co.cask.cdap.internal.app.services.DefaultServiceConfigurer.java Source code

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Here is the source code for co.cask.cdap.internal.app.services.DefaultServiceConfigurer.java

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/*
 * Copyright  2014 Cask Data, Inc.
 *
 * 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 co.cask.cdap.internal.app.services;

import co.cask.cdap.api.Resources;
import co.cask.cdap.api.metrics.MetricsContext;
import co.cask.cdap.api.service.Service;
import co.cask.cdap.api.service.ServiceConfigurer;
import co.cask.cdap.api.service.ServiceSpecification;
import co.cask.cdap.api.service.http.HttpServiceContext;
import co.cask.cdap.api.service.http.HttpServiceHandler;
import co.cask.cdap.api.service.http.HttpServiceHandlerSpecification;
import co.cask.cdap.common.metrics.NoOpMetricsCollectionService;
import co.cask.cdap.internal.app.runtime.service.http.DelegatorContext;
import co.cask.cdap.internal.app.runtime.service.http.HttpHandlerFactory;
import co.cask.http.HttpHandler;
import co.cask.http.NettyHttpService;
import com.google.common.base.Preconditions;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.reflect.TypeToken;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * A default implementation of {@link ServiceConfigurer}.
 */
public class DefaultServiceConfigurer implements ServiceConfigurer {
    private final String className;
    private String name;
    private String description;
    private List<HttpServiceHandler> handlers;
    private Resources resources;
    private int instances;
    private static final Logger LOG = LoggerFactory.getLogger(DefaultServiceConfigurer.class);

    /**
     * Create an instance of {@link DefaultServiceConfigurer}
     */
    public DefaultServiceConfigurer(Service service) {
        this.className = service.getClass().getName();
        this.name = service.getClass().getSimpleName();
        this.description = "";
        this.handlers = Lists.newArrayList();
        this.resources = new Resources();
        this.instances = 1;
    }

    @Override
    public void setName(String name) {
        this.name = name;
    }

    @Override
    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public void addHandlers(Iterable<? extends HttpServiceHandler> serviceHandlers) {
        Iterables.addAll(handlers, serviceHandlers);
    }

    @Override
    public void setInstances(int instances) {
        Preconditions.checkArgument(instances > 0, "Instances must be > 0.");
        this.instances = instances;
    }

    @Override
    public void setResources(Resources resources) {
        Preconditions.checkArgument(resources != null, "Resources cannot be null.");
        this.resources = resources;
    }

    public ServiceSpecification createSpecification() {
        Map<String, HttpServiceHandlerSpecification> handleSpecs = createHandlerSpecs(handlers);
        return new ServiceSpecification(className, name, description, handleSpecs, resources, instances);
    }

    /**
     * Constructs HttpServiceSpecifications for each of the handlers in the {@param handlers} list.
     * Also performs verifications on these handlers (that a NettyHttpService can be constructed from them).
     */
    private Map<String, HttpServiceHandlerSpecification> createHandlerSpecs(
            List<? extends HttpServiceHandler> handlers) {
        verifyHandlers(handlers);
        Map<String, HttpServiceHandlerSpecification> handleSpecs = Maps.newHashMap();
        for (HttpServiceHandler handler : handlers) {
            DefaultHttpServiceHandlerConfigurer configurer = new DefaultHttpServiceHandlerConfigurer(handler);
            handler.configure(configurer);
            HttpServiceHandlerSpecification spec = configurer.createSpecification();
            Preconditions.checkArgument(!handleSpecs.containsKey(spec.getName()),
                    "Handler with name %s already existed.", spec.getName());
            handleSpecs.put(spec.getName(), spec);
        }
        return handleSpecs;
    }

    private void verifyHandlers(List<? extends HttpServiceHandler> handlers) {
        Preconditions.checkArgument(!Iterables.isEmpty(handlers), "Service %s should have at least one handler",
                name);
        try {
            List<HttpHandler> httpHandlers = Lists.newArrayList();
            for (HttpServiceHandler handler : handlers) {
                httpHandlers.add(createHttpHandler(handler));
            }

            // Constructs a NettyHttpService, to verify that the handlers passed in by the user are valid.
            NettyHttpService.builder().addHttpHandlers(httpHandlers).build();
        } catch (Throwable t) {
            String errMessage = String.format("Invalid handlers in service: %s.", name);
            LOG.error(errMessage, t);
            throw new IllegalArgumentException(errMessage, t);
        }

    }

    private <T extends HttpServiceHandler> HttpHandler createHttpHandler(T handler) {
        MetricsContext noOpsMetricsContext = new NoOpMetricsCollectionService()
                .getContext(new HashMap<String, String>());
        HttpHandlerFactory factory = new HttpHandlerFactory("", noOpsMetricsContext);
        @SuppressWarnings("unchecked")
        TypeToken<T> type = (TypeToken<T>) TypeToken.of(handler.getClass());
        return factory.createHttpHandler(type, new VerificationDelegateContext<>(handler));
    }

    private static final class VerificationDelegateContext<T extends HttpServiceHandler>
            implements DelegatorContext<T> {

        private final T handler;

        private VerificationDelegateContext(T handler) {
            this.handler = handler;
        }

        @Override
        public T getHandler() {
            return handler;
        }

        @Override
        public HttpServiceContext getServiceContext() {
            // Never used. (It's only used during server runtime, which we don't verify).
            return null;
        }
    }
}