Spring provides a JMS integration framework that simplifies the use of the JMS API much like Spring's integration does for the JDBC API.
JMS can be roughly divided into two areas of functionality, namely
the production and consumption of messages. The
JmsTemplate
class is used for message production
and synchronous message reception. For asynchronous reception similar to
Java EE's message-driven bean style, Spring provides a number of message
listener containers that are used to create Message-Driven POJOs
(MDPs).
The package org.springframework.jms.core
provides
the core functionality for using JMS. It contains JMS template classes
that simplify the use of the JMS by handling the creation and release of
resources, much like the JdbcTemplate
does for
JDBC. The design principle common to Spring template classes is to provide
helper methods to perform common operations and for more sophisticated
usage, delegate the essence of the processing task to user implemented
callback interfaces. The JMS template follows the same design. The classes
offer various convenience methods for the sending of messages, consuming a
message synchronously, and exposing the JMS session and message producer
to the user.
The package org.springframework.jms.support
provides JMSException
translation functionality.
The translation converts the checked JMSException
hierarchy to a mirrored hierarchy of unchecked exceptions. If there are
any provider specific subclasses of the checked
javax.jms.JMSException
, this exception is wrapped
in the unchecked UncategorizedJmsException
.
The package
org.springframework.jms.support.converter
provides a
MessageConverter
abstraction to convert
between Java objects and JMS messages.
The package
org.springframework.jms.support.destination
provides
various strategies for managing JMS destinations, such as providing a
service locator for destinations stored in JNDI.
Finally, the package
org.springframework.jms.connection
provides an
implementation of the ConnectionFactory
suitable
for use in standalone applications. It also contains an implementation of
Spring's PlatformTransactionManager
for JMS
(the cunningly named JmsTransactionManager
). This
allows for seamless integration of JMS as a transactional resource into
Spring's transaction management mechanisms.
The JmsTemplate
class is the central class
in the JMS core package. It simplifies the use of JMS since it handles
the creation and release of resources when sending or synchronously
receiving messages.
Code that uses the JmsTemplate
only needs
to implement callback interfaces giving them a clearly defined high
level contract. The MessageCreator
callback
interface creates a message given a
Session
provided by the calling code in
JmsTemplate
. In order to allow for more complex
usage of the JMS API, the callback
SessionCallback
provides the user with the JMS
session and the callback ProducerCallback
exposes
a Session
and
MessageProducer
pair.
The JMS API exposes two types of send methods, one that takes
delivery mode, priority, and time-to-live as Quality of Service (QOS)
parameters and one that takes no QOS parameters which uses default
values. Since there are many send methods in
JmsTemplate
, the setting of the QOS parameters
have been exposed as bean properties to avoid duplication in the number
of send methods. Similarly, the timeout value for synchronous receive
calls is set using the property
setReceiveTimeout
.
Some JMS providers allow the setting of default QOS values
administratively through the configuration of the ConnectionFactory.
This has the effect that a call to
MessageProducer
's send method
send(Destination destination, Message message)
will use different QOS default values than those specified in the JMS
specification. In order to provide consistent management of QOS values,
the JmsTemplate
must therefore be specifically
enabled to use its own QOS values by setting the boolean property
isExplicitQosEnabled to
true
.
Note | |
---|---|
Instances of the |
The JmsTemplate
requires a reference to a
ConnectionFactory
. The
ConnectionFactory
is part of the JMS
specification and serves as the entry point for working with JMS. It is
used by the client application as a factory to create connections with
the JMS provider and encapsulates various configuration parameters, many
of which are vendor specific such as SSL configuration options.
When using JMS inside an EJB, the vendor provides implementations
of the JMS interfaces so that they can participate in declarative
transaction management and perform pooling of connections and sessions.
In order to use this implementation, Java EE containers typically
require that you declare a JMS connection factory as a
resource-ref inside the EJB or servlet deployment
descriptors. To ensure the use of these features with the
JmsTemplate
inside an EJB, the client application
should ensure that it references the managed implementation of the
ConnectionFactory
.
The standard API involves creating many intermediate objects. To send a message the following 'API' walk is performed
ConnectionFactory->Connection->Session->MessageProducer->send
Between the ConnectionFactory and the Send operation there are three intermediate objects that are created and destroyed. To optimise the resource usage and increase performance two implementations of IConnectionFactory are provided.
Spring provides an implementation of the
ConnectionFactory
interface,
SingleConnectionFactory
, that will return the
same Connection
on all
createConnection()
calls and ignore calls to
close()
. This is useful for testing and
standalone environments so that the same connection can be used for
multiple JmsTemplate
calls that may span any
number of transactions. SingleConnectionFactory
takes a reference to a standard
ConnectionFactory
that would typically come
from JNDI.
The CachingConnectionFactory
extends the
functionality of SingleConnectionFactory
and
adds the caching of Sessions, MessageProducers, and MessageConsumers.
The initial cache size is set to 1, use the property
SessionCacheSize to increase the number of cached
sessions. Note that the number of actual cached sessions will be more
than that number as sessions are cached based on their acknowledgment
mode, so there can be up to 4 cached session instances when
SessionCacheSize is set to one, one for each
AcknowledgementMode. MessageProducers and MessageConsumers are cached
within their owning session and also take into account the unique
properties of the producers and consumers when caching.
MessageProducers are cached based on their destination.
MessageConsumers are cached based on a key composed of the
destination, selector, noLocal delivery flag, and the durable
subscription name (if creating durable consumers).
Destinations, like ConnectionFactories, are JMS administered
objects that can be stored and retrieved in JNDI. When configuring a
Spring application context you can use the JNDI factory class
JndiObjectFactoryBean
/
<jee:jndi-lookup>
to perform dependency
injection on your object's references to JMS destinations. However,
often this strategy is cumbersome if there are a large number of
destinations in the application or if there are advanced destination
management features unique to the JMS provider. Examples of such
advanced destination management would be the creation of dynamic
destinations or support for a hierarchical namespace of destinations.
The JmsTemplate
delegates the resolution of a
destination name to a JMS destination object to an implementation of the
interface DestinationResolver
.
DynamicDestinationResolver
is the default
implementation used by JmsTemplate
and
accommodates resolving dynamic destinations. A
JndiDestinationResolver
is also provided that
acts as a service locator for destinations contained in JNDI and
optionally falls back to the behavior contained in
DynamicDestinationResolver
.
Quite often the destinations used in a JMS application are only
known at runtime and therefore cannot be administratively created when
the application is deployed. This is often because there is shared
application logic between interacting system components that create
destinations at runtime according to a well-known naming convention.
Even though the creation of dynamic destinations is not part of the JMS
specification, most vendors have provided this functionality. Dynamic
destinations are created with a name defined by the user which
differentiates them from temporary destinations and are often not
registered in JNDI. The API used to create dynamic destinations varies
from provider to provider since the properties associated with the
destination are vendor specific. However, a simple implementation choice
that is sometimes made by vendors is to disregard the warnings in the
JMS specification and to use the TopicSession
method createTopic(String topicName)
or the
QueueSession
method
createQueue(String queueName)
to create a new
destination with default destination properties. Depending on the vendor
implementation, DynamicDestinationResolver
may
then also create a physical destination instead of only resolving
one.
The boolean property pubSubDomain is used to
configure the JmsTemplate
with knowledge of what
JMS domain is being used. By default the value of this property is
false, indicating that the point-to-point domain, Queues, will be used.
This property used by JmsTemplate
determines the
behavior of dynamic destination resolution via implementations of the
DestinationResolver
interface.
You can also configure the JmsTemplate
with
a default destination via the property
defaultDestination. The default destination will be
used with send and receive operations that do not refer to a specific
destination.
One of the most common uses of JMS messages in the EJB world is to drive message-driven beans (MDBs). Spring offers a solution to create message-driven POJOs (MDPs) in a way that does not tie a user to an EJB container. (See Section 22.4.2, “Asynchronous Reception - Message-Driven POJOs” for detailed coverage of Spring's MDP support.)
A message listener container is used to receive messages from a JMS message queue and drive the MessageListener that is injected into it. The listener container is responsible for all threading of message reception and dispatches into the listener for processing. A message listener container is the intermediary between an MDP and a messaging provider, and takes care of registering to receive messages, participating in transactions, resource acquisition and release, exception conversion and suchlike. This allows you as an application developer to write the (possibly complex) business logic associated with receiving a message (and possibly responding to it), and delegates boilerplate JMS infrastructure concerns to the framework.
There are two standard JMS message listener containers packaged with Spring, each with its specialised feature set.
This message listener container is the simpler of the two
standard flavors. It creates a fixed number of JMS sessions and
consumers at startup, registers the listener using the standard JMS
MessageConsumer.setMessageListener()
method,
and leaves it up the JMS provider to perform listener callbacks.
This variant does not allow for dynamic adaption to runtime demands or
for participation in externally managed transactions. Compatibility-wise,
it stays very close to the spirit of the standalone JMS specification
- but is generally not compatible with Java EE's JMS restrictions.
This message listener container is the one used in most cases.
In contrast to SimpleMessageListenerContainer
,
this container variant does allow for dynamic adaption to runtime
demands and is able to participate in externally managed transactions.
Each received message is registered with an XA transaction when
configured with a JtaTransactionManager
; so
processing may take advantage of XA transaction semantics. This
listener container strikes a good balance between low requirements on
the JMS provider, advanced functionality such as transaction
participation, and compatibility with Java EE environments.
Spring provides a JmsTransactionManager
that manages transactions for a single JMS
ConnectionFactory
. This allows JMS applications
to leverage the managed transaction features of Spring as described in
Chapter 11, Transaction Management. The
JmsTransactionManager
performs local resource
transactions, binding a JMS Connection/Session pair from the specified
ConnectionFactory
to the thread.
JmsTemplate
automatically detects such
transactional resources and operates on them accordingly.
In a Java EE environment, the
ConnectionFactory
will pool Connections and
Sessions, so those resources are efficiently reused across transactions.
In a standalone environment, using Spring's
SingleConnectionFactory
will result in a shared
JMS Connection
, with each transaction having its
own independent Session
. Alternatively, consider
the use of a provider-specific pooling adapter such as ActiveMQ's
PooledConnectionFactory
class.
JmsTemplate
can also be used with the
JtaTransactionManager
and an XA-capable JMS
ConnectionFactory
for performing distributed
transactions. Note that this requires the use of a JTA transaction
manager as well as a properly XA-configured ConnectionFactory! (Check
your Java EE server's / JMS provider's documentation.)
Reusing code across a managed and unmanaged transactional
environment can be confusing when using the JMS API to create a
Session
from a Connection
.
This is because the JMS API has only one factory method to create a
Session
and it requires values for the
transaction and acknowledgement modes. In a managed environment, setting
these values is the responsibility of the environment's transactional
infrastructure, so these values are ignored by the vendor's wrapper to
the JMS Connection. When using the JmsTemplate
in
an unmanaged environment you can specify these values through the use of
the properties sessionTransacted
and
sessionAcknowledgeMode
. When using a
PlatformTransactionManager
with
JmsTemplate
, the template will always be given a
transactional JMS Session
.
The JmsTemplate
contains many convenience
methods to send a message. There are send methods that specify the
destination using a javax.jms.Destination
object
and those that specify the destination using a string for use in a JNDI
lookup. The send method that takes no destination argument uses the
default destination. Here is an example that sends a message to a queue
using the 1.0.2 implementation.
import javax.jms.ConnectionFactory; import javax.jms.JMSException; import javax.jms.Message; import javax.jms.Queue; import javax.jms.Session; import org.springframework.jms.core.MessageCreator; import org.springframework.jms.core.JmsTemplate; public class JmsQueueSender { private JmsTemplate jmsTemplate; private Queue queue; public void setConnectionFactory(ConnectionFactory cf) { this.jmsTemplate = new JmsTemplate(cf); } public void setQueue(Queue queue) { this.queue = queue; } public void simpleSend() { this.jmsTemplate.send(this.queue, new MessageCreator() { public Message createMessage(Session session) throws JMSException { return session.createTextMessage("hello queue world"); } }); } }
This example uses the MessageCreator
callback
to create a text message from the supplied Session
object. The JmsTemplate
is constructed by passing a
reference to a ConnectionFactory
. As an alternative,
a zero argument constructor and connectionFactory
is provided and can be used for constructing the instance in JavaBean style
(using a BeanFactory or plain Java code). Alternatively, consider deriving
from Spring's JmsGatewaySupport
convenience base class,
which provides pre-built bean properties for JMS configuration.
The method send(String destinationName, MessageCreator
creator)
lets you send a message using the string name of
the destination. If these names are registered in JNDI, you should set the
destinationResolver property of the template to an
instance of JndiDestinationResolver
.
If you created the JmsTemplate
and specified
a default destination, the send(MessageCreator c)
sends a message to that destination.
In order to facilitate the sending of domain model objects, the
JmsTemplate
has various send methods that take a
Java object as an argument for a message's data content. The overloaded
methods convertAndSend()
and
receiveAndConvert()
in
JmsTemplate
delegate the conversion process to an
instance of the MessageConverter
interface. This
interface defines a simple contract to convert between Java objects and
JMS messages. The default implementation
SimpleMessageConverter
supports conversion
between String
and
TextMessage
, byte[]
and
BytesMesssage
, and
java.util.Map
and
MapMessage
. By using the converter, you and your
application code can focus on the business object that is being sent or
received via JMS and not be concerned with the details of how it is
represented as a JMS message.
The sandbox currently includes a
MapMessageConverter
which uses reflection to
convert between a JavaBean and a MapMessage
.
Other popular implementation choices you might implement yourself are
Converters that use an existing XML marshalling package, such as JAXB,
Castor, XMLBeans, or XStream, to create a
TextMessage
representing the
object.
To accommodate the setting of a message's properties, headers, and
body that can not be generically encapsulated inside a converter class,
the MessagePostProcessor
interface gives
you access to the message after it has been converted, but before it is
sent. The example below demonstrates how to modify a message header and
a property after a java.util.Map
is
converted to a message.
public void sendWithConversion() { Map map = new HashMap(); map.put("Name", "Mark"); map.put("Age", new Integer(47)); jmsTemplate.convertAndSend("testQueue", map, new MessagePostProcessor() { public Message postProcessMessage(Message message) throws JMSException { message.setIntProperty("AccountID", 1234); message.setJMSCorrelationID("123-00001"); return message; } }); }
This results in a message of the form:
MapMessage={ Header={ ... standard headers ... CorrelationID={123-00001} } Properties={ AccountID={Integer:1234} } Fields={ Name={String:Mark} Age={Integer:47} } }
While the send operations cover many common usage scenarios, there
are cases when you want to perform multiple operations on a JMS
Session
or
MessageProducer
. The
SessionCallback
and
ProducerCallback
expose the JMS
Session
and
Session
/
MessageProducer
pair respectively. The
execute()
methods on
JmsTemplate
execute these callback
methods.
While JMS is typically associated with asynchronous processing, it
is possible to consume messages synchronously. The overloaded
receive(..)
methods provide this functionality.
During a synchronous receive, the calling thread blocks until a message
becomes available. This can be a dangerous operation since the calling
thread can potentially be blocked indefinitely. The property
receiveTimeout specifies how long the receiver
should wait before giving up waiting for a message.
In a fashion similar to a Message-Driven Bean (MDB) in the EJB
world, the Message-Driven POJO (MDP) acts as a receiver for JMS
messages. The one restriction (but see also below for the discussion of
the MessageListenerAdapter
class) on an MDP is
that it must implement the
javax.jms.MessageListener
interface.
Please also be aware that in the case where your POJO will be receiving
messages on multiple threads, it is important to ensure that your
implementation is thread-safe.
Below is a simple implementation of an MDP:
import javax.jms.JMSException; import javax.jms.Message; import javax.jms.MessageListener; import javax.jms.TextMessage; public class ExampleListener implements MessageListener { public void onMessage(Message message) { if (message instanceof TextMessage) { try { System.out.println(((TextMessage) message).getText()); } catch (JMSException ex) { throw new RuntimeException(ex); } } else { throw new IllegalArgumentException("Message must be of type TextMessage"); } } }
Once you've implemented your
MessageListener
, it's time to create a
message listener container.
Find below an example of how to define and configure one of the
message listener containers that ships with Spring (in this case the
DefaultMessageListenerContainer
).
<!-- this is the Message Driven POJO (MDP) --> <bean id="messageListener" class="jmsexample.ExampleListener" /> <!-- and this is the message listener container --> <bean id="jmsContainer" class="org.springframework.jms.listener.DefaultMessageListenerContainer"> <property name="connectionFactory" ref="connectionFactory"/> <property name="destination" ref="destination"/> <property name="messageListener" ref="messageListener" /> </bean>
Please refer to the Spring Javadoc of the various message listener containers for a full description of the features supported by each implementation.
The SessionAwareMessageListener
interface is a Spring-specific interface that provides a similar
contract to the JMS MessageListener
interface, but also provides the message handling method with access to
the JMS Session
from which the
Message
was received.
package org.springframework.jms.listener; public interface SessionAwareMessageListener { void onMessage(Message message, Session session) throws JMSException; }
You can choose to have your MDPs implement this interface (in
preference to the standard JMS
MessageListener
interface) if you want
your MDPs to be able to respond to any received messages (using the
Session
supplied in the
onMessage(Message, Session)
method). All of the
message listener container implementations that ship with Spring have
support for MDPs that implement either the
MessageListener
or
SessionAwareMessageListener
interface.
Classes that implement the
SessionAwareMessageListener
come with the
caveat that they are then tied to Spring through the interface. The
choice of whether or not to use it is left entirely up to you as an
application developer or architect.
Please note that the 'onMessage(..)'
method of
the SessionAwareMessageListener
interface
throws JMSException
. In contrast to the standard
JMS MessageListener
interface, when using
the SessionAwareMessageListener
interface, it is the responsibility of the client code to handle any
exceptions thrown.
The MessageListenerAdapter
class is the
final component in Spring's asynchronous messaging support: in a
nutshell, it allows you to expose almost any class
as a MDP (there are of course some constraints).
Consider the following interface definition. Notice that although
the interface extends neither the
MessageListener
nor
SessionAwareMessageListener
interfaces,
it can still be used as a MDP via the use of the
MessageListenerAdapter
class. Notice also how the
various message handling methods are strongly typed according to the
contents of the various
Message
types that they can receive and
handle.
public interface MessageDelegate { void handleMessage(String message); void handleMessage(Map message); void handleMessage(byte[] message); void handleMessage(Serializable message); }
public class DefaultMessageDelegate implements MessageDelegate { // implementation elided for clarity... }
In particular, note how the above implementation of the
MessageDelegate
interface (the above
DefaultMessageDelegate
class) has
no JMS dependencies at all. It truly is a POJO that
we will make into an MDP via the following configuration.
<!-- this is the Message Driven POJO (MDP) --> <bean id="messageListener" class="org.springframework.jms.listener.adapter.MessageListenerAdapter"> <constructor-arg> <bean class="jmsexample.DefaultMessageDelegate"/> </constructor-arg> </bean> <!-- and this is the message listener container... --> <bean id="jmsContainer" class="org.springframework.jms.listener.DefaultMessageListenerContainer"> <property name="connectionFactory" ref="connectionFactory"/> <property name="destination" ref="destination"/> <property name="messageListener" ref="messageListener" /> </bean>
Below is an example of another MDP that can only handle the
receiving of JMS TextMessage
messages.
Notice how the message handling method is actually called
'receive'
(the name of the message handling method in
a MessageListenerAdapter
defaults to
'handleMessage'
), but it is configurable (as you will
see below). Notice also how the 'receive(..)'
method
is strongly typed to receive and respond only to JMS
TextMessage
messages.
public interface TextMessageDelegate { void receive(TextMessage message); }
public class DefaultTextMessageDelegate implements TextMessageDelegate { // implementation elided for clarity... }
The configuration of the attendant
MessageListenerAdapter
would look like
this:
<bean id="messageListener" class="org.springframework.jms.listener.adapter.MessageListenerAdapter"> <constructor-arg> <bean class="jmsexample.DefaultTextMessageDelegate"/> </constructor-arg> <property name="defaultListenerMethod" value="receive"/> <!-- we don't want automatic message context extraction --> <property name="messageConverter"> <null/> </property> </bean>
Please note that if the above 'messageListener'
receives a JMS Message
of a type other
than TextMessage
, an
IllegalStateException
will be thrown (and
subsequently swallowed). Another of the capabilities of the
MessageListenerAdapter
class is the ability to
automatically send back a response
Message
if a handler method returns a
non-void value. Consider the interface and class:
public interface ResponsiveTextMessageDelegate { // notice the return type... String receive(TextMessage message); }
public class DefaultResponsiveTextMessageDelegate implements ResponsiveTextMessageDelegate { // implementation elided for clarity... }
If the above
DefaultResponsiveTextMessageDelegate
is used in
conjunction with a MessageListenerAdapter
then
any non-null value that is returned from the execution of the
'receive(..)'
method will (in the default
configuration) be converted into a
TextMessage
. The resulting
TextMessage
will then be sent to the
Destination
(if one exists) defined in
the JMS Reply-To property of the original
Message
, or the default
Destination
set on the
MessageListenerAdapter
(if one has been
configured); if no Destination
is found
then an InvalidDestinationException
will be
thrown (and please note that this exception will
not be swallowed and will propagate up
the call stack).
Invoking a message listener within a transaction only requires reconfiguration of the listener container.
Local resource transactions can simply be activated through the
sessionTransacted
flag on the listener container
definition. Each message listener invocation will then operate within an
active JMS transaction, with message reception rolled back in case of
listener execution failure. Sending a response message (via
SessionAwareMessageListener
) will be part
of the same local transaction, but any other resource operations (such
as database access) will operate independently. This usually requires
duplicate message detection in the listener implementation, covering the
case where database processing has committed but message processing
failed to commit.
<bean id="jmsContainer" class="org.springframework.jms.listener.DefaultMessageListenerContainer"> <property name="connectionFactory" ref="connectionFactory"/> <property name="destination" ref="destination"/> <property name="messageListener" ref="messageListener"/> <property name="sessionTransacted" value="true"/> </bean>
For participating in an externally managed transaction, you will
need to configure a transaction manager and use a listener container
which supports externally managed transactions: typically
DefaultMessageListenerContainer
.
To configure a message listener container for XA transaction
participation, you'll want to configure a
JtaTransactionManager
(which, by default,
delegates to the Java EE server's transaction subsystem). Note that the
underlying JMS ConnectionFactory needs to be XA-capable and properly
registered with your JTA transaction coordinator! (Check your Java EE
server's configuration of JNDI resources.) This allows message reception
as well as e.g. database access to be part of the same transaction (with
unified commit semantics, at the expense of XA transaction log
overhead).
<bean id="transactionManager" class="org.springframework.transaction.jta.JtaTransactionManager"/>
Then you just need to add it to our earlier container configuration. The container will take care of the rest.
<bean id="jmsContainer" class="org.springframework.jms.listener.DefaultMessageListenerContainer"> <property name="connectionFactory" ref="connectionFactory"/> <property name="destination" ref="destination"/> <property name="messageListener" ref="messageListener"/> <property name="transactionManager" ref="transactionManager"/> </bean>
Beginning with version 2.5, Spring also provides support for a
JCA-based MessageListener
container. The
JmsMessageEndpointManager
will attempt to
automatically determine the ActivationSpec
class name from the provider's
ResourceAdapter
class name. Therefore, it
is typically possible to just provide Spring's generic
JmsActivationSpecConfig
as shown in the following
example.
<bean class="org.springframework.jms.listener.endpoint.JmsMessageEndpointManager"> <property name="resourceAdapter" ref="resourceAdapter"/> <property name="activationSpecConfig"> <bean class="org.springframework.jms.listener.endpoint.JmsActivationSpecConfig"> <property name="destinationName" value="myQueue"/> </bean> </property> <property name="messageListener" ref="myMessageListener"/> </bean>
Alternatively, you may set up a
JmsMessageEndpointManager
with a given
ActivationSpec
object. The
ActivationSpec
object may also come from a
JNDI lookup (using <jee:jndi-lookup>
).
<bean class="org.springframework.jms.listener.endpoint.JmsMessageEndpointManager"> <property name="resourceAdapter" ref="resourceAdapter"/> <property name="activationSpec"> <bean class="org.apache.activemq.ra.ActiveMQActivationSpec"> <property name="destination" value="myQueue"/> <property name="destinationType" value="javax.jms.Queue"/> </bean> </property> <property name="messageListener" ref="myMessageListener"/> </bean>
Using Spring's ResourceAdapterFactoryBean
,
the target ResourceAdapter
may be
configured locally as depicted in the following example.
<bean id="resourceAdapter" class="org.springframework.jca.support.ResourceAdapterFactoryBean"> <property name="resourceAdapter"> <bean class="org.apache.activemq.ra.ActiveMQResourceAdapter"> <property name="serverUrl" value="tcp://localhost:61616"/> </bean> </property> <property name="workManager"> <bean class="org.springframework.jca.work.SimpleTaskWorkManager"/> </property> </bean>
The specified WorkManager
may also
point to an environment-specific thread pool - typically through
SimpleTaskWorkManager's
"asyncTaskExecutor"
property. Consider defining a shared thread pool for all your
ResourceAdapter
instances if you happen to
use multiple adapters.
In some environments (e.g. WebLogic 9 or above), the entire
ResourceAdapter
object may be obtained from
JNDI instead (using <jee:jndi-lookup>
). The
Spring-based message listeners can then interact with the server-hosted
ResourceAdapter
, also using the server's
built-in WorkManager
.
Please consult the JavaDoc for
JmsMessageEndpointManager
,
JmsActivationSpecConfig
, and
ResourceAdapterFactoryBean
for more details.
Spring also provides a generic JCA message endpoint manager which is
not tied to JMS:
org.springframework.jca.endpoint.GenericMessageEndpointManager
.
This component allows for using any message listener type (e.g. a CCI
MessageListener) and any provider-specific ActivationSpec object. Check
out your JCA provider's documentation to find out about the actual
capabilities of your connector, and consult
GenericMessageEndpointManager
's JavaDoc for the
Spring-specific configuration details.
Note | |
---|---|
JCA-based message endpoint management is very analogous to EJB 2.1 Message-Driven Beans; it uses the same underlying resource provider contract. Like with EJB 2.1 MDBs, any message listener interface supported by your JCA provider can be used in the Spring context as well. Spring nevertheless provides explicit 'convenience' support for JMS, simply because JMS is the most common endpoint API used with the JCA endpoint management contract. |
Spring 2.5 introduces an XML namespace for simplifying JMS configuration. To use the JMS namespace elements you will need to reference the JMS schema:
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jms="http://www.springframework.org/schema/jms" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/jms http://www.springframework.org/schema/jms/spring-jms-3.0.xsd"> <!-- <bean/> definitions here --> </beans>
The namespace consists of two top-level elements:
<listener-container/>
and
<jca-listener-container/>
both of which may
contain one or more <listener/>
child elements.
Here is an example of a basic configuration for two listeners.
<jms:listener-container> <jms:listener destination="queue.orders" ref="orderService" method="placeOrder"/> <jms:listener destination="queue.confirmations" ref="confirmationLogger" method="log"/> </jms:listener-container>
The example above is equivalent to creating two distinct listener
container bean definitions and two distinct
MessageListenerAdapter
bean definitions as
demonstrated in Section 22.4.4, “The MessageListenerAdapter”.
In addition to the attributes shown above, the listener
element
may contain several optional ones. The following table describes all available
attributes:
Table 22.1. Attributes of the JMS <listener>
element
Attribute | Description |
---|---|
id | A bean name for the hosting listener container. If not specified, a bean name will be automatically generated. |
destination (required) | The destination name for this listener, resolved
through the |
ref (required) | The bean name of the handler object. |
method | The name of the handler method to invoke. If the
|
response-destination | The name of the default response destination to send response messages to. This will be applied in case of a request message that does not carry a "JMSReplyTo" field. The type of this destination will be determined by the listener-container's "destination-type" attribute. Note: This only applies to a listener method with a return value, for which each result object will be converted into a response message. |
subscription | The name of the durable subscription, if any. |
selector | An optional message selector for this listener. |
The <listener-container/>
element also
accepts several optional attributes. This allows for customization of the
various strategies (for example, taskExecutor and
destinationResolver) as well as basic JMS settings
and resource references. Using these attributes, it is possible to define
highly-customized listener containers while still benefiting from the
convenience of the namespace.
<jms:listener-container connection-factory="myConnectionFactory" task-executor="myTaskExecutor" destination-resolver="myDestinationResolver" transaction-manager="myTransactionManager" concurrency="10"> <jms:listener destination="queue.orders" ref="orderService" method="placeOrder"/> <jms:listener destination="queue.confirmations" ref="confirmationLogger" method="log"/> </jms:listener-container>
The following table describes all available attributes. Consult the
class-level Javadoc of the
AbstractMessageListenerContainer
and its concrete
subclasses for more details on the individual properties. The Javadoc also
provides a discussion of transaction choices and message redelivery
scenarios.
Table 22.2. Attributes of the JMS
<listener-container>
element
Attribute | Description |
---|---|
container-type | The type of this listener container. Available
options are: |
connection-factory | A reference to the JMS
|
task-executor | A reference to the Spring
|
destination-resolver | A reference to the
|
message-converter | A reference to the
|
destination-type | The JMS destination type for this listener:
|
client-id | The JMS client id for this listener container. Needs to be specified when using durable subscriptions. |
cache | The cache level for JMS resources:
|
acknowledge | The native JMS acknowledge mode:
|
transaction-manager | A reference to an external
|
concurrency | The number of concurrent sessions/consumers to start for each listener. Can either be a simple number indicating the maximum number (e.g. "5") or a range indicating the lower as well as the upper limit (e.g. "3-5"). Note that a specified minimum is just a hint and might be ignored at runtime. Default is 1; keep concurrency limited to 1 in case of a topic listener or if queue ordering is important; consider raising it for general queues. |
prefetch | The maximum number of messages to load into a single session. Note that raising this number might lead to starvation of concurrent consumers! |
Configuring a JCA-based listener container with the "jms" schema support is very similar.
<jms:jca-listener-container resource-adapter="myResourceAdapter" destination-resolver="myDestinationResolver" transaction-manager="myTransactionManager" concurrency="10"> <jms:listener destination="queue.orders" ref="myMessageListener"/> </jms:jca-listener-container>
The available configuration options for the JCA variant are described in the following table:
Table 22.3. Attributes of the JMS
<jca-listener-container/>
element
Attribute | Description |
---|---|
resource-adapter | A reference to the JCA
|
activation-spec-factory | A reference to the
|
destination-resolver | A reference to the
|
message-converter | A reference to the
|
destination-type | The JMS destination type for this listener:
|
client-id | The JMS client id for this listener container. Needs to be specified when using durable subscriptions. |
acknowledge | The native JMS acknowledge mode:
|
transaction-manager | A reference to a Spring
|
concurrency | The number of concurrent sessions/consumers to start for each listener. Can either be a simple number indicating the maximum number (e.g. "5") or a range indicating the lower as well as the upper limit (e.g. "3-5"). Note that a specified minimum is just a hint and will typically be ignored at runtime when using a JCA listener container. Default is 1. |
prefetch | The maximum number of messages to load into a single session. Note that raising this number might lead to starvation of concurrent consumers! |