Matcher policies can be used to find out if a parameter is included in a list, or which elements of a list correspond to a certain parameter), and influence the behavior of the proxy class based on the results. Matchers can be used for a wide range of tasks, for example, to determine if the particular IP address or URL that a client is trying to access is on a black or whitelist, or to verify that a particular e-mail address is valid.

MatcherPolicy instances are reusable matchers that contain configured instances of the matcher classes (e.g., DNSMatcher, RegexpMatcher). For examples, see the specific matcher classes.