Spring Security（07）——缓存UserDetails

浏览数：21 / 时间：2015年06月08日

? ? ? ?Spring Security提供了一个实现了可以缓存UserDetails的UserDetailsService实现类，CachingUserDetailsService。该类的构造接收一个用于真正加载UserDetails的UserDetailsService实现类。当需要加载UserDetails时，其首先会从缓存中获取，如果缓存中没有对应的UserDetails存在，则使用持有的UserDetailsService实现类进行加载，然后将加载后的结果存放在缓存中。UserDetails与缓存的交互是通过UserCache接口来实现的。CachingUserDetailsService默认拥有UserCache的一个空实现引用，NullUserCache。以下是CachingUserDetailsService的类定义。

public?class CachingUserDetailsService implements UserDetailsService {

??? private UserCache userCache = new NullUserCache();

??? private?final UserDetailsService delegate;

??? CachingUserDetailsService(UserDetailsService delegate) {

??????? this.delegate = delegate;

??? }

??? public UserCache getUserCache() {

??????? return?userCache;

??? }

??? public?void setUserCache(UserCache userCache) {

??????? this.userCache = userCache;

??? }

??? public UserDetails loadUserByUsername(String username) {

??????? UserDetails user = userCache.getUserFromCache(username);

??????? if (user == null) {

??????????? user = delegate.loadUserByUsername(username);

??????? }

??????? Assert.notNull(user, "UserDetailsService " + delegate + " returned null for username " + username + ". " +

??????????????? "This is an interface contract violation");

??????? userCache.putUserInCache(user);

??????? return user;

??? }

}

?????? 我们可以看到当缓存中不存在对应的UserDetails时将使用引用的UserDetailsService类型的delegate进行加载。加载后再把它存放到Cache中并进行返回。除了NullUserCache之外，Spring Security还为我们提供了一个基于Ehcache的UserCache实现类，EhCacheBasedUserCache，其源码如下所示。

public?class EhCacheBasedUserCache implements UserCache, InitializingBean {

??? private?static?final Log logger = LogFactory.getLog(EhCacheBasedUserCache.class);

??? private Ehcache cache;

??? public?void afterPropertiesSet() throws Exception {

??????? Assert.notNull(cache, "cache mandatory");

??? }

??? public Ehcache getCache() {

??????? returncache;

??? }

??? public UserDetails getUserFromCache(String username) {

??????? Element element = cache.get(username);

??????? if (logger.isDebugEnabled()) {

??????????? logger.debug("Cache hit: " + (element != null) + "; username: " + username);

??????? }

??????? if (element == null) {

??????????? returnnull;

??????? } else {

??????????? return (UserDetails) element.getValue();

??????? }

??? }

??? public?void putUserInCache(UserDetails user) {

??????? Element element = new Element(user.getUsername(), user);

??????? if (logger.isDebugEnabled()) {

??????????? logger.debug("Cache put: " + element.getKey());

??????? }

??????? cache.put(element);

??? }

??? public?void removeUserFromCache(UserDetails user) {

??????? if (logger.isDebugEnabled()) {

??????????? logger.debug("Cache remove: " + user.getUsername());

??????? }

????? ??this.removeUserFromCache(user.getUsername());

??? }

??? public?void removeUserFromCache(String username) {

??????? cache.remove(username);

??? }

??? public?void setCache(Ehcache cache) {

??????? this.cache = cache;

??? }

}

?????? 从上述源码我们可以看到EhCacheBasedUserCache所引用的Ehcache是空的，所以，当我们需要对UserDetails进行缓存时，我们只需要定义一个Ehcache实例，然后把它注入给EhCacheBasedUserCache就可以了。接下来我们来看一下定义一个支持缓存UserDetails的CachingUserDetailsService的示例。

?? <security:authentication-manager alias="authenticationManager">

?????

????? <security:authentication-provider

???????? user-service-ref="cachingUserDetailsService" />

?? </security:authentication-manager>

??

?? <bean id="cachingUserDetailsService" class="org.springframework.security.config.authentication.CachingUserDetailsService">

?????

????? <constructor-arg ref="userDetailsService"/>

?????

????? <property name="userCache">

???????? <bean class="org.springframework.security.core.userdetails.cache.EhCacheBasedUserCache">

???????????

??????????? <property name="cache" ref="ehcache4UserDetails"/>

???????? </bean>

????? </property>

?? </bean>

??

?? <bean id="ehcache4UserDetails" class="org.springframework.cache.ehcache.EhCacheFactoryBean"/>

??

?? <bean id="userDetailsService"

????? class="org.springframework.security.core.userdetails.jdbc.JdbcDaoImpl">

????? <property name="dataSource" ref="dataSource" />

?? </bean>

?????? 在上面的配置中，我们通过EhcacheFactoryBean定义的Ehcache bean对象采用的是默认配置，其将使用默认的CacheManager，即直接通过CacheManager.getInstance()获取当前已经存在的CacheManager对象，如不存在则使用默认配置自动创建一个，当然这可以通过cacheManager属性指定我们需要使用的CacheManager，CacheManager可以通过EhCacheManagerFactoryBean进行定义。此外，如果没有指定对应缓存的名称，默认将使用beanName，在上述配置中即为ehcache4UserDetails，可以通过cacheName属性进行指定。此外，缓存的配置信息也都是使用的默认的。更多关于Spring使用Ehcache的信息可以参考我的另一篇文章《Spring使用Cache》。