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
015package org.apache.tapestry.enhance;
016
017import java.lang.reflect.Modifier;
018
019import org.apache.hivemind.Location;
020import org.apache.hivemind.service.BodyBuilder;
021import org.apache.hivemind.service.ClassFabUtils;
022import org.apache.hivemind.service.MethodSignature;
023import org.apache.hivemind.util.Defense;
024import org.apache.tapestry.engine.state.ApplicationStateManager;
025import org.apache.tapestry.event.PageDetachListener;
026import org.apache.tapestry.spec.InjectSpecification;
027
028/**
029 * Worker for injecting application state objects as properties of the component. These properties
030 * are read/write and must be "live" (changes are propogated back into the
031 * {@link org.apache.tapestry.engine.state.ApplicationStateManager}). They should also cache in a
032 * local variable for efficiency, and clear out that variable at the end of the request.
033 * 
034 * @author Howard M. Lewis Ship
035 * @since 4.0
036 */
037public class InjectStateWorker implements InjectEnhancementWorker
038{
039    private ApplicationStateManager _applicationStateManager;
040
041    public void performEnhancement(EnhancementOperation op, InjectSpecification spec)
042    {
043        injectState(op, spec.getObject(), spec.getProperty(), spec.getLocation());
044    }
045
046    void injectState(EnhancementOperation op, String objectName, String propertyName,
047            Location location)
048    {
049        Defense.notNull(op, "op");
050        Defense.notNull(objectName, "objectName");
051        Defense.notNull(propertyName, "propertyName");
052
053        Class propertyType = EnhanceUtils.extractPropertyType(op, propertyName, null);
054        String fieldName = "_$" + propertyName;
055
056        // State properties are read/write
057
058        op.claimProperty(propertyName);
059
060        op.addField(fieldName, propertyType);
061
062        String managerField = op.addInjectedField(
063                "_$applicationStateManager",
064                ApplicationStateManager.class,
065                _applicationStateManager);
066
067        BodyBuilder builder = new BodyBuilder();
068
069        // Accessor
070
071        builder.begin();
072        builder.addln("if ({0} == null)", fieldName);
073        builder.addln("  {0} = ({1}) {2}.get(\"{3}\");", new Object[]
074        { fieldName, ClassFabUtils.getJavaClassName(propertyType), managerField, objectName });
075        builder.addln("return {0};", fieldName);
076        builder.end();
077
078        String methodName = op.getAccessorMethodName(propertyName);
079
080        MethodSignature sig = new MethodSignature(propertyType, methodName, null, null);
081
082        op.addMethod(Modifier.PUBLIC, sig, builder.toString(), location);
083
084        // Mutator
085
086        builder.clear();
087        builder.begin();
088        builder.addln("{0}.store(\"{1}\", $1);", managerField, objectName);
089        builder.addln("{0} = $1;", fieldName);
090        builder.end();
091
092        sig = new MethodSignature(void.class, EnhanceUtils.createMutatorMethodName(propertyName),
093                new Class[]
094                { propertyType }, null);
095
096        op.addMethod(Modifier.PUBLIC, sig, builder.toString(), location);
097
098        // Extend pageDetached() to clean out the cached field value.
099
100        op.extendMethodImplementation(
101                PageDetachListener.class,
102                EnhanceUtils.PAGE_DETACHED_SIGNATURE,
103                fieldName + " = null;");
104    }
105
106    public void setApplicationStateManager(ApplicationStateManager applicationStateManager)
107    {
108        _applicationStateManager = applicationStateManager;
109    }
110}