Added javascript language to gitbook
Project: http://git-wip-us.apache.org/repos/asf/camel/repo Commit: http://git-wip-us.apache.org/repos/asf/camel/commit/705951bf Tree: http://git-wip-us.apache.org/repos/asf/camel/tree/705951bf Diff: http://git-wip-us.apache.org/repos/asf/camel/diff/705951bf Branch: refs/heads/master Commit: 705951bf05f9df52b5e7392bad8cc394b6077e38 Parents: f70ae04 Author: Andrea Cosentino <anco...@gmail.com> Authored: Thu Aug 25 12:09:21 2016 +0200 Committer: Andrea Cosentino <anco...@gmail.com> Committed: Thu Aug 25 12:09:21 2016 +0200 ---------------------------------------------------------------------- .../src/main/docs/javaScript-language.adoc | 199 +++++++++++++++++++ 1 file changed, 199 insertions(+) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/camel/blob/705951bf/components/camel-script/src/main/docs/javaScript-language.adoc ---------------------------------------------------------------------- diff --git a/components/camel-script/src/main/docs/javaScript-language.adoc b/components/camel-script/src/main/docs/javaScript-language.adoc new file mode 100644 index 0000000..cbb267e --- /dev/null +++ b/components/camel-script/src/main/docs/javaScript-language.adoc @@ -0,0 +1,199 @@ +[[JavaScript-JavaScript]] +JavaScript +~~~~~~~~~~ + +Camel supports +http://en.wikipedia.org/wiki/JavaScript[JavaScript/ECMAScript] among +other link:scripting-languages.html[Scripting Languages] to allow an +link:expression.html[Expression] or link:predicate.html[Predicate] to be +used in the link:dsl.html[DSL] or link:xml-configuration.html[Xml +Configuration]. + +To use a JavaScript expression use the following Java code + +[source,java] +----------------------------------------------- +... javaScript("someJavaScriptExpression") ... +----------------------------------------------- + +For example you could use the *javaScript* function to create an +link:predicate.html[Predicate] in a link:message-filter.html[Message +Filter] or as an link:expression.html[Expression] for a +link:recipient-list.html[Recipient List] + +[[JavaScript-Language-options]] +Javascript Language Options +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +// language options: START +The JavaScript language supports 1 options which are listed below. + + + +{% raw %} +[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 +|======================================================================= +{% endraw %} +// language options: END + +[[JavaScript-Example]] +Example +^^^^^^^ + +In the sample below we use JavaScript to create a +link:predicate.html[Predicate] use in the route path, to route exchanges +from admin users to a special queue. + +[source,java] +---------------------------------------------------------------------------------------------- + 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: + +[source,xml] +------------------------------------------------------------------------------- + <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> +------------------------------------------------------------------------------- + +[[JavaScript-ScriptContext]] +ScriptContext +^^^^^^^^^^^^^ + +The JSR-223 scripting languages ScriptContext is pre configured with the +following attributes all set at `ENGINE_SCOPE`: + +[width="100%",cols="10%,10%,80%",options="header",] +|======================================================================= +|Attribute |Type |Value + +|context |`org.apache.camel.CamelContext` |The Camel Context ( It cannot be used in groovy) + +|camelContext |`org.apache.camel.CamelContext` |The Camel Context + +|exchange |`org.apache.camel.Exchange` |The current Exchange + +|request |`org.apache.camel.Message` |The message (IN message) + +|response |`org.apache.camel.Message` |*Deprecated*: The OUT message. The OUT message if null by default. Use +IN message instead. + +|properties |`org.apache.camel.builder.script.PropertiesFunction` |*Camel 2.9:* Function with a `resolve` method to make it easier to use +Camels link:properties.html[Properties] component from scripts. See +further below for example. +|======================================================================= + +See link:scripting-languages.html[Scripting Languages] for the list of +languages with explicit DSL support. + +[[JavaScript-AdditionalargumentstoScriptingEngine]] +Additional arguments to ScriptingEngine +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +*Available as of Camel 2.8* + +You can provide additional arguments to the `ScriptingEngine` using a +header on the Camel message with the key `CamelScriptArguments`. + + See this example: + +[[JavaScript-Usingpropertiesfunction]] +Using properties function +^^^^^^^^^^^^^^^^^^^^^^^^^ + +*Available as of Camel 2.9* + +If you need to use the link:properties.html[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, which key is provided in a header named "foo". + +[source,java] +-------------------------------------------------------------------------------------------------------------- +.setHeader("myHeader").groovy("context.resolvePropertyPlaceholders('{{' + request.headers.get('foo') + '}}')") +-------------------------------------------------------------------------------------------------------------- + +From Camel 2.9 onwards you can now use the properties function and the +same example is simpler: + +[source,java] +------------------------------------------------------------------------------- +.setHeader("myHeader").groovy("properties.resolve(request.headers.get('foo'))") +------------------------------------------------------------------------------- + +[[JavaScript-Loadingscriptfromexternalresource]] +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").groovy("resource:classpath:mygroovy.groovy") +------------------------------------------------------------------- + +[[JavaScript-Howtogettheresultfrommultiplestatementsscript]] +How to get the result from multiple statements script +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +*Available as of Camel 2.14* + +As the scripteengine evale method just return a Null if it runs a +multiple statments script. Camel now look up the value of script result +by using the key of "result" from the value set. If you have multiple +statements script, you need to make sure you set the value of result +variable as the script return value. + +[source,text] +------------------------------------------------------------- +bar = "baz"; +# some other statements ... +# camel take the result value as the script evaluation result +result = body * 2 + 1 +------------------------------------------------------------- + +Â + +[[JavaScript-Dependencies]] +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 +link:download.html[the download page for the latest versions]). + +[source,xml] +--------------------------------------- +<dependency> + <groupId>org.apache.camel</groupId> + <artifactId>camel-script</artifactId> + <version>x.x.x</version> +</dependency> +---------------------------------------
