Passing parameters to Java programs

There is a quote by Alexander Pope

A little learning is a dangerous thing.
Drink deep, or taste not the Pierian Spring;
There shallow draughts intoxicate the brain,
and drinking largely sobers us again.”

I was having problems passing parameters to Java. I had a little knowledge about Java web servers on z/OS, so I was confident I knew how to configure a web browser; unfortunately I did not have enough knowledge.

I was trying to get keyrings working with a web server on z/OS, but what I specified was not being picked up. In this post I’ll focus on keyrings, but it applies to other parameters are well.

Setting the default values

You can give Java a default keyring name

-Djavax.net.ssl.keyStore=safkeyring://START1/MQRING

Which says, if the user does not specify a keystore then use this value. If the user does not create a keystore, then a default keystore is created using these parameters.

Specify the value yourself

You can create your own keystore, passing keystore name and keystore type. You could use you own option, such as -DCOLINKEYRINGNAME=safkeyring://START1/MQRING and use that when configuring the keystore to Java. In this case the -Djavax.net.ssl.keyStore=safkeyring://START1/MQRING is not used. This is the same for other parameters.

Web server configuation

The Apache web server, and IBM Liberty web servers, are configured using server.xml files, and the web server creates the keystores etc using the information in the file.

For example a web server may have content like

<Connector port="${port.http}" protocol="${http.protocol}" 
     SSLEnabled="true" 
     maxThreads="550" scheme="https" secure="true" 
     clientAuth="false" sslProtocol="TLS" 
     keystoreFile="${keystoreFile}" 
     keystorePass="${keystorePass}" 
     keystoreType="${keystoreType}" 
     sslEnabledProtocols="${ssl.enabled.protocols}" /> 

where the ${…} is an environment variable. ${keystoreFile} would use the environment variable keystoreFile or option -DkeystoreFile=”safkeyring//START1/MYRING”

You can have multiple <Connector..> each with different parameters, so using -Djavax.net.ssl.keyStore etc would not work.

You need to know which options to use, because setting the Java defaults using -Djavax.net.ssl.keyStore… may be overridden.

You also need to know which server.xml file to use! I was getting frustrated when the changes I made to the server.xml was not the server.xml being used!