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JavaScriptCamel supports JavaScript/ECMAScript among other Scripting Languages to allow an Expression or Predicate to be used in the DSL or Xml Configuration. To use a JavaScript expression use the following Java code
... javaScript("someJavaScriptExpression") ...
For example you could use the javaScript function to create an Predicate in a Message Filter or as an Expression for a Recipient List ExampleIn the sample below we use JavaScript to create a Predicate use in the route path, to route exchanges from admin users to a special queue.
from("direct:start")
.choice()
.when().javaScript("request.headers.get('user') == 'admin'").to("seda:adminQueue")
.otherwise()
.to("seda:regularQueue");
And a Spring DSL sample as well:
<route>
<from uri="direct:start"/>
<choice>
<when>
<javaScript>request.headers.get('user') == 'admin'</javaScript>
<to uri="seda:adminQueue"/>
</when>
<otherwise>
<to uri="seda:regularQueue"/>
</otherwise>
</choice>
</route>
|
Attribute | Type | Value |
|---|---|---|
|
| The Camel Context. |
|
| The Camel Context (cannot be used in groovy). |
|
| The current Exchange. |
|
| Camel 2.9: Function with a |
|
| The |
|
| Deprecated: The |
See Scripting Languages for the list of languages with explicit DSL support.
Passing Additional Arguments to the ScriptingEngine
Available from Camel 2.8
You can provide additional arguments to the ScriptingEngine using a header on the Camel message with the key CamelScriptArguments.
Example:
public void testArgumentsExample() throws Exception {
getMockEndpoint("mock:result").expectedMessageCount(0);
getMockEndpoint("mock:unmatched").expectedMessageCount(1);
// additional arguments to ScriptEngine
Map<String, Object> arguments = new HashMap<>();
arguments.put("foo", "bar");
arguments.put("baz", 7);
// those additional arguments is provided as a header on the Camel Message
template.sendBodyAndHeader("direct:start", "hello", ScriptBuilder.ARGUMENTS, arguments);
assertMockEndpointsSatisfied();
Using Properties Function
Available from Camel 2.9
If you need to use the Properties component from a script to lookup property placeholders, then its a bit cumbersome to do so. For example, to set a header name myHeader with a value from a property placeholder, whose key is taken from a header named foo.
.setHeader("myHeader").groovy("context.resolvePropertyPlaceholders('{{' + request.headers.get('foo') + '}}')")
From Camel 2.9: you can now use the properties function and the same example is simpler:
.setHeader("myHeader").groovy("properties.resolve(request.headers.get('foo'))")
Loading Script From External Resource
Available from 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 e.g. to refer to a file on the classpath you can do:
.setHeader("myHeader").groovy("resource:classpath:mygroovy.groovy")
How to Get the Result from Multiple Statements Script
Available from Camel 2.14
The script engine's eval method returns a null when it runs a multi-statement script. However, Camel can look up the value of a script's result by using the key result from the value set. When writing a multi-statement script set the value of the result variable as the script return value.
textbar = "baz"; # some other statements ... # camel take the result value as the script evaluation result result = body * 2 + 1
Dependencies
To use scripting languages in your camel routes you need to add the a dependency on camel-script which integrates the JSR-223 scripting engine.
If you use maven you could just add the following to your pom.xml, substituting the version number for the latest & greatest release (see the download page for the latest versions).
<dependency> <groupId>org.apache.camel</groupId> <artifactId>camel-script</artifactId> <version>x.x.x</version> </dependency>
