Chapter 83. Language
Language
Available as of Camel 2.5
The language component allows you to send Exchange to an endpoint which executes a script by any of the supported Languages in Camel. By having a component to execute language scripts, it allows more dynamic routing capabilities. For example by using the Routing SlipRouting Slip or Dynamic RouterDynamic Router EIPs you can send messages to
language endpoints where the script is dynamic defined as well.
This component is provided out of the box in
camel-core and hence no additional JARs is needed. You only have to include additional Camel components if the language of choice mandates it, such as using Groovy or JavaScript languages.
And from Camel 2.11 onwards you can refer to an external resource for the script using same notation as supported by the other Languages in Camel
language://languageName:resource:scheme:location][?options]
URI format
language://languageName[:script][?options]
URI Options
The component supports the following options.
| Name | Default Value | Type | Description |
|---|---|---|---|
languageName
|
null
|
String
|
The name of the Language to use, such as simple, groovy, javascript etc. This option is mandatory.
|
script
|
null
|
String
|
The script to execute. |
transform
|
true
|
boolean
|
Whether or not the result of the script should be used as the new message body. By setting to false the script is executed but the result of the script is discarded.
|
contentCache
|
true
|
boolean
|
Camel 2.9: Whether to cache the script if loaded from a resource. Note: from Camel 2.10.3 a cached script can be forced to reload at runtime via JMX using the clearContentCache operation.
|
cacheScript
|
false
|
boolean
|
Camel 2.13/2.12.2/2.11.3: Whether to cache the compiled script. Turning this option on can gain performance as the script is only compiled/created once, and reuse when processing Camel messages. But this may cause side-effects with data left from previous evaluation spills into the next, and concurrency issues as well. If the script being evaluated is idempotent then this option can be turned on.
|
binary
|
false
|
boolean
|
Camel 2.14.1: Whether the script is binary content. This is intended to be used for loading resources using the Constant language, such as loading binary files. |
Message Headers
The following message headers can be used to affect the behavior of the component
| Header | Description |
|---|---|
CamelLanguageScript
|
The script to execute provided in the header. Takes precedence over script configured on the endpoint. |
Examples
For example you can use the Simple language to Message TranslatorMessage Translator a message:
String script = URLEncoder.encode("Hello ${body}", "UTF-8");
from("direct:start").to("language:simple:" + script).to("mock:result");
In case you want to convert the message body type you can do this as well:
String script = URLEncoder.encode("${mandatoryBodyAs(String)}", "UTF-8");
from("direct:start").to("language:simple:" + script).to("mock:result");
You can also use the Groovy language, such as this example where the input message will by multiplied with 2:
from("direct:start").to("language:groovy:request.body * 2").to("mock:result");
You can also provide the script as a header as shown below. Here we use XPath language to extract the text from the
<foo> tag.
Object out = producer.requestBodyAndHeader("language:xpath", "<foo>Hello World</foo>", Exchange.LANGUAGE_SCRIPT, "/foo/text()");
assertEquals("Hello World", out);Loading scripts from resources
Available as of Camel 2.9
You can specify a resource uri for a script to load in either the endpoint uri, or in the
Exchange.LANGUAGE_SCRIPT header. The uri must start with one of the following schemes: file:, classpath:, or http:
For example to load a script from the classpath:
from("direct:start")
// load the script from the classpath
.to("language:simple:classpath:org/apache/camel/component/language/mysimplescript.txt")
.to("mock:result");
By default the script is loaded once and cached. However you can disable the
contentCache option and have the script loaded on each evaluation. For example if the file myscript.txt is changed on disk, then the updated script is used:
from("direct:start")
// the script will be loaded on each message, as we disabled cache
.to("language:simple:file:target/script/myscript.txt?contentCache=false")
.to("mock:result");
From Camel 2.11 onwards you can refer to the resource similar to the other Languages in Camel by prefixing with
"resource:" as shown below:
from("direct:start")
// load the script from the classpath
.to("language:simple:resource:classpath:org/apache/camel/component/language/mysimplescript.txt")
.to("mock:result");- Routing SlipRouting Slip
- Dynamic RouterDynamic Router
