001// Copyright 2006, 2007, 2010, 2011, 2012 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.tapestry5.ioc.internal.services; 016 017import org.apache.tapestry5.ioc.services.*; 018import org.apache.tapestry5.plastic.*; 019 020import java.lang.reflect.Method; 021 022public class PropertyShadowBuilderImpl implements PropertyShadowBuilder 023{ 024 private final PropertyAccess propertyAccess; 025 026 private final PlasticProxyFactory proxyFactory; 027 028 public PropertyShadowBuilderImpl(@Builtin 029 PlasticProxyFactory proxyFactory, 030 031 PropertyAccess propertyAccess) 032 { 033 this.proxyFactory = proxyFactory; 034 this.propertyAccess = propertyAccess; 035 } 036 037 public <T> T build(final Object source, final String propertyName, final Class<T> propertyType) 038 { 039 final Class sourceClass = source.getClass(); 040 final PropertyAdapter adapter = propertyAccess.getAdapter(sourceClass).getPropertyAdapter(propertyName); 041 042 // TODO: Perhaps extend ClassPropertyAdapter to do these checks? 043 044 if (adapter == null) 045 throw new RuntimeException(ServiceMessages.noSuchProperty(sourceClass, propertyName)); 046 047 if (!adapter.isRead()) 048 { 049 throw new RuntimeException( 050 String.format("Class %s does not provide an accessor ('getter') method for property '%s'.", 051 source.getClass().getName(), propertyName)); 052 } 053 054 if (!propertyType.isAssignableFrom(adapter.getType())) 055 throw new RuntimeException(ServiceMessages.propertyTypeMismatch(propertyName, sourceClass, 056 adapter.getType(), propertyType)); 057 058 ClassInstantiator instantiator = proxyFactory.createProxy(propertyType, new PlasticClassTransformer() 059 { 060 public void transform(PlasticClass plasticClass) 061 { 062 final PlasticField sourceField = plasticClass.introduceField(sourceClass, "source").inject(source); 063 064 PlasticMethod delegateMethod = plasticClass.introducePrivateMethod(propertyType.getName(), 065 "readProperty", null, null); 066 067 // You don't do this using MethodAdvice, because then we'd have to use reflection to access the read 068 // method. 069 070 delegateMethod.changeImplementation(new InstructionBuilderCallback() 071 { 072 public void doBuild(InstructionBuilder builder) 073 { 074 builder.loadThis().getField(sourceField); 075 builder.invoke(sourceClass, propertyType, adapter.getReadMethod().getName()); 076 077 // Now add the null check. 078 079 builder.dupe().when(Condition.NULL, new InstructionBuilderCallback() 080 { 081 public void doBuild(InstructionBuilder builder) 082 { 083 builder.throwException( 084 NullPointerException.class, 085 String.format( 086 "Unable to delegate method invocation to property '%s' of %s, because the property is null.", 087 propertyName, source)); 088 } 089 }); 090 091 builder.returnResult(); 092 } 093 }); 094 095 for (Method m : propertyType.getMethods()) 096 { 097 plasticClass.introduceMethod(m).delegateTo(delegateMethod); 098 } 099 100 plasticClass.addToString(String.format("<Shadow: property %s of %s>", propertyName, source)); 101 } 102 }); 103 104 return propertyType.cast(instantiator.newInstance()); 105 } 106}