// Copyright 2008 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.tapestry5.internal.transform;
import org.apache.tapestry5.Binding;
import org.apache.tapestry5.BindingConstants;
import org.apache.tapestry5.annotations.Cached;
import org.apache.tapestry5.ioc.util.BodyBuilder;
import org.apache.tapestry5.model.MutableComponentModel;
import org.apache.tapestry5.services.*;
import static java.lang.reflect.Modifier.PRIVATE;
import java.util.List;
/**
* Caches method return values for methods annotated with {@link Cached}.
*/
public class CachedWorker implements ComponentClassTransformWorker
{
private final BindingSource bindingSource;
public CachedWorker(BindingSource bindingSource)
{
this.bindingSource = bindingSource;
}
public void transform(ClassTransformation transformation, MutableComponentModel model)
{
List<TransformMethodSignature> methods = transformation.findMethodsWithAnnotation(Cached.class);
if (methods.isEmpty())
return;
for (TransformMethodSignature method : methods)
{
if (method.getReturnType().equals("void"))
throw new IllegalArgumentException(TransformMessages.cachedMethodMustHaveReturnValue(method));
if (method.getParameterTypes().length != 0)
throw new IllegalArgumentException(TransformMessages.cachedMethodsHaveNoParameters(method));
String propertyName = method.getMethodName();
// add a property to store whether or not the method has been called
String fieldName = transformation.addField(PRIVATE, method.getReturnType(), propertyName);
String calledField = transformation.addField(PRIVATE, "boolean", fieldName + "$called");
Cached once = transformation.getMethodAnnotation(method, Cached.class);
String bindingField = null;
String bindingValueField = null;
boolean watching = once.watch().length() > 0;
if (watching)
{
// add fields to store the binding and the value
bindingField = transformation.addField(PRIVATE, Binding.class.getCanonicalName(),
fieldName + "$binding");
bindingValueField = transformation.addField(PRIVATE, "java.lang.Object", fieldName + "$bindingValue");
String bindingSourceField = transformation.addInjectedField(BindingSource.class,
fieldName + "$bindingsource",
bindingSource);
String body = String.format("%s = %s.newBinding(\"Watch expression\", %s, \"%s\", \"%s\");",
bindingField,
bindingSourceField,
transformation.getResourcesFieldName(),
BindingConstants.PROP,
once.watch());
transformation.extendMethod(TransformConstants.CONTAINING_PAGE_DID_LOAD_SIGNATURE, body);
}
BodyBuilder b = new BodyBuilder();
// on cleanup, reset the field values
b.begin();
if (!TransformUtils.isPrimitive(method.getReturnType()))
b.addln("%s = null;", fieldName);
b.addln("%s = false;", calledField);
if (watching)
b.addln("%s = null;", bindingValueField);
b.end();
// TAPESTRY-2338: Cleanup at page detach, not render cleanup. In an Ajax request, the rendering
// objects may reference properties of components that don't render and so won't execute the
// PostCleanupRender phase.
transformation.extendMethod(TransformConstants.CONTAINING_PAGE_DID_DETACH_SIGNATURE, b.toString());
// prefix the existing method to cache the result
b.clear();
b.begin();
// if it has been called and watch is set and the old value is the same as the new value then return
// get the old value and cache it
/* NOTE: evaluates the binding twice when checking the new value.
* this is probably not a problem because in most cases properties
* that are being watched are not expensive operations. plus, we
* never guaranteed that it would be called exactly once when
* watching.
*/
if (watching)
{
b.addln("if (%s && %s == %s.get()) return %s;",
calledField, bindingValueField, bindingField, fieldName);
b.addln("%s = %s.get();", bindingValueField, bindingField);
}
else
{
b.addln("if (%s) return %s;", calledField, fieldName);
}
b.addln("%s = true;", calledField);
b.end();
transformation.prefixMethod(method, b.toString());
// cache the return value
b.clear();
b.begin();
b.addln("%s = $_;", fieldName);
b.end();
transformation.extendExistingMethod(method, b.toString());
}
}
}