Java 9 greatly supports the cloud-based distributed application development with its latest features, including Modular Java Application Packaging or Self-Contained Application Packaging.

Java packaging tools now provide built-in support for multiple formats of self-contained application package development. The basic package contains only one folder on the hard drive that comprises all the required application resources along with the JRE. This package is readily redistributable as is, or we can also build an installable package, such as exe or dmg.

Self-contained application packages have the following advantages:

• Operations can directly install the applications with the installer that is known to them and launch the application
• We can control the JRE version to be used by the application as it is packaged
• Applications are ready to be deployed on a new system without having to install the JRE separately
• No explicit system admin rights are required to perform the deployment with ZIP or other installer types
• Applications can have file associations
• Applications are deployed as a single self-contained package with support for secondary launchers

However, there are a small set of uncomfortable facts regarding self-contained application packages, including:

• It requires additional steps for deploying applications, for example, applications that allow system security
• With the inclusion of the JRE, the application package size gets larger
• The application needs to be separately packaged, based on the variety of operating systems you may want to deploy
• JRE needs to be explicitly managed and updated with a project package instead of direct system installation

Spring framework observed this move toward the cloud and came up with modules that support the building of distributed applications that were cloud-ready in Java a little earlier. Let's quickly discuss some of the important features these Spring modules (Boot, Cloud, and Cloud Data Flow) offer to build production-ready self-contained cloud applications/microservices.