// Copyright 2004, 2005 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.hivemind.impl.servicemodel;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hivemind.ApplicationRuntimeException;
import org.apache.hivemind.HiveMind;
import org.apache.hivemind.ShutdownCoordinator;
import org.apache.hivemind.impl.ConstructableServicePoint;
import org.apache.hivemind.impl.InterceptorStackImpl;
import org.apache.hivemind.impl.ProxyBuilder;
import org.apache.hivemind.internal.ServiceImplementationConstructor;
import org.apache.hivemind.internal.ServiceInterceptorContribution;
import org.apache.hivemind.internal.ServiceModel;
import org.apache.hivemind.service.ClassFab;
import org.apache.hivemind.util.ConstructorUtils;
/**
* Base class for implementing {@link org.apache.hivemind.internal.ServiceModel}.
*
* @author Howard Lewis Ship
*/
public abstract class AbstractServiceModelImpl implements ServiceModel
{
/**
* This log is created from the log's service id, which is the appropriate place to log any
* messages related to creating (or managing) the service implementation, proxy, etc. Subclasses
* should make use of this Log as well.
*/
protected final Log _log;
private ConstructableServicePoint _servicePoint;
/** @since 1.1 */
private Class _bridgeProxyClass;
public AbstractServiceModelImpl(ConstructableServicePoint servicePoint)
{
_log = LogFactory.getLog(servicePoint.getExtensionPointId());
_servicePoint = servicePoint;
}
protected Object addInterceptors(Object core)
{
List interceptors = _servicePoint.getOrderedInterceptorContributions();
int count = interceptors == null ? 0 : interceptors.size();
if (count == 0)
return core;
InterceptorStackImpl stack = new InterceptorStackImpl(_log, _servicePoint, core);
// They are sorted into runtime execution order. Since we build from the
// core service impl outwarads, we have to reverse the runtime execution
// order to get the build order.
// That is, if user expects interceptors in order A B C (perhaps using
// the rules: A before B, C after B).
// Then that's the order for interceptors list: A B C
// To get that runtime execution order, we wrap C around the core,
// wrap B around C, and wrap A around B.
for (int i = count - 1; i >= 0; i--)
{
ServiceInterceptorContribution ic = (ServiceInterceptorContribution) interceptors
.get(i);
stack.process(ic);
}
// Whatever's on top is the final service.
return stack.peek();
}
/**
* Constructs the core service implementation (by invoking the
* {@link ServiceImplementationConstructor}), and checks that the result is non-null and
* assignable to the service interface.
*/
protected Object constructCoreServiceImplementation()
{
if (_log.isDebugEnabled())
_log.debug("Constructing core service implementation for service "
+ _servicePoint.getExtensionPointId());
Class serviceInterface = _servicePoint.getServiceInterface();
Class declaredInterface = _servicePoint.getDeclaredInterface();
ServiceImplementationConstructor constructor = _servicePoint.getServiceConstructor();
Object result = constructor.constructCoreServiceImplementation();
if (result == null)
throw new ApplicationRuntimeException(ServiceModelMessages
.factoryReturnedNull(_servicePoint), constructor.getLocation(), null);
// The factory should provice something that either implements the service interface
// or the declared interface. Again, they are normally the same, but with services
// defined in terms of a class (not an interface), the service interface is
// synthetic, and the declared interface is the actual class.
if (!(serviceInterface.isInstance(result) || declaredInterface.isInstance(result)))
throw new ApplicationRuntimeException(ServiceModelMessages.factoryWrongInterface(
_servicePoint,
result,
serviceInterface), constructor.getLocation(), null);
HiveMind.setLocation(result, constructor.getLocation());
return result;
}
/**
* Constructs the service implementation; this is invoked from
* {@link org.apache.hivemind.internal.ServicePoint#getService(Class)} (for singletons),
* or from the generated deferrable proxy (for most service models). Primarily, invokes
* {@link #constructNewServiceImplementation()}from within a block that checks for recursive
* builds.
*/
protected Object constructServiceImplementation()
{
Object result = constructNewServiceImplementation();
// After succesfully building, we don't need
// some of the definition stuff again.
_servicePoint.clearConstructorInformation();
return result;
}
/**
* Constructs a new implementation of the service, starting with a core implementation, then
* adding any interceptors.
*/
protected Object constructNewServiceImplementation()
{
try
{
Object core = constructCoreServiceImplementation();
Object intercepted = addInterceptors(core);
return intercepted;
}
catch (Exception ex)
{
throw new ApplicationRuntimeException(ServiceModelMessages.unableToConstructService(
_servicePoint,
ex), ex);
}
}
public ConstructableServicePoint getServicePoint()
{
return _servicePoint;
}
/**
* Need to bridge from the service interface to the actual type.
*
* @since 1.1
*/
protected synchronized Object constructBridgeProxy(Object service)
{
if (_bridgeProxyClass == null)
_bridgeProxyClass = constructBridgeProxyClass(service);
return ConstructorUtils.invokeConstructor(_bridgeProxyClass, new Object[]
{ service });
}
/**
* Assumes that the factory will keep cranking out instances of the same class.
*
* @since 1.1
*/
private Class constructBridgeProxyClass(Object service)
{
ProxyBuilder builder = new ProxyBuilder("BridgeProxy", getServicePoint());
ClassFab cf = builder.getClassFab();
Class serviceType = service.getClass();
cf.addField("_service", serviceType);
cf.addConstructor(new Class[]
{ serviceType }, null, "{ super(); _service = $1; }");
builder.addServiceMethods("_service");
return cf.createClass();
}
protected ShutdownCoordinator getShutdownCoordinatorService()
{
return ( ( ShutdownCoordinator )getServicePoint().getModule().getService( ShutdownCoordinator.class ) );
}
}