Networking Properties

There are a few standard system properties used to alter the mechanisms and behavior of the various classes of the package. Some are checked only once at startup of the VM, and therefore are best set using the -D option of the java command, while others have a more dynamic nature and can also be changed using the System.setProperty() API. The purpose of this document is to list and detail all of these properties.

If there is no special note, a property value is checked every time it is used.

IPv4 / IPv6

Both of these properties are checked only once, at startup.


A proxy server allows indirect connection to network services and is used mainly for security (to get through firewalls) and performance reasons (proxies often do provide caching mechanisms). The following properties allow for configuration of the various type of proxies.

Misc HTTP URL stream protocol handler properties

All these properties are checked only once at startup.

Address Cache

The package, when doing name resolution, uses an address cache for both security and performance reasons. Any address resolution attempt, be it forward (name to IP address) or reverse (IP address to name), will have its result cached, whether it was successful or not, so that subsequent identical requests will not have to access the naming service. These properties allow for some tuning on how the cache is operating.

Since these 2 properties are part of the security policy, they are not set by either the -D option or the System.setProperty() API, instead they are set as security properties.

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