// Copyright 2006, 2007 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.internal.services;
import org.apache.tapestry.annotations.OnEvent;
import org.apache.tapestry.ioc.util.BodyBuilder;
import org.apache.tapestry.model.MutableComponentModel;
import org.apache.tapestry.runtime.Component;
import org.apache.tapestry.runtime.ComponentEventException;
import org.apache.tapestry.services.*;
import java.util.List;
/**
* Provides implementations of the
* {@link Component#handleComponentEvent(org.apache.tapestry.runtime.ComponentEvent)} method, based
* on {@link OnEvent} annotations.
*/
public class OnEventWorker implements ComponentClassTransformWorker
{
static final String OBJECT_ARRAY_TYPE = "java.lang.Object[]";
private final static int ANY_NUMBER_OF_PARAMETERS = -1;
public void transform(final ClassTransformation transformation, MutableComponentModel model)
{
MethodFilter filter = new MethodFilter()
{
public boolean accept(TransformMethodSignature signature)
{
return signature.getMethodName().startsWith("on") || transformation.getMethodAnnotation(signature,
OnEvent.class) != null;
}
};
List<TransformMethodSignature> methods = transformation.findMethods(filter);
// No methods, no work.
if (methods.isEmpty()) return;
BodyBuilder builder = new BodyBuilder();
builder.begin();
builder.addln("if ($1.isAborted()) return $_;");
builder.addln("String methodDescription = null;");
// Because we track the methodDescription inside a local variable, we can have a single
// encompassing try..catch for all possible events for this component.
builder.addln("try");
builder.begin();
for (TransformMethodSignature method : methods)
addCodeForMethod(builder, method, transformation);
builder.end(); // try
builder.addln("catch (Exception ex)");
builder.begin();
builder.addln("throw new %s(ex.getMessage(), methodDescription, ex);", ComponentEventException.class.getName());
builder.end();
builder.end();
transformation.extendMethod(TransformConstants.HANDLE_COMPONENT_EVENT, builder.toString());
}
private void addCodeForMethod(BodyBuilder builder, TransformMethodSignature method,
ClassTransformation transformation)
{
// $1 is the event
int parameterCount = getParameterCount(method);
OnEvent annotation = transformation.getMethodAnnotation(method, OnEvent.class);
String eventType = extractEventType(method, annotation);
String componentId = extractComponentId(method, annotation);
builder.addln("if ($1.matches(\"%s\", \"%s\", %d))", eventType, componentId, parameterCount);
builder.begin();
// Ensure that we return true, because *some* event handler method was invoked,
// even if it chose not to abort the event.
builder.addln("$_ = true;");
// Several subsequent calls need to know the method name.
builder.addln("methodDescription = \"%s\";", transformation.getMethodIdentifier(method));
builder.addln("$1.setSource(this, methodDescription);");
boolean isNonVoid = !method.getReturnType().equals("void");
// Store the result, converting primitives to wrappers automatically.
if (isNonVoid) builder.add("if ($1.storeResult(($w) ");
builder.add("%s(", method.getMethodName());
buildMethodParameters(builder, method);
if (isNonVoid) builder.addln("))) return true;");
else builder.addln(");");
builder.end();
}
private String extractComponentId(TransformMethodSignature method, OnEvent annotation)
{
if (annotation != null) return annotation.component();
// Method name started with "on". Extract the component id, if present.
String name = method.getMethodName();
int fromx = name.indexOf("From");
if (fromx < 0) return "";
return name.substring(fromx + 4);
}
private String extractEventType(TransformMethodSignature method, OnEvent annotation)
{
if (annotation != null) return annotation.value();
// Method name started with "on". Extract the event type.
String name = method.getMethodName();
int fromx = name.indexOf("From");
return fromx == -1 ? name.substring(2) : name.substring(2, fromx);
}
private int getParameterCount(TransformMethodSignature method)
{
String[] types = method.getParameterTypes();
if (types.length == 0) return 0;
if (types[0].equals(OBJECT_ARRAY_TYPE)) return ANY_NUMBER_OF_PARAMETERS;
// TODO: If the first parameter is Object[], that should be the only parameter.
// Otherwise, Object[] should not be allowed.
return types.length;
}
private void buildMethodParameters(BodyBuilder builder, TransformMethodSignature method)
{
int contextIndex = 0;
for (int i = 0; i < method.getParameterTypes().length; i++)
{
if (i > 0) builder.add(", ");
String type = method.getParameterTypes()[i];
// Type Object[] is a special case, it gets all of the context parameters in one go.
if (type.equals(OBJECT_ARRAY_TYPE))
{
builder.add("$1.getContext()");
continue;
}
boolean isPrimitive = TransformUtils.isPrimitive(type);
String wrapperType = TransformUtils.getWrapperTypeName(type);
// Add a cast to the wrapper type up front
if (isPrimitive) builder.add("(");
// A cast is always needed (i.e. from java.lang.Object to, say, java.lang.String, etc.).
// The wrapper type will be the actual type unless its a primitive, in which case it
// really will be the wrapper type.
builder.add("(%s)", wrapperType);
// The strings for desired type name will likely repeat a bit; it may be
// worth it to inject them as final fields. Could increase the number
// of constructor parameters pretty dramatically, however, and will reduce
// the readability of the output method bodies.
builder.add("$1.coerceContext(%d, \"%s\")", contextIndex++, wrapperType);
// and invoke a method on the cast value to get back to primitive
if (isPrimitive) builder.add(").%s()", TransformUtils.getUnwrapperMethodName(type));
}
}
}