Grace Software

Runtime JavaLog

$Revision: 1.1 $
$Date: 1999/10/28 12:14:50 $




Introduction

JavaLog can be controlled at runtime using properties or in code. Using properties specified on the command line or in a file is the better than using code controls because it means the end user has the ultimate control over the logging.

Properties can be specified on the command line or in one or more files. Since the number of properties that one needs to specify at runtime to control JavaLog can be large, properties can be read from files in special locations in the user's environment. The rest of this document describes these two forms of specifying properties.

Loading Precedence

JavaLog loads properties first from the command line (system properties), then from files, and then from the command line again. The first load of the system properties is to allow the user to override the names of the files. The second load of the system properties is to make sure that the command line overrides the contents of any files. Here's a summary of the actions:
  1. Command line
  2. ${user.home}/.logrc
  3. .logrc (or name specified by property -Dlog.rc=filename)
  4. Command line (again)
So, the command line properties are highest priority, the local .logrc is next and the ${user.home}/.logrc is last.

Note: currently, all properties used by JavaLog are read into the System properties object. This means they may collide with similarly names properties in your software.

Command Line

The entry of properties on the command line is specified by the java runtime environment. The basic syntax is: 
    $ java -Dname-1=value-with-no-spaces ... -Dname-N="value with spaces" MyClass args...
There are a few things to notice in this syntax:
  1. names must be unique (must not be the same as other names)
  2. names must not contain white space (spaces, tabs, etc)
  3. values must be in quotes if they contain white space
  4. the command line arguments args... are not used by JavaLog

Files

Property files allow less typing on the command line and can be used to store preferences and customizations to JavaLog. As indicated above in the section on loading, after loading the system properties, JavaLog tries to load a file called .logrc in the user's home directory (notice the leading period, Windows users). It then tries to load the same named file in the current run directory. Then it loads the system properties again (see above). These files contain the exact same properties as can be specified on the command line (but without the -D).

Types

JavaLog recognizes a few different types of property values. More information is presented in further JavaLog documentation but these are the basics of the types recognized by JavaLog.