Chapter 51. Ref Both producer and consumer are supported The Ref component is used for lookup of existing endpoints bound in the Registry. 51.1. URI format 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. 51.2. Configuring Options Camel components are configured on two separate levels: component level endpoint level 51.2.1. Configuring Component Options The component level is the highest level which holds general and common configurations that are inherited by the endpoints. 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. Configuring components can be done with the Component DSL , in a configuration file (application.properties|yaml), or directly with Java code. 51.2.2. Configuring Endpoint Options Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both. Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL as a type safe way of configuring endpoints. A good practice when configuring options is to use Property Placeholders , which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse. The following two sections lists all the options, firstly for the component followed by the endpoint. 51.3. 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 51.4. Endpoint Options The Ref endpoint is configured using URI syntax: with the following path and query parameters: 51.4.1. Path Parameters (1 parameters) Name Description Default Type name (common) Required Name of endpoint to lookup in the registry. String 51.4.2. 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: InOnly InOut InOptionalOut 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 51.5. 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> 51.6. 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. 51.7. Spring Boot Auto-Configuration When using ref 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-ref-starter</artifactId> </dependency> 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

Commands:
ref:someName[?options]
ref:name
// 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);
<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>
<to uri="ref:endpoint2"/>
<dependency> <groupId>org.apache.camel.springboot</groupId> <artifactId>camel-ref-starter</artifactId> </dependency>