org.sglj.service.rmi.AbstractRemoteServiceManager.java Source code

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Here is the source code for org.sglj.service.rmi.AbstractRemoteServiceManager.java

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/*
 * AbstractRemoteServiceManager.java
 * 
 * Copyright (C) 2010 Leo Osvald <leo.osvald@gmail.com>
 * 
 * This file is part of SGLJ.
 * 
 * SGLJ is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * SGLJ is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.sglj.service.rmi;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.apache.commons.lang.Validate;
import org.sglj.service.rmi.annotations.RemoteMethod;
import org.sglj.util.Pair;

/**
 * The abstract implementation of the {@link RemoteServiceManager} interface.<br>
 * 
 * Services to be registered are provided via constructor as variable
 * argument list.
 * 
 * 
 * @author Leo Osvald
 * @version 1.0
 */
abstract class AbstractRemoteServiceManager<T extends RemoteService> implements RemoteServiceManager<T> {

    /**
     * Unmodifiable list of remote services
     */
    private final List<T> services;

    /**
     * 
     * @param remoteServices services to be registered
     * @throws IllegalArgumentException if the contract defined in 
     * the {@link RemoteServiceManager} interface is broken.
     */
    public <T2 extends T> AbstractRemoteServiceManager(T2... remoteServices) throws IllegalArgumentException {
        Validate.noNullElements(remoteServices, "Remote service cannot be null");

        Set<T> uniqueServices = new HashSet<T>(remoteServices.length);
        for (T remoteService : remoteServices) {
            uniqueServices.add(remoteService);
        }

        // ensure that there are no duplicate services
        Validate.isTrue(uniqueServices.size() == remoteServices.length, "Duplicate services detected");

        // ensure that services have distinct identifiers
        Set<Byte> ids = new HashSet<Byte>(uniqueServices.size());
        for (RemoteService service : remoteServices) {
            ids.add(service.getId());
        }
        Validate.isTrue(uniqueServices.size() == ids.size(), "Services with identical id detected");
        ids.clear(); // free memory before allocating new

        services = Collections.unmodifiableList(new ArrayList<T>(uniqueServices));

        // retrieve all remote methods and store them in a map by name
        for (RemoteService service : services) {
            Method[] methods = service.getClass().getMethods();
            Set<Pair<String, Integer>> set = new HashSet<Pair<String, Integer>>();
            for (Method m : methods) {
                if (m.isAnnotationPresent(RemoteMethod.class)) {
                    int paramCount = m.getParameterTypes().length;
                    if (!set.add(new Pair<String, Integer>(m.getName(), paramCount))) {
                        throw new IllegalArgumentException("Two methods with the same name \"" + m.getName()
                                + "\" and with " + paramCount + " parameters detected in service" + service);
                    }
                    registerRemoteMethod(service.getId(), m);
                }
            }
        }
    }

    @Override
    public List<T> availableServices() {
        return services;
    }

    @Override
    public boolean existsRemoteMethod(byte serviceId, String methodName, int parameterCount) {
        return getRemoteMethod(serviceId, methodName, parameterCount) != null;
    }

    /**
     * A method called by the constructor to "permanently" register a 
     * remote method in the specified service.<br>
     * The method is guaranteed to be remote so there is no need to
     * check again whether it is annotated by the 
     * {@link RemoteMethod} annotation. The implementor also does not
     * need to check whether two methods with the same name and the same
     * number of the arguments belong to the same service - that check
     * is already implemented by the {@link AbstractRemoteServiceManager}
     * class.
     * 
     * @param serviceId identifier of the service that this method belongs to
     * @param remoteMethod the method that should registered
     */
    protected abstract void registerRemoteMethod(byte serviceId, Method remoteMethod);

}