    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.util.List;
    018
    019    /**
    020     * A method of a {@linkplain PlasticClass transformed class}.
    021     * <p/>
    022     * No methods of this object should be invoked after the class transformation is
    023     * {@linkplain PlasticClassTransformation#createInstantiator() completed}.
    024     */
    025    public interface PlasticMethod extends AnnotationAccess
    026    {
    027        /**
    028         * Returns the PlasticClass containing this method.
    029         */
    030        PlasticClass getPlasticClass();
    031
    032        /**
    033         * Returns a representation of the method's name, return value, argument types, etc.
    034         */
    035        MethodDescription getDescription();
    036
    037        /**
    038         * Returns a handle that can be used to invoke a method of a transformed class instance.
    039         */
    040        MethodHandle getHandle();
    041
    042        /**
    043         * Clears the instructions for this method, and creates a new empty InstructionBuilder so that the implementation of
    044         * the method can be specified. This may be considered a kind of last resort when no other approach is sufficient.
    045         * <p/>
    046         * If the method is currently abstract, it will have its abstract flag cleared.
    047         * <p/>
    048         * If the method has advice, the advice is <em>not</em> lost but will instead wrap around the new method
    049         * implementation.
    050         *
    051         * @param callback passed the InstructionBuilder so that an implementation of the method can be created
    052         * @return this method, for further configuration
    053         */
    054        PlasticMethod changeImplementation(InstructionBuilderCallback callback);
    055
    056        /**
    057         * Adds advice to the method. Adding advice implicitly rewrites the implementation of the method (this occurs
    058         * inside at the end of the class transformation). When the method is invoked, control will flow
    059         * through the MethodAdvice <em>in the order they are added</em>. Each piece of advice will receive the
    060         * {@link MethodInvocation} and should invoke {@link MethodInvocation#proceed()} to pass control to the next piece
    061         * of advice (and ultimately, to the actual method invocation).
    062         * <p/>
    063         * If a method implementation is changed, using {@link #changeImplementation(InstructionBuilderCallback)}, that
    064         * change will be honored, but the logic will only be invoked at the end of the chain of MethodAdvice. Internally, a
    065         * new method is created with the same parameters, exceptions, return type and implementation (bytecode) as the
    066         * advised method, <em>then</em> the advised method's implementation is changed.
    067         * <p/>
    068         * Note additionally that a recursive method invocation will still invoke the MethodAdvice chain on each recursive
    069         * call (this is an intended side-effect of copying the exact bytecode of the method implementation.
    070         *
    071         * @param advice advice to add to the method
    072         * @return this method, for further configuration
    073         */
    074        PlasticMethod addAdvice(MethodAdvice advice);
    075
    076        /**
    077         * Changes the implementation of the method to delegate to the provided field. The field must implement the
    078         * correct interface (or extend the correct class). The original implementation of the method is lost,
    079         * though (as with {@link #changeImplementation(InstructionBuilderCallback)}), method advice is retained.
    080         *
    081         * @param field to delegate to
    082         * @return this method, for further configuration
    083         */
    084        PlasticMethod delegateTo(PlasticField field);
    085
    086        /**
    087         * Much like {@link #delegateTo(PlasticField)}, but the object to delegate to
    088         * is dynamically computed by another method of the class. The method should take no parameters
    089         * and must not return null, or throw any exceptions not compatible with the method being proxied.
    090         *
    091         * @param method to provide the dynamic delegate
    092         * @return this method, for further configuration
    093         */
    094        PlasticMethod delegateTo(PlasticMethod method);
    095
    096        /**
    097         * Returns access to the parameters of the method and, in particular,
    098         * the visible annotations on those parameters.
    099         */
    100        List<MethodParameter> getParameters();
    101
    102        /**
    103         * Returns true if the method is an override of a method from the parent class.
    104         *
    105         * @return true if the parent class contains a method with the name signature
    106         */
    107        boolean isOverride();
    108
    109        /**
    110         * Returns a short identifier for the method that includes the class name, the method name,
    111         * and the types of all parameters. This is often used when producing debugging output
    112         * about the method.
    113         *
    114         * @return short identifier
    115         * @see org.apache.tapestry5.plastic.MethodDescription#toShortString()
    116         */
    117        String getMethodIdentifier();
    118
    119        /**
    120         * Returns true if this method is type void.
    121         *
    122         * @return true for void methods.
    123         */
    124        boolean isVoid();
    125    }