Java Doc for SystemProperties.java in  » Science » Cougaar12_4 » org » cougaar » bootstrap » Java Source Code / Java DocumentationJava Source Code and Java Documentation

The purpose of the property expansion is to make Java properties clearer and easier to maintain.

This method return a Map of all properties that start with the specified prefix. Unlike the System.getProperties() method, this method does not require "write property" privileges.
Parameters:
  prefix - Used to return property names that start with this specified prefix.

This method allow us to:

1. Define properties in secure environments where System properties access is restricted, e.g.

The purpose of the property expansion is to make Java properties clearer and easier to maintain. Use the "${}" tag to introduce substitutable parameters, so they can be expanded to values indicated with tag names during property retrieval at runtime. Properties may be nested as shown in the example below:

 a       = "foo"
 a.subA  = "bob"
 c       = "subA"
 b = "${a} ${a.${c}}/smith"  => b = "foo bob/smith" after
 property expansion.
 

See Also:   SystemProperties.overrideProperties
See Also:    notes on why these methods should be used instead
See Also:   of "System.getProperty(..)" / "Boolean.getBoolean(..)" / etc.

This method retrieve system properties without requiring write access privileges (which could be a potential security vulnerability).

This method return a Map of all properties that start with the specified prefix. Unlike the System.getProperties() method, this method does not require "write property" privileges.
Parameters:
  prefix - Used to return property names that start with this specified prefix. A Map of system properties.

This is easy in JDK 1.5, but in JDK 1.4 we need this workaround.

This method allow us to:

1. Define properties in secure environments where System properties access is restricted, e.g. Applets.
2. Define properties when multiple Nodes will run in the same JVM. A possible solution in that environment is to use Classloader-scoped properties, as in

    org.apache.commons.discovery.tools.ManagedProperties
    

This is a decent approximation that handles the common cases, but it doesn't handle all the oddities..

For example, on Linux, this will resolve:
  a/$USER/b
to (say):
  a/root/b

Parameters:
  env_override - optional SystemProperties.getenv override map, which canbe null
Parameters:
  default_to_getenv - if a variable is not found in the "env_override"and this parameter is set to true, then look in SystemProperties.getenv