// 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.hivemind.lib.impl;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.hivemind.ApplicationRuntimeException;
import org.apache.hivemind.ServiceImplementationFactory;
import org.apache.hivemind.internal.Module;
import org.apache.hivemind.service.BodyBuilder;
import org.apache.hivemind.service.ClassFab;
import org.apache.hivemind.service.ClassFabUtils;
import org.apache.hivemind.service.ClassFactory;
import org.apache.hivemind.service.MethodSignature;
import org.apache.hivemind.util.ConstructorUtils;
import org.apache.hivemind.util.PropertyAdaptor;
import org.apache.hivemind.util.PropertyUtils;
/**
* Factory that dynamically exposes a property of another service. A proxy
* is constructed that accesses the target service and obtains a property from that.
* The service interface of the constructed service must match the
* type of the exposed property.
*
* @author Howard Lewis Ship
*/
public class ServicePropertyFactory implements ServiceImplementationFactory
{
private ClassFactory _classFactory;
public Object createCoreServiceImplementation(
String serviceId,
Class serviceInterface,
Log serviceLog,
Module invokingModule,
List parameters)
{
ServicePropertyFactoryParameter p = (ServicePropertyFactoryParameter) parameters.get(0);
Object targetService = p.getService();
String propertyName = p.getPropertyName();
PropertyAdaptor pa = PropertyUtils.getPropertyAdaptor(targetService, propertyName);
String readMethodName = pa.getReadMethodName();
if (readMethodName == null)
throw new ApplicationRuntimeException(
ImplMessages.servicePropertyNotReadable(propertyName, targetService),
null,
p.getLocation(),
null);
if (!(serviceInterface.isAssignableFrom(pa.getPropertyType())))
throw new ApplicationRuntimeException(
ImplMessages.servicePropertyWrongType(
propertyName,
targetService,
pa.getPropertyType(),
serviceInterface),
p.getLocation(),
null);
// Now we're good to go.
String name = ClassFabUtils.generateClassName("ServicePropertyProxy");
ClassFab cf =
_classFactory.newClass(
name,
Object.class,
invokingModule.getClassResolver().getClassLoader());
addInfrastructure(cf, targetService, serviceInterface, propertyName, readMethodName);
addMethods(cf, serviceId, serviceInterface, propertyName, targetService);
Class proxyClass = cf.createClass();
try
{
return ConstructorUtils.invokeConstructor(proxyClass, new Object[] { targetService });
}
catch (Throwable ex)
{
throw new ApplicationRuntimeException(ex.getMessage(), p.getLocation(), ex);
}
}
private void addInfrastructure(
ClassFab cf,
Object targetService,
Class serviceInterface,
String propertyName,
String readPropertyMethodName)
{
cf.addInterface(serviceInterface);
Class targetServiceClass = targetService.getClass();
cf.addField("_targetService", targetServiceClass);
cf.addConstructor(
new Class[] { targetServiceClass },
null,
"{ super(); _targetService = $1; }");
BodyBuilder b = new BodyBuilder();
b.begin();
b.addln(
"{0} property = _targetService.{1}();",
serviceInterface.getName(),
readPropertyMethodName);
b.addln("if (property == null)");
b.add(" throw new java.lang.NullPointerException(");
b.addQuoted(ImplMessages.servicePropertyWasNull(propertyName, targetService));
b.addln(");");
b.addln("return property;");
b.end();
MethodSignature sig =
new MethodSignature(serviceInterface, "_targetServiceProperty", null, null);
cf.addMethod(Modifier.FINAL | Modifier.PRIVATE, sig, b.toString());
}
private void addMethods(
ClassFab cf,
String serviceId,
Class serviceInterface,
String propertyName,
Object targetService)
{
boolean toString = false;
Method[] methods = serviceInterface.getMethods();
for (int i = 0; i < methods.length; i++)
{
Method method = methods[i];
toString |= ClassFabUtils.isToString(method);
String body = "return ($r) _targetServiceProperty()." + method.getName() + "($$);";
cf.addMethod(Modifier.PUBLIC, new MethodSignature(method), body);
}
if (!toString)
ClassFabUtils.addToStringMethod(
cf,
ImplMessages.servicePropertyToString(
serviceId,
serviceInterface,
propertyName,
targetService));
}
public void setClassFactory(ClassFactory factory)
{
_classFactory = factory;
}
}