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Module providing Spring specific helper functionality to ease configuration / set-up of an Axon application, as well as some Spring specific infrastructure components.
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/*
 * Copyright (c) 2010-2018. Axon Framework
 *
 * 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.axonframework.spring.messaging;

import org.axonframework.eventhandling.DomainEventMessage;
import org.axonframework.eventhandling.EventMessage;
import org.axonframework.eventhandling.GenericDomainEventMessage;
import org.axonframework.eventhandling.GenericEventMessage;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHeaders;
import org.springframework.messaging.support.GenericMessage;
import org.springframework.util.NumberUtils;

import java.time.Instant;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.stream.Collectors;

/**
 * An {@link EventMessageConverter} that will convert an Axon event message into a Spring message by:
 * 
 * Copying axon event payload into Spring message payload
 * Copying axon event metadata into Spring message headers
 * Adding axon event message specific attributes - that are not part of axon metadata - to the Spring message Headers.
 * Among those specific attributes are {@link DomainEventMessage} specific properties
 * 
 *
 * @author Reda.Housni-Alaoui
 * @since 3.1
 */
public class DefaultEventMessageConverter implements EventMessageConverter {

    private static final String AXON_MESSAGE_PREFIX = "axon-message-";
    private static final String MESSAGE_ID = AXON_MESSAGE_PREFIX + "id";
    private static final String AGGREGATE_ID = AXON_MESSAGE_PREFIX + "aggregate-id";
    private static final String AGGREGATE_SEQ = AXON_MESSAGE_PREFIX + "aggregate-seq";
    private static final String AGGREGATE_TYPE = AXON_MESSAGE_PREFIX + "aggregate-type";

    @Override
    public  Message convertToOutboundMessage(EventMessage event) {
        Map headers = new HashMap<>();
        event.getMetaData().forEach(headers::put);
        headers.put(MESSAGE_ID, event.getIdentifier());
        if (event instanceof DomainEventMessage) {
            headers.put(AGGREGATE_ID, ((DomainEventMessage) event).getAggregateIdentifier());
            headers.put(AGGREGATE_SEQ, ((DomainEventMessage) event).getSequenceNumber());
            headers.put(AGGREGATE_TYPE, ((DomainEventMessage) event).getType());
        }
        return new GenericMessage<>(event.getPayload(), new SettableTimestampMessageHeaders(headers, event.getTimestamp().toEpochMilli()));
    }

    @Override
    public  EventMessage convertFromInboundMessage(Message message) {
        MessageHeaders headers = message.getHeaders();
        Map metaData = headers.entrySet()
                .stream()
                .filter(entry -> !entry.getKey().startsWith(AXON_MESSAGE_PREFIX))
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

        String messageId = Objects.toString(headers.get(MESSAGE_ID));
        Long timestamp = headers.getTimestamp();

        org.axonframework.messaging.GenericMessage genericMessage
                = new org.axonframework.messaging.GenericMessage<>(messageId, message.getPayload(), metaData);
        if (headers.containsKey(AGGREGATE_ID)) {
            return new GenericDomainEventMessage<>(Objects.toString(headers.get(AGGREGATE_TYPE)),
                                                   Objects.toString(headers.get(AGGREGATE_ID)),
                                                   NumberUtils.convertNumberToTargetClass(headers.get(AGGREGATE_SEQ, Number.class), Long.class),
                                                   genericMessage, () -> Instant.ofEpochMilli(timestamp));
        } else {
            return new GenericEventMessage<>(genericMessage, () -> Instant.ofEpochMilli(timestamp));
        }
    }

    private static class SettableTimestampMessageHeaders extends MessageHeaders {
        protected SettableTimestampMessageHeaders(Map headers, Long timestamp) {
            super(headers, null, timestamp);
        }
    }
}