Apache Camel is designed to work nicely with the Spring Framework in a number of ways.
- Camel uses Spring Transactions as the default transaction handling in components like JMS and JPA
- Camel works with Spring 2 XML processing with the Xml Configuration
- Camel Spring XML Schema's is defined at Xml Reference
- Camel supports a powerful version of Spring Remoting which can use powerful routing between the client and server side along with using all of the available Components for the transport
- Camel provides powerful Bean Integration with any bean defined in a Spring ApplicationContext
- Camel integrates with various Spring helper classes; such as providing Type Converter support for Spring Resources etc
- Allows Spring to dependency inject Component instances or the CamelContext instance itself and auto-expose Spring beans as components and endpoints.
- Allows you to reuse the Spring Testing framework to simplify your unit and integration testing using Enterprise Integration Patterns and Camel's powerful Mock and Test endpoints
- From Camel 2.15 onwards Camel supports Spring Boot using the
Using Spring to configure the CamelContext
You can configure a CamelContext inside any spring.xml using the CamelContextFactoryBean. This will automatically start the CamelContext along with any referenced Routes along any referenced Component and Endpoint instances.
- Adding Camel schema
- Configure Routes in two ways:
- Using Java Code
- Using Spring XML
Adding Camel Schema
You need to add Camel to the
So the XML file looks like this:
Using camel: namespace
Or you can refer to camel XSD in the XML declaration:
... so the declaration is:
... and then use the camel: namespace prefix, and you can omit the inline namespace declaration:
Advanced configuration using Spring
See more details at Advanced configuration of CamelContext using Spring
Using Java Code
You can use Java Code to define your RouteBuilder implementations. These can be defined as beans in spring and then referenced in your camel context e.g.
Camel also provides a powerful feature that allows for the automatic discovery and initialization of routes in given packages. This is configured by adding tags to the camel context in your spring context definition, specifying the packages to be recursively searched for RouteBuilder implementations. To use this feature in 1.X, requires a <package></package> tag specifying a comma separated list of packages that should be searched e.g.
In Camel 2.0 this has been extended to allow selective inclusion and exclusion of discovered route classes using Ant like path matching. In spring this is specified by adding a <packageScan/> tag. The tag must contain one or more 'package' elements (similar to 1.x), and optionally one or more 'includes' or 'excludes' elements specifying patterns to be applied to the fully qualified names of the discovered classes. e.g.
Exclude patterns are applied before the include patterns. If no include or exclude patterns are defined then all the Route classes discovered in the packages will be returned.
In the above example, camel will scan all the 'org.example.routes' package and any subpackages for RouteBuilder classes. Say the scan finds two RouteBuilders, one in org.example.routes called 'MyRoute" and another 'MyExcludedRoute' in a subpackage 'excluded'. The fully qualified names of each of the classes are extracted (org.example.routes.MyRoute, org.example.routes.excluded.MyExcludedRoute) and the include and exclude patterns are applied.
The exclude pattern **.*Excluded* is going to match the fqcn 'org.example.routes.excluded.MyExcludedRoute' and veto camel from initializing it.
Under the covers, this is using Spring's AntPatternMatcher implementation, which matches as follows
**.*Excluded* would match org.simple.Excluded, org.apache.camel.SomeExcludedRoute or org.example.RouteWhichIsExcluded
**.??cluded* would match org.simple.IncludedRoute, org.simple.Excluded but not match org.simple.PrecludedRoute
Available as of Camel 2.4
You can allow Camel to scan the container context, e.g. the Spring
ApplicationContext for route builder instances. This allow you to use the Spring
<component-scan> feature and have Camel pickup any RouteBuilder instances which was created by Spring in its scan process.
This allows you to just annotate your routes using the Spring
@Component and have those routes included by Camel
You can also use the ANT style for inclusion and exclusion, as mentioned above in the
How do I import routes from other XML files
Available as of Camel 2.3
When defining routes in Camel using Xml Configuration you may want to define some routes in other XML files. For example you may have many routes and it may help to maintain the application if some of the routes are in separate XML files. You may also want to store common and reusable routes in other XML files, which you can simply import when needed.
In Camel 2.3 it is now possible to define routes outside
<camelContext/> which you do in a new
For example we could have a file named
myCoolRoutes.xml which contains a couple of routes as shown:
Then in your XML file which contains the CamelContext you can use Spring to import the
And then inside
<camelContext/> you can refer to the
<routeContext/> by its id as shown below:
Also notice that you can mix and match, having routes inside CamelContext and also externalized in RouteContext.
You can have as many
<routeContextRef/> as you like.
Test time exclusion.
At test time it is often desirable to be able to selectively exclude matching routes from being initalized that are not applicable or useful to the test scenario. For instance you might a spring context file routes-context.xml and three Route builders RouteA, RouteB and RouteC in the 'org.example.routes' package. The packageScan definition would discover all three of these routes and initialize them.
Say RouteC is not applicable to our test scenario and generates a lot of noise during test. It would be nice to be able to exclude this route from this specific test. The SpringTestSupport class has been modified to allow this. It provides two methods (excludedRoute and excludedRoutes) that may be overridden to exclude a single class or an array of classes.
In order to hook into the camelContext initialization by spring to exclude the MyExcludedRouteBuilder.class we need to intercept the spring context creation. When overriding createApplicationContext to create the spring context, we call the getRouteExcludingApplicationContext() method to provide a special parent spring context that takes care of the exclusion.
RouteC will now be excluded from initialization. Similarly, in another test that is testing only RouteC, we could exclude RouteB and RouteA by overriding
Using Spring XML
Configuring Components and Endpoints
Which allows you to configure a component using some name (activemq in the above example), then you can refer to the component using activemq:[queue:|topic:]destinationName. This works by the SpringCamelContext lazily fetching components from the spring context for the scheme name you use for Endpoint URIs.
For more detail see Configuring Endpoints and Components.
If you want to be injected with the CamelContext in your POJO just implement the CamelContextAware interface; then when Spring creates your POJO the CamelContext will be injected into your POJO. Also see the Bean Integration for further injections.
To avoid a hung route when testing using Spring Transactions see the note about Spring Integration Testing under Transactional Client.