libraries/rest-server/src/main/java/org/apache/zest/library/rest/server/api/constraint/ServiceAvailable.java

/**
 *
 * Copyright 2009-2011 Rickard Öberg AB
 *
 * 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.zest.library.rest.server.api.constraint;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import org.apache.zest.api.injection.scope.Structure;
import org.apache.zest.api.service.ServiceReference;
import org.apache.zest.api.structure.Module;
import org.apache.zest.library.rest.server.api.ObjectSelection;

/**
 * Annotate interaction methods with ServiceAvailable. They will only be valid
 * if a service with the given type is available.
 */
@InteractionConstraintDeclaration( ServiceAvailable.ServiceAvailableConstraint.class )
@Retention( RetentionPolicy.RUNTIME )
public @interface ServiceAvailable
{
    Class value();

    public class ServiceAvailableConstraint
        implements InteractionConstraint<ServiceAvailable>
    {
        @Structure
        Module module;

        @Override
        public boolean isValid( ServiceAvailable serviceAvailable, ObjectSelection objectSelection )
        {
            ServiceReference ref = module.findService( serviceAvailable.value() );
            return ref != null && ref.isAvailable();
        }
    }
}