001    // Copyright 2009 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.ioc.services;
016    
017    import org.apache.tapestry5.ioc.MethodAdviceReceiver;
018    
019    /**
020     * An advisor that identifies methods which can be evaluated lazily and advises them. A method can be evaluated lazily
021     * if it returns an interface type and if it throws no checked exceptions. Lazy evaluation should be handled carefully,
022     * as if any of the parameters to a method are mutable, or the internal state of the invoked service changes, the lazily
023     * evaluated results may not match the immediately evaluated result. This effect is greatly exaggerated if the lazy
024     * return object is evaluated in a different thread than when it was generated.
025     * <p/>
026     * Another consideration is that exceptions that would occur immediately in the non-lazy case are also deferred, often
027     * losing much context in the process.
028     * <p/>
029     * Use laziness with great care.
030     * <p/>
031     * Use the {@link org.apache.tapestry5.ioc.annotations.NotLazy} annotation on methods that should not be advised.
032     *
033     * @since 5.1.0.0
034     */
035    public interface LazyAdvisor
036    {
037        void addLazyMethodInvocationAdvice(MethodAdviceReceiver methodAdviceReceiver);
038    
039    }