core/camel-api/src/main/java/org/apache/camel/FluentProducerTemplate.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.camel;

import java.util.concurrent.Future;
import java.util.function.Supplier;

/**
 * Template for working with Camel and sending {@link Message} instances in an
 * {@link Exchange} to an {@link Endpoint} using a <i>fluent</i> build style.
 * <br/>
 * <p/><b>Important:</b> Read the javadoc of each method carefully to ensure the behavior of the method is understood.
 * Some methods is for <tt>InOnly</tt>, others for <tt>InOut</tt> MEP. And some methods throws
 * {@link org.apache.camel.CamelExecutionException} while others stores any thrown exception on the returned
 * {@link Exchange}.
 * <br/>
 * <p/>The {@link FluentProducerTemplate} is <b>thread safe</b>.
 * <br/>
 * <p/>All the methods which sends a message may throw {@link FailedToCreateProducerException} in
 * case the {@link Producer} could not be created. Or a {@link NoSuchEndpointException} if the endpoint could
 * not be resolved. There may be other related exceptions being thrown which occurs <i>before</i> the {@link Producer}
 * has started sending the message.
 * <br/>
 * <p/>All the send or request methods will return the content according to this strategy:
 * <ul>
 *   <li>throws {@link org.apache.camel.CamelExecutionException} if processing failed <i>during</i> routing
 *       with the caused exception wrapped</li>
 *   <li>The <tt>fault.body</tt> if there is a fault message set and its not <tt>null</tt></li>
 *   <li>Either <tt>IN</tt> or <tt>OUT</tt> body according to the message exchange pattern. If the pattern is
 *   Out capable then the <tt>OUT</tt> body is returned, otherwise <tt>IN</tt>.
 * </ul>
 * <br/>
 * <p/>Before using the template it must be started.
 * And when you are done using the template, make sure to {@link #stop()} the template.
 * <br/>
 * <p/><b>Important note on usage:</b> See this
 * <a href="http://camel.apache.org/why-does-camel-use-too-many-threads-with-producertemplate.html">FAQ entry</a>
 * before using.
 *
 * @see ProducerTemplate
 * @see ConsumerTemplate
 */
public interface FluentProducerTemplate extends Service {

    /**
     * Get the {@link CamelContext}
     *
     * @return camelContext the Camel context
     */
    CamelContext getCamelContext();

    // Configuration methods
    // -----------------------------------------------------------------------

    /**
     * Gets the maximum cache size used in the backing cache pools.
     *
     * @return the maximum cache size
     */
    int getMaximumCacheSize();

    /**
     * Sets a custom maximum cache size to use in the backing cache pools.
     *
     * @param maximumCacheSize the custom maximum cache size
     */
    void setMaximumCacheSize(int maximumCacheSize);

    /**
     * Gets an approximated size of the current cached resources in the backing cache pools.
     *
     * @return the size of current cached resources
     */
    int getCurrentCacheSize();

    /**
     * Get the default endpoint to use if none is specified
     *
     * @return the default endpoint instance
     */
    Endpoint getDefaultEndpoint();

    /**
     * Sets the default endpoint to use if none is specified
     *
     * @param defaultEndpoint the default endpoint instance
     */
    void setDefaultEndpoint(Endpoint defaultEndpoint);

    /**
     * Sets the default endpoint uri to use if none is specified
     *
     *  @param endpointUri the default endpoint uri
     */
    void setDefaultEndpointUri(String endpointUri);

    /**
     * Sets whether the {@link org.apache.camel.spi.EventNotifier} should be
     * used by this {@link ProducerTemplate} to send events about the {@link Exchange}
     * being sent.
     * <p/>
     * By default this is enabled.
     *
     * @param enabled <tt>true</tt> to enable, <tt>false</tt> to disable.
     */
    void setEventNotifierEnabled(boolean enabled);

    /**
     * Whether the {@link org.apache.camel.spi.EventNotifier} should be
     * used by this {@link ProducerTemplate} to send events about the {@link Exchange}
     * being sent.
     *
     * @return <tt>true</tt> if enabled, <tt>false</tt> otherwise
     */
    boolean isEventNotifierEnabled();

    /**
     * Cleanup the cache (purging stale entries)
     */
    void cleanUp();

    // Fluent methods
    // -----------------------------------------------------------------------

    /**
     * Remove the body and headers.
     */
    FluentProducerTemplate clearAll();

    /**
     * Set the header
     *
     * @param key the key of the header
     * @param value the value of the header
     */
    FluentProducerTemplate withHeader(String key, Object value);

    /**
     * Remove the headers.
     */
    FluentProducerTemplate clearHeaders();

    /**
     * Set the message body
     *
     * @param body the body
     */
    FluentProducerTemplate withBody(Object body);

    /**
     * Set the message body after converting it to the given type
     *
     * @param body the body
     * @param type the type which the body should be converted to
     */
    FluentProducerTemplate withBodyAs(Object body, Class<?> type);

    /**
     * Remove the body.
     */
    FluentProducerTemplate clearBody();

    /**
     * To customize the producer template for advanced usage like to set the
     * executor service to use.
     *
     * <pre>
     * {@code
     * FluentProducerTemplate.on(context)
     *     .withTemplateCustomizer(
     *         template -> {
     *             template.setExecutorService(myExecutor);
     *             template.setMaximumCacheSize(10);
     *         }
     *      )
     *     .withBody("the body")
     *     .to("direct:start")
     *     .request()}
     * </pre>
     *
     * Note that it is invoked only once.
     *
     * @param templateCustomizer the customizer
     */
    FluentProducerTemplate withTemplateCustomizer(java.util.function.Consumer<ProducerTemplate> templateCustomizer);

    /**
     * Set the exchange to use for send.
     *
     * When using withExchange then you must use the send method (request is not supported).
     *
     * @param exchange the exchange
     */
    FluentProducerTemplate withExchange(Exchange exchange);

    /**
     * Set the exchangeSupplier which will be invoke to get the exchange to be
     * used for send.
     *
     * When using withExchange then you must use the send method (request is not supported).
     *
     * @param exchangeSupplier the supplier
     */
    FluentProducerTemplate withExchange(Supplier<Exchange> exchangeSupplier);

    /**
     * Set the processor to use for send/request.
     *
     * <pre>
     * {@code
     * FluentProducerTemplate.on(context)
     *     .withProcessor(
     *         exchange -> {
     *             exchange.getIn().setHeader("Key1", "Val1");
     *             exchange.getIn().setHeader("Key2", "Val2");
     *             exchange.getIn().setBody("the body");
     *         }
     *      )
     *     .to("direct:start")
     *     .request()}
     * </pre>
     *
     * @param processor 
     */
    FluentProducerTemplate withProcessor(Processor processor);

    /**
     * Set the processorSupplier which will be invoke to get the processor to be
     * used for send/request.
     *
     * @param processorSupplier the supplier
     */
    FluentProducerTemplate withProcessor(Supplier<Processor> processorSupplier);

    /**
     * Endpoint to send to
     *
     * @param endpointUri the endpoint URI to send to
     */
    FluentProducerTemplate to(String endpointUri);

    /**
     * Endpoint to send to
     *
     * @param endpoint the endpoint to send to
     */
    FluentProducerTemplate to(Endpoint endpoint);

    /**
     * Send to an endpoint (InOut) returning any result output body.
     *
     * @return the result
     * @throws CamelExecutionException is thrown if error occurred
     */
    Object request() throws CamelExecutionException;

    /**
     * Send to an endpoint (InOut).
     *
     * @param type the expected response type
     * @return the result
     * @throws CamelExecutionException is thrown if error occurred
     */
    <T> T request(Class<T> type) throws CamelExecutionException;

    /**
     * Sends asynchronously to the given endpoint (InOut).
     *
     * @return a handle to be used to get the response in the future
     */
    Future<Object> asyncRequest();

    /**
     * Sends asynchronously to the given endpoint (InOut).
     *
     * @param type the expected response type
     * @return a handle to be used to get the response in the future
     */
    <T> Future<T> asyncRequest(Class<T> type);

    /**
     * Send to an endpoint (InOnly)
     *
     * @throws CamelExecutionException is thrown if error occurred
     */
    Exchange send() throws CamelExecutionException;

    /**
     * Sends asynchronously to the given endpoint (InOnly).
     *
     * @return a handle to be used to get the response in the future
     */
    Future<Exchange> asyncSend();
}