[[spel-language]]
== SpEL Language

*Available as of Camel version 2.7*

Camel allows
https://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#expressions[Spring Expression Language (SpEL)]
to be used as an Expression or Predicate in the DSL or XML Configuration.

NOTE: It is recommended to use SpEL in Spring runtimes. However from Camel 2.21 onwards you can
use SpEL in other runtimes (there may be functionality SpEL cannot do when not running in a Spring runtime)

=== Variables

The following variables are available in expressions and predicates written in SpEL:

[width="100%",cols="10%,10%,80%",options="header",]
|===
|Variable |Type |Description

|this |Exchange |the Exchange is the root object

|exchange |Exchange |the Exchange object

|exception |Throwable |the Exchange exception (if any)

|exchangeId |String |the exchange id

|fault |Message |the Fault message (if any)

|body |Object | The IN message body.

|request |Message |the exchange.in message

|response |Message |the exchange.out message (if any)

|properties |Map |the exchange properties

|property(name) |Object |the property by the given name

|property(name, type) |Type |the property by the given name as the given type
|===

=== Options

// language options: START
The SpEL language supports 1 options, which are listed below.



[width="100%",cols="2,1m,1m,6",options="header"]
|===
| Name | Default | Java Type | Description
| trim | true | Boolean | Whether to trim the value to remove leading and trailing whitespaces and line breaks
|===
// language options: END

=== Samples

==== Expression templating

SpEL expressions need to be surrounded by `#{` `}` delimiters since
expression templating is enabled. This allows you to combine SpEL
expressions with regular text and use this as extremely lightweight
template language.

For example if you construct the following route:

[source,java]
----
from("direct:example")
    .setBody(spel("Hello #{request.body}! What a beautiful #{request.headers['dayOrNight']}"))
    .to("mock:result");
----

In the route above, notice spel is a static method which we need to
import from `org.apache.camel.language.spel.SpelExpression.spel`, as we
use spel as an Expression passed in as a parameter
to the `setBody` method. Though if we use the fluent API we can do this
instead:

[source,java]
----
from("direct:example")
    .setBody().spel("Hello #{request.body}! What a beautiful #{request.headers['dayOrNight']}")
    .to("mock:result");
----

Notice we now use the `spel` method from the `setBody()` method. And
this does not require us to static import the spel method from
`org.apache.camel.language.spel.SpelExpression.spel`.

And sent a message with the string "World" in the body, and a header
"dayOrNight" with value "day":

[source,java]
----
template.sendBodyAndHeader("direct:example", "World", "dayOrNight", "day");
----

The output on `mock:result` will be _"Hello World! What a beautiful
day"_

==== Bean integration

You can reference beans defined in the Registry
(most likely an `ApplicationContext`) in your SpEL expressions. For
example if you have a bean named "foo" in your `ApplicationContext` you
can invoke the "bar" method on this bean like this:

[source,text]
----
#{@foo.bar == 'xyz'}
----

==== SpEL in enterprise integration patterns

You can use SpEL as an expression for link:recipient-list.html[Recipient
List] or as a predicate inside a link:message-filter.html[Message
Filter]:

[source,xml]
----
<route>
  <from uri="direct:foo"/>
  <filter>
    <spel>#{request.headers['foo'] == 'bar'}</spel>
    <to uri="direct:bar"/>
  </filter>
</route>
----

And the equivalent in Java DSL:

[source,java]
----
from("direct:foo")
    .filter().spel("#{request.headers['foo'] == 'bar'}")
    .to("direct:bar");
----

=== Loading script from external resource

*Available as of Camel 2.11*

You can externalize the script and have Camel load it from a resource
such as `"classpath:"`, `"file:"`, or `"http:"`. +
 This is done using the following syntax: `"resource:scheme:location"`,
eg to refer to a file on the classpath you can do:

[source,java]
----
.setHeader("myHeader").spel("resource:classpath:myspel.txt")
----

