Set Java system properties with a configuration file

There is a way to set java.library.path programatically, see this.

The code is a hack to set the sys_path field on the ClassLoader,

System.setProperty( "java.library.path", "/path/to/libs" );

Field fieldSysPath = ClassLoader.class.getDeclaredField( "sys_paths" );
fieldSysPath.setAccessible( true );
fieldSysPath.set( null, null );

It would be pretty simple to do yourself:

public static void main(String[] args) {
    Properties p = new Properties();
    p.load(...); // Load the properties from a file in your jar
    for (String name : p.stringPropertyNames()) {
        String value = p.getProperty(name);
        System.setProperty(name, value);
    }
}

Use JAVA_TOOL_OPTIONS environment variable. _JAVA_OPTIONS may also work, but it's not documented at all. The JAVA_TOOL_OPTIONS is weakly documented, but here are some links:

• http://www.oracle.com/technetwork/java/javase/envvars-138887.html#gbmsy
• https://docs.oracle.com/javase/8/docs/technotes/guides/troubleshoot/envvars002.html
• https://bugs.openjdk.java.net/browse/JDK-4971166

An example of use:

set JAVA_TOOL_OPTIONS=-Dmy.property=sth

When launching JVM you should see a message:

Picked up JAVA_TOOL_OPTIONS: ...