Bean Integration

Camel supports the integration of beans and POJOs in a number of ways.

Annotations

If a bean is defined in Spring XML or scanned using the Spring component scanning mechanism, and a <camelContext> is used or a CamelBeanPostProcessor then we process a number of Camel annotations to do various things such as injecting resources or producing, consuming or routing messages.

The following annotations is supported and inject by Camel’s CamelBeanPostProcessor

Annotation Description

@EndpointInject

To inject an endpoint, see more details at POJO Producing.

@BeanInject

To inject a bean obtained from the Registry. See Bean Injection.

@BeanConfigInject

To inject a configuration bean obtained from the Registry. The bean is a POJO that represents a set of configuration options, which is automatically configured with values loaded via Camel Property Placeholders.

@PropertyInject

To inject a value using property placeholder.

@Produce

To inject a producer to send a message to an endpoint. See POJO Producing.

@Consume

To inject a consumer on a method. See POJO Consuming.

@BindToRegistry

Used for binding a bean to the registry. If no name is specified, then the bean will have its name auto computed based on the class name, field name, or method name where the annotation is configured.

@DeferredContextBinding

Used to indicate that if the target type is CamelContextAware then the CamelContext is deferred and injected later; after the bootstrap of Camel so the CamelContext is ready for use.

See more details at:

  • POJO Consuming to consume and possibly route messages from Camel

  • POJO Producing to make it easy to produce camel messages from your POJOs

  • @DynamicRouter Annotation for creating a Dynamic Router from a POJO method

  • @RecipientList Annotation for creating a Recipient List from a POJO method

  • @RoutingSlip Annotation for creating a Routing Slip for a POJO method

  • Bean Injection to inject Camel related resources into your POJOs

  • Using Exchange Pattern Annotations describes how the pattern annotations can be used to change the behaviour of method invocations with Spring Remoting or POJO Producing

Example

See the POJO Messaging Example for how to use the annotations for routing and messaging.

Using @PropertyInject

Camel allows injecting property placeholders in POJOs using the @PropertyInject annotation which can be set on fields and setter methods. For example, you can use that with RouteBuilder classes, such as shown below:

public class MyRouteBuilder extends RouteBuilder {

    @PropertyInject("hello")
    private String greeting;

    @Override
    public void configure() throws Exception {
        from("direct:start")
            .transform().constant(greeting)
            .to("{{result}}");
    }
}

Notice we have annotated the greeting field with @PropertyInject and define it to use the key hello. Camel will then lookup the property with this key and inject its value, converted to a String type.

You can also use multiple placeholders and text in the key, for example we can do:

@PropertyInject("Hello {{name}} how are you?")
private String greeting;

This will lookup the placeholder with they key name.

You can also add a default value if the key does not exist, such as:

@PropertyInject(value = "myTimeout", defaultValue = "5000")
private int timeout;

Using @PropertyInject with arrays, lists, sets or maps

You can also use @PropertyInject to inject an array of values. For example, you may configure multiple hostnames in the configuration file, and need to inject this into an String[] or List<String> field. To do this, you need to tell Camel that the property value should be split using a separator, as follows:

@PropertyInject(value = "myHostnames", separator = ",")
private String[] servers;
You can also use list/set types, such as List<String> or Set<String> instead of array.

Then in the application.properties file you can define the servers:

myHostnames = serverA, serverB, serverC
This also works for fields that are not String based, such as int[] for numeric values.

For Map types then the values are expected to be in key=value format, such as:

myServers = serverA=http://coolstore:4444,serverB=http://megastore:5555

You can then inject this into a Map as follows:

@PropertyInject(value = "myServers", separator = ",")
private Map servers;

You can use generic types in the Map such as the values should be Integer values:

@PropertyInject(value = "ports", separator = ",")
private Map<String, Integer> ports;
The generic type can only be a single class type, and cannot be a nested complex type such as Map<String,Map<Kind,Priority>>.

See Also

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