Spring Boot

CloudCaptain supports Spring Boot 1.x and 2.x apps packaged as either a Spring Boot Executable Jar or a Spring Boot Executable War using OpenJDK 7, 8, 11 or 17.

Get Started

If you haven't already, start by following Spring Boot & CloudCaptain tutorial that will get you up and running in 5-10 minutes.

Also check out our blog post on how to create a Spring Boot application and deploy it on EC2 using CloudCaptain.

For databases, check out our blog post on how to build a Spring Boot microservice that uses a CloudCaptain-managed PostgreSQL database.

Additionally here are also a number of articles on how to use CloudCaptain with Spring Boot.

Java Runtime Environment

By default CloudCaptain uses the latest OpenJDK 17 version (headless JRE).

OpenJDK version

If you want to switch to OpenJDK 7.x or simply an older version, you can do so using the -components.openjdk configuration setting:

> boxfuse run my-app-1.0.jar -components.openjdk=7.80.32

To find out which OpenJDK versions are available from the CloudCaptain Inventory you can simply issue:

> boxfuse inventory openjdk

Custom JRE

If you prefer to use a different JRE, including the Oracle JRE, rather than the default OpenJDK one, you can do so by including the Linux x64 JRE distribution of your choice in a /jre folder inside the Spring Boot jar file.

If you use Maven or Gradle, this means the /jre folder should be put into the src/main/resources directory:


Tip for Git users

To avoid file corruption due to Git line-ending normalization, add the following line to .gitattributes

src/main/resources/jre/* binary


By default CloudCaptain looks for an application-boxfuse.properties file inside the Spring Boot jar file and runs your app with the Spring profile boxfuse activated by default.

If you use Maven or Gradle, this means the application-boxfuse.properties file should be put into the src/main/resources directory. When the Spring Boot Maven or Gradle plugin packages the executable jar, it will include it in the root of your class path, where CloudCaptain can see it.


CloudCaptain parses application-boxfuse.properties and automatically configures the ports and the healthcheck based on the information it contains.

If no application-boxfuse.properties is found in the jar file, CloudCaptain will automatically look for the following configuration files both at the root of the classpath and in the config package:

  • application-boxfuse.yml
  • application-default.properties
  • application-default.yml
  • application.properties
  • application.yml

The overriding order matches the default Spring Boot one.

Note: Other config files (including the ones for other specific Spring profiles) are not taken into account for auto-configuration and you will have to specify the appropriate port and healthcheck configuration settings yourself.


CloudCaptain will automatically configure your application ports to be either http or https based on the value of server.ssl.enabled. The actual port numbers are automatically configured according to the values of the server.port and management.port properties.


CloudCaptain will automatically configure the healthcheck port and path based on the discovered Spring Boot configuration. If your application also includes the Spring Boot Actuator, CloudCaptain will automatically configures its healthcheck to match the Spring Boot health endpoint.

Spring Profiles

By default CloudCaptain activates a Spring Profile called boxfuse. You can however easily specify a different profile by setting the SPRING_PROFILES_ACTIVE environment variable or the spring.profiles.active JVM system property to the value you need using the envvars and jvm.args arguments.

To use a different Spring Profile for each CloudCaptain environment, set the Spring Boot profile to the value of the BOXFUSE_ENV environment variable which contains the name of the current environment (dev, test, prod): -jvm.args=-Dspring.profiles.active=$BOXFUSE_ENV

Tip for Mac OSX and Linux users

The BOXFUSE_ENV environment variable is only available within the CloudCaptain instance, so you must prevent variable expansion by using single quotes: '-jvm.args=-Dspring.profiles.active=$BOXFUSE_ENV'

Note that selecting a Spring Profile via an environment variables or any other means does not affect how CloudCaptain configures ports and healthchecks. CloudCaptain will only read the files described in that section to extract that information, regardless of which Spring profile gets selected at runtime. You can override those auto-configured values by explicitly setting the port numbers and healthcheck paths using CloudCaptain parameters when fusing images or launching instances. At runtime those parameters will then override any other Spring Boot configuration.


Database auto-provisioning

If your app includes the PostgreSQL or MySQL JDBC driver, CloudCaptain will automatically provision the necessary PostgreSQL or MySQL database in each environment and auto-configure Spring Boot's DataSource.

CloudCaptain auto-configures Spring Boot's DataSource by setting the SPRING_DATASOURCE_URL, SPRING_DATASOURCE_USERNAME and SPRING_DATASOURCE_PASSWORD environment variables to the correct JDBC url, user and password for the current environment.


If your application experiences long periods of inactivity your database connections may time out and throw errors upon checkout.

Add the following configuration to your application.properties to fix this:

spring.datasource.validationQuery=SELECT 1

Using an existing database

To disable database auto-provisioning and use an existing database set db.type to none when creating your app.

TLS (SSL) Certificates / HTTPS

Automatic TLS (SSL) Certificate management

To expose your app via HTTPS make sure you have a custom domain configured for the environment where you want to run it. Also make sure that you have obtained a valid TLS (SSL) certificate and that your app has been created with app.type set to load-balanced and tls.type set to acm (AWS Certificate Manager).

With that in place your Spring Boot app will be automatically configured to run with HTTPS and a green lock will appear in the browser.

You can also manually force the correct configuration by adding these properties to your Spring Boot config file:


This will ensure that all network traffic between the ELB and your instances will be encrypted as well.

Manual TLS (SSL) Certificate management

To use HTTPS with your own certificate, you first have to obtain a valid certificate from a Certificate Authority and add a KeyStore containing your TLS (SSL) certificate to the root of the classpath to ensure it is packaged inside the Spring Boot jar file.

If you use Maven or Gradle, this means your .jks or .keystore KeyStore file should be put into the src/main/resources directory. When Maven or Gradle packages the jar, it will include it in the root of your Spring Boot jar file, where CloudCaptain can see it.


You can then configure the Spring Boot connector to use it. So if for example you have a KeyStore named example.jks inside your Spring Boot jar file, application-boxfuse.properties should look like this:


Root Certificates

By default, CloudCaptain uses the same root certificate bundle as the latest version of Firefox. Additionally CloudCaptain also includes the root certificates for Amazon RDS, so you can connect securely to RDS databases out of the box.

You can, however, ship your own set of root certificates, by placing them in a KeyStore inside the Jar file as /cacerts. If you use Maven or Gradle, this means your cacerts KeyStore file should be put into the src/main/resources directory. CloudCaptain will then automatically configure the JRE to use these instead.


If you choose to secure your cacerts TrustStore with a password different than the default changeit, you have to add the following to your Spring Boot configuration:


JCE unlimited strength cryptography

Using CloudCaptain's default JRE

This is already enabled by default (starting with OpenJDK 8.162.12) and no further action is required.

Using an older CloudCaptain JRE

To enable JCE unlimited cryptography (for AES-256, RSA-4096, ...), download the policy zip from the Oracle website for either Java 7 or Java 8.

Extract both local_policy.jar and US_export_policy.jar and place them at the root of your Jar file. If you use Maven or Gradle, this means both policy jar files should be put into the src/main/resources directory. CloudCaptain will then automatically configure the JRE to use these instead.


Using a custom JRE

If you use a custom JRE it is your responsibility to ensure it is configured for unlimited strength cryptography if you need it.

Java Agents

If you wish to launch the JRE with one or more Java Agents, simply place the Java Agent files inside the Jar file under /javaagents/. In a Maven or Gradle project this means you have to put your agent jar and whatever other files it requires under src/main/resources/javaagents:


CloudCaptain will then automatically configure the JRE to use these Java Agents

JVM Memory

By default CloudCaptain will dynamically configure your JVM heap to use 85% of the available memory in the instance. All other settings use the JVM defaults. You can override this by specifying the required JVM arguments like -Xmx via the jvm.args configuration setting.

Temporary Files

CloudCaptain configures the JVM to use /tmp as the directory to store temporary files and provisions 1 GB of space by default.

To increase this (up to a maximum of 16 TB), simply set the tmp configuration setting to the number of GB of temp space you need. To prevent CloudCaptain from provisioning any temp space set tmp to 0.

CloudCaptain also automatically configures the Spring Boot Actuator disk space health check to monitor /tmp. When you disable the temp space (by setting tmp to 0), CloudCaptain will also automatically disable the Actuator disk space health check.


Remote debugging (including hot-code replace) with your favorite IDE is fully supported. Details and setup instructions on our debugging page.


Profiling with tools like JVisualVM and Java Flight Recorder is fully supported. Details and setup instructions on our profiling page.

Live Reloading

CloudCaptain supports Live Reloading of exploded Spring Boot jar and war files. However in most cases you're probably better off using Spring Boot's own solution, the Spring Boot Dev Tools, as they work great on both VirtualBox and AWS.

Check out our blog post for details.

Spring Boot Dev Tools

CloudCaptain supports the Spring Boot Dev Tools, including running as a remote application both on VirtualBox and on AWS.

Simply include the spring-boot-devtools dependency either in your Maven pom.xml:


Or in your build.gradle:


And ensure the Spring Boot Dev Tools are enabled in the final jar by setting the excludeDevtools flag of the Spring Boot Maven plugin to false:


Or in your build.gradle:

bootRepackage {
    excludeDevtools = false

Then define an application secret in application.properties:


Now package, fuse and run your application:

> mvn package
> boxfuse run

Payload started in 00:07.682s ->

All that is left is to go to your IDE project for your app and run org.springframework.boot.devtools.RemoteSpringApplication with the same classpath as your project and one argument with the address where your app is running, for example

The RemoteSpringApplication now starts:

  .   ____          _                                              __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _          ___               _      \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` |        | _ \___ _ __  ___| |_ ___ \ \ \ \
 \\/  ___)| |_)| | | | | || (_| []::::::[]   / -_) '  \/ _ \  _/ -_) ) ) ) )
  '  |____| .__|_| |_|_| |_\__, |        |_|_\___|_|_|_\___/\__\___|/ / / /
 :: Spring Boot Remote ::  (v1.3.6.RELEASE)

2016-07-07 17:04:40.996  INFO 5280 --- [           main] o.s.b.devtools.RemoteSpringApplication   : Starting RemoteSpringApplication v1.3.6.RELEASE on axel-silencio with PID 5280 (C:\Users\myuser\.m2\repository\org\springframework\boot\spring-boot-devtools\1.3.6.RELEASE\spring-boot-devtools-1.3.6.RELEASE.jar started by myuser in C:\Workspaces\getstarted-springboot)
2016-07-07 17:04:40.998  INFO 5280 --- [           main] o.s.b.devtools.RemoteSpringApplication   : No active profile set, falling back to default profiles: default
2016-07-07 17:04:41.021  INFO 5280 --- [           main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@365c30cc: startup date [Thu Jul 07 17:04:41 CEST 2016]; root of context hierarchy
2016-07-07 17:04:41.378  WARN 5280 --- [           main] o.s.b.d.r.c.RemoteClientConfiguration    : The connection to https://localhost:8080 is insecure. You should use a URL starting with 'https://'.
2016-07-07 17:04:41.432  INFO 5280 --- [           main] o.s.b.d.a.OptionalLiveReloadServer       : LiveReload server is running on port 35729
2016-07-07 17:04:41.456  INFO 5280 --- [           main] o.s.b.devtools.RemoteSpringApplication   : Started RemoteSpringApplication in 0.684 seconds (JVM running for 0.981)

Any change you now make in your IDE (don't forget to save and build) will be reflected within your running CloudCaptain instance, regardless of whether it is on VirtualBox or AWS.

More details and info in our blog post.

Time Zone

By default all CloudCaptain instance use the UTC time zone.

We don't recommend changing this as this greatly simplifies time zone issues in machine to machine communication and cleanly relegates all time zones related aspects to a pure presentation layer concern.

If however you still do want to change this, you can override the default time zone of the instance using the TZ environment variable. For example to change the time zone of your instance to America/Los_Angeles you would do so like this:

> boxfuse fuse -envvars.TZ=America/Los_Angeles

Native binaries and libs

Some JVM applications also depend on native Linux x64 binaries and libs to do their work. CloudCaptain makes it easy to integrate them into your image.

Simply place your binaries under /native/bin on the classpath and CloudCaptain will automatically add them to the PATH at runtime in your instances.

If those binaries also depend on additional shared libraries beyond the C library, place the .so files of your libraries under /native/lib on the classpath and CloudCaptain will automatically add them to the LD_LIBRARY_PATH at runtime in your instances.


To list all the shared libraries your Linux x64 binary requires, you can use the following command on a Linux system:

$ ldd -v my-native-binary

If you use Maven or Gradle, the native directory should be put into the src/main/resources directory. CloudCaptain will then automatically configure the PATH and LD_LIBRARY_PATH to use it.


You can then simply invoke them in your code using

Runtime.getRuntime().exec("my-native-binary arg1 arg2 arg3");

New Relic support

To monitor your app using New Relic simply pass in your New Relic license key when fusing your image and CloudCaptain will automatically install and configure the New Relic Servers Linux x64 and New Relic Java agents for you.

> boxfuse fuse -newrelic.licensekey=0123456789abcdef0123456789abcdef01234567

Alternatively you can also supply a newrelic.yml configuration file for the Java agent and CloudCaptain will automatically use that instead. CloudCaptain will then install the agent for you, but won't override any application name you may have configured. If you haven't configured a New Relic license key as described above, CloudCaptain will use the license key contained in your newrelic.yml configuration file instead.

If you use Maven or Gradle, the newrelic.yml file should be put into the src/main/resources directory. CloudCaptain will then automatically configure the New Relic Java agent to use it.


Linux Kernel Tuning (experts only)

Kernel arguments

To tune the arguments passed Linux kernel from the bootloader, simply pass them using the -linux.args setting when fusing your image.


If you need to tune the Linux kernel running in your instance, simply place a sysctl.conf file at the root inside your jar file. In a Maven or Gradle project this means you have to put it under src/main/resources:


You can then for example tune the maximum number of file descriptors by simply including the following in sysctl.conf:

fs.file-max = 131072

CloudCaptain will then automatically configure the Linux kernel to use these settings.