Bean method Language

The purpose of the Bean Language is to be able to implement an Expression or Predicate using a simple method on a bean. The bean name is resolved using a Registry, such as the Spring ApplicationContext, then a method is invoked to evaluate the Expression or Predicate. If no method name is provided then one is chosen using the rules for Bean Binding; using the type of the message body and using any annotations on the bean methods.

The Bean Binding rules are used to bind the Message Exchange to the method parameters; so you can annotate the bean to extract headers or other expressions such as XPath or XQuery from the message.

Bean Language options

The Bean method language supports 4 options, which are listed below.

Name Default Java Type Description

ref

String

Reference to bean to lookup in the registry

method

String

Name of method to call

beanType

String

Class name of the bean to use

trim

true

Boolean

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

Using Bean Expressions in Java

from("activemq:topic:OrdersTopic")
  .filter().method("myBean", "isGoldCustomer")
    .to("activemq:BigSpendersQueue");

Using Bean Expressions in Spring XML

<route>
  <from uri="activemq:topic:OrdersTopic"/>
  <filter>
    <method ref="myBean" method="isGoldCustomer"/>
    <to uri="activemq:BigSpendersQueue"/>
  </filter>
</route>
**Bean Attribute Now Deprecated**

The bean attribute of the method expression element is now deprecated. Use the ref attribute instead.

Writing the Expression Bean

The bean in the above examples is just any old Java Bean with a method called isGoldCustomer() that returns some object that is easily converted to a boolean value in this case, as its used as a predicate.

Example:

public class MyBean {
  public boolean isGoldCustomer(Exchange exchange) {
     // ...
  }
}

We can also use the Bean Integration annotations.

Example:

public boolean isGoldCustomer(String body) {...}

or

public boolean isGoldCustomer(@Header(name = "foo") Integer fooHeader) {...}

So you can bind parameters of the method to the Exchange, the Message or individual headers, properties, the body or other expressions.

Non-Registry Beans

The Bean Language also supports invoking beans that isn’t registered in the Registry. This is usable for quickly to invoke a bean from Java DSL where you don’t need to register the bean in the Registry such as the Spring ApplicationContext. Camel can instantiate the bean and invoke the method if given a class or invoke an already existing instance.

Example:

from("activemq:topic:OrdersTopic")
  .filter().expression(BeanLanguage(MyBean.class, "isGoldCustomer"))
  .to("activemq:BigSpendersQueue");

The 2nd parameter isGoldCustomer is an optional parameter to explicit set the method name to invoke. If not provided Camel will try to invoke the most suitable method. If case of ambiguity Camel will thrown an Exception. In these situations the 2nd parameter can solve this problem. Also the code is more readable if the method name is provided. The 1st parameter can also be an existing instance of a Bean such as:

private MyBean my;

from("activemq:topic:OrdersTopic")
  .filter().expression(BeanLanguage.bean(my, "isGoldCustomer"))
  .to("activemq:BigSpendersQueue");

In Camel 2.2: you can avoid the BeanLanguage and have it just as:

private MyBean my;

from("activemq:topic:OrdersTopic")
  .filter().expression(bean(my, "isGoldCustomer"))
  .to("activemq:BigSpendersQueue");

Which also can be done in a bit shorter and nice way:

private MyBean my;

from("activemq:topic:OrdersTopic")
  .filter().method(my, "isGoldCustomer")
  .to("activemq:BigSpendersQueue");

Other Examples

We have some test cases you can look at if it’ll help

  • MethodFilterTest is a JUnit test case showing the Java DSL use of the bean expression being used in a filter

  • aggregator.xml is a Spring XML test case for the Aggregator which uses a bean method call to test for the completion of the aggregation.

Spring Boot Auto-Configuration

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

The component supports 12 options, which are listed below.

Name Description Default Type

camel.component.bean.basic-property-binding

Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities

false

Boolean

camel.component.bean.enabled

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

Boolean

camel.component.bean.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

camel.component.bean.scope

Scope of bean. When using singleton scope (default) the bean is created or looked up only once and reused for the lifetime of the endpoint. The bean should be thread-safe in case concurrent threads is calling the bean at the same time. When using request scope the bean is created or looked up once per request (exchange). This can be used if you want to store state on a bean while processing a request and you want to call the same bean instance multiple times while processing the request. The bean does not have to be thread-safe as the instance is only called from the same request. When using delegate scope, then the bean will be looked up or created per call. However in case of lookup then this is delegated to the bean registry such as Spring or CDI (if in use), which depends on their configuration can act as either singleton or prototype scope. so when using prototype then this depends on the delegated registry.

BeanScope

camel.component.class.basic-property-binding

Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities

false

Boolean

camel.component.class.enabled

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

Boolean

camel.component.class.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

camel.component.class.scope

Scope of bean. When using singleton scope (default) the bean is created or looked up only once and reused for the lifetime of the endpoint. The bean should be thread-safe in case concurrent threads is calling the bean at the same time. When using request scope the bean is created or looked up once per request (exchange). This can be used if you want to store state on a bean while processing a request and you want to call the same bean instance multiple times while processing the request. The bean does not have to be thread-safe as the instance is only called from the same request. When using delegate scope, then the bean will be looked up or created per call. However in case of lookup then this is delegated to the bean registry such as Spring or CDI (if in use), which depends on their configuration can act as either singleton or prototype scope. so when using prototype then this depends on the delegated registry.

BeanScope

camel.language.bean.enabled

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

Boolean

camel.language.bean.trim

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

true

Boolean

camel.component.bean.cache

Deprecated Use singleton option instead.

true

Boolean

camel.component.class.cache

Deprecated Use singleton option instead.

true

Boolean