001    //
002    // Licensed under the Apache License, Version 2.0 (the "License");
003    // you may not use this file except in compliance with the License.
004    // You may obtain a copy of the License at
005    //
006    //     http://www.apache.org/licenses/LICENSE-2.0
007    //
008    // Unless required by applicable law or agreed to in writing, software
009    // distributed under the License is distributed on an "AS IS" BASIS,
010    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
011    // See the License for the specific language governing permissions and
012    // limitations under the License.
013    
014    package net.sf.tacos.annotations;
015    
016    import java.lang.reflect.Method;
017    import java.lang.reflect.Modifier;
018    
019    import org.apache.hivemind.ApplicationRuntimeException;
020    import org.apache.hivemind.Location;
021    import org.apache.hivemind.service.BodyBuilder;
022    import org.apache.hivemind.service.MethodSignature;
023    import org.apache.tapestry.annotations.MethodAnnotationEnhancementWorker;
024    import org.apache.tapestry.enhance.EnhancementOperation;
025    import org.apache.tapestry.enhance.EnhanceUtils;
026    import org.apache.tapestry.spec.IComponentSpecification;
027    import org.apache.tapestry.IComponent;
028    
029    /**
030     * @author Andreas Andreou
031     */
032    
033    public class CachedAnnotationWorker implements MethodAnnotationEnhancementWorker {
034    
035            public void performEnhancement(EnhancementOperation op, IComponentSpecification spec,
036                    Method method, Location location) {
037            Class<?> type = method.getReturnType();
038            if (type.equals(void.class))
039                        throw new ApplicationRuntimeException(
040                                        "Cached annotation cannot be used with a method that returns void");
041    
042            String fieldName = "_$cached$" + method.getName();
043            MethodSignature signature = new MethodSignature(method);
044    
045            op.addField(fieldName, type);
046    
047            BodyBuilder builder = createCacheMethod(signature, fieldName);
048            op.addMethod(Modifier.PUBLIC, signature, builder.toString(), location);
049    
050            extendCleanupAfterRender(op, fieldName);
051        }
052    
053        BodyBuilder createCacheMethod(MethodSignature sig, String cacheField)
054        {
055            BodyBuilder result = new BodyBuilder();
056    
057            result.begin();
058    
059            result.addln("if (this.{0}==null)", cacheField);
060            result.addln("this.{0} = super.{1}($$);", cacheField, sig.getName());
061    
062            result.addln("return this.{0};", cacheField);
063    
064            result.end();
065    
066            return result;
067        }
068    
069        void extendCleanupAfterRender(EnhancementOperation op, String fieldName)
070        {
071            BodyBuilder cleanupBody = new BodyBuilder();
072            cleanupBody.addln("{0} = null;", fieldName);
073            op.extendMethodImplementation(IComponent.class,
074                    EnhanceUtils.CLEANUP_AFTER_RENDER_SIGNATURE, cleanupBody.toString());
075        }
076    }