ankushs92 · February 9, 2016 17:27 · Feb 9, 2016
diff --git a/SomeClass.java b/SomeClass.java
@@ -0,0 +1,33 @@
+// Jwt requires an authentication on every request.Assuming that you are storing your User objects in a relational database like MySQL,
+// and that your API gets moderate traffic,it is not a good idea to fetch the User object directly from the database every time.
+//Instead,once it is retreived ,we cache it locally using Spring Caching abstraction.The cache backend is Google guava.
+
+public class UserServiceImpl implements UserService { //Which further extends UserDetailsService .
+
+  @Override
+	@Cacheable(cacheNames=CacheConstants.USER_CACHE,key="#username") // We cache this  guy by its username.
+	public UserDetails loadUserByUsername(final String username) throws UsernameNotFoundException {
+  		final User user = userRepository.findOneByEmail(username);
+  		if(user==null){
+  			throw new UsernameNotFoundException("User with username " + username + " not found");
+  		}
+  		return user;
+	}
+}
+//This is the cache used.
+public class CacheConfig{
+    @Bean(name="localGauvaCaches")
+  	public SimpleCacheManager localGuavaCaches(){
+  		final SimpleCacheManager simpleCacheManager = new SimpleCacheManager();
+  		final GuavaCache userCache = new GuavaCache(CacheConstants.USER_CACHE,CacheBuilder.newBuilder()
+  												  .concurrencyLevel(3) //Choose per your own will.
+  												  .expireAfterAccess(2, TimeUnit.MINUTES) //Expire if not accessed within 2 minutes.
+  									 			  .maximumSize(1000).build()); //For a maximum of 1000 User Objects.
+
+  		simpleCacheManager.setCaches(Arrays.asList(userCache));
+
+  		return simpleCacheManager;
+  	}
+
+
+}