[[bean-language]]
= Bean method Language
:docTitle: Bean method
:artifactId: camel-bean
:description: Call a method of the specified Java bean passing the Exchange, Body or specific headers to it.
:since: 1.3
:supportLevel: Stable
include::{cq-version}@camel-quarkus:ROOT:partial$reference/languages/bean.adoc[opts=optional]

*Since Camel {since}*

The purpose of the Bean Language is to be able to implement an
xref:manual::expression.adoc[Expression] or xref:manual::predicate.adoc[Predicate] using
a simple method on a bean. The bean name is resolved using a xref:manual::registry.adoc[Registry], such as the
xref:ROOT:spring-summary.adoc[Spring] *`ApplicationContext`*, then a method is
invoked to evaluate the xref:manual::expression.adoc[Expression] or
xref:manual::predicate.adoc[Predicate]. If no method name is provided then one
is chosen using the rules for xref:manual::bean-binding.adoc[Bean Binding];
using the type of the message body and using any annotations on the bean
methods.

The xref:manual::bean-binding.adoc[Bean Binding] rules are used to bind the
xref:{eip-vc}:eips:message.adoc[Message] Exchange to the method parameters; so you can
annotate the bean to extract headers or other expressions such as
xref:xpath-language.adoc[XPath] or xref:xquery-language.adoc[XQuery] from the message.

== Bean Language options

// language options: START
The Bean method language supports 5 options, which are listed below.



[width="100%",cols="2,1m,1m,6",options="header"]
|===
| Name | Default | Java Type | Description
| ref |  | String | Reference to an existing bean (bean id) to lookup in the registry
| method |  | String | Name of method to call
| beanType |  | String | Class name (fully qualified) of the bean to use Will lookup in registry and if there is a single instance of the same type, then the existing bean is used, otherwise a new bean is created (requires a default no-arg constructor).
| scope | Singleton | String | 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 prototype 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 scope then this depends on the bean registry implementation.
| trim | true | Boolean | Whether to trim the value to remove leading and trailing whitespaces and line breaks
|===
// language options: END


[[BeanLanguage-UsingBeanExpressionsinJava]]
== Using Bean Expressions in Java

[source,syntaxhighlighter-pre]
----
from("activemq:topic:OrdersTopic")
  .filter().method("myBean", "isGoldCustomer")
    .to("activemq:BigSpendersQueue");
----

[[BeanLanguage-UsingBeanExpressionsinSpringXML]]
== Using Bean Expressions in Spring XML

[source,syntaxhighlighter-pre]
----
<route>
  <from uri="activemq:topic:OrdersTopic"/>
  <filter>
    <method ref="myBean" method="isGoldCustomer"/>
    <to uri="activemq:BigSpendersQueue"/>
  </filter>
</route>
----

[WARNING]
====
 **Bean Attribute Now Deprecated**

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

====

[[BeanLanguage-WritingtheExpressionBean]]
== 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:

[source,syntaxhighlighter-pre]
----
public class MyBean {
  public boolean isGoldCustomer(Exchange exchange) {
     // ...
  }
}
----

We can also use the xref:manual::bean-integration.adoc[Bean Integration]
annotations.

Example:

[source,syntaxhighlighter-pre]
----
public boolean isGoldCustomer(String body) {...}
----

or

[source,syntaxhighlighter-pre]
----
public boolean isGoldCustomer(@Header(name = "foo") Integer fooHeader) {...}
----

So you can bind parameters of the method to the Exchange, the
xref:{eip-vc}:eips:message.adoc[Message] or individual headers, properties, the body
or other expressions.

[[BeanLanguage-Non-RegistryBeans]]
== Non-Registry Beans

The xref:bean-language.adoc[Bean Language] also supports invoking beans
that isn't registered in the xref:manual::registry.adoc[Registry]. This is
usable for quickly to invoke a bean from Java DSL where you don't need
to register the bean in the xref:manual::registry.adoc[Registry] such as the
xref:ROOT:spring-summary.adoc[Spring] *`ApplicationContext`*. Camel can instantiate
the bean and invoke the method if given a class or invoke an already
existing instance.

Example:

[source,syntaxhighlighter-pre]
----
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:

[source,syntaxhighlighter-pre]
----
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:

[source,syntaxhighlighter-pre]
----
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:

[source,syntaxhighlighter-pre]
----
private MyBean my;

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

[[BeanLanguage-OtherExamples]]
== Other Examples

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

* https://github.com/apache/camel/blob/main/core/camel-core/src/test/java/org/apache/camel/processor/MethodFilterTest.java[MethodFilterTest]
is a JUnit test case showing the Java xref:manual::dsl.adoc[DSL] use of the bean
expression being used in a filter
* https://github.com/apache/camel/blob/main/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/aggregator.xml[aggregator.xml]
is a Spring XML test case for the xref:{eip-vc}:eips:aggregate-eip.adoc[Aggregator] which
uses a bean method call to test for the completion of the aggregation.

include::{page-component-version}@camel-spring-boot::page$bean-starter.adoc[]
