Queues definition

The AWE Jms engine allows integration with queue servers. Both JMS typologies, point to point and publish/subscribe.

tip

Every element and attribute of JMS queues is listed in the generated XSD reference.

The Java Message Service (JMS) API is a Java Message Oriented Middleware (MOM) API for sending messages between two or more clients. JMS is a part of the Java Platform, Enterprise Edition, and is defined by a specification developed under the Java Community Process as JSR 914.

It is a messaging standard that allows application components based on the Java Enterprise Edition (Java EE) to create, send, receive, and read messages. It allows the communication between different components of a distributed application to be loosely coupled, reliable, and asynchronous.

• Point-to-point model

In point-to-point messaging system, messages are routed to an individual consumer which maintains a queue of "incoming" messages. This messaging type is built on the concept of message queues, senders, and receivers. Each message is addressed to a specific queue, and the receiving clients extract messages from the queues established to hold their messages. While any number of producers can send messages to the queue, each message is guaranteed to be delivered, and consumed by one consumer. Queues retain all messages sent to them until the messages are consumed or until the messages expire. If no consumers are registered to consume the messages, the queue holds them until a consumer registers to consume them.

• Publish - Subscribe model

The publish/subscribe model supports publishing messages to a particular message topic. Subscribers may register interest in receiving messages on a particular message topic. In this model, neither the publisher nor the subscriber knows about each other. A good analogy for this is an anonymous bulletin board zero or more consumers will receive the message.

There is a timing dependency between publishers and subscribers. The publisher has to create a message topic for clients to subscribe. The subscriber has to remain continuously active to receive messages, unless it has established a durable subscription. In that case, messages published while the subscriber is not connected will be redistributed whenever it reconnects.

info

Note: All queues are defined in the Queues.xml file at global folder. View project structure for more info.

Queue xml structure

The full queue structure is the next one:

<queues xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="https://aweframework.gitlab.io/awe/docs/schemas/queues.xsd">
<queue id="[queue_ID]">
  <request-message destination="[queue_name]" type="[message_type]" [selector="[selector]" separator="[separator_char]" timeout="[timeOut]"]>
   <message-parameter id="[param_message_id]" type="[param_type]"   name="[param_name]" [list="[list]" value="[static_value]"] />
   <message-wrapper name="[name_wrapper]" type="[type_wrapper]" classname="[classname]" />
	… More <message-parameter/>
	… More <message-wrapper/>
  </request-message>
  <response-message destination="[queue_name]" type="[message_type]" [selector="[selector]" separator="[separator_char]" timeout="[timeOut]"]>
   <message-parameter id="[param_message_id]" type="[type_param]" name="[param_name]" [list="[list]" value="[static_value]"] />
   <message-wrapper name="[name_wrapper]" type="[type_wrapper]" classname="[classname]" />
	… More <message-parameter/>
	… More <message-wrapper/>
  </response-message>
 </queue>
 ... More <queue></queue>
</queues>

For easier development of queues, not all elements are required.

Element	Use	Multiples instances	Description
queues	Required	No	Root element of Queues structure
queue	Required	Yes	It outlines the queue
request-message	Optional	No	Used to define the request in the jms comunication
response-message	Optional	No	Used to define the response in the jms comunication
message-parameter	Optional	Yes	Are parameters of message for the request or response
message-wrapper	Optional	No	Java class that builds the request or reads the response, instead of message-parameter elements
message-status	Optional	No	Fields of a MAP response that carry the answer type, title and description

Queue element

The queue element has the following attributes:

Attribute	Use	Type	Description	Values
id	Required	String	Queue identifier	Note: Must be the same name of attribute queue in query.xml or maintain.xml

request-message element

The request-message element has the following attributes:

Attribute	Use	Type	Description	Values
destination	Required	String	Physical name of queue in JMS Server	Note: Must be exist one record in AweQue table with this name
type	Required	String	Message type to send/receive	MAP (send a set of name-value pairs) or TEXT (sent a text info)
selector	Optional	String	Set a a selector to filter the message consumption	Ex.: selector="EUR" It will consume only messages whose header "JMSType=EUR"
separator	Optional	String	Separator character of the message fields
timeout	Optional	Long	Time to wait for the message

response-message element

The response-message element defines the message that is received as the answer of the queue. It has the same attributes as the request-message element (destination, type, selector, separator and timeout) and contains message-parameter elements, or a message-wrapper or message-status element.

message-parameter element

The message-parameter element, inside a request-message or a response-message, has the following attributes:

Attribute	Use	Type	Description	Values
id	Required	String	Identifier of the parameter
type	Required	String	Data type of the parameter	STRING, INTEGER, LONG, FLOAT, DOUBLE, BOOLEAN, DATE, TIME, TIMESTAMP, OBJECT... (the same types as the other definition files)
name	Optional	String	Name of the parameter in the message
value	Optional	String	Static value of the parameter
list	Optional	Boolean	Whether the parameter is a list of values	true or false

message-wrapper element

The message-wrapper element, inside a request-message or a response-message, maps the whole message to a Java class instead of listing message-parameter elements. A response wrapper class implements ResponseWrapper, and its toServiceData() result is the answer of the queue.

Attribute	Use	Type	Description	Values
type	Required	String	How the message is mapped to the class	XML (the message text, or one field of a map message, is an XML document) or OBJECT (each field of a map message is copied to the class field with the same name)
classname	Required	String	Fully qualified name of the wrapper class
name	Optional	String	Field of a MAP message that holds the wrapped value	Required with XML on a MAP response; must be omitted with OBJECT

message-status element

The message-status element, inside a response-message of type MAP, reads the result of the operation from the response and shows it to the user like the answer of any other action. Its attributes are the names of the map fields that hold each value, not the values themselves.

Attribute	Use	Type	Description	Values
type	Required	String	Field with the answer type	ok, error, warning or info (case insensitive)
translate	Optional	String	Enumerated group used to translate the received value into an answer type	Ex.: the response sends 0 and the enumerated group maps 0 to ok
title	Optional	String	Field with the title of the message
description	Optional	String	Field with the text of the message