CICS and Java

CICS® provides the tools and runtime environment to develop and run Java™ applications in a Java Virtual Machine (JVM) that is under the control of a CICS region.

CICS provides a JVM server runtime environment for Java application development. You can develop, build, and deploy applications using the IBM® CICS SDK for Java, Gradle modules, or Maven modules.

If you are a Java developer, check out Get started with Java in CICS.

IBM Semeru Runtime Certified Edition for z/OS Java 11Java 17

Java on z/OS® provides comprehensive support for running Java applications. CICS uses the IBM Semeru Runtime Certified Edition for z/OS Version 11.0.17.0 or Version 17.0.7.0 as the minimum release level.

Some Liberty features require specific Java versions, and these are called out in Liberty features. In addition, if any of your applications perform an RMI call, you must ensure you have the same Java level at client and run time.

The Certified Edition contains a Java Runtime Environment that supports the full set of Java APIs and a set of development tools. In Java 11 and Java 17, the base JRE is different from the Java 8 JRE. While your Java 8 bytecode might run in later Java versions, it is worth reviewing your applications.

To allow remote debug of a Java 11 or Java 17 runtime (JVM) there is a change to the syntax. The agentlib property now requires an explicit hostname:port. Specifying the port alone is no longer enough to successfully connect to and debug a Java 11 or Java 17 runtime.

You need to download the Java 11 or Java 17 version of the JZOS jar if your applications use it. To download the file, and for more information, see JZOS JAR for IBM Semeru Runtime Certified Edition for z/OS. To download and install the latest Explorer SDK, and for more information, see CICS Explorer product documentation.

IBM 64-bit SDK for z/OS, Java Technology Edition Java 8

Java on z/OS provides comprehensive support for running Java applications. CICS uses the IBM 64-bit SDK for z/OS, Java Technology Edition, Version 8. Some Liberty features require specific Java versions, and these are called out in Liberty features.

The SDK contains a Java Runtime Environment that supports the full set of Java APIs and a set of development tools. To help increase general purpose processor productivity and contribute to lowering the overall cost of computing for z/OS Java technology-based applications, special processors are available in certain z Systems® hardware. The IBM zEnterprise® Application Assist Processor (zAAP) can provide additional processor capacity to run eligible Java workloads, including Java workloads in CICS.

Find information about Java on the z/OS platform and download the 64-bit version of the SDK at Java Standard Edition Products on z/OS.

JVM server

The JVM server is the runtime environment for Java applications in CICS. A JVM server can handle many concurrent requests from different Java applications in a single JVM. Use of a JVM server reduces the number of JVMs that are required to run Java applications in a CICS region. To use a JVM server, Java applications must be threadsafe and must comply with the OSGi or Java EE specifications. JVM server provides the following benefits:
  • Eligible Java workloads can run on specialty engine processors, reducing the cost of transactions.
  • Different types of work such as threadsafe Java programs and web services, can run in a JVM server.
  • Application life cycle can be managed in the OSGi framework, without restarting the JVM server.
  • Java applications that are packaged using OSGi can be ported more easily between CICS and other platforms.
  • Java EE applications can be deployed into the Liberty JVM server.
    Note: OSGi applications in CICS can be installed in a Liberty JVM server but cannot use any of the Liberty services or features as they are not supported.

IBM CICS SDK for Java

CICS Explorer® is a freely available download for Eclipse-based Integrated Development Environments (IDEs). The IBM CICS SDK for Java that is included with CICS Explorer provides support for developing and deploying applications that comply with the OSGi Service Platform specification.

The OSGi Service Platform provides a mechanism for developing applications using a component model and deploying those applications into a framework as OSGi bundles. An OSGi bundle is the unit of deployment for an application component and contains version control information, dependencies, and application code. The main benefit of OSGi is that you can create applications from reusable components that are accessed only though well-defined interfaces called OSGi services. You can also manage the life cycle and dependencies of Java applications in a granular way.

The IBM CICS SDK for Java allows development of Java applications for any supported release of CICS. The SDK includes the Java CICS library (JCICS) to access CICS services along with examples to get started with developing applications for CICS. You can also use the tool to convert existing Java applications to OSGi.

The IBM CICS SDK for Enterprise Java (Liberty) is included as an option with CICS Explorer and supports packaging of Liberty applications into CICS bundles that can be deployed to CICS.

Gradle and Maven modules

As an alternative to the IBM CICS SDK for Java, you can define your projects as Maven or Gradle modules, express dependencies by referencing the Maven Central artifacts, and then package and deploy your application in a CICS bundle using the CICS-provided Gradle or Maven plug-in.

Why use Gradle or Maven for CICS development?
  • Simplified dependency management with Maven Central artifacts: Java developers can easily add dependencies on the Java CICS APIs and other CICS libraries with a few lines of configuration.
  • More flexibility with the development environment: Gradle and Maven support is available in most Java IDEs, such as Eclipse, IntelliJ IDEA, and Visual Studio Code. Java developers can write application code in a familiar IDE.
  • Bundle deployment with ease and confidence at development time with the Gradle and Maven plug-ins (Requires the CICS bundle deployment API):
    • Java developers can redeploy a bundle into a CICS region within seconds, without the need for a zFS connection or to disable, discard, and reinstall the bundle manually.
    • Java developers can integrate CICS bundle build and deployment into their toolchain, saving lots of manual work.
    • The API ensures controlled access both to the CICS system definition data set (CSD) for BUNDLE definition installation and to the bundle directory on zFS, so that system programmers can allow Java developers to deploy bundles without granting additional access.
What you can do with Gradle or Maven in CICS
  • Resolving compilation dependencies from Maven Central

    A list of CICS Java APIs and other libraries are provided on Maven Central under the com.ibm.cics group ID. Depending on your organization’s policy, you can either reference these artifacts directly from Maven Central, or have them mirrored to your enterprise repository by using repository managers such as Artifactory or Nexus.

  • Building and deploying CICS bundles using Gradle or Maven plug-ins

    The Gradle and Maven plug-ins are open source and provided on GitHub (cics-bundle-maven and cics-bundle-gradle). You can use them to build CICS bundles and, when the CICS bundle deployment API is configured, to deploy CICS bundles. A subset of CICS bundle parts, including WAR files (.war), EAR files (.ear), and OSGi bundles (.jar), is supported.

    For instructions on how to configure CICS for the CICS bundle deployment API, see Configuring the CMCI JVM server for the CICS bundle deployment API.