SEC-2114: Provide Spring Cache Abstraction based cache implementations

As of Spring 3.1 spring has its own cache abstraction. This commit adds cache
imlpementations based on that abstraction.

core/src/main/java/org/springframework/security/core/userdetails/cache/SpringCacheBasedUserCache.java

@@ -0,0 +1,74 @@
+package org.springframework.security.core.userdetails.cache;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.cache.Cache;
+import org.springframework.security.core.userdetails.UserCache;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.util.Assert;
+
+/**
+ * Caches {@link UserDetails} intances in a Spring defined {@link Cache}.
+ *
+ * @author Marten Deinum
+ * @since 3.2
+ */
+public class SpringCacheBasedUserCache implements UserCache, InitializingBean {
+
+
+    //~ Static fields/initializers =====================================================================================
+
+    private static final Log logger = LogFactory.getLog(SpringCacheBasedUserCache.class);
+
+    //~ Instance fields ================================================================================================
+
+    private Cache cache;
+
+    //~ Methods ========================================================================================================
+
+    public void afterPropertiesSet() throws Exception {
+        Assert.notNull(cache, "cache mandatory");
+    }
+
+    public Cache getCache() {
+        return cache;
+    }
+
+    public UserDetails getUserFromCache(String username) {
+        Cache.ValueWrapper element = username != null ? cache.get(username) : null;
+
+        if (logger.isDebugEnabled()) {
+            logger.debug("Cache hit: " + (element != null) + "; username: " + username);
+        }
+
+        if (element == null) {
+            return null;
+        } else {
+            return (UserDetails) element.get();
+        }
+    }
+
+    public void putUserInCache(UserDetails user) {
+        if (logger.isDebugEnabled()) {
+            logger.debug("Cache put: " + user.getUsername());
+        }
+        cache.put(user.getUsername(), user);
+    }
+
+    public void removeUserFromCache(UserDetails user) {
+        if (logger.isDebugEnabled()) {
+            logger.debug("Cache remove: " + user.getUsername());
+        }
+
+        this.removeUserFromCache(user.getUsername());
+    }
+
+    public void removeUserFromCache(String username) {
+        cache.evict(username);
+    }
+
+    public void setCache(Cache cache) {
+        this.cache = cache;
+    }
+}