052     *             if the method's return type is a primitive and null is provided
    053     */
    054    MethodInvocation setReturnValue(Object returnValue);
    055
    056    /**
    057     * Returns the parameter at the given index. Primitive types will be wrapped as they are returned.
    058     *
    059     * @param index
    060     *            of parameter to access
    061     * @return parameter value
    062     */
    063    Object getParameter(int index);
    064
    065    /**
    066     * Changes a parameter value. The value will be cast to the parameter's type. For primitive types, the
    067     * value will be cast to the corresponding wrapper type.
    068     *
    069     * @param index
    070     *            index of parameter to modify
    071     * @param newValue
    072     *            new value for parameter
    073     * @return this method invocation, for a fluent API
    074     */
    075    MethodInvocation setParameter(int index, Object newValue);
    076
    077    /**
    078     * Sets the checked exception; this can be used to indicate failure for the method, or
    079     * to cancel the thrown exception (by setting the exception to null).
    080     *
    081     * @param exception
    082     *            new checked exception, or null
    083     * @return this method invocation, for a fluent API
    084     */
    085    MethodInvocation setCheckedException(Exception exception);
    086
    087    /** Returns the method being invoked. */
    088    Method getMethod();
    089}