OpenLiberty is a Java EE solution for running Microservices made by IBM. OpenLiberty was introduced as an evolution of the former WebSphere Liberty in 2017. As its name suggests, it is available under an open source license, without any warranties implied. IBM was quick to deliver basic support for crucial Java EE 8 parts, including Servlet 4.0, CDI 2.0, and JPA 2.2, even though the whole set of Java EE 8 specifications wasn't supported at the time. What really stands out is the support for the Eclipse MicroProfile specification in its latest version, 1.2, implying health checks, fail-safe mechanisms, circuit breakers, and configuration APIs are fully supported.

The following are key factors of OpenLiberty:

• Homepage: https://openliberty.io/
• Eclipse Public License 1.0
• MicroProfile 1.2 full support
• Java EE 7
• Partial support for Java EE 8

OpenLiberty is available in two flavors. First, it is available for download as a whole package, acting as an application server with all the dependencies in one place. Second, there is a plugin for both Maven and Gradle that downloads only the parts required by the actual application, producing a rightsized package.

One of the comparative advantages of OpenLiberty is fast redeployments. IBM designed OpenLiberty with fast redeployments in mind, resulting in almost instant code changes without the need to redeploy the application or even restart it.