Spring
Spring components
See the following for usage of each component:
- Spring Batch
-
Send messages to Spring Batch for further processing.
- Spring Event
-
Listen for Spring Application Events.
- Spring Integration
-
Bridge Camel with Spring Integration.
- Spring JDBC
-
Access databases through SQL and JDBC with Spring Transaction support.
- Spring LDAP
-
Perform searches in LDAP servers using filters as the message payload.
- Spring RabbitMQ
-
Send and receive messages from RabbitMQ using Spring RabbitMQ client.
- Spring Redis
-
Send and receive messages from Redis.
- Spring WebService
-
Access external web services as a client or expose your own web services.
Apache Camel is designed to work nicely with the Spring Framework in a number of ways.
-
Camel supports Spring Boot using the
camel-spring-boot
component. -
Allows Spring to dependency inject Component instances or the CamelContext instance itself and auto-expose Spring beans as components and endpoints.
-
Camel works with Spring XML processing with the XML DSL via
camel-spring-xml
component -
Camel provides powerful Bean Integration with any bean defined in a Spring ApplicationContext
-
Camel uses Spring Transactions as the default transaction handling in components like JMS and JPA
-
Camel integrates with various Spring helper classes; such as providing Type Converter support for Spring Resources etc
-
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
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 schemaLocation
declaration
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd
So the XML file looks like this:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
Using camel: namespace
Or you can refer to camel XSD in the XML declaration:
xmlns:camel="http://camel.apache.org/schema/spring"
-
so the declaration is:
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:camel="http://camel.apache.org/schema/spring"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
-
and then use the camel: namespace prefix, and you can omit the inline namespace declaration:
<camel:camelContext>
<camel:package>org.apache.camel.spring.example</camel:package>
</camel:camelContext>
Additional configuration of Spring XML
See more details at Camel Spring XML Auto Configuration.
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.
Using <package>
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, requires a
<package></package>
tag specifying a comma
separated list of packages that should be searched e.g.
<camelContext xmlns="http://camel.apache.org/schema/spring">
<package>org.apache.camel.spring.config.scan.route</package>
</camelContext>
Use caution when specifying the package name as org.apache.camel or a
sub package of this. This causes Camel to search in its own packages for
your routes which could cause problems.
|
Will ignore already instantiated classes The |
Using <packageScan>
The component allows 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, 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.
<camelContext xmlns="http://camel.apache.org/schema/spring">
<packageScan>
<package>org.example.routes</package>
<excludes>**.*Excluded*</excludes>
<includes>**.*</includes>
</packageScan>
</camelContext>
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 ant path styles, which matches as follows
? matches one character
* matches zero or more characters
** matches zero or more segments of a fully qualified name
For example:
*.*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
Using contextScan
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
@Component
public class MyRoute extends SpringRouteBuilder {
@Override
public void configure() throws Exception {
from("direct:start").to("mock:result");
}
}
You can also use the ant style for inclusion and exclusion, as mentioned
above in the <packageScan>
documentation.
How do I import routes from other XML files
When defining routes in Camel using Spring XML 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.
It is possible to define routes outside
<camelContext/>
which you do in a new <routeContext/>
tag.
When you use <routeContext> then they are separated, and cannot reuse existing <onException>, <intercept>, <dataFormats> and similar cross cutting functionality defined in the <camelContext>. In other words the <routeContext> is currently isolated. |
For example we could have a file named myCoolRoutes.xml
which contains
a couple of routes as shown:
<!-- this is an included XML file where we only the routeContext -->
<routeContext id="myCoolRoutes" xmlns="http://camel.apache.org/schema/spring">
<!-- we can have a route -->
<route id="cool">
<from uri="direct:start"/>
<to uri="mock:result"/>
</route>
<!-- and another route, you can have as many your like -->
<route id="bar">
<from uri="direct:bar"/>
<to uri="mock:bar"/>
</route>
</routeContext>
Then in your XML file which contains the CamelContext you can use Spring
to import the myCoolRoute.xml
file.
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.
Reusable routes
The routes defined in <routeContext/>
can be reused by multiple
<camelContext/>
. However its only the definition which is reused. At
runtime each CamelContext will create its own instance of the route
based on the definition.
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.
public class RouteAandRouteBOnlyTest extends SpringTestSupport {
@Override
protected Class excludeRoute() {
return RouteC.class;
}
}
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.
@Override
protected AbstractXmlApplicationContext createApplicationContext() {
return new ClassPathXmlApplicationContext(new String[] {"routes-context.xml"}, getRouteExcludingApplicationContext());
}
RouteC will now be excluded from initialization. Similarly, in another test that is testing only RouteC, we could exclude RouteB and RouteA by overriding
@Override
protected Class[] excludeRoutes() {
return new Class[]{RouteA.class, RouteB.class};
}
Using Spring XML
You can use Spring XML configuration to specify your XML Configuration for Routes such as in the following
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd
">
<camelContext id="camel-A" xmlns="http://camel.apache.org/schema/spring">
<route>
<from uri="seda:start"/>
<to uri="mock:result"/>
</route>
</camelContext>
</beans>
Configuring Components and Endpoints
You can configure your Component or Endpoint instances in your Spring XML as follows:
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
<jmxAgent id="agent" disabled="true"/>
</camelContext>
<bean id="activemq" class="org.apache.camel.component.jms.JmsComponent">
<property name="connectionFactory">
<bean class="org.apache.activemq.ActiveMQConnectionFactory">
<property name="brokerURL" value="vm://localhost?broker.persistent=false&broker.useJmx=false"/>
</bean>
</property>
</bean>
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.
CamelContextAware
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.
Integration Testing
To avoid a hung route when testing using Spring Transactions see the note about Spring Integration Testing under Transactional Client.
Cron Component Support
The camel-spring
module can be used as implementation of the Camel Cron component.
Maven users will need to add the following additional dependency to their pom.xml
:
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-cron</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
Users can then use the cron component inside routes of their Spring or Spring Boot application:
<route>
<from uri="cron:tab?schedule=0/1+*+*+*+*+?"/>
<to uri="log:info"/>
</route>
Spring Boot Auto-Configuration
When using spring 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-spring-starter</artifactId>
<version>x.x.x</version>
<!-- use the same version as your Camel core version -->
</dependency>
The component supports 6 options, which are listed below.
Name | Description | Default | Type |
---|---|---|---|
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 |
|
Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored. |
false |
Boolean |
|
Whether to enable auto configuration of the spring-event 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 spel language. This is enabled by default. |
Boolean |
||
Whether to trim the value to remove leading and trailing whitespaces and line breaks. |
true |
Boolean |