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    }