Chapter 11. Bean
Bean Component
The bean: component binds beans to Apache Camel message exchanges.
URI format
bean:beanID[?options]
Where beanID can be any string which is used to lookup look up the bean in the Registry
Options
| Name | Type | Default | Description |
|---|---|---|---|
method
|
String
|
null
|
The method name from the bean that will be invoked. If not provided, Camel will try to determine the method itself. In case of ambiguity an exception will be thrown. See Bean Binding for more details. From Camel 2.8 onwards you can specify type qualifiers to pin-point exact method to use for overloaded methods. From Camel 2.9 onwards you can specify parameter values directly in the method syntax. |
cache
|
boolean
|
false
|
If enabled, Apache Camel will cache the result of the first Registry look-up. Cache can be enabled if the bean in the Registry is defined as a singleton scope. |
multiParameterArray
|
boolean
|
false
|
How to treat the parameters which are passed from the message body; if it is true, the In message body should be an array of parameters.
|
bean.xxx
|
null
|
Camel 2.17: To configure additional options on the create bean instance from the class name. For example, to configure a
foo option on the bean, use bean.foo=123.
|
You can append query options to the URI in the following format,
?option=value&option=value&...
Using
The object instance that is used to consume messages must be explicitly registered with the Registry. For example, if you are using Spring you must define the bean in the Spring configuration,
spring.xml; or if you don't use Spring, put the bean in JNDI.
// lets populate the context with the services we need
// note that we could just use a spring.xml file to avoid this step
JndiContext context = new JndiContext();
context.bind("bye", new SayService("Good Bye!"));
CamelContext camelContext = new DefaultCamelContext(context);
Once an endpoint has been registered, you can build routes that use it to process exchanges.
// lets add simple route
camelContext.addRoutes(new RouteBuilder() {
public void configure() {
from("direct:hello").to("bean:bye");
}
});
A bean: endpoint cannot be defined as the input to the route; i.e. you cannot consume from it, you can only route from some inbound message Endpoint to the bean endpoint as output. So consider using a direct: or queue: endpoint as the input.
You can use the
createProxy() methods on ProxyHelper to create a proxy that will generate BeanExchanges and send them to any endpoint:
Endpoint endpoint = camelContext.getEndpoint("direct:hello");
ISay proxy = ProxyHelper.createProxy(endpoint, ISay.class);
String rc = proxy.say();
assertEquals("Good Bye!", rc);
And the same route using Spring DSL:
<route>
<from uri="direct:hello">
<to uri="bean:bye"/>
</route>Bean as endpoint
Apache Camel also supports invoking Bean as an Endpoint. In the route below:
<camelContext xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="direct:start"/>
<to uri="myBean"/>
<to uri="mock:results"/>
</route>
</camelContext>
<bean id="myBean" class="org.apache.camel.spring.bind.ExampleBean"/>
What happens is that when the exchange is routed to the
myBean, Apache Camel will use the Bean Binding to invoke the bean. The source for the bean is just a plain POJO:
public class ExampleBean {
public String sayHello(String name) {
return "Hello " + name + "!";
}
}
Apache Camel will use Bean Binding to invoke the
sayHello method, by converting the Exchange's In body to the String type and storing the output of the method on the Exchange Out body.
Java DSL bean syntax
Java DSL comes with syntactic sugar for the Bean component. Instead of specifying the bean explicitly as the endpoint (i.e.
to("bean:beanName")) you can use the following syntax:
// Send message to the bean endpoint
// and invoke method resolved using Bean Binding.
from("direct:start").beanRef("beanName");
// Send message to the bean endpoint
// and invoke given method.
from("direct:start").beanRef("beanName", "methodName");
Instead of passing name of the reference to the bean (so that Camel will lookup for it in the registry), you can specify the bean itself:
// Send message to the given bean instance.
from("direct:start").bean(new ExampleBean());
// Explicit selection of bean method to be invoked.
from("direct:start").bean(new ExampleBean(), "methodName");
// Camel will create the instance of bean and cache it for you.
from("direct:start").bean(ExampleBean.class);
Bean Binding
How bean methods to be invoked are chosen (if they are not specified explicitly through the method parameter) and how parameter values are constructed from the Message are all defined by the Bean Binding mechanism which is used throughout all of the various Bean Integration mechanisms in Apache Camel.
- Class component
Bean Language
The purpose of the Bean language is to implement an expression or predicate using a simple method on a bean.If you specify a bean name in the registry such as the Spring
For more information, refer the Bean Language chapter.
ApplicationContext, then it invokes the method to evaluate the Expression or Predicate. However, if you do not provide any method name, then you can choose by using:
- the rules for bean binding
- the type of message body
- any annotations on bean methods
Note
From Camel 2.17, the Bean language is able to invoke static methods on pure static classes. When the bean language fails to invoke a method from the OGNL method chain, the method returns a null value. However, it prevent further method invocation that gives the
NullPointerException.
