Header

Since Camel 1.5

The Header Expression Language allows you to extract values of named headers.

Header Options

The Header language supports 1 options, which are listed below.

Name Default Java Type Description

trim (advanced)

true

Boolean

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

Example usage

The recipientList EIP can utilize a header:

<route>
  <from uri="direct:a" />
  <recipientList>
    <header>myHeader</header>
  </recipientList>
</route>

In this case, the list of recipients are contained in the header 'myHeader'.

And the same example in Java DSL:

from("direct:a").recipientList(header("myHeader"));

Dependencies

The Header language is part of camel-core.

Spring Boot Auto-Configuration

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

The component supports 112 options, which are listed below.

Name Description Default Type

camel.cloud.consul.service-discovery.acl-token

Sets the ACL token to be used with Consul.

String

camel.cloud.consul.service-discovery.block-seconds

The seconds to wait for a watch event, default 10 seconds.

10

Integer

camel.cloud.consul.service-discovery.configurations

Define additional configuration definitions.

Map

camel.cloud.consul.service-discovery.connect-timeout-millis

Connect timeout for OkHttpClient.

Long

camel.cloud.consul.service-discovery.datacenter

The data center.

String

camel.cloud.consul.service-discovery.enabled

Enable the component.

true

Boolean

camel.cloud.consul.service-discovery.password

Sets the password to be used for basic authentication.

String

camel.cloud.consul.service-discovery.properties

Set client properties to use. These properties are specific to what service call implementation are in use. For example if using a different one, then the client properties are defined according to the specific service in use.

Map

camel.cloud.consul.service-discovery.read-timeout-millis

Read timeout for OkHttpClient.

Long

camel.cloud.consul.service-discovery.url

The Consul agent URL.

String

camel.cloud.consul.service-discovery.user-name

Sets the username to be used for basic authentication.

String

camel.cloud.consul.service-discovery.write-timeout-millis

Write timeout for OkHttpClient.

Long

camel.cloud.dns.service-discovery.configurations

Define additional configuration definitions.

Map

camel.cloud.dns.service-discovery.domain

The domain name;.

String

camel.cloud.dns.service-discovery.enabled

Enable the component.

true

Boolean

camel.cloud.dns.service-discovery.properties

Set client properties to use. These properties are specific to what service call implementation are in use. For example if using a different one, then the client properties are defined according to the specific service in use.

Map

camel.cloud.dns.service-discovery.proto

The transport protocol of the desired service.

_tcp

String

camel.cloud.kubernetes.service-discovery.api-version

Sets the API version when using client lookup.

String

camel.cloud.kubernetes.service-discovery.ca-cert-data

Sets the Certificate Authority data when using client lookup.

String

camel.cloud.kubernetes.service-discovery.ca-cert-file

Sets the Certificate Authority data that are loaded from the file when using client lookup.

String

camel.cloud.kubernetes.service-discovery.client-cert-data

Sets the Client Certificate data when using client lookup.

String

camel.cloud.kubernetes.service-discovery.client-cert-file

Sets the Client Certificate data that are loaded from the file when using client lookup.

String

camel.cloud.kubernetes.service-discovery.client-key-algo

Sets the Client Keystore algorithm, such as RSA when using client lookup.

String

camel.cloud.kubernetes.service-discovery.client-key-data

Sets the Client Keystore data when using client lookup.

String

camel.cloud.kubernetes.service-discovery.client-key-file

Sets the Client Keystore data that are loaded from the file when using client lookup.

String

camel.cloud.kubernetes.service-discovery.client-key-passphrase

Sets the Client Keystore passphrase when using client lookup.

String

camel.cloud.kubernetes.service-discovery.configurations

Define additional configuration definitions.

Map

camel.cloud.kubernetes.service-discovery.dns-domain

Sets the DNS domain to use for DNS lookup.

String

camel.cloud.kubernetes.service-discovery.enabled

Enable the component.

true

Boolean

camel.cloud.kubernetes.service-discovery.lookup

How to perform service lookup. Possible values: client, dns, environment. When using client, then the client queries the kubernetes master to obtain a list of active pods that provides the service, and then random (or round robin) select a pod. When using dns the service name is resolved as name.namespace.svc.dnsDomain. When using dnssrv the service name is resolved with SRV query for .…​svc…​ When using environment then environment variables are used to lookup the service. By default environment is used.

environment

String

camel.cloud.kubernetes.service-discovery.master-url

Sets the URL to the master when using client lookup.

String

camel.cloud.kubernetes.service-discovery.namespace

Sets the namespace to use. Will by default use namespace from the ENV variable KUBERNETES_MASTER.

String

camel.cloud.kubernetes.service-discovery.oauth-token

Sets the OAUTH token for authentication (instead of username/password) when using client lookup.

String

camel.cloud.kubernetes.service-discovery.password

Sets the password for authentication when using client lookup.

String

camel.cloud.kubernetes.service-discovery.port-name

Sets the Port Name to use for DNS/DNSSRV lookup.

String

camel.cloud.kubernetes.service-discovery.port-protocol

Sets the Port Protocol to use for DNS/DNSSRV lookup.

String

camel.cloud.kubernetes.service-discovery.properties

Set client properties to use. These properties are specific to what service call implementation are in use. For example if using a different one, then the client properties are defined according to the specific service in use.

Map

camel.cloud.kubernetes.service-discovery.trust-certs

Sets whether to turn on trust certificate check when using client lookup.

false

Boolean

camel.cloud.kubernetes.service-discovery.username

Sets the username for authentication when using client lookup.

String

camel.language.constant.enabled

Whether to enable auto configuration of the constant language. This is enabled by default.

Boolean

camel.language.constant.trim

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

true

Boolean

camel.language.csimple.enabled

Whether to enable auto configuration of the csimple language. This is enabled by default.

Boolean

camel.language.csimple.trim

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

true

Boolean

camel.language.exchange-property.enabled

Whether to enable auto configuration of the exchangeProperty language. This is enabled by default.

Boolean

camel.language.exchange-property.trim

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

true

Boolean

camel.language.file.enabled

Whether to enable auto configuration of the file language. This is enabled by default.

Boolean

camel.language.file.trim

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

true

Boolean

camel.language.header.enabled

Whether to enable auto configuration of the header language. This is enabled by default.

Boolean

camel.language.header.trim

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

true

Boolean

camel.language.ref.enabled

Whether to enable auto configuration of the ref language. This is enabled by default.

Boolean

camel.language.ref.trim

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

true

Boolean

camel.language.simple.enabled

Whether to enable auto configuration of the simple language. This is enabled by default.

Boolean

camel.language.simple.trim

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

true

Boolean

camel.language.tokenize.enabled

Whether to enable auto configuration of the tokenize language. This is enabled by default.

Boolean

camel.language.tokenize.group-delimiter

Sets the delimiter to use when grouping. If this has not been set then token will be used as the delimiter.

String

camel.language.tokenize.source

Source to use, instead of message body. You can prefix with variable:, header:, or property: to specify kind of source. Otherwise, the source is assumed to be a variable. Use empty or null to use default source, which is the message body.

String

camel.language.tokenize.trim

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

true

Boolean

camel.language.variable.enabled

Whether to enable auto configuration of the variable language. This is enabled by default.

Boolean

camel.language.variable.trim

Whether to trim the value to remove leading and trailing whitespaces and line breaks.

true

Boolean

camel.resilience4j.automatic-transition-from-open-to-half-open-enabled

Enables automatic transition from OPEN to HALF_OPEN state once the waitDurationInOpenState has passed.

false

Boolean

camel.resilience4j.bulkhead-enabled

Whether bulkhead is enabled or not on the circuit breaker. Default is false.

false

Boolean

camel.resilience4j.bulkhead-max-concurrent-calls

Configures the max amount of concurrent calls the bulkhead will support.

25

Integer

camel.resilience4j.bulkhead-max-wait-duration

Configures a maximum amount of time which the calling thread will wait to enter the bulkhead. If bulkhead has space available, entry is guaranteed and immediate. If bulkhead is full, calling threads will contest for space, if it becomes available. maxWaitDuration can be set to 0. Note: for threads running on an event-loop or equivalent (rx computation pool, etc), setting maxWaitDuration to 0 is highly recommended. Blocking an event-loop thread will most likely have a negative effect on application throughput.

0

Integer

camel.resilience4j.circuit-breaker

Refers to an existing io.github.resilience4j.circuitbreaker.CircuitBreaker instance to lookup and use from the registry. When using this, then any other circuit breaker options are not in use.

String

camel.resilience4j.config

Refers to an existing io.github.resilience4j.circuitbreaker.CircuitBreakerConfig instance to lookup and use from the registry.

String

camel.resilience4j.configurations

Define additional configuration definitions.

Map

camel.resilience4j.enabled

Enable the component.

true

Boolean

camel.resilience4j.failure-rate-threshold

Configures the failure rate threshold in percentage. If the failure rate is equal or greater than the threshold the CircuitBreaker transitions to open and starts short-circuiting calls. The threshold must be greater than 0 and not greater than 100. Default value is 50 percentage.

Float

camel.resilience4j.ignore-exception

Configure a list of exceptions that are ignored and neither count as a failure nor success. Any exception matching or inheriting from one of the list will not count as a failure nor success, even if the exceptions is part of recordExceptions.

List

camel.resilience4j.minimum-number-of-calls

Configures the minimum number of calls which are required (per sliding window period) before the CircuitBreaker can calculate the error rate. For example, if minimumNumberOfCalls is 10, then at least 10 calls must be recorded, before the failure rate can be calculated. If only 9 calls have been recorded the CircuitBreaker will not transition to open even if all 9 calls have failed. Default minimumNumberOfCalls is 100.

100

Integer

camel.resilience4j.permitted-number-of-calls-in-half-open-state

Configures the number of permitted calls when the CircuitBreaker is half open. The size must be greater than 0. Default size is 10.

10

Integer

camel.resilience4j.record-exception

Configure a list of exceptions that are recorded as a failure and thus increase the failure rate. Any exception matching or inheriting from one of the list counts as a failure, unless explicitly ignored via ignoreExceptions.

List

camel.resilience4j.sliding-window-size

Configures the size of the sliding window which is used to record the outcome of calls when the CircuitBreaker is closed. slidingWindowSize configures the size of the sliding window. Sliding window can either be count-based or time-based. If slidingWindowType is COUNT_BASED, the last slidingWindowSize calls are recorded and aggregated. If slidingWindowType is TIME_BASED, the calls of the last slidingWindowSize seconds are recorded and aggregated. The slidingWindowSize must be greater than 0. The minimumNumberOfCalls must be greater than 0. If the slidingWindowType is COUNT_BASED, the minimumNumberOfCalls cannot be greater than slidingWindowSize . If the slidingWindowType is TIME_BASED, you can pick whatever you want. Default slidingWindowSize is 100.

100

Integer

camel.resilience4j.sliding-window-type

Configures the type of the sliding window which is used to record the outcome of calls when the CircuitBreaker is closed. Sliding window can either be count-based or time-based. If slidingWindowType is COUNT_BASED, the last slidingWindowSize calls are recorded and aggregated. If slidingWindowType is TIME_BASED, the calls of the last slidingWindowSize seconds are recorded and aggregated. Default slidingWindowType is COUNT_BASED.

COUNT_BASED

String

camel.resilience4j.slow-call-duration-threshold

Configures the duration threshold (seconds) above which calls are considered as slow and increase the slow calls percentage. Default value is 60 seconds.

60

Integer

camel.resilience4j.slow-call-rate-threshold

Configures a threshold in percentage. The CircuitBreaker considers a call as slow when the call duration is greater than slowCallDurationThreshold Duration. When the percentage of slow calls is equal or greater the threshold, the CircuitBreaker transitions to open and starts short-circuiting calls. The threshold must be greater than 0 and not greater than 100. Default value is 100 percentage which means that all recorded calls must be slower than slowCallDurationThreshold.

Float

camel.resilience4j.throw-exception-when-half-open-or-open-state

Whether to throw io.github.resilience4j.circuitbreaker.CallNotPermittedException when the call is rejected due circuit breaker is half open or open.

false

Boolean

camel.resilience4j.timeout-cancel-running-future

Configures whether cancel is called on the running future. Defaults to true.

true

Boolean

camel.resilience4j.timeout-duration

Configures the thread execution timeout. Default value is 1 second.

1000

Integer

camel.resilience4j.timeout-enabled

Whether timeout is enabled or not on the circuit breaker. Default is false.

false

Boolean

camel.resilience4j.timeout-executor-service

References to a custom thread pool to use when timeout is enabled (uses ForkJoinPool#commonPool() by default).

ExecutorService

camel.resilience4j.wait-duration-in-open-state

Configures the wait duration (in seconds) which specifies how long the CircuitBreaker should stay open, before it switches to half open. Default value is 60 seconds.

60

Integer

camel.resilience4j.writable-stack-trace-enabled

Enables writable stack traces. When set to false, Exception.getStackTrace returns a zero length array. This may be used to reduce log spam when the circuit breaker is open as the cause of the exceptions is already known (the circuit breaker is short-circuiting calls).

true

Boolean

camel.rest.api-component

The name of the Camel component to use as the REST API. If no API Component has been explicit configured, then Camel will lookup if there is a Camel component responsible for servicing and generating the REST API documentation, or if a org.apache.camel.spi.RestApiProcessorFactory is registered in the registry. If either one is found, then that is being used.

String

camel.rest.api-context-path

Sets a leading context-path the REST API will be using. This can be used when using components such as camel-servlet where the deployed web application is deployed using a context-path.

String

camel.rest.api-context-route-id

Sets the route id to use for the route that services the REST API. The route will by default use an auto assigned route id.

String

camel.rest.api-host

To use a specific hostname for the API documentation (such as swagger or openapi) This can be used to override the generated host with this configured hostname.

String

camel.rest.api-property

Allows to configure as many additional properties for the api documentation. For example set property api.title to my cool stuff.

Map

camel.rest.api-vendor-extension

Whether vendor extension is enabled in the Rest APIs. If enabled then Camel will include additional information as vendor extension (eg keys starting with x-) such as route ids, class names etc. Not all 3rd party API gateways and tools supports vendor-extensions when importing your API docs.

false

Boolean

camel.rest.binding-mode

Sets the binding mode to use. The default value is off.

off

RestBindingMode

camel.rest.binding-package-scan

Package name to use as base (offset) for classpath scanning of POJO classes are located when using binding mode is enabled for JSon or XML. Multiple package names can be separated by comma.

String

camel.rest.client-request-validation

Whether to enable validation of the client request to check: 1) Content-Type header matches what the Rest DSL consumes; returns HTTP Status 415 if validation error. 2) Accept header matches what the Rest DSL produces; returns HTTP Status 406 if validation error. 3) Missing required data (query parameters, HTTP headers, body); returns HTTP Status 400 if validation error. 4) Parsing error of the message body (JSon, XML or Auto binding mode must be enabled); returns HTTP Status 400 if validation error.

false

Boolean

camel.rest.component

The Camel Rest component to use for the REST transport (consumer), such as netty-http, jetty, servlet, undertow. If no component has been explicit configured, then Camel will lookup if there is a Camel component that integrates with the Rest DSL, or if a org.apache.camel.spi.RestConsumerFactory is registered in the registry. If either one is found, then that is being used.

String

camel.rest.component-property

Allows to configure as many additional properties for the rest component in use.

Map

camel.rest.consumer-property

Allows to configure as many additional properties for the rest consumer in use.

Map

camel.rest.context-path

Sets a leading context-path the REST services will be using. This can be used when using components such as camel-servlet where the deployed web application is deployed using a context-path. Or for components such as camel-jetty or camel-netty-http that includes a HTTP server.

String

camel.rest.cors-headers

Allows to configure custom CORS headers.

Map

camel.rest.data-format-property

Allows to configure as many additional properties for the data formats in use. For example set property prettyPrint to true to have json outputted in pretty mode. The properties can be prefixed to denote the option is only for either JSON or XML and for either the IN or the OUT. The prefixes are: json.in. json.out. xml.in. xml.out. For example a key with value xml.out.mustBeJAXBElement is only for the XML data format for the outgoing. A key without a prefix is a common key for all situations.

Map

camel.rest.enable-cors

Whether to enable CORS headers in the HTTP response. The default value is false.

false

Boolean

camel.rest.enable-no-content-response

Whether to return HTTP 204 with an empty body when a response contains an empty JSON object or XML root object. The default value is false.

false

Boolean

camel.rest.endpoint-property

Allows to configure as many additional properties for the rest endpoint in use.

Map

camel.rest.host

The hostname to use for exposing the REST service.

String

camel.rest.host-name-resolver

If no hostname has been explicit configured, then this resolver is used to compute the hostname the REST service will be using.

alllocalip

RestHostNameResolver

camel.rest.inline-routes

Inline routes in rest-dsl which are linked using direct endpoints. Each service in Rest DSL is an individual route, meaning that you would have at least two routes per service (rest-dsl, and the route linked from rest-dsl). By inlining (default) allows Camel to optimize and inline this as a single route, however this requires to use direct endpoints, which must be unique per service. If a route is not using direct endpoint then the rest-dsl is not inlined, and will become an individual route. This option is default true.

true

Boolean

camel.rest.json-data-format

Name of specific json data format to use. By default jackson will be used. Important: This option is only for setting a custom name of the data format, not to refer to an existing data format instance.

String

camel.rest.port

The port number to use for exposing the REST service. Notice if you use servlet component then the port number configured here does not apply, as the port number in use is the actual port number the servlet component is using. eg if using Apache Tomcat its the tomcat http port, if using Apache Karaf its the HTTP service in Karaf that uses port 8181 by default etc. Though in those situations setting the port number here, allows tooling and JMX to know the port number, so its recommended to set the port number to the number that the servlet engine uses.

String

camel.rest.producer-api-doc

Sets the location of the api document the REST producer will use to validate the REST uri and query parameters are valid accordingly to the api document. The location of the api document is loaded from classpath by default, but you can use file: or http: to refer to resources to load from file or http url.

String

camel.rest.producer-component

Sets the name of the Camel component to use as the REST producer.

String

camel.rest.scheme

The scheme to use for exposing the REST service. Usually http or https is supported. The default value is http.

String

camel.rest.skip-binding-on-error-code

Whether to skip binding on output if there is a custom HTTP error code header. This allows to build custom error messages that do not bind to json / xml etc, as success messages otherwise will do.

false

Boolean

camel.rest.use-x-forward-headers

Whether to use X-Forward headers to set host etc. for OpenApi. This may be needed in special cases involving reverse-proxy and networking going from HTTP to HTTPS etc. Then the proxy can send X-Forward headers (X-Forwarded-Proto) that influences the host names in the OpenAPI schema that camel-openapi-java generates from Rest DSL routes.

false

Boolean

camel.rest.xml-data-format

Name of specific XML data format to use. By default jaxb will be used. Important: This option is only for setting a custom name of the data format, not to refer to an existing data format instance.

String