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 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 the 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"

  1. 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">

  1. 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 subpackage of this. This causes Camel to search in its own packages for your routes, which could cause problems.

Will ignore already instantiated classes

The <package> and <packageScan> will skip all classes that Spring has already created etc. So if you define a route builder as a spring bean tag, then that class will be skipped. You can include those beans using <routeBuilder ref="theBeanId"/> or the <contextScan> feature.

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 allows you to use the Spring <component-scan> feature and have Camel pickup any RouteBuilder instances which were 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 routes are in separate XML files. You may also want to store common and reusable routes in other XML files, which you can 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 functionalities 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:

<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
    ">
    <!-- 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 you like -->
        <route id="bar">
            <from uri="direct:bar"/>
            <to uri="mock:bar"/>
        </route>
    </routeContext>
</beans>

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:

 <!-- import the routes from another XML file -->
 <import resource="myCoolRoutes.xml"/>

 <camelContext xmlns="http://camel.apache.org/schema/spring">

     <!-- refer to a given route to be used -->
     <routeContextRef ref="myCoolRoutes"/>

     <!-- we can still use routes inside camelContext -->
     <route id="inside">
         <from uri="direct:inside"/>
         <to uri="mock:inside"/>
     </route>
 </camelContext>

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, it is only the definition that 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 initialized that are not applicable or useful to the test scenario. For instance, you might have 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 the 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 (excludeRoute and excludeRoutes) 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;
    }
}

To hook into the camelContext initialization by spring to exclude the class MyExcludedRouteBuilder, 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 the method excludeRoutes.

@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&amp;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 details, see Configuring Endpoints and Components.

CamelContextAware

If you want the CamelContext to be injected 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>