7.2.3 System properties

System properties are a way of getting information into Java (they are the Java equivalent of environment variables). The following ones have special significance within TOPCAT:

java.io.tmpdir
The directory in which TOPCAT will write any temporary files it needs. This is usually only done if the -disk flag has been specified (see Section 7.1).
jdbc.drivers
Can be set to a (colon-separated) list of JDBC driver classes using which SQL databases can be accessed (see Section 7.3).
jel.classes
Can be set to a (colon-separated) list of classes containing static methods which define user-provided functions for synthetic columns or subsets. (see Section 6.8).
jel.classes.activation
Can be set to a (colon-separated) list of classes containing static methods which define user-provided functions for use in custom activation expressions. (see Section 6.8).
star.connectors
Can be set to a (colon-separated) list of classes which provide access to remote filespace implementations. Thus-named classes should implement the uk.ac.starlink.connect.Connector interface which specifies how you can log on to such a service and provides a hierarchical view of the filespace it contains.
startable.load.dialogs
Can be set to a (colon-separated) list of custom table load dialogue classes. Briefly, you can install your own table import dialogues at runtime by providing classes which implement the uk.ac.starlink.table.gui.TableLoadDialog interface and naming them in this property. See STIL documentation for more detail.
startable.readers
Can be set to a (colon-separated) list of custom table format input handler classes (see Section 3.3).
startable.storage
Can be set to determine the default storage policy. Setting it to "disk" has basically the same effect as supplying the "-disk" argument on the TOPCAT command line (see Section 7.1).
startable.writers
Can be set to a (colon-separated) list of custom table format output handler classes (see Section 3.3).
votable.strict
Set true for strict enforcement of the VOTable standard when parsing VOTables. This prevents the parser from working round certain common errors, such as missing arraysize attributes on FIELD/PARAM elements with datatype="char". False by default.
apple.laf.useScreenMenuBar
On the Apple Macintosh platform only, this property controls whether menus appear at the top of the screen as usual for Mac, or at the top of individual windows as usual for Java. By default it is set to true for TOPCAT, so menus mostly appear at the top of the screen (though it's not true to say that TOPCAT obeys the Mac look and feel completely); if you prefer the more Java-like look and feel, set it to false.

To define these properties on the command line you use the -D flag, which has the form 

    -D<property-name>=<value>
If you're using the TOPCAT startup script, you can write something like: 
    topcat -Djdbc.drivers=org.postgresql.Driver ...
or if you're using the java command directly: 
    java -Djdbc.drivers=org.postgresql.Driver ...

Alternatively you may find it more convenient to write these definitions in a file named .starjava.properties in your home directory; the above command-line flag would be equivalent to inserting the line: 

    jdbc.drivers=org.postgresql.Driver
in your .starjava.properties file.