讲解完http标签的解析过程，authentication-manager标签解析部分就很容易理解了
authentication-manager标签在spring的配置文件中的定义一般如下
<authentication-manager alias="authenticationManager">
<authentication-provider user-service-ref="userDetailsManager"/>
</authentication-manager>
authentication-manager标签的解析类是：
org.springframework.security.config.authentication.AuthenticationManagerBeanDefinitionParser
具体解析方法parse的代码为
public BeanDefinition parse(Element element, ParserContext pc) {
Assert.state(!pc.getRegistry().containsBeanDefinition(BeanIds.AUTHENTICATION_MANAGER),
"AuthenticationManager has already been registered!");
pc.pushContainingComponent(new CompositeComponentDefinition(element.getTagName(), pc.extractSource(element)));
//构造ProviderManager的BeanDefinition
BeanDefinitionBuilder providerManagerBldr = BeanDefinitionBuilder.rootBeanDefinition(ProviderManager.class);
//获取alias属性
String alias = element.getAttribute(ATT_ALIAS);
//检查session-controller-ref属性，提示通过标签<concurrent-session-control>取代
checkForDeprecatedSessionControllerRef(element, pc);
List<BeanMetadataElement> providers = new ManagedList<BeanMetadataElement>();
NamespaceHandlerResolver resolver = pc.getReaderContext().getNamespaceHandlerResolver();
//获取authentication-manager的子节点
NodeList children = element.getChildNodes();
//循环节点，一般子节点主要是authentication-provider或者
//ldap-authentication-provider
for (int i = 0; i < children.getLength(); i++) {
Node node = children.item(i);
if (node instanceof Element) {
Element providerElt = (Element)node;
//判断子标签是否有ref属性，如果有，则直接将ref属性
//引用的bean id添加到providers集合中
if (StringUtils.hasText(providerElt.getAttribute(ATT_REF))) {
providers.add(new RuntimeBeanReference(providerElt.getAttribute(ATT_REF)));
} else {
//如果没有ref属性，则通过子标签的解析类完成标签解析
//如子标签：authentication-provider,解析过程在后面
BeanDefinition provider = resolver.resolve(providerElt.getNamespaceURI()).parse(providerElt, pc);
Assert.notNull(provider, "Parser for " + providerElt.getNodeName() + " returned a null bean definition");
String id = pc.getReaderContext().generateBeanName(provider);
//注册provider的BeanDefinition
pc.registerBeanComponent(new BeanComponentDefinition(provider, id));
//添加注册过的bean到provider集合中
providers.add(new RuntimeBeanReference(id));
}
}
}
if (providers.isEmpty()) {
providers.add(new RootBeanDefinition(NullAuthenticationProvider.class));
}
providerManagerBldr.addPropertyValue("providers", providers);
//添加默认的事件发布类
BeanDefinition publisher = new RootBeanDefinition(DefaultAuthenticationEventPublisher.class);
String id = pc.getReaderContext().generateBeanName(publisher);
pc.registerBeanComponent(new BeanComponentDefinition(publisher, id));
//将事件发布类的bean注入到ProviderManager的
//authenticationEventPublisher属性中
providerManagerBldr.addPropertyReference("authenticationEventPublisher", id);
//注册ProviderManager的bean
pc.registerBeanComponent(
new BeanComponentDefinition(providerManagerBldr.getBeanDefinition(), BeanIds.AUTHENTICATION_MANAGER));
if (StringUtils.hasText(alias)) {
pc.getRegistry().registerAlias(BeanIds.AUTHENTICATION_MANAGER, alias);
pc.getReaderContext().fireAliasRegistered(BeanIds.AUTHENTICATION_MANAGER, alias, pc.extractSource(element));
}
pc.popAndRegisterContainingComponent();
return null;
}
通过上面的代码片段，能够知道authentication-manager标签解析的步骤是
1.构造ProviderManager的BeanDefinition
2.循环authentication-manager的子标签，构造provider的BeanDefinition，并添加到providers集合中
3.将第2步的providers设置为ProviderManager的providers属性
4.构造异常事件发布类DefaultAuthenticationEventPublisher的BeanDefinition，并设置为ProviderManager的属性authenticationEventPublisher
5.通过registerBeanComponent方法完成bean的注册任务
authentication-provider标签的解析类为
org.springframework.security.config.authentication.AuthenticationProviderBeanDefinitionParser
public BeanDefinition parse(Element element, ParserContext parserContext) {
//首先构造DaoAuthenticationProvider的BeanDefinition
RootBeanDefinition authProvider = new RootBeanDefinition(DaoAuthenticationProvider.class);
authProvider.setSource(parserContext.extractSource(element));
//获取password-encoder子标签
Element passwordEncoderElt = DomUtils.getChildElementByTagName(element, Elements.PASSWORD_ENCODER);
if (passwordEncoderElt != null) {
//如果有password-encoder子标签，把解析任务交给
//PasswordEncoderParser完成
PasswordEncoderParser pep = new PasswordEncoderParser(passwordEncoderElt, parserContext);
authProvider.getPropertyValues().addPropertyValue("passwordEncoder", pep.getPasswordEncoder());
//如果有salt-source标签，将值注入到saltSource属性中
if (pep.getSaltSource() != null) {
authProvider.getPropertyValues().addPropertyValue("saltSource", pep.getSaltSource());
}
}
//下面获取子标签user-service、jdbc-user-service、ldap-user-service
Element userServiceElt = DomUtils.getChildElementByTagName(element, Elements.USER_SERVICE);
Element jdbcUserServiceElt = DomUtils.getChildElementByTagName(element, Elements.JDBC_USER_SERVICE);
Element ldapUserServiceElt = DomUtils.getChildElementByTagName(element, Elements.LDAP_USER_SERVICE);
String ref = element.getAttribute(ATT_USER_DETAILS_REF);
if (StringUtils.hasText(ref)) {
if (userServiceElt != null || jdbcUserServiceElt != null || ldapUserServiceElt != null) {
parserContext.getReaderContext().error("The " + ATT_USER_DETAILS_REF + " attribute cannot be used in combination with child" +
"elements '" + Elements.USER_SERVICE + "', '" + Elements.JDBC_USER_SERVICE + "' or '" +
Elements.LDAP_USER_SERVICE + "'", element);
}
} else {
// Use the child elements to create the UserDetailsService
AbstractUserDetailsServiceBeanDefinitionParser parser = null;
Element elt = null;
//下面的if语句，主要是根据子标签的不同，选择子标签对应的解析器处理
if (userServiceElt != null) {
elt = userServiceElt;
parser = new UserServiceBeanDefinitionParser();
} else if (jdbcUserServiceElt != null) {
elt = jdbcUserServiceElt;
parser = new JdbcUserServiceBeanDefinitionParser();
} else if (ldapUserServiceElt != null) {
elt = ldapUserServiceElt;
parser = new LdapUserServiceBeanDefinitionParser();
} else {
parserContext.getReaderContext().error("A user-service is required", element);
}
parser.parse(elt, parserContext);
ref = parser.getId();
String cacheRef = elt.getAttribute(AbstractUserDetailsServiceBeanDefinitionParser.CACHE_REF);
if (StringUtils.hasText(cacheRef)) {
authProvider.getPropertyValues().addPropertyValue("userCache", new RuntimeBeanReference(cacheRef));
}
}
//将解析后的bean id注入到userDetailsService属性中
authProvider.getPropertyValues().addPropertyValue("userDetailsService", new RuntimeBeanReference(ref));
return authProvider;
}
如果学习过acegi的配置，应该知道，acegi有这么一段配置
<bean id="authenticationManager" class="org.acegisecurity.providers.ProviderManager">
<property name="providers">
<list>
<ref local="daoAuthenticationProvider"/>
<ref local="anonymousAuthenticationProvider"/>
</list>
</property>
</bean>
实际上authentication-manager标签所要达到的目标就是构造上面的bean。其中anonymousAuthenticationProvider是在http解析过程添加的。
其实可以完全像acegi那样自定义每个bean。
<authentication-manager alias="authenticationManager">
<authentication-provider user-service-ref="userDetailsManager"/>
</authentication-manager>
上面的标签如果用bean来定义，则可以完全由下面的xml来替代。
<bean id="org.springframework.security.authenticationManager" class="org.springframework.security.authentication.ProviderManager">
<property name="authenticationEventPublisher" ref="defaultAuthenticationEventPublisher"></property>
<property name="providers">
<list>
<ref local="daoAuthenticationProvider"/>
<ref local="anonymousAuthenticationProvider"/>
</list>
</property>
</bean> <bean id="defaultAuthenticationEventPublisher" class="org.springframework.security.authentication.DefaultAuthenticationEventPublisher"></bean> <bean id="anonymousAuthenticationProvider" class="org.springframework.security.authentication.AnonymousAuthenticationProvider">
<property name="key"><value>work</value></property>
</bean> <bean id="daoAuthenticationProvider" class="org.springframework.security.authentication.dao.DaoAuthenticationProvider">
<property name="userDetailsService" ref="userDetailsManager"></property>
</bean>
需要注意的是anonymousAuthenticationProvider的bean中，需要增加key属性。如果采用authentication-manager标签的方式，key虽然没有定义，在增加AnonymousAuthenticationFilter过滤器中，是通过java.security.SecureRandom.nextLong()来生成的。
显而易见，如果采用bean的方式来定义，非常复杂，而且需要了解底层的组装过程才行，不过能够提高更大的扩展性。采用authentication-manager标签的方式，很简洁，只需要提供UserDetailsService即可。