Java Stand-alone Applications on z/OS, Volume I

18 Java Stand-alone Applications on z/OS Volume 1

2.2.2 Writing JCL for a Java batch job

Just like any other program written for the mainframe operating environments,

Java batch jobs must be submitted and controlled using JCL scripts. IBM

provides a utility program called BPXBATCH

to run shell scripts and executable

files that reside in the HFS from JCL scripts. Sample JCL to invoke the simple

Java program we discussed in the previous section is in Example 2-3.

Example 2-3 Sample JCL to invoke a Java program

//JAVAP JOB (ITSO),'USER1',REGION=30M,

// CLASS=A,MSGCLASS=X,NOTIFY=&SYSUID

//* ----------------------------------------------------

//* Run Java program

//* ----------------------------------------------------

//RUN EXEC PGM=BPXBATCH,

// PARM='SH java -cp /u/user1/examples Example'

//SYSPRINT DD SYSOUT=*

//SYSOUT DD SYSOUT=*

//STDOUT DD PATH='/u/user1/java.stdout',

// PATHOPTS=(OWRONLY,OCREAT,OTRUNC),

// PATHMODE=SIRWXU

//STDERR DD PATH='/u/user1/java.stderr',

// PATHOPTS=(OWRONLY,OCREAT,OTRUNC),

// PATHMODE=SIRWXU

//STDENV DD DUMMY

//* ----------------------------------------------------

//* Copy the output of Java program

//* ----------------------------------------------------

//COPYOUT EXEC PGM=IKJEFT01,DYNAMNBR=300,COND=EVEN

//SYSTSPRT DD SYSOUT=*

//HFSOUT DD PATH='/u/user1/java.stdout'

//HFSERR DD PATH='/u/user1/java.stderr'

//STDOUTL DD SYSOUT=*,DCB=(RECFM=VB,LRECL=133,BLKSIZE=137)

//STDERRL DD SYSOUT=*,DCB=(RECFM=VB,LRECL=133,BLKSIZE=137)

//SYSPRINT DD SYSOUT=*

//SYSTSIN DD DATA,DLM='/>'

ocopy indd(HFSOUT) outdd(STDOUTL)

ocopy indd(HFSERR) outdd(STDERRL)

/>

BPXBATCH takes either SH or PGM as a first parameter. When SH is specified,

it expects the name of a shell script to run. When PGM is specified, it expects the

name of an executable file in the HFS. The SH option is the default.

BPXBATCH uses four DD cards: STDOUT, STDIN, STDERR and STDENV.

BPXBATCH directs the standard output of the step to STDOUT, the standard

error to STDERR, the standard input from STDIN, and sets the USS

Chapter 2. Job management 19

environmental variables of the step from STDENV. All of the DD cards are

optional and have the default value of /dev/null. So, if any of the DD cards is not

specified, it is simply ignored by the job.

When STDENV does not set the HOME and LOGNAME variables, they are set

using the logon RACF® profile. When the SH option is used, variables set by

STDENV are overridden by the values specified in /etc/profile, which are

overridden again by the setting in the .profile file in the user’s home directory.

The output of the standard output and error cannot be directly directed to the

SYSPRINT output stream of JCL. Alternatively, in the JCL script, these output

streams should be directed to temporary files (/u/user1/java.stdout and

/u/user1/java.stderr, respectively). Then, the contents of these temporary files

are copied back to the SYSPRINT output stream in the following job step (called

COPYOUT). Consequently, the output of the Java program cannot be examined

until the entire job step is completed. This is a known limitation of the

BPXBATCH utility program.

In the previous example, the environment variables are set using the profile file

of the user who submitted the job before running the specified Java program. If

different settings are required for a job, it is possible to set up the variables in one

of the following three ways:

򐂰 Set the variables in JCL.

//STDENV DD *

PATH=/bin

JAVA_HOME=/usr/lpp/java/J1.4

/*

򐂰 Set the variables in a file in HFS. It must be a text file with read-only access.

The variables should be set as variable=value pairs in the file.

//STDENV DD PATH=’/u/user1/env.profile’,PATHOPTS=ORDONLY

򐂰 Set the variables in a data set. It can be a sequential, PDS, or SYSIN data

set. The variables should be set as variable=value pairs in the data set.

//STDENV DD DSN=USER1.ENV.PROFILE’,DISP=SHR

BPXBATCH is not limited to running batch Java programs; it is able to run any

shell scripts or executable files residing in HFS.

Tip: The contents of temporary files used to store the standard output and

error of Java program in HFS can be examined under USS using tools like

cat, head, and tail while the batch Java program is running (tail -f displays

the last several lines of the file and updates as more lines become available).