I have a small Spring boot based application that uses a Postgres database as a datastore. I wanted to document the steps involved in deploying this sample application to Cloud Foundry. 

Some of the steps are described in the Spring Boot reference guide, however the guides do not sufficiently explain how to integrate with the datastore provided in a cloud based environment. 

Spring-cloud provides the glue to connect Spring based applications deployed on a Cloud to discover and connect to bound services, so the first step is to pull in the Spring-cloud libraries into the project with the following pom entries:

<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-spring-service-connector</artifactId>
<version>1.0.0.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-cloudfoundry-connector</artifactId>
<version>1.0.0.RELEASE</version>
</dependency>

Once this dependency is pulled in, connecting to a bound service is easy, just define a configuration along these lines:

@Configuration
public class PostgresCloudConfig extends AbstractCloudConfig {

@Bean
public DataSource dataSource() {
  return connectionFactory().dataSource();
}

}

This application can now deploy cleanly to a Cloud Foundry based Cloud. The sample application can be tried out in a version of Cloud Foundry deployed with bosh-lite, these are how the steps in my machine looks like once Cloud Foundry is up and running with bosh-lite:

The following command creates a user provided service in Cloud Foundry:

cf create-user-provided-service psgservice -p '{"uri":"postgres://postgres:p0stgr3s@bkunjummen-mbp.local:5432/hotelsdb"}'

cf push spring-boot-mvc-test -p target/spring-boot-mvc-test-1.0.0-SNAPSHOT.war --no-start

Bind the service to the app and restart the app:

cf bind-service spring-boot-mvc-test psgservice
cf restart spring-boot-mvc-test

That is essentially it, Spring Cloud should ideally take over at the point and cleanly parse the credentials from the bound service which within Cloud Foundry translates to an environment variable called VCAP_SERVICES, and create the datasource from it.


There is however an issue with this approach - once the datasource bean is created using spring-cloud approach, it does not work in a local environment anymore. 

The potential fix for this is to use Spring profiles, assume that there is a different "cloud" Spring profile available in Cloud environment where the Spring-cloud based datasource gets returned:

@Profile("cloud")
@Configuration
public class PostgresCloudConfig extends AbstractCloudConfig {

@Bean
public DataSource dataSource() {
return connectionFactory().dataSource();
}
}

and let Spring-boot auto-configuration create a datasource in the default local environment, this way the configuration works both local as well as in Cloud. Where does this "cloud" profile come from, it can be created using a ApplicationContextInitializer, and looks this way:

public class SampleWebApplicationInitializer implementsApplicationContextInitializer<AnnotationConfigEmbeddedWebApplicationContext> {

private static final Log logger = LogFactory.getLog(SampleWebApplicationInitializer.class);

@Override
public void initialize(AnnotationConfigEmbeddedWebApplicationContext applicationContext) {
Cloud cloud = getCloud();
ConfigurableEnvironment appEnvironment = applicationContext.getEnvironment();
if (cloud!=null) {
appEnvironment.addActiveProfile("cloud");
}
logger.info("Cloud profile active");
}

private Cloud getCloud() {
try {
CloudFactory cloudFactory = new CloudFactory();
return cloudFactory.getCloud();
} catch (CloudException ce) {
return null;
}
}
}

This initializer makes use of the Spring-cloud's scanning capabilities to activate the "cloud" profile.


One last thing which I wanted to try was to make my local behave like Cloud atleast in the eyes of Spring-Cloud and this can be done by adding in some environment variables using which Spring-Cloud makes the determination of the type of cloud where the application is deployed, the following is my startup script in local for the app to pretend as if it is deployed in Cloud Foundry:

read -r -d '' VCAP_APPLICATION <<'ENDOFVAR'
{"application_version":"1","application_name":"spring-boot-mvc-test","application_uris":[""],"version":"1.0","name":"spring-boot-mvc-test","instance_id":"abcd","instance_index":0,"host":"0.0.0.0","port":61008}
ENDOFVAR

export VCAP_APPLICATION=$VCAP_APPLICATION

read -r -d '' VCAP_SERVICES <<'ENDOFVAR'
{"postgres":[{"name":"psgservice","label":"postgresql","tags":["postgresql"],"plan":"Standard","credentials":{"uri":"postgres://postgres:p0stgr3s@bkunjummen-mbp.local:5432/hotelsdb"}}]}
ENDOFVAR

export VCAP_SERVICES=$VCAP_SERVICES

mvn spring-boot:run

This entire sample is available at this github location:https://github.com/bijukunjummen/spring-boot-mvc-test

Conclusion

Spring Boot along with Spring-Cloud project now provide an excellent toolset to create Spring-powered cloud ready applications, and hopefully these notes are useful in integrating Spring Boot with Spring-Cloud and using these for seamless local and Cloud deployments.