Nats :: Apache Camel

URI format

nats:topic[?options]

Where topic is the topic name

Configuring Options

Camel components are configured on two separate levels:

component level
endpoint level

Configuring Component Options

At the component level, you set general and shared configurations that are, then, inherited by the endpoints. It is the highest configuration level.

For example, a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre-configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

You can configure components using:

the Component DSL.
in a configuration file (application.properties, *.yaml files, etc).
directly in the Java code.

Configuring Endpoint Options

You usually spend more time setting up endpoints because they have many options. These options help you customize what you want the endpoint to do. The options are also categorized into whether the endpoint is used as a consumer (from), as a producer (to), or both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders.

Property placeholders provide a few benefits:

They help prevent using hardcoded urls, port numbers, sensitive information, and other settings.
They allow externalizing the configuration from the code.
They help the code to become more flexible and reusable.

The following two sections list all the options, firstly for the component followed by the endpoint.

Component Options

The Nats component supports 7 options, which are listed below.

Name	Description	Default	Type
servers (common)	URLs to one or more NAT servers. Use comma to separate URLs when specifying multiple servers.		String
verbose (common)	Whether or not running in verbose mode.	false	boolean
bridgeErrorHandler (consumer)	Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.	false	boolean
lazyStartProducer (producer)	Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.	false	boolean
autowiredEnabled (advanced)	Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.	true	boolean
headerFilterStrategy (filter)	To use a custom org.apache.camel.spi.HeaderFilterStrategy to filter header to and from Camel message.		HeaderFilterStrategy
useGlobalSslContextParameters (security)	Enable usage of global SSL context parameters.	false	boolean

Name

Description

Default

Type

servers (common)

URLs to one or more NAT servers. Use comma to separate URLs when specifying multiple servers.

String

verbose (common)

Whether or not running in verbose mode.

false

boolean

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

headerFilterStrategy (filter)

To use a custom org.apache.camel.spi.HeaderFilterStrategy to filter header to and from Camel message.

HeaderFilterStrategy

useGlobalSslContextParameters (security)

Enable usage of global SSL context parameters.

false

boolean

Endpoint Options

The Nats endpoint is configured using URI syntax:

nats:topic

With the following path and query parameters:

Path Parameters (1 parameters)

Name	Description	Default	Type
topic (common)	Required The name of topic we want to use.		String

Name

Description

Default

Type

topic (common)

Required The name of topic we want to use.

String

Query Parameters (30 parameters)

Name	Description	Default	Type
connectionTimeout (common)	Timeout for connection attempts. (in milliseconds).	2000	int
flushConnection (common)	Define if we want to flush connection when stopping or not.	true	boolean
flushTimeout (common)	Set the flush timeout (in milliseconds).	1000	int
maxPingsOut (common)	maximum number of pings have not received a response allowed by the client.	2	int
maxReconnectAttempts (common)	Max reconnection attempts.	60	int
noEcho (common)	Turn off echo. If supported by the gnatsd version you are connecting to this flag will prevent the server from echoing messages back to the connection if it has subscriptions on the subject being published to.	false	boolean
noRandomizeServers (common)	Whether or not randomizing the order of servers for the connection attempts.	false	boolean
pedantic (common)	Whether or not running in pedantic mode (this affects performance).	false	boolean
pingInterval (common)	Ping interval to be aware if connection is still alive (in milliseconds).	120000	int
reconnect (common)	Whether or not using reconnection feature.	true	boolean
reconnectTimeWait (common)	Waiting time before attempts reconnection (in milliseconds).	2000	int
requestCleanupInterval (common)	Interval to clean up cancelled/timed out requests.	5000	int
servers (common)	URLs to one or more NAT servers. Use comma to separate URLs when specifying multiple servers.		String
verbose (common)	Whether or not running in verbose mode.	false	boolean
maxMessages (consumer)	Stop receiving messages from a topic we are subscribing to after maxMessages.		String
poolSize (consumer)	Consumer thread pool size (default is 10).	10	int
queueName (consumer)	The Queue name if we are using nats for a queue configuration.		String
replyToDisabled (consumer)	Can be used to turn off sending back reply message in the consumer.	false	boolean
bridgeErrorHandler (consumer (advanced))	Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.	false	boolean
exceptionHandler (consumer (advanced))	To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.		ExceptionHandler
exchangePattern (consumer (advanced))	Sets the exchange pattern when the consumer creates an exchange. Enum values: InOnly InOut		ExchangePattern
replySubject (producer)	the subject to which subscribers should send response.		String
requestTimeout (producer)	Request timeout in milliseconds.	20000	long
lazyStartProducer (producer (advanced))	Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.	false	boolean
connection (advanced)	Reference an already instantiated connection to Nats server.		Connection
headerFilterStrategy (advanced)	Define the header filtering strategy.		HeaderFilterStrategy
traceConnection (advanced)	Whether or not connection trace messages should be printed to standard out for fine grained debugging of connection issues.	false	boolean
credentialsFilePath (security)	If we use useCredentialsFile to true we’ll need to set the credentialsFilePath option. It can be loaded by default from classpath, but you can prefix with classpath:, file:, or http: to load the resource from different systems.		String
secure (security)	Set secure option indicating TLS is required.	false	boolean
sslContextParameters (security)	To configure security using SSLContextParameters.		SSLContextParameters

Name

Description

Default

Type

connectionTimeout (common)

Timeout for connection attempts. (in milliseconds).

2000

int

flushConnection (common)

Define if we want to flush connection when stopping or not.

true

boolean

flushTimeout (common)

Set the flush timeout (in milliseconds).

1000

int

maxPingsOut (common)

maximum number of pings have not received a response allowed by the client.

2

int

maxReconnectAttempts (common)

Max reconnection attempts.

60

int

noEcho (common)

Turn off echo. If supported by the gnatsd version you are connecting to this flag will prevent the server from echoing messages back to the connection if it has subscriptions on the subject being published to.

false

boolean

noRandomizeServers (common)

Whether or not randomizing the order of servers for the connection attempts.

false

boolean

pedantic (common)

Whether or not running in pedantic mode (this affects performance).

false

boolean

pingInterval (common)

Ping interval to be aware if connection is still alive (in milliseconds).

120000

int

reconnect (common)

Whether or not using reconnection feature.

true

boolean

reconnectTimeWait (common)

Waiting time before attempts reconnection (in milliseconds).

2000

int

requestCleanupInterval (common)

Interval to clean up cancelled/timed out requests.

5000

int

servers (common)

URLs to one or more NAT servers. Use comma to separate URLs when specifying multiple servers.

String

verbose (common)

Whether or not running in verbose mode.

false

boolean

maxMessages (consumer)

Stop receiving messages from a topic we are subscribing to after maxMessages.

String

poolSize (consumer)

Consumer thread pool size (default is 10).

10

int

queueName (consumer)

The Queue name if we are using nats for a queue configuration.

String

replyToDisabled (consumer)

Can be used to turn off sending back reply message in the consumer.

false

boolean

bridgeErrorHandler (consumer (advanced))

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

exceptionHandler (consumer (advanced))

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.

ExceptionHandler

exchangePattern (consumer (advanced))

Sets the exchange pattern when the consumer creates an exchange.

Enum values:

InOnly
InOut

ExchangePattern

replySubject (producer)

the subject to which subscribers should send response.

String

requestTimeout (producer)

Request timeout in milliseconds.

20000

long

lazyStartProducer (producer (advanced))

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

connection (advanced)

Reference an already instantiated connection to Nats server.

Connection

headerFilterStrategy (advanced)

Define the header filtering strategy.

HeaderFilterStrategy

traceConnection (advanced)

Whether or not connection trace messages should be printed to standard out for fine grained debugging of connection issues.

false

boolean

credentialsFilePath (security)

If we use useCredentialsFile to true we’ll need to set the credentialsFilePath option. It can be loaded by default from classpath, but you can prefix with classpath:, file:, or http: to load the resource from different systems.

String

secure (security)

Set secure option indicating TLS is required.

false

boolean

sslContextParameters (security)

To configure security using SSLContextParameters.

SSLContextParameters

Message Headers

The Nats component supports 5 message header(s), which is/are listed below:

Name Description Default Type

Name	Description	Type
CamelNatsMessageTimestamp (common) Constant: `NATS_MESSAGE_TIMESTAMP`	The timestamp of a consumed message.	long
CamelNatsSID (common) Constant: `NATS_SID`	The SID of a consumed message.	String
CamelNatsReplyTo (common) Constant: `NATS_REPLY_TO`	The ReplyTo of a consumed message (may be null).	String
CamelNatsSubject (common) Constant: `NATS_SUBJECT`	The Subject of a consumed message.	String
CamelNatsQueueName (common) Constant: `NATS_QUEUE_NAME`	The Queue name of a consumed message (may be null).	String

CamelNatsMessageTimestamp (common)

Constant: NATS_MESSAGE_TIMESTAMP

The timestamp of a consumed message.

long

CamelNatsSID (common)

Constant: NATS_SID

The SID of a consumed message.

String

CamelNatsReplyTo (common)

Constant: NATS_REPLY_TO

The ReplyTo of a consumed message (may be null).

String

CamelNatsSubject (common)

Constant: NATS_SUBJECT

The Subject of a consumed message.

String

CamelNatsQueueName (common)

Constant: NATS_QUEUE_NAME

The Queue name of a consumed message (may be null).

String

Usage

Configuring servers

You configure the NATS servers on either the component or the endpoint.

For example, to configure this once on the component, you can do:

NatsComponent nats = context.getComponent("nats", NatsComponent.class);
nats.setServers("someserver:4222,someotherserver:42222");

Notice how you can specify multiple servers separated by comma.

Or you can specify the servers in the endpoint URI

from("direct:send").to("nats:test?servers=localhost:4222");

The endpoint configuration will override any server configuration on the component level.

Configuring username and password or token

You can specify username and password for the servers in the server URLs, where its username:password@url, or token@url etc:

NatsComponent nats = context.getComponent("nats", NatsComponent.class);
nats.setServers("scott:tiger@someserver:4222,superman:123@someotherserver:42222");

If you are using Camel Main or Spring Boot, you can configure the server urls in the application.properties file

camel.component.nats.servers=scott:tiger@someserver:4222,superman:123@someotherserver:42222

Request/Reply support

The producer supports request/reply where it can wait for an expected reply message.

The consumer will, when routing the message is complete, send back the message as reply-message if required.

Examples

Producer example

from("direct:send")
  .to("nats:mytopic");

In case of using authorization, you can directly specify your credentials in the server URL

from("direct:send")
  .to("nats:mytopic?servers=username:password@localhost:4222");

or your token

from("direct:send")
  .to("nats:mytopic?servers=token@localhost:4222);

Consumer example

from("nats:mytopic?maxMessages=5&queueName=myqueue")
  .to("mock:result");

Spring Boot Auto-Configuration

When using nats with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-nats-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 8 options, which are listed below.

Name	Description	Default	Type
camel.component.nats.autowired-enabled	Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.	true	Boolean
camel.component.nats.bridge-error-handler	Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.	false	Boolean
camel.component.nats.enabled	Whether to enable auto configuration of the nats component. This is enabled by default.		Boolean
camel.component.nats.header-filter-strategy	To use a custom org.apache.camel.spi.HeaderFilterStrategy to filter header to and from Camel message. The option is a org.apache.camel.spi.HeaderFilterStrategy type.		HeaderFilterStrategy
camel.component.nats.lazy-start-producer	Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.	false	Boolean
camel.component.nats.servers	URLs to one or more NAT servers. Use comma to separate URLs when specifying multiple servers.		String
camel.component.nats.use-global-ssl-context-parameters	Enable usage of global SSL context parameters.	false	Boolean
camel.component.nats.verbose	Whether or not running in verbose mode.	false	Boolean

Name

Description

Default

Type

camel.component.nats.autowired-enabled

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

Boolean

camel.component.nats.bridge-error-handler

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

Boolean

camel.component.nats.enabled

Whether to enable auto configuration of the nats component. This is enabled by default.

Boolean

camel.component.nats.header-filter-strategy

To use a custom org.apache.camel.spi.HeaderFilterStrategy to filter header to and from Camel message. The option is a org.apache.camel.spi.HeaderFilterStrategy type.

HeaderFilterStrategy

camel.component.nats.lazy-start-producer

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

Boolean

camel.component.nats.servers

URLs to one or more NAT servers. Use comma to separate URLs when specifying multiple servers.

String

camel.component.nats.use-global-ssl-context-parameters

Enable usage of global SSL context parameters.

false

Boolean

camel.component.nats.verbose

Whether or not running in verbose mode.

false

Boolean