NotificationRequestConverter.java

/*
 * Copyright 2013-2014 the original author or authors.
 *
 * 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.springframework.cloud.aws.messaging.support.converter;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.cloud.aws.messaging.core.MessageAttributeDataTypes;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHeaders;
import org.springframework.messaging.MessagingException;
import org.springframework.messaging.converter.MessageConversionException;
import org.springframework.messaging.converter.MessageConverter;
import org.springframework.messaging.support.GenericMessage;
import org.springframework.util.Assert;
import org.springframework.util.MimeType;
import org.springframework.util.NumberUtils;

import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.UUID;

/**
 * @author Agim Emruli
 * @author Alain Sahli
 * @since 1.0
 */
public class NotificationRequestConverter implements MessageConverter {

    private final ObjectMapper jsonMapper = new ObjectMapper();
    private final MessageConverter payloadConverter;


    public NotificationRequestConverter(MessageConverter payloadConverter) {
        this.payloadConverter = payloadConverter;
    }

    @Override
    public Object fromMessage(Message<?> message, Class<?> targetClass) {
        Assert.notNull(message, "message must not be null");
        Assert.notNull(targetClass, "target class must not be null");

        JsonNode jsonNode;
        try {
            jsonNode = this.jsonMapper.readTree(message.getPayload().toString());
        } catch (Exception e) {
            throw new MessageConversionException("Could not read JSON", e);
        }
        if (!jsonNode.has("Type")) {
            throw new MessageConversionException("Payload: '" + message.getPayload() + "' does not contain a Type attribute", null);
        }

        if (!"Notification".equals(jsonNode.findValue("Type").asText())) {
            throw new MessageConversionException("Payload: '" + message.getPayload() + "' is not a valid notification", null);
        }

        if (!jsonNode.has("Message")) {
            throw new MessageConversionException("Payload: '" + message.getPayload() + "' does not contain a message", null);
        }

        String messagePayload = jsonNode.findPath("Message").asText();
        GenericMessage<String> genericMessage = new GenericMessage<>(messagePayload,
                getMessageAttributesAsMessageHeaders(jsonNode.findPath("MessageAttributes")));
        return new NotificationRequest(jsonNode.findPath("Subject").asText(),
                this.payloadConverter.fromMessage(genericMessage, targetClass));
    }

    @Override
    public Message<?> toMessage(Object payload, MessageHeaders headers) {
        throw new UnsupportedOperationException("This converter only supports reading a SNS notification and not writing them");
    }

    public static class NotificationRequest {

        private final String subject;
        private final Object message;

        public NotificationRequest(String subject, Object message) {
            this.subject = subject;
            this.message = message;
        }

        public String getSubject() {
            return this.subject;
        }

        public Object getMessage() {
            return this.message;
        }
    }


    private static Map<String, Object> getMessageAttributesAsMessageHeaders(JsonNode message) {
        Map<String, Object> messageHeaders = new HashMap<>();
        Iterator<String> fieldNames = message.fieldNames();
        while (fieldNames.hasNext()) {
            String attributeName = fieldNames.next();
            String attributeValue = message.get(attributeName).get("Value").asText();
            String attributeType = message.get(attributeName).get("Type").asText();
            if (MessageHeaders.CONTENT_TYPE.equals(attributeName)) {
                messageHeaders.put(MessageHeaders.CONTENT_TYPE, MimeType.valueOf(attributeValue));
            } else if (MessageHeaders.ID.equals(attributeName)) {
                messageHeaders.put(MessageHeaders.ID, UUID.fromString(attributeValue));
            } else {
                if (MessageAttributeDataTypes.STRING.equals(attributeType)) {
                    messageHeaders.put(attributeName, attributeValue);
                } else if (attributeType.startsWith(MessageAttributeDataTypes.NUMBER)) {
                    Object numberValue = getNumberValue(attributeType, attributeValue);
                    if (numberValue != null) {
                        messageHeaders.put(attributeName, numberValue);
                    }
                } else if (MessageAttributeDataTypes.BINARY.equals(attributeName)) {
                    messageHeaders.put(attributeName, ByteBuffer.wrap(attributeType.getBytes()));
                }
            }
        }

        return messageHeaders;
    }

    private static Object getNumberValue(String attributeType, String attributeValue) {
        String numberType = attributeType.substring(MessageAttributeDataTypes.NUMBER.length() + 1);
        try {
            Class<? extends Number> numberTypeClass = Class.forName(numberType).asSubclass(Number.class);
            return NumberUtils.parseNumber(attributeValue, numberTypeClass);
        } catch (ClassNotFoundException e) {
            throw new MessagingException(String.format("Message attribute with value '%s' and data type '%s' could not be converted " +
                    "into a Number because target class was not found.", attributeValue, attributeType), e);
        }
    }
}