Deploying into Spring Boot

In standalone deployment mode, a Spring Boot application is packaged as a Jar file and runs directly inside the Java Virtual Machine (JVM). That is, the Spring Boot application can be run directly using the java command with the -jar option — for example:

java -jar SpringBootApplication.jar

Where Spring Boot provides the main class for the executable Jar. This approach to packaging and running the application is consistent with the microservices philosophy, where a service is packaged with the minimum set of requirements. The container is also minimal, being just the JVM itself.

The following elements are required for building a Spring Boot standalone application in Fuse:

Red Hat Fuse provides the following boosters to help you get started with Fuse applications and demonstrate useful components:

The Netflix/Hystrix circuit breaker component enables distributed applications to cope with interruptions to network connectivity and temporary unavailability of backend services. The basic idea of the circuit breaker pattern is that the loss of a dependent service is detected automatically and an alternative behavior can be programmed, in case the backend service is temporarily unavailable.

The Fuse circuit breaker booster consists of two related services:

In this demonstration, the Hystrix circuit breaker is inserted between the greetings service and the name service. If the name service becomes unavailable, the greetings service can fall back to an alternative behavior and respond to the client immediately, instead of blocking or timing out while it waits for the name service to restart.

The Externalized Configuration booster provides an example of how to externalize configuration for an Apache Camel route. For Spring Boot standalone deployments, the configuration data is stored in an application.properties file.

The REST API Level 0 mission shows how to map business operations to a remote procedure call endpoint over HTTP by using a REST framework. This mission corresponds to Level 0 in the Richardson Maturity Model.

This booster introduces the mechanics of interacting with a remote (exposed by Apache Camel) service using the HTTP protocol. By using this Fuse booster, you can quickly prototype and flexibly design a REST API.

Use this booster to:

Fuse provides a selection of quickstarts, based on Maven archetypes, which you can use to generate an initial Maven project for a Spring Boot application. To save you having to remember the location information and versions for various Maven archetypes, Fuse provides tooling to help you generate Maven projects for standalone Spring Boot projects.

After creating and building your first Spring Boot project, you will soon want to add more components. But how do you know which versions of the Maven dependencies to add to your project? The simplest (and recommended) approach is to use the relevant Bill of Materials (BOM) file, which automatically defines all of the version dependencies for you.

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<project ...>
  ...
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <!-- configure the versions you want to use here -->
    <fuse.version>7.3.0.fuse-730058-redhat-00001</fuse.version>
    <spring-boot.version>1.5.17.RELEASE</spring-boot.version>
  </properties>

  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.jboss.redhat-fuse</groupId>
        <artifactId>fuse-springboot-bom</artifactId>
        <version>${fuse.version}</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>
  ...
</project>

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-hystrix-starter</artifactId>
</dependency>

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<project ...>
  ...
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <!-- configure the versions you want to use here -->
    <fuse.version>7.3.0.fuse-730058-redhat-00001</fuse.version>

  </properties>
  ...
  <build>
    <plugins>
      <plugin>
        <groupId>org.jboss.redhat-fuse</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
        <version>${fuse.version}</version>
        <executions>
          <execution>
            <goals>
              <goal>repackage</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
  ...
</project>

The Camel Spring Boot component provides auto configuration for Apache Camel. Auto-configuration of the Camel context auto-detects Camel routes available in the Spring context and registers the key Camel utilities such as producer template, consumer template, and the type converter as beans.

Every Camel Spring Boot application should use dependencyManagement with productized versions, see quickstart pom. Versions that are tagged later can be omitted to not override the versions from BOM.

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.jboss.redhat-fuse</groupId>
			<artifactId>fuse-springboot-bom</artifactId>
			<version>${fuse.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

Apache Camel includes a Spring Boot starter module that allows you to develop Spring Boot applications using starters.

To use the starter, add the following snippet to your Spring Boot pom.xml file:

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-spring-boot-starter</artifactId>
</dependency>

The starter allows you to add classes with your Camel routes, as shown in the snippet below. Once these routes are added to the class path the routes are started automatically.

package com.example;

import org.apache.camel.builder.RouteBuilder;
import org.springframework.stereotype.Component;

@Component
public class MyRoute extends RouteBuilder {

    @Override
    public void configure() throws Exception {
        from("timer:foo").to("log:bar");
    }
}

You can customize the Camel application in the application.properties or application.yml file. 

Camel Spring Boot now supports referring to bean by the id name in the configuration files (application.properties or yaml file) when you configure any of the Camel starter components. In the src/main/resources/application.properties (or yaml) file you can now easily configure the options on the Camel that refers to other beans by refering to the beans ID name. For example, the xslt component can refer to a custom bean using the bean ID as follows:

Refer to a custom bean by the id myExtensionFactory as follows:

camel.component.xslt.saxon-extension-functions=myExtensionFactory

Which you can then create using Spring Boot @Bean annotation as follows:

@Bean(name = "myExtensionFactory")
public ExtensionFunctionDefinition myExtensionFactory() {
    }

Or, in case of a Jackson ObjectMapper in the camel-jackson data-format:

camel.dataformat.json-jackson.object-mapper=myJacksonMapper

Camel auto-configuration provides a CamelContext instance and creates a SpringCamelContext. It also initializes and performs shutdown of that context. This Camel context is registered in the Spring application context under camelContext bean name and you can access it like other Spring bean.

For example, you can access the camelContext as shown below:

@Configuration
public class MyAppConfig {

  @Autowired
  CamelContext camelContext;

  @Bean
  MyService myService() {
    return new DefaultMyService(camelContext);
  }

}

Camel auto configuration collects all the RouteBuilder instances from the Spring context and automatically injects them into the CamelContext. It simplifies the process of creating new Camel route with the Spring Boot starter. You can create the routes by adding the @Component annotated class to your classpath.

@Component
public class MyRouter extends RouteBuilder {

  @Override
  public void configure() throws Exception {
    from("jms:invoices").to("file:/invoices");
  }

}

To create a new route RouteBuilder bean in your @Configuration class, see below:

@Configuration
public class MyRouterConfiguration {

  @Bean
  RoutesBuilder myRouter() {
    return new RouteBuilder() {

      @Override
      public void configure() throws Exception {
        from("jms:invoices").to("file:/invoices");
      }

    };
  }
 
}

Spring Boot auto configuration automatically connects to Spring Boot external configuration such as properties placeholders, OS environment variables, or system properties with Camel properties support.

These properties are defined in application.properties file:  

route.from = jms:invoices

Use as system property

java -Droute.to=jms:processed.invoices -jar mySpringApp.jar

Use as placeholders in Camel route:

@Component
public class MyRouter extends RouteBuilder {

  @Override
  public void configure() throws Exception {
    from("{{route.from}}").to("{{route.to}}");
  }

}

To perform operations on CamelContext bean created by Camel auto configuration, you need to register CamelContextConfiguration instance in your Spring context as shown below:

@Configuration
public class MyAppConfig {

  ...

  @Bean
  CamelContextConfiguration contextConfiguration() {
    return new CamelContextConfiguration() {
      @Override
      void beforeApplicationStart(CamelContext context) {
        // your custom configuration goes here
      }
    };
  }

}

To disable JMX of the auto-configured CamelContext use camel.springboot.jmxEnabled property as JMX is enabled by default.

For example, you could add the following property to your application.properties file:

camel.springboot.jmxEnabled = false

Camel auto configuration provides pre-configured ConsumerTemplate and ProducerTemplate instances. You can inject them into your Spring-managed beans:

@Component
public class InvoiceProcessor {

  @Autowired
  private ProducerTemplate producerTemplate;

  @Autowired
  private ConsumerTemplate consumerTemplate;
  public void processNextInvoice() {
    Invoice invoice = consumerTemplate.receiveBody("jms:invoices", Invoice.class);
    ...
    producerTemplate.sendBody("netty-http:http://invoicing.com/received/" + invoice.id());
  }

}

By default consumer templates and producer templates come with the endpoint cache sizes set to 1000. You can change those values using the following Spring properties:

camel.springboot.consumerTemplateCacheSize = 100
camel.springboot.producerTemplateCacheSize = 200

Camel auto configuration registers a TypeConverter instance named typeConverter in the Spring context.

@Component
public class InvoiceProcessor {

  @Autowired
  private TypeConverter typeConverter;

  public long parseInvoiceValue(Invoice invoice) {
    String invoiceValue = invoice.grossValue();
    return typeConverter.convertTo(Long.class, invoiceValue);
  }

}

Spring consist of  type conversion API. Spring API is similar to the Camel type converter API. Due to the similarities between the two APIs Camel Spring Boot automatically registers a bridge converter (SpringTypeConverter) that delegates to the Spring conversion API. That means that out-of-the-box Camel will treat Spring Converters similar to Camel.

This allows you to access both Camel and Spring converters using the Camel TypeConverter API, as shown below:

@Component
public class InvoiceProcessor {

  @Autowired
  private TypeConverter typeConverter;

  public UUID parseInvoiceId(Invoice invoice) {
    // Using Spring's StringToUUIDConverter
    UUID id = invoice.typeConverter.convertTo(UUID.class, invoice.getId());
  }

}

Here, Spring Boot delegates conversion to the Spring’s ConversionService instances available in the application context. If no ConversionService instance is available, Camel Spring Boot auto configuration creates an instance of ConversionService.

To disable registering type conversion features of Camel Spring Boot such as TypeConverter instance or Spring bridge, set the camel.springboot.typeConversion property to false as shown below:

camel.springboot.typeConversion = false

By default, you can put Camel XML routes in the classpath under the directory camel, which camel-spring-boot will auto detect and include. From Camel version 2.17 onwards you can configure the directory name or disable this feature using the configuration option, as shown below:

// turn off
camel.springboot.xmlRoutes = false
// scan in the com/foo/routes classpath
camel.springboot.xmlRoutes = classpath:com/foo/routes/*.xml

   <routes xmlns="http://camel.apache.org/schema/spring">
        <route id="test">
            <from uri="timer://trigger"/>
            <transform>
                <simple>ref:myBean</simple>
            </transform>
            <to uri="log:out"/>
        </route>
    </routes>

When using Spring XML files with <camelContext>, you can configure Camel in the Spring XML file as well as in the application.properties file. For example, to set a name on Camel and turn On the stream caching, add:

camel.springboot.name = MyCamel
camel.springboot.stream-caching-enabled=true

By default, you can put Camel Rest-DSL XML routes in the classpath under the directory camel-rest, which camel-spring-boot will auto detect and include. You can configure the directory name or disable this feature using the configuration option, as shown below:

// turn off
camel.springboot.xmlRests = false
// scan in the com/foo/routes classpath
camel.springboot.xmlRests = classpath:com/foo/rests/*.xml

   <rests xmlns="http://camel.apache.org/schema/spring">
      <rest>
         <post uri="/persons">
            <to uri="direct:postPersons"/>
         </post>
         <get uri="/persons">
            <to uri="direct:getPersons"/>
         </get>
         <get uri="/persons/{personId}">
             <to uri="direct:getPersionId"/>
         </get>
         <put uri="/persons/{personId}">
             <to uri="direct:putPersionId"/>
         </put>
         <delete uri="/persons/{personId}">
             <to uri="direct:deletePersionId"/>
         </delete>
      </rest>
    </rests>

In case on Camel running on Spring Boot, Spring Boot automatically embeds Camel and all its routes, which are annotated with @Component. When testing with Spring boot you use @SpringBootTest instead of @ContextConfiguration to specify which configuration class to use.

When you have multiple Camel routes in different RouteBuilder classes, Camel Spring Boot will include all these routes. Hence, when you wish to test routes from only one RouteBuilder class you can use the following patterns to include or exclude which RouteBuilders to enable:

You can specify these patterns in your unit test classes as properties to @SpringBootTest annonation, as shown below:

@RunWith(CamelSpringBootRunner.class)
@SpringBootTest(classes = {MyApplication.class);
   properties = {"camel.springboot.java-routes-include-pattern=**/Foo*"})
public class FooTest {

In the FooTest class, the include pattern is **/Foo*, which represents an Ant style pattern. Here, the pattern starts with double asterisk, which matches with any leading package name. /Foo* means the class name must start with Foo, for example, FooRoute. You can run a test using following maven command:

mvn test -Dtest=FooTest