Spring-Security (学习记录六)--采用ehcache缓存UserDetails

[Toc]

1. spring-security提供了缓存UserDetails的UserDetailsService实现类。

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;

}

}

2. 通过配置来完成缓存 UserDetails （使用ehcache）

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。

<!-- 认证管理器,配置了管理员与角色的关系  -->
<security:authentication-manager alias="authenticationManager">
<!-- 配置账号密码所属的角色  角色以 ROLE_开头，为spring获取名称的标识 (xml方式的才需要)
user-service-ref="accountService" : 配置启动数据库方式获取用户和角色，xml失效
-->
<security:authentication-provider user-service-ref="cachingUserDetailsService">
<!-- 密码采用md5加密  -->
<security:password-encoder hash="md5" />
</security:authentication-provider>
</security:authentication-manager>

<bean id="cachingUserDetailsService" class="org.springframework.security.config.authentication.CachingUserDetailsService">
<!-- 真正加载UserDetails的UserDetailsService -->
<constructor-arg ref="accountService"/>
<!-- 缓存UserDetails的UserCache -->
<property name="userCache">
<bean class="org.springframework.security.core.userdetails.cache.EhCacheBasedUserCache">
<!-- 用于真正缓存的Ehcache对象 -->
<property name="cache" ref="ehcache4UserDetails"/>
</bean>
</property>
</bean>

<!-- 将使用默认的CacheManager创建一个名为ehcache4UserDetails的Ehcache对象 -->
<bean id="ehcache4UserDetails" class="org.springframework.cache.ehcache.EhCacheFactoryBean"/>

3. 引入ehcache

pom.xml中引入

<!-- ehcache需要的依赖 -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>3.2.5.RELEASE</version>
</dependency>
<!-- 加入ehcache -->
<dependency>
<groupId>net.sf.ehcache</groupId>
<artifactId>ehcache</artifactId>
<version>2.7.4</version>
</dependency>

添加ehcache.xml配置文件（详见附件）

项目中添加spring-ehcache.xml (详见附件)

<!-- 开启spring缓存 -->
<cache:annotation-driven cache-manager="cacheManager" />
<bean id="cacheManagerFactory" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean" p:configLocation="classpath:ehcache.xml" p:shared="false" />
<bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheCacheManager" p:cacheManager-ref="cacheManagerFactory" />
</beans>

这样。缓存UserDetails就成功了。

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