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Chapter 106. Ref
Both producer and consumer are supported
The Ref component is used for lookup of existing endpoints bound in the Registry.
106.1. Dependencies
When using ref with Red Hat build of Camel 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-ref-starter</artifactId> </dependency>
106.2. URI format
ref:someName[?options]
Where someName is the name of an endpoint in the Registry (usually, but not always, the Spring registry). If you are using the Spring registry, someName would be the bean ID of an endpoint in the Spring registry.
106.3. Configuring Options
Camel components are configured on two levels:
- Component level
- Endpoint level
106.3.1. Component Level Options
The component level is the highest level. The configurations you define at this level are inherited by all the endpoints. For example, a component can have security settings, credentials for authentication, urls for network connection, and so on.
Since components typically have pre-configured defaults for the most common cases, you may need to only configure a few component options, or maybe none at all.
You can configure components with Component DSL in a configuration file (application.properties|yaml), or directly with Java code.
106.3.2. Endpoint Level Options
At the Endpoint level you have many options, which you can use to configure what you want the endpoint to do. The options are categorized according to whether the endpoint is used as a consumer (from) or as a producer (to) or used for both.
You can configure endpoints directly in the endpoint URI as path and query parameters. You can also use Endpoint DSL and DataFormat DSL as type safe ways of configuring endpoints and data formats in Java.
When configuring options, use Property Placeholders for urls, port numbers, sensitive information, and other settings.
Placeholders allows you to externalize the configuration from your code, giving you more flexible and reusable code.
106.4. Component Options
The Ref 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 occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. 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 |
106.5. Endpoint Options
The Ref endpoint is configured using URI syntax:
ref:name
with the following path and query parameters:
106.5.1. Path Parameters (1 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
| name (common) | Required Name of endpoint to lookup in the registry. | String |
106.5.2. Query Parameters (4 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
| bridgeErrorHandler (consumer) | Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. 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:
| ExchangePattern | |
| 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 |
106.6. Runtime lookup
This component can be used when you need dynamic discovery of endpoints in the Registry where you can compute the URI at runtime. Then you can look up the endpoint using the following code:
// lookup the endpoint
String myEndpointRef = "bigspenderOrder";
Endpoint endpoint = context.getEndpoint("ref:" + myEndpointRef);
Producer producer = endpoint.createProducer();
Exchange exchange = producer.createExchange();
exchange.getIn().setBody(payloadToSend);
// send the exchange
producer.process(exchange);And you could have a list of endpoints defined in the Registry such as:
<camelContext id="camel" xmlns="http://activemq.apache.org/camel/schema/spring">
<endpoint id="normalOrder" uri="activemq:order.slow"/>
<endpoint id="bigspenderOrder" uri="activemq:order.high"/>
</camelContext>106.7. Sample
In the sample below we use the ref: in the URI to reference the endpoint with the spring ID, endpoint2:
You could, of course, have used the ref attribute instead:
<to uri="ref:endpoint2"/>
Which is the more common way to write it.
106.8. Spring Boot Auto-Configuration
The component supports 4 options, which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
| camel.component.ref.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.ref.bridge-error-handler | Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. 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.ref.enabled | Whether to enable auto configuration of the ref component. This is enabled by default. | Boolean | |
| camel.component.ref.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 |
