apache-shiro杂记(二) 关于多realm认证的策略
一直以为给定的下面配置是短路方式的，即defaultJdbcRealm可以成功认证，backDoorJdbcRealm就不会被调用。
其实不然，org.apache.shiro.authc.pam.FirstSuccessfulStrategy并不是这个意思，所有的realm依然都会被调用。
只不过是第一个认证成功的AuthenticationInfo作为最后的结果返回。

<bean id="authenticator" class="org.apache.shiro.authc.pam.ModularRealmAuthenticator">
	<property name="realms">
		<list>
			<ref bean="defaultJdbcRealm" />
			<ref bean="backDoorJdbcRealm" />
		</list>
	</property>
	<property name="authenticationStrategy">
		<bean class="org.apache.shiro.authc.pam.FirstSuccessfulStrategy" />
	</property>
</bean>

为了实现目的，必须对org.apache.shiro.authc.pam.ModularRealmAuthenticator改造。

package xxx.yyy.security;

import java.util.Collection;
import org.apache.shiro.authc.AuthenticationInfo;
import org.apache.shiro.authc.AuthenticationToken;
import org.apache.shiro.authc.pam.AuthenticationStrategy;
import org.apache.shiro.realm.Realm;
import org.apache.shiro.util.CollectionUtils;

public class ModularRealmAuthenticator extends org.apache.shiro.authc.pam.ModularRealmAuthenticator {

	@Override
	protected AuthenticationInfo doMultiRealmAuthentication(Collection<Realm> realms, AuthenticationToken token) {
		
		AuthenticationStrategy strategy = getAuthenticationStrategy();
		AuthenticationInfo aggregate = strategy.beforeAllAttempts(realms, token);
		
		for (Realm realm : realms) {
			aggregate = strategy.beforeAttempt(realm, token, aggregate);
			if (realm.supports(token)) {
				AuthenticationInfo info = null;
				Throwable t = null;
				try {
					info = realm.getAuthenticationInfo(token);
				} catch (Throwable throwable) {
					t = throwable;
				}
				aggregate = strategy.afterAttempt(realm, token, info, aggregate, t);
				// dirty dirty hack
				if (aggregate != null && !CollectionUtils.isEmpty(aggregate.getPrincipals())) {
					return aggregate;
				}
				// end dirty dirty hack
			} else {

			}
		}
		aggregate = strategy.afterAllAttempts(token, aggregate);
		return aggregate;
	}
}

<!-- 认证管理器 -->
<bean id="authenticator" class="xxx.yyy.security.ModularRealmAuthenticator">
	<property name="realms">
		<list>
			<ref bean="defaultJdbcRealm" />
			<ref bean="backDoorJdbcRealm" />
		</list>
	</property>
	<property name="authenticationStrategy">
		<bean class="org.apache.shiro.authc.pam.FirstSuccessfulStrategy" />
	</property>
</bean>