Defining a client

A program or method that requests services from one or more methods in a class is called a client of that class.

About this task

In a COBOL or Java™ client, you can:

Create object instances of Java and COBOL classes.
Invoke instance methods on Java and COBOL objects.
Invoke COBOL factory methods and Java static methods.

In a COBOL client, you can also call services provided by the Java Native Interface (JNI).

A COBOL client program consists of the usual four divisions:

Table 1. **Structure of COBOL clients**
Division	Purpose	Syntax
`IDENTIFICATION` (required)	Name a client.	Code as usual, except that a client program must be: Recursive (declared `RECURSIVE` in the `PROGRAM-ID` paragraph) Thread-enabled (compiled with the `THREAD` option, and conforming to the coding guidelines for threaded applications)
`ENVIRONMENT` (required)	Describe the computing environment. Relate class-names used in the client to the corresponding external class-names known outside the compilation unit.	`CONFIGURATION SECTION` (required) REPOSITORY paragraph for defining a client (required)
`DATA` (optional)	Describe the data that the client needs.	DATA DIVISION for defining a client (optional)
`PROCEDURE` (optional)	Create instances of classes, manipulate object reference data items, and invoke methods.	Code using `INVOKE`, `IF`, and `SET` statements.

Because you must compile all COBOL programs that contain object-oriented syntax or that interoperate with Java with the THREAD compiler option, you cannot use the following language elements in a COBOL client:

SORT or MERGE statements
Nested programs

Any programs that you compile with the THREAD compiler option must be recursive. You must specify the RECURSIVE clause in the PROGRAM-ID paragraph of each OO COBOL client program.

Example: defining a client

Related references
THREAD