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Common Router Parameters
This section describes the parameters common to all router parameters (the parameters with all their boxes ticked in the two tables shown earlier in this chapter).
Inside and Outside a Chain
The following parameters are valid for all routers inside and outside of chains.
apply-sequence
-
This attribute specifies whether sequence number and size headers should be added to each message. This optional attribute defaults to
false
. default-output-channel
-
If set, this attribute provides a reference to the channel where messages should be sent if channel resolution fails to return any channels. If no default output channel is provided, the router throws an exception. If you would like to silently drop those messages instead, set the default output channel attribute value to
nullChannel
.Starting with version 6.0, setting a default output channel also resets the channelKeyFallback
option tofalse
. So, no attempts will be made to resolve a channel from its name, but rather fallback to this default output channel - similar to a Javaswitch
statement. IfchannelKeyFallback
is set totrue
explicitly, the further logic depends on theresolutionRequired
option: the message to non-resolved channel from key can reach adefaultOutputChannel
only ifresolutionRequired
isfalse
. Therefore, a configuration wheredefaultOutputChannel
is provided and bothchannelKeyFallback
&resolutionRequired
are set totrue
is rejected by theAbstractMappingMessageRouter
initialization phase. resolution-required
-
This attribute specifies whether channel names must always be successfully resolved to channel instances that exist. If set to
true
, aMessagingException
is raised when the channel cannot be resolved. Setting this attribute tofalse
causes any unresolvable channels to be ignored. This optional attribute defaults totrue
.A Message is sent only to the default-output-channel
, if specified, whenresolution-required
isfalse
and the channel is not resolved. ignore-send-failures
-
If set to
true
, failures to send to a message channel is ignored. If set tofalse
, aMessageDeliveryException
is thrown instead, and, if the router resolves more than one channel, any subsequent channels do not receive the message.The exact behavior of this attribute depends on the type of the
Channel
to which the messages are sent. For example, when using direct channels (single threaded), send failures can be caused by exceptions thrown by components much further downstream. However, when sending messages to a simple queue channel (asynchronous), the likelihood of an exception to be thrown is rather remote.While most routers route to a single channel, they can return more than one channel name. The recipient-list-router
, for instance, does exactly that. If you set this attribute totrue
on a router that only routes to a single channel, any caused exception is swallowed, which usually makes little sense. In that case, it would be better to catch the exception in an error flow at the flow entry point. Therefore, setting theignore-send-failures
attribute totrue
usually makes more sense when the router implementation returns more than one channel name, because the other channel(s) following the one that fails would still receive the message.This attribute defaults to
false
. timeout
-
The
timeout
attribute specifies the maximum amount of time in milliseconds to wait when sending messages to the target Message Channels.
Top-Level (Outside a Chain)
The following parameters are valid only across all top-level routers that are outside of chains.
id
-
Identifies the underlying Spring bean definition, which, in the case of routers, is an instance of
EventDrivenConsumer
orPollingConsumer
, depending on whether the router’sinput-channel
is aSubscribableChannel
or aPollableChannel
, respectively. This is an optional attribute. auto-startup
-
This “lifecycle” attribute signaled whether this component should be started during startup of the application context. This optional attribute defaults to
true
. input-channel
-
The receiving message channel of this endpoint.
order
-
This attribute defines the order for invocation when this endpoint is connected as a subscriber to a channel. This is particularly relevant when that channel uses a failover dispatching strategy. It has no effect when this endpoint itself is a polling consumer for a channel with a queue.