java.net.CookieManager provides a concrete implementation of a CookieHandler and for most users is sufficient for handling HTTP state management. CookieManager separates the storage of cookies from the policy surrounding, accepting, and rejecting them. A CookieManager is initialized with a java.net.CookieStore and a java.net.CookiePolicy. CookieStore manages the storage of the cookies. CookiePolicy makes policy decisions on cookie acceptance and rejection.

The following code shows how to create and set a system-wide CookieManager:

  java.net.CookieManager cm = new java.net.CookieManager();
  java.net.CookieHandler.setDefault(cm);

The first line calls the default CookieManager constructor to create the instance. The second line calls the static setDefault method of CookieHander to set the system-wide handler.

The default CookieManager constructor creates a new CookieManager instance with a default cookie store and accept policy. CookieStore is the place where any accepted HTTP cookie is stored. If not specified when created, a CookieManager instance will use an internal in-memory implementation. This implementation is not persistent and only lives for the lifetime of the Java Virtual Machine. Users requiring a persistent store must implement their own store.

The default cookie policy used by CookieManager is CookiePolicy.ACCEPT_ORIGINAL_SERVER, which only accepts cookies from the original server. So, the Set-Cookie response from the server must have a “domain” attribute set, and it must match the domain of the host in the URL. For more information, see java.net.HttpCookie.domainMatches. Users requiring a different policy must implement the CookiePolicy interface and pass it to the CookieManager constructor or set it to an already constructed CookieManager instance by using the setCookiePolicy(cookiePolicy) method.

When retrieving cookies from the cookie store, CookieManager also enforces the path-match rule from section 3.3.4 of RFC 2965. So, a cookie must also have its “path” attribute set so that the path-match rule can be applied before the cookie is retrieved from the cookie store.

In summary, CookieManager provides the framework for handling cookies and provides a good default implementation for CookieStore. CookieManager is highly customizable by enabling you to set your own CookieStore, CookiePolicy, or both.