Spring provides a JMS integration framework that simplifies the use of the JMS API and shields the user from differences between the JMS 1.0.2 and 1.1 APIs. 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 J2EE's message-driven bean style, Spring provides a number of message listener containers that are used to create Message-Driven POJOs (MDPs). There are two major releases of the JMS specification, 1.0.2 and 1.1. JMS 1.0.2 defined two types of messaging domains, point-to-point (Queues) and publish/subscribe (Topics). The 1.0.2 API reflected these two messaging domains by providing a parallel class hierarchy for each domain. As a result, a client application became domain specific in its use of the JMS API. JMS 1.1 introduced the concept of domain unification that minimized both the functional differences and client API differences between the two domains. As an example of a functional difference that was removed, if you use a JMS 1.1 provider you can transactionally consume a message from one domain and produce a message on the other using the same Session. The JMS 1.1 specification was released in April 2002 and incorporated as part of J2EE 1.4 in November 2003. As a result, common J2EE 1.3 application servers which are still in widespread use (such as BEA WebLogic 8.1 and IBM WebSphere 5.1) are based on JMS 1.0.2. The package org.springframework.jms.core provides the core functionality for using JMS. It contains JMS template classes that simplifies 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.

There are two variants of the functionality offered by the JmsTemplate: the JmsTemplate uses the JMS 1.1 API, and the subclass JmsTemplate102 uses the JMS 1.0.2 API. Code that uses the JmsTemplate only needs to implement callback interfaces giving them a clearly defined 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. Instances of the JmsTemplate class are thread-safe once configured. This is important because it means that you can configure a single instance of a JmsTemplate and then safely inject this shared reference into multiple collaborators. To be clear, the JmsTemplate is stateful, in that it maintains a reference to a ConnectionFactory, but this state is not conversational state.

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 session. In order to use this implementation, J2EE 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. 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.

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 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 are 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. In the 1.0.2 implementation the value of this property determines if the JmsTemplate's send operations will send a message to a Queue or to a Topic. This flag has no effect on send operations for the 1.1 implementation. However, in both implementations, this property 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 the section entitled 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 three standard JMS message listener containers packaged with Spring, each with its specialised feature set.

This message listener container is the simplest of the three standard flavors. It simply creates a fixed number of JMS sessions at startup and uses them throughout the lifespan of the container. This container doesn't allow for dynamic adaption to runtime demands or participate in externally managed transactions. However, it does have the fewest requirements on the JMS provider: This listener container only requires simple JMS API compliance.

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); processing can take advantage of XA transation semantics. This listener container strikes a good balance between low requirements on the JMS provider and good functionality including transaction participation.

This listener container leverages the JMS ServerSessionPool SPI to allow for dynamic management of JMS sessions. The use of this variety of message listener container enables the provider to perform dynamic runtime tuning but, at the expense of requiring the JMS provider to support the ServerSessionPool SPI. If there is no need for provider-driven runtime tuning, look at the DefaultMessageListenerContainer or the SimpleMessageListenerContainer instead.

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 . 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 J2EE 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 J2EE 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. This example uses the MessageCreator callback to create a text message from the supplied Session object and the JmsTemplate is constructed by passing a reference to a ConnectionFactory and a boolean specifying the messaging domain. A zero argument constructor and connectionFactory / queue bean properties are provided and can be used for constructing the instance (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. When configuring the JMS 1.0.2 support in an application context, it is important to remember setting the value of the boolean property pubSubDomain property in order to indicate if you want to send to Queues or Topics. The method send(String destinationName, MessageCreator creator) lets you send to 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 implementations 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. This results in a message of the form:

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 respectfully. 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: 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) --> ]]><!-- and this is the message listener container --> ]]>]]>]]> 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 the JMS MessageListener interface, but also provides the message handling method with access to the JMS Session from which the Message was received. 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 wth 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). If you are using the JMS 1.0.2 API, you will want to use the MessageListenerAdapter102 class which provides the exact same functionality and value add as the MessageListenerAdapter class, but for the JMS 1.0.2 API. 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. // 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) --> ]]> <!-- and this is the message listener container... --> ]]>]]>]]> 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. // implementation elided for clarity... The configuration of the attendant MessageListenerAdapter would look like this: ]]><!-- we don't want automatic message context extraction --> ]]> 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: // notice the return type... // 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. ]]>]]>]]> 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 J2EE 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 J2EE server's configuration of JNDI resources.) This allows message recepton 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). ]]> Then you just need to add it to our earlier container configuration. The container will take care of the rest. ]]>]]>]]>

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. ]]> 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>). ]]> Using Spring's ResourceAdapterFactoryBean, the target ResourceAdapter may be configured locally as depicted in the following example. ]]> 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 provided-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. 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: xmlns:jms="http://www.springframework.org/schema/jms"http://www.springframework.org/schema/jms http://www.springframework.org/schema/jms/spring-jms-2.5.xsd" ]]><!-- <bean/> definitions here -->]]> 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. ]]> The example above is equivalent to creating two distinct listener container bean definitions and two distinct MessageListenerAdapter bean definitions as demonstrated in the section entitled . In addition to the attributes shown above, the listener element may contain several optional ones. The following table describes all available attributes: 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 DestinationResolver strategy. ref (required) The bean name of the handler object. method The name of the handler method to invoke. If the ref points to a MessageListener or Spring SessionAwareMessageListener, this attribute may be omitted. 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. ]]> The following table describes all available attributes. Consult the class-level Javadoc of the AbstractMessageListenerContainer and its concrete subclasses for more detail on the individual properties. The Javadoc also provides a discussion of transaction choices and message redelivery scenarios. Attribute Description container-type The type of this listener container. Available options are: default, simple, default102, or simple102 (the default value is 'default'). connection-factory A reference to the JMS ConnectionFactory bean (the default bean name is 'connectionFactory'). task-executor A reference to the Spring TaskExecutor for the JMS listener invokers. destination-resolver A reference to the DestinationResolver strategy for resolving JMS Destinations. message-converter A reference to the MessageConverter strategy for converting JMS Messages to listener method arguments. Default is a SimpleMessageConverter. destination-type The JMS destination type for this listener: queue, topic or durableTopic. The default is queue. 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: none, connection, session, consumer or auto. By default (auto), the cache level will effectively be "consumer", unless an external transaction manager has been specified - in which case the effective default will be none (assuming J2EE-style transaction management where the given ConnectionFactory is an XA-aware pool). acknowledge The native JMS acknowledge mode: auto, client, dups-ok or transacted. A value of transacted activates a locally transacted Session. As an alternative, specify the transaction-manager attribute described below. Default is auto. transaction-manager A reference to an external PlatformTransactionManager (typically an XA-based transaction coordinator, e.g. Spring's JtaTransactionManager). If not specified, native acknowledging will be used (see "acknowledge" attribute). 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. ]]> The available configuration options for the JCA variant are described in the following table: Attribute Description resource-adapter A reference to the JCA ResourceAdapter bean (the default bean name is 'resourceAdapter'). activation-spec-factory A reference to the JmsActivationSpecFactory. The default is to autodetect the JMS provider and its ActivationSpec class (see DefaultJmsActivationSpecFactory) destination-resolver A reference to the DestinationResolver strategy for resolving JMS Destinations. message-converter A reference to the MessageConverter strategy for converting JMS Messages to listener method arguments. Default is a SimpleMessageConverter. destination-type The JMS destination type for this listener: queue, topic or durableTopic. The default is queue. client-id The JMS client id for this listener container. Needs to be specified when using durable subscriptions. acknowledge The native JMS acknowledge mode: auto, client, dups-ok or transacted. A value of transacted activates a locally transacted Session. As an alternative, specify the transaction-manager attribute described below. Default is auto. transaction-manager A reference to a Spring JtaTransactionManager or a javax.transaction.TransactionManager for kicking off an XA transaction for each incoming message. If not specified, native acknowledging will be used (see the "acknowledge" attribute). 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!