    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
    015    package org.apache.tapestry5.plastic;
    016
    017    import 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     */
    026    public 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    }