Chapter 4. Develop an Application for the Spring Boot Image

This chapter explains how to develop applications for the Spring Boot image.

To create a Spring Boot project, follow these steps:

Then, follow the instructions in the quickstart on how to build and deploy the example.

The directory structure of a Camel Spring Boot application is as follows:

  ├── LICENSE.md
  ├── pom.xml
  ├── README.md
  ├── configuration
  │   └── settings.xml
  └── src
      ├── main
      │   ├── fabric8
      │   │   └── deployment.yml
      │   ├── java
      │   │   └── org
      │   │       └── example
      │   │           └── fis
      │   │               ├── Application.java
      │   │               └── MyTransformer.java
      │   └── resources
      │       ├── application.properties
      │       ├── logback.xml
      │       └── spring
      │           └── camel-context.xml
      └── test
          └── java
              └── org
                  └── example
                      └── fis
                          └── KubernetesIntegrationKT.java

Where the following files are important for developing an application:

The Spring Boot Archetype catalog includes the following examples.

The following components do not have a starter because of compatibility issues:

The purpose of a Maven Bill of Materials (BOM) file is to provide a curated set of Maven dependency versions that work well together, saving you from having to define versions individually for every Maven artifact.

The Fuse BOM for Spring Boot offers the following advantages:

To incorporate a BOM file into your Maven project, specify a dependencyManagement element in your project’s pom.xml file (or, possibly, in a parent POM file), as shown in the following example:

<?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>7.1.0.fuse-710019-redhat-00002</fuse.version>
    <spring-boot.version>1.5.13.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>

After specifying the BOM using the dependency management mechanism, it becomes possible to add Maven dependencies to your POM without specifying the version of the artifact. For example, to add a dependency for the camel-hystrix component, you would add the following XML fragment to the dependencies element in your POM:

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

Note how the Camel artifact ID is specified with the -starter suffix — that is, you specify the Camel Hystrix component as camel-hystrix-starter, not as camel-hystrix. The Camel starter components are packaged in a way that is optimized for the Spring Boot environment.

The Spring Boot Maven plugin is provided by Spring Boot and it is a developer utility for building and running a Spring Boot project:

To incorporate the Spring Boot Maven plugin into your project POM file, add the plugin configuration to the project/build/plugins section of your pom.xml file, as shown in the following example:

<?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>7.1.0.fuse-710019-redhat-00002</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>