001    // Copyright 2005 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.tapestry.enhance;
016    
017    import org.apache.hivemind.ApplicationRuntimeException;
018    import org.apache.hivemind.Location;
019    import org.apache.hivemind.service.BodyBuilder;
020    import org.apache.hivemind.service.MethodSignature;
021    import org.apache.hivemind.util.Defense;
022    import org.apache.tapestry.engine.state.ApplicationStateManager;
023    import org.apache.tapestry.spec.InjectSpecification;
024    
025    import java.lang.reflect.Modifier;
026    
027    /**
028     * Injects a boolean property that indicates if a particular application state object already
029     * exists. This is useful in situations where you are trying to prevent the creation of the ASO (and
030     * thus, prevent the creation of the HttpSession).
031     * 
032     * @author Howard M. Lewis Ship
033     * @since 4.0
034     */
035    public class InjectStateFlagWorker implements InjectEnhancementWorker
036    {
037        private ApplicationStateManager _applicationStateManager;
038    
039        public void performEnhancement(EnhancementOperation op, InjectSpecification spec)
040        {
041            injectStateFlag(op, spec.getObject(), spec.getProperty(), spec.getLocation());
042        }
043    
044        void injectStateFlag(EnhancementOperation op, String objectName, String propertyName,
045                Location location)
046        {
047            Defense.notNull(op, "op");
048            Defense.notNull(objectName, "objectName");
049            Defense.notNull(propertyName, "propertyName");
050    
051            Class propertyType = op.getPropertyType(propertyName);
052    
053            // null means no property at all; it's just in the XML
054            // which is ok. Otherwise, make sure it is exactly boolean.
055    
056            if (propertyType != null && propertyType != boolean.class)
057                throw new ApplicationRuntimeException(EnhanceMessages.mustBeBoolean(propertyName),
058                        location, null);
059    
060            op.claimReadonlyProperty(propertyName);
061    
062            String managerField = op.addInjectedField(
063                    "_$applicationStateManager",
064                    ApplicationStateManager.class,
065                    _applicationStateManager);
066    
067            BodyBuilder builder = new BodyBuilder();
068            builder.begin();
069            builder.add("return {0}.exists(", managerField);
070            builder.addQuoted(objectName);
071            builder.addln(");");
072            builder.end();
073    
074            String methodName = op.getAccessorMethodName(propertyName);
075    
076            MethodSignature sig = new MethodSignature(boolean.class, methodName, null, null);
077    
078            op.addMethod(Modifier.PUBLIC, sig, builder.toString(), location);
079        }
080    
081        public void setApplicationStateManager(ApplicationStateManager applicationStateManager)
082        {
083            _applicationStateManager = applicationStateManager;
084        }
085    
086    }