Spring Security授权 AccessDecisionManager

在前面那篇博客有一段配置：

   <http auto-config="false" disable-url-rewriting="true" use-expressions="true" entry-point-ref="dtAuth"
        create-session="never">
        <!-- <session-management session-authentication-strategy-ref="dtsession"/> -->
        <intercept-url pattern="/unread/get" access="isAuthenticated()"/>
        <intercept-url pattern="/authtest.xhtm" access="hasRole('working')"/>
        <intercept-url pattern="/authtest1.xhtm" access="hasRole('trac')"/>
        <intercept-url pattern="/cmmt/uc" access="isAuthenticated()"/>
        <intercept-url pattern="/favicon.ico" access="denyAll"/>
        <intercept-url pattern="/**" access="permitAll"/>
        <custom-filter position="PRE_AUTH_FILTER" ref="dtSessionMgr"/>
    </http>

pattern表示url,access表示url的权限，但这个isAuthenticated()具体在哪里执行呢？原来Spring提供授权机制，由org.springframework.security.access.AccessDecisionManager这个接口来实现。

这个接口定义了这个方法：

    void decide(Authentication authentication, Object object, Collection<ConfigAttribute> configAttributes)
        throws AccessDeniedException, InsufficientAuthenticationException;

对应上面的配置：object就是url,configAttributes就是一个access。常用的实现类是AffirmativeBased