关于Shiro的认证策略

 在ModularRealmAuthenticator认证器中，Shiro在认证过程中会调用认证策略，在认证器的是有策略成员变量的，

所以我们可以自定的设置策略方式即可以在applicationContext.xml中在配置securityManager时引用认证器时，

在认证器中配置认证策略：

/**
     * Allows overriding the default {@code AuthenticationStrategy} utilized during multi-realm log-in attempts.
     * This object is only used when two or more Realms are configured.
     *
     * @param authenticationStrategy the strategy implementation to use during log-in attempts.
     * @since 0.2
     */
    public void setAuthenticationStrategy(AuthenticationStrategy authenticationStrategy) {
        this.authenticationStrategy = authenticationStrategy;
    }

 /**
     * Performs the multi-realm authentication attempt by calling back to a {@link AuthenticationStrategy} object
     * as each realm is consulted for {@code AuthenticationInfo} for the specified {@code token}.
     *
     * @param realms the multiple realms configured on this Authenticator instance.
     * @param token  the submitted AuthenticationToken representing the subject's (user's) log-in principals and credentials.
     * @return an aggregated AuthenticationInfo instance representing account data across all the successfully
     *         consulted realms.
     */
    protected AuthenticationInfo doMultiRealmAuthentication(Collection<Realm> realms, AuthenticationToken token) {

        AuthenticationStrategy strategy = getAuthenticationStrategy();

        AuthenticationInfo aggregate = strategy.beforeAllAttempts(realms, token);

        if (log.isTraceEnabled()) {
            log.trace("Iterating through {} realms for PAM authentication", realms.size());
        }

        for (Realm realm : realms) {

            aggregate = strategy.beforeAttempt(realm, token, aggregate);

            if (realm.supports(token)) {

                log.trace("Attempting to authenticate token [{}] using realm [{}]", token, realm);

                AuthenticationInfo info = null;
                Throwable t = null;
                try {
                    info = realm.getAuthenticationInfo(token);
                } catch (Throwable throwable) {
                    t = throwable;
                    if (log.isWarnEnabled()) {
                        String msg = "Realm [" + realm + "] threw an exception during a multi-realm authentication attempt:";
                        log.warn(msg, t);
                    }
                }

                aggregate = strategy.afterAttempt(realm, token, info, aggregate, t);

            } else {
                log.debug("Realm [{}] does not support token {}.  Skipping realm.", realm, token);
            }
        }

        aggregate = strategy.afterAllAttempts(token, aggregate);

        return aggregate;
    }

     <bean id="securityManager" class="org.apache.shiro.web.mgt.DefaultWebSecurityManager">
        <property name="cacheManager" ref="cacheManager"/>
        <property name="auticationtor" ref="auticationtor"></property>
     </bean>
     <bean name="auticationtor" class="org.apache.shiro.authc.pam.ModularRealmAuthenticator">
        <property name="realms">
           <list>
                <ref bean=""/>
                <ref bean=""/>
           </list>
        </property>
        <property name="authenticationStrategy" ref="allSuccessfulStrategy"/>
     </bean>
     <bean id="allSuccessfulStrategy" class="org.apache.shiro.authc.pam.AllSuccessfulStrategy"></bean>