MVEL
Since Camel 2.0
Camel supports MVEL to do message transformations using MVEL templates.
MVEL is powerful for templates, but can also be used for Expression or Predicate
For example, you can use MVEL in a Predicate with the Content Based Router EIP.
You can use MVEL dot notation to invoke operations. If you for instance
have a body that contains a POJO that has a getFamilyName
method then
you can construct the syntax as follows:
request.body.familyName
Or use similar syntax as in Java:
getRequest().getBody().getFamilyName()
Variables
The following Camel related variables are made available:
Variable | Type | Description |
---|---|---|
this |
Exchange |
the Exchange is the root object |
context |
CamelContext |
the CamelContext |
exchange |
Exchange |
the Exchange |
exchangeId |
String |
the exchange id |
exception |
Throwable |
the Exchange exception (if any) |
request |
Message |
the message |
message |
Message |
the message |
headers |
Map |
the message headers |
header(name) |
Object |
the message header by the given name |
header(name, type) |
Type |
the message header by the given name as the given type |
properties |
Map |
the exchange properties |
property(name) |
Object |
the exchange property by the given name |
property(name, type) |
Type |
the exchange property by the given name as the given type |
Example
For example, you could use MVEL inside a Message Filter
from("seda:foo")
.filter().mvel("headers.foo == 'bar'")
.to("seda:bar");
And in XML:
<route>
<from uri="seda:foo"/>
<filter>
<mvel>headers.foo == 'bar'</mvel>
<to uri="seda:bar"/>
</filter>
</route>
Loading script from external resource
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").mvel("resource:classpath:script.mvel")
Dependencies
To use MVEL in your camel routes you need to add the dependency on camel-mvel which implements the MVEL language.
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-mvel</artifactId>
<version>x.x.x</version>
</dependency>
Spring Boot Auto-Configuration
When using mvel with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:
<dependency>
<groupId>org.apache.camel.springboot</groupId>
<artifactId>camel-mvel-starter</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
The component supports 7 options, which are listed below.
Name | Description | Default | Type |
---|---|---|---|
Sets whether the context map should allow access to all details. By default only the message body and headers can be accessed. This option can be enabled for full access to the current Exchange and CamelContext. Doing so impose a potential security risk as this opens access to the full power of CamelContext API. |
false |
Boolean |
|
Whether to allow to use resource template from header or not (default false). Enabling this allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care. |
false |
Boolean |
|
Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc. |
true |
Boolean |
|
Whether to enable auto configuration of the mvel component. This is enabled by default. |
Boolean |
||
Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. |
false |
Boolean |
|
Whether to enable auto configuration of the mvel language. This is enabled by default. |
Boolean |
||
Whether to trim the value to remove leading and trailing whitespaces and line breaks. |
true |
Boolean |