ProxySelector class in Java

java.net.ProxySelector

Selects the proxy server to use, if any, when connecting to the network resource referenced by a URL. A proxy selector is a concrete sub-class of this class and is registered by invoking the setDefault method. The currently registered proxy selector can be retrieved by calling the getDefault method.

When a proxy selector is registered, for instance, a subclass of URLConnection class should call the select method for each URL request so that the proxy selector can decide if a direct, or proxied connection should be used. The select method returns an iterator over a collection with the preferred connection approach.

If a connection cannot be established to a proxy (PROXY orSOCKS) server then the caller should call the proxy selector's connectFailed method to notify the proxy selector that the proxy server is unavailable.

The default proxy selector does enforce a set of System Properties related to proxy settings.

Some methods of ProxySelector class

connectFailed(URI, SocketAddress, IOException): This method is called to indicate that a connection could not be established to a proxy/socks server.

getDefault(): This method gets the system-wide proxy selector.

ProxySelector.of(InetSocketAddress):  This method returns a ProxySelector which uses the given proxy address for all HTTP and HTTPS requests. If the proxy is null then proxying is disabled.

select(URI): This method selects all the applicable proxies based on the protocol to access the resource with and a destination address to access the resource at.

ProxySelector.setDefault(ProxySelector): This method sets (or unsets) the system-wide proxy selector.