Repository: camel Updated Branches: refs/heads/master 0149a2239 -> e058d67bc
Added bean-language.adoc and constant.adoc to camel-core docs directory Project: http://git-wip-us.apache.org/repos/asf/camel/repo Commit: http://git-wip-us.apache.org/repos/asf/camel/commit/e058d67b Tree: http://git-wip-us.apache.org/repos/asf/camel/tree/e058d67b Diff: http://git-wip-us.apache.org/repos/asf/camel/diff/e058d67b Branch: refs/heads/master Commit: e058d67bcbcf4317a88a5500c9cce1e7243ba513 Parents: 0149a22 Author: Andrea Cosentino <anco...@gmail.com> Authored: Mon May 2 09:07:44 2016 +0200 Committer: Andrea Cosentino <anco...@gmail.com> Committed: Mon May 2 09:08:44 2016 +0200 ---------------------------------------------------------------------- camel-core/src/main/docs/bean-language.adoc | 156 +++++++++++++++++++++++ camel-core/src/main/docs/constant.adoc | 41 ++++++ 2 files changed, 197 insertions(+) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/camel/blob/e058d67b/camel-core/src/main/docs/bean-language.adoc ---------------------------------------------------------------------- diff --git a/camel-core/src/main/docs/bean-language.adoc b/camel-core/src/main/docs/bean-language.adoc new file mode 100644 index 0000000..573ef96 --- /dev/null +++ b/camel-core/src/main/docs/bean-language.adoc @@ -0,0 +1,156 @@ +[[BeanLanguage-BeanLanguage]] +Bean Language +~~~~~~~~~~~~~ + +The purpose of the Bean Language is to be able to implement an +link:expression.html[Expression] or link:predicate.html[Predicate] using +a simple method on a bean. + +So the idea is you specify a bean name which will then be resolved in +the link:registry.html[Registry] such as the link:spring.html[Spring] +ApplicationContext then a method is invoked to evaluate the +link:expression.html[Expression] or link:predicate.html[Predicate]. + +If no method name is provided then one is attempted to be chosen using +the rules for link:bean-binding.html[Bean Binding]; using the type of +the message body and using any annotations on the bean methods. + +The link:bean-binding.html[Bean Binding] rules are used to bind the +link:message.html[Message] Exchange to the method parameters; so you can +annotate the bean to extract headers or other expressions such as +link:xpath.html[XPath] or link:xquery.html[XQuery] from the message. + +[[BeanLanguage-UsingBeanExpressionsfromtheJavaDSL]] +Using Bean Expressions from the Java DSL +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +[source,java] +---------------------------------------------- +from("activemq:topic:OrdersTopic"). + filter().method("myBean", "isGoldCustomer"). + to("activemq:BigSpendersQueue"); +---------------------------------------------- + +[[BeanLanguage-UsingBeanExpressionsfromXML]] +Using Bean Expressions from XML +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +[source,xml] +-------------------------------------------------- +<route> + <from uri="activemq:topic:OrdersTopic"/> + <filter> + <method ref="myBean" method="isGoldCustomer"/> + <to uri="activemq:BigSpendersQueue"/> + </filter> +</route> +-------------------------------------------------- + +*Bean attribute now deprecated* + +Note, the `bean` attribute of the method expression element is now +deprecated. You should now make use of `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. + +So we could implement it like this... + +[source,java] +---------------------------------------------------- +public class MyBean { + public boolean isGoldCustomer(Exchange exchange) { + ... + } +} +---------------------------------------------------- + +We can also use the link:bean-integration.html[Bean Integration] +annotations. For example you could do... + +[source,java] +------------------------------------------------ +public boolean isGoldCustomer(String body) {...} +------------------------------------------------ + +or + +[source,java] +---------------------------------------------------------------------------- +public boolean isGoldCustomer(@Header(name = "foo") Integer fooHeader) {...} +---------------------------------------------------------------------------- + +So you can bind parameters of the method to the Exchange, the +link:message.html[Message] or individual headers, properties, the body +or other expressions. + +[[BeanLanguage-Nonregistrybeans]] +Non registry beans +^^^^^^^^^^^^^^^^^^ + +The link:bean-language.html[Bean Language] also supports invoking beans +that isn't registered in the link:registry.html[Registry]. This is +usable for quickly to invoke a bean from Java DSL where you don't need +to register the bean in the link:registry.html[Registry] such as the +link:spring.html[Spring] ApplicationContext. + +Camel can instantiate the bean and invoke the method if given a class or +invoke an already existing instance. This is illustrated from the +example below: + +[source,java] +---------------------------------------------------------------------------------- + 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 best suited 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,java] +----------------------------------------------------------------------------- + private MyBean my; + + from("activemq:topic:OrdersTopic"). + filter().expression(BeanLanguage.bean(my, "isGoldCustomer")). + to("activemq:BigSpendersQueue"); +----------------------------------------------------------------------------- + +In Camel 2.2 onwards you can avoid the `BeanLanguage` and have it just +as: + +[source,java] +---------------------------------------------------------------- + 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,java] +------------------------------------------------------ + private MyBean my; + + from("activemq:topic:OrdersTopic"). + filter().method(my, "isGoldCustomer"). + to("activemq:BigSpendersQueue"); +------------------------------------------------------ + +[[BeanLanguage-Dependencies]] +Dependencies +^^^^^^^^^^^^ + +The Bean language is part of *camel-core*. http://git-wip-us.apache.org/repos/asf/camel/blob/e058d67b/camel-core/src/main/docs/constant.adoc ---------------------------------------------------------------------- diff --git a/camel-core/src/main/docs/constant.adoc b/camel-core/src/main/docs/constant.adoc new file mode 100644 index 0000000..b54df7d --- /dev/null +++ b/camel-core/src/main/docs/constant.adoc @@ -0,0 +1,41 @@ +[[Constant-ConstantExpressionLanguage]] +Constant Expression Language +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The Constant Expression Language is really just a way to specify +constant strings as a type of expression. + +[[Constant-Exampleusage]] +Example usage +^^^^^^^^^^^^^ + +The setHeader element of the Spring DSL can utilize a constant +expression like: + +[source,xml] +------------------------------------------ +<route> + <from uri="seda:a"/> + <setHeader headerName="theHeader"> + <constant>the value</constant> + </setHeader> + <to uri="mock:b"/> +</route> +------------------------------------------ + +in this case, the link:message.html[Message] coming from the seda:a +link:endpoint.html[Endpoint] will have 'theHeader' header set to the +constant value 'the value'. + +And the same example using Java DSL: + +[source,java] +-------------------------------------------------------------------------- +from("seda:a").setHeader("theHeader", constant("the value")).to("mock:b"); +-------------------------------------------------------------------------- + +[[Constant-Dependencies]] +Dependencies +^^^^^^^^^^^^ + +The Constant language is part of *camel-core*.
