Calling a COBOL method from a Java application under IMS

You can use the object-oriented language support in Enterprise COBOL to write COBOL methods that a Java™ program can call under IMS.

About this task

When you define a COBOL class and compile it using Enterprise COBOL, the compiler generates a Java class definition with native methods and the object code that implements those native methods. You can then create an instance and invoke the methods of this class from a Java program that runs in a Java dependent region, just as you would use any other class.

For example, you can define a COBOL class that uses the appropriate DL/I calls to access an IMS database. To make the implementation of this class available to a Java program, do the following steps:

Procedure

  1. Compile the COBOL class using Enterprise COBOL.
    The compiler generates a Java source file (.java) that contains the class definition, and an object module (.o) that contains the implementation of the native methods.
  2. Compile the generated Java source file using the Java compiler.
    The Java compiler creates a class file (.class).
  3. Link the object code into a dynamic link library (DLL) in the z/OS® UNIX file system (.so). The directory that contains the COBOL DLLs must be listed in the LIBPATH, as specified in the IMS.PROCLIB member that is indicated by the ENVIRON= parameter of the IMS region procedure.
  4. Update the sharable application class path in the main JVM options member (ibm.jvm.sharable.application.class.path in the IMS.PROCLIB member that is specified by the JVMOPMAS= parameter of the IMS region procedure) to enable the JVM to access the Java class file.

Results

A Java program cannot call procedural COBOL programs directly. To reuse existing COBOL IMS code, use one of the following techniques:

  • Restructure the COBOL code as a method in a COBOL class.
  • Write a COBOL class definition and method that serves as a wrapper for the existing procedural code. The wrapper code can use COBOL CALL statements to access procedural COBOL programs.

Related tasks  
Compiling, linking, and running OO applications  
Structuring OO applications  
Wrapping procedure-oriented COBOL programs  
IMS Application Programming Guide