Since content-based routing often requires some domain-specific logic, most use-cases will require Spring Integration's options for delegating to POJOs using the XML namespace support and/or Annotations. Both of these are discussed below, but first we present a couple implementations that are available out-of-the-box since they fulfill generic, but common, requirements.

A PayloadTypeRouter will send Messages to the channel as defined by payload-type mappings. ]]> Configuration of PayloadTypeRouter is also supported via namespace support provided by Spring Integration (see ), which essentially simplifies configuration by combining <router/> configuration and its corresponding implementation defined using <bean/> element into a single and more concise configuration element. Example below demonstrates PayloadTypeRouter configuration which is equivalent to the one above using Spring Integration namespace support: ]]>

A HeaderValueRouter will send Messages to the channel based on the individual header value mappings. When HeaderValueRouter is created it is initialized with the name of the header to be evaluated, using constructor-arg. The value of the header could be one of two things: 1. Arbitrary value 2. Channel name If arbitrary value, then channelResolver should be provided to map header values to channel names. Example below uses MapBasedChannelResolver to set up a map of header values to channel names. ]]> If channelResolver is not specified, then header value will be treated as channel name making configuration much simpler, where no channelResolver needs to be specified. ]]> Similar to the PayloadTypeRouter, configuration of HeaderValueRouter is also supported via namespace support provided by Spring Integration (see ). Example below demonstrates two types of namespace-based configuration of HeaderValueRouter which are equivalent to the ones above using Spring Integration namespace support: 1. Configuration where mapping of header values to channels is required ]]> 2. Configuration where mapping of header values is not required if header values themselves represent the channel names ]]>

A RecipientListRouter will send each received Message to a statically-defined list of Message Channels: ]]>

The router implementations share some common properties, such as "defaultOutputChannel" and "resolutionRequired". If "resolutionRequired" is set to "true", and the router is unable to determine a target channel (e.g. there is no matching payload for a PayloadTypeRouter and no "defaultOutputChannel" has been specified), then an Exception will be thrown.

The "router" element provides a simple way to connect a router to an input channel, and also accepts the optional default output channel. The "ref" may provide the bean name to one of the implementations described above or a custom Router implementation (extending AbstractMessageRouter): ]]> Alternatively, the "ref" may point to a simple Object that contains the @Router annotation (see below), or the "ref" may be combined with an explicit "method" name. When specifying a "method", the same behavior applies as described in the @Router annotation section below. ]]> Using a "ref" attribute is generally recommended if the custom router implementation can be reused in other <router> definitions. However if the custom router implementation should be scoped to a concrete definition of the <router>, starting with v1.0.3, Spring Integration supports inner bean definitions for custom routers within the <router> element: ]]> Using both the "ref" attribute and an inner handler definition in the same <router> configuration is not allowed, as it creates an ambiguous condition and will result in Exception being thrown.

When using the @Router annotation, the annotated method can return either the MessageChannel or String type. In the case of the latter, the endpoint will resolve the channel name as it does for the default output. Additionally, the method can return either a single value or a collection. When a collection is returned, the reply message will be sent to multiple channels. To summarize, the following method signatures are all valid. @Router public MessageChannel route(Message message) {...} @Router public List<MessageChannel> route(Message message) {...} @Router public String route(Foo payload) {...} @Router public List<String> route(Foo payload) {...} In addition to payload-based routing, a common requirement is to route based on metadata available within the message header as either a property or attribute. Rather than requiring use of the Message type as the method parameter, the @Router annotation may also use the @Header parameter annotation that is documented in section . @Router public List<String> route(@Header("orderStatus") OrderStatus status)

For routing of XML-based Messages, including XPath support, see .