CoAP

Since Camel 2.16

Both producer and consumer are supported

Camel-CoAP is an Apache Camel component that allows you to work with CoAP, a lightweight REST-type protocol for machine-to-machine operation. CoAP, Constrained Application Protocol is a specialized web transfer protocol for use with constrained nodes and constrained networks, and it is based on RFC 7252.

Maven users will need to add the following dependency to their pom.xml for this component:

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

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 CoAP component supports 3 options, which are listed below.

Name Description Default Type

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

Endpoint Options

The CoAP endpoint is configured using URI syntax:

coap:uri

With the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

uri (common)

The URI for the CoAP endpoint.

URI

Query Parameters (17 parameters)

Name Description Default Type

coapMethodRestrict (consumer)

Comma separated list of methods that the CoAP consumer will bind to. The default is to bind to all methods (DELETE, GET, POST, PUT).

Enum values:

  • DELETE

  • GET

  • POST

  • PUT

String

observable (consumer)

Make CoAP resource observable for source endpoint, based on RFC 7641.

false

boolean

observe (consumer)

Send an observe request from a source endpoint, based on RFC 7641.

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

notify (producer)

Notify observers that the resource of this URI has changed, based on RFC 7641. Use this flag on a destination endpoint, with a URI that matches an existing source endpoint URI.

false

boolean

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

advancedCertificateVerifier (security)

Set the AdvancedCertificateVerifier to use to determine trust in raw public keys.

NewAdvancedCertificateVerifier

advancedPskStore (security)

Set the AdvancedPskStore to use for pre-shared key.

AdvancedPskStore

alias (security)

Sets the alias used to query the KeyStore for the private key and certificate. This parameter is used when we are enabling TLS with certificates on the service side, and similarly on the client side when TLS is used with certificates and client authentication. If the parameter is not specified then the default behavior is to use the first alias in the keystore that contains a key entry. This configuration parameter does not apply to configuring TLS via a Raw Public Key or a Pre-Shared Key.

Enum values:

  • NONE

  • WANT

  • REQUIRE

String

cipherSuites (security)

Sets the cipherSuites String. This is a comma separated String of ciphersuites to configure. If it is not specified, then it falls back to getting the ciphersuites from the sslContextParameters object.

String

clientAuthentication (security)

Sets the configuration options for server-side client-authentication requirements. The value must be one of NONE, WANT, REQUIRE. If this value is not specified, then it falls back to checking the sslContextParameters.getServerParameters().getClientAuthentication() value.

Enum values:

  • NONE

  • WANTED

  • NEEDED

CertificateAuthenticationMode

privateKey (security)

Set the configured private key for use with Raw Public Key.

PrivateKey

publicKey (security)

Set the configured public key for use with Raw Public Key.

PublicKey

recommendedCipherSuitesOnly (security)

The CBC cipher suites are not recommended. If you want to use them, you first need to set the recommendedCipherSuitesOnly option to false.

true

boolean

sslContextParameters (security)

Set the SSLContextParameters object for setting up TLS. This is required for coapstcp, and for coaps when we are using certificates for TLS (as opposed to RPK or PKS).

SSLContextParameters

Message Headers

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

Name Description Default Type

CamelCoapETag (common)

Constant: COAP_ETAG

The CoAP ETag for the response.

byte[]

CamelCoapMaxAge (common)

Constant: COAP_MAX_AGE

The CoAP Max-Age for the response body.

Long

CamelCoapMethod (common)

Constant: COAP_METHOD

The request method that the CoAP producer should use when calling the target CoAP server URI. Valid options are DELETE, GET, PING, POST & PUT.

String

CamelCoapResponseCode (common)

Constant: COAP_RESPONSE_CODE

The CoAP response code sent by the external server. See RFC 7252 for details of what each code means.

String

Content-Type (common)

Constant: CONTENT_TYPE

The content type.

String

Usage

Camel supports the DTLS, TCP and TLS protocols via the following URI schemes:

Scheme Protocol

coap

UDP

coaps

UDP + DTLS

coap+tcp

TCP

coaps+tcp

TCP + TLS

There are a number of different configuration options to configure TLS. For both DTLS (the "coaps" uri scheme) and TCP + TLS (the "coaps+tcp" uri scheme), it is possible to use a "sslContextParameters" parameter, from which the camel-coap component will extract the required truststore / keystores etc. to set up TLS. In addition, the DTLS protocol supports two alternative configuration mechanisms. To use a pre-shared key, configure a pskStore, and to work with raw public keys, configure privateKey + publicKey objects.

Configuring the CoAP producer request method

The following rules determine which request method the CoAP producer will use to invoke the target URI:

  1. The value of the CamelCoapMethod header

  2. GE if a query string is provided on the target CoAP server URI.

  3. POST if the message exchange body is not null.

  4. GET otherwise.

Spring Boot Auto-Configuration

When using coap 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-coap-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 4 options, which are listed below.

Name Description Default Type

camel.component.coap.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.coap.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.coap.enabled

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

Boolean

camel.component.coap.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
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