検索

このコンテンツは選択した言語では利用できません。

Chapter 99. MVEL Component

download PDF

MVEL Component

Available as of Camel 2.12
The mvel: component allows you to process a message using an MVEL template. This can be ideal when using Templating to generate responses for requests.
Maven users will need to add the following dependency to their pom.xml for this component:
<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-mvel</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel core version -->
</dependency>

URI format

mvel:templateName[?options]
Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template (eg: file://folder/myfile.mvel).
You can append query options to the URI in the following format, ?option=value&option=value&...

Options

Option Default Description
contentCache true Cache for the resource content when it is loaded. The cached resource content can be cleared via JMX using the endpoint's clearContentCache operation.
encoding null Character encoding of the resource content.

Message Headers

The mvel component sets a couple headers on the message.
Header Description
CamelMvelResourceUri The templateName as a String object.

MVEL Context

Camel will provide exchange information in the MVEL context (just a Map). The Exchange is transfered as:
key value
exchange The Exchange itself.
exchange.properties The Exchange properties.
headers The headers of the In message.
camelContext The Camel Context intance.
request The In message.
in The In message.
body The In message body.
out The Out message (only for InOut message exchange pattern).
response The Out message (only for InOut message exchange pattern).

Hot reloading

The mvel template resource is, by default, hot reloadable for both file and classpath resources (expanded jar). If you set contentCache=true, Camel will only load the resource once, and thus hot reloading is not possible. This scenario can be used in production, when the resource never changes.

Dynamic templates

Camel provides two headers by which you can define a different resource location for a template or the template content itself. If any of these headers is set then Camel uses this over the endpoint configured resource. This allows you to provide a dynamic template at runtime.
Header Type Description
CamelMvelResourceUri String A URI for the template resource to use instead of the endpoint configured.
CamelMvelTemplate String The template to use instead of the endpoint configured.

Samples

For example you could use something like
from("activemq:My.Queue").
  to("mvel:com/acme/MyResponse.mvel");
To use a MVEL template to formulate a response to a message for InOut message exchanges (where there is a JMSReplyTo header).
To specify what template the component should use dynamically via a header, so for example:
from("direct:in").
  setHeader("CamelMvelResourceUri").constant("path/to/my/template.mvel").
  to("mvel:dummy");
To specify a template directly as a header the component should use dynamically via a header, so for example:
from("direct:in").
  setHeader("CamelMvelTemplate").constant("@{\"The result is \" + request.body * 3}\" }").
  to("velocity:dummy");
Red Hat logoGithubRedditYoutubeTwitter

詳細情報

試用、購入および販売

コミュニティー

Red Hat ドキュメントについて

Red Hat をお使いのお客様が、信頼できるコンテンツが含まれている製品やサービスを活用することで、イノベーションを行い、目標を達成できるようにします。

多様性を受け入れるオープンソースの強化

Red Hat では、コード、ドキュメント、Web プロパティーにおける配慮に欠ける用語の置き換えに取り組んでいます。このような変更は、段階的に実施される予定です。詳細情報: Red Hat ブログ.

会社概要

Red Hat は、企業がコアとなるデータセンターからネットワークエッジに至るまで、各種プラットフォームや環境全体で作業を簡素化できるように、強化されたソリューションを提供しています。

© 2024 Red Hat, Inc.