com.r3corda.node.services.api / AbstractNodeService / addMessageHandler

# addMessageHandler

`protected inline fun <reified Q : AbstractRequestMessage, reified R : Any> addMessageHandler(topic: String, crossinline handler: (Q) -> R, crossinline exceptionConsumer: (Message, Exception) -> Unit): Unit`

Register a handler for a message topic. In comparison to using net.addMessageHandler() this manages a lot of common boilerplate code. Exceptions are caught and passed to the provided consumer.

### Parameters

`topic` - the topic, without the default session ID postfix (".0)
`handler` - a function to handle the deserialised request and return a response
`exceptionConsumer` - a function to which any thrown exception is passed.
`protected inline fun <reified Q : AbstractRequestMessage, reified R : Any> addMessageHandler(topic: String, crossinline handler: (Q) -> R): Unit`

Register a handler for a message topic. In comparison to using net.addMessageHandler() this manages a lot of common boilerplate code. Exceptions are propagated to the messaging layer.

### Parameters

`topic` - the topic, without the default session ID postfix (".0)
`handler` - a function to handle the deserialised request and return a response