// Copyright 2004 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package org.apache.tapestry.enhance;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.tapestry.ApplicationRuntimeException;
import org.apache.tapestry.IResourceResolver;
import org.apache.tapestry.Tapestry;
import org.apache.tapestry.engine.IComponentClassEnhancer;
import org.apache.tapestry.enhance.javassist.EnhancedClassFactory;
import org.apache.tapestry.spec.IComponentSpecification;
/**
* Default implementation of {@link IComponentClassEnhancer}.
*
* @author Howard Lewis Ship
* @version $Id: DefaultComponentClassEnhancer.java,v 1.14 2004/02/19 17:37:52 hlship Exp $
* @since 3.0
*
**/
public class DefaultComponentClassEnhancer implements IComponentClassEnhancer
{
private static final Log LOG = LogFactory.getLog(DefaultComponentClassEnhancer.class);
/**
* Map of Class, keyed on IComponentSpecification.
*
**/
private Map _cachedClasses;
private IResourceResolver _resolver;
private IEnhancedClassFactory _factory;
public DefaultComponentClassEnhancer(IResourceResolver resolver)
{
_cachedClasses = Collections.synchronizedMap(new HashMap());
_resolver = resolver;
_factory = createEnhancedClassFactory();
}
protected IEnhancedClassFactory createEnhancedClassFactory()
{
return new EnhancedClassFactory(getResourceResolver());
}
public synchronized void reset()
{
_cachedClasses.clear();
_factory.reset();
}
public IResourceResolver getResourceResolver()
{
return _resolver;
}
public Class getEnhancedClass(IComponentSpecification specification, String className)
{
Class result = getCachedClass(specification);
if (result == null)
{
synchronized (this)
{
result = getCachedClass(specification);
if (result == null)
{
result = constructComponentClass(specification, className);
storeCachedClass(specification, result);
}
}
}
return result;
}
protected void storeCachedClass(IComponentSpecification specification, Class cachedClass)
{
_cachedClasses.put(specification, cachedClass);
}
protected Class getCachedClass(IComponentSpecification specification)
{
return (Class) _cachedClasses.get(specification);
}
/**
* Returns the class to be used for the component, which is either
* the class with the given name, or an enhanced subclass.
*
**/
protected Class constructComponentClass(
IComponentSpecification specification,
String className)
{
Class result = null;
try
{
result = _resolver.findClass(className);
}
catch (Exception ex)
{
throw new ApplicationRuntimeException(ex.getMessage(), specification.getLocation(), ex);
}
try
{
ComponentClassFactory factory = createComponentClassFactory(specification, result);
if (factory.needsEnhancement())
{
result = factory.createEnhancedSubclass();
validateEnhancedClass(result, className, specification);
}
}
catch (CodeGenerationException e)
{
throw new ApplicationRuntimeException(
Tapestry.format("ComponentClassFactory.code-generation-error", className),
e);
}
return result;
}
/**
* Constructs a new factory for enhancing the specified class. Advanced users
* may want to provide thier own enhancements to classes and this method
* is the hook that allows them to provide a subclass of
* {@link org.apache.tapestry.enhance.ComponentClassFactory} adding those
* enhancements.
*
**/
protected ComponentClassFactory createComponentClassFactory(
IComponentSpecification specification,
Class componentClass)
{
return new ComponentClassFactory(_resolver, specification, componentClass, _factory);
}
/**
* Invoked to validate that an enhanced class is acceptible. Primarily, this is to ensure
* that the class contains no unimplemented abstract methods or fields. Normally,
* this kind of checking is done at compile time, but for generated
* classes, there is no compile time check (!) and you can get runtime
* errors when accessing unimplemented abstract methods.
*
*
**/
protected void validateEnhancedClass(
Class subject,
String className,
IComponentSpecification specification)
{
boolean debug = LOG.isDebugEnabled();
if (debug)
LOG.debug("Validating " + subject);
Set implementedMethods = new HashSet();
Class current = subject;
while (true)
{
Method m = checkForAbstractMethods(current, implementedMethods);
if (m != null)
throw new ApplicationRuntimeException(
Tapestry.format(
"DefaultComponentClassEnhancer.no-impl-for-abstract-method",
new Object[] { m, current, className, subject.getName()}),
specification.getLocation(),
null);
// An earlier version of this code walked the interfaces directly,
// but it appears that implementing an interface actually
// puts abstract method declarations into the class
// (at least, in terms of what getDeclaredMethods() returns).
// March up to the super class.
current = current.getSuperclass();
// Once advanced up to a concrete class, we trust that
// the compiler did its checking.
if (!Modifier.isAbstract(current.getModifiers()))
break;
}
}
/**
* Searches the class for abstract methods, returning the first found.
* Records non-abstract methods in the implementedMethods set.
*
**/
private Method checkForAbstractMethods(Class current, Set implementedMethods)
{
boolean debug = LOG.isDebugEnabled();
if (debug)
LOG.debug("Searching for abstract methods in " + current);
Method[] methods = current.getDeclaredMethods();
for (int i = 0; i < methods.length; i++)
{
Method m = methods[i];
if (debug)
LOG.debug("Checking " + m);
boolean isAbstract = Modifier.isAbstract(m.getModifiers());
MethodSignature s = new MethodSignature(m);
if (isAbstract)
{
if (implementedMethods.contains(s))
continue;
return m;
}
implementedMethods.add(s);
}
return null;
}
}