spring security源码分析之一springSecurityFilterChain

1. spring和spring security的集成，配置web.xml如下：

<context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>
            /WEB-INF/spring-security.xml
        </param-value>
    </context-param>

    <!-- Spring Security -->
    <filter>
        <filter-name>springSecurityFilterChain</filter-name>
        <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>springSecurityFilterChain</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

2. springSecurityFilterChain的来龙去脉

在org.springframework.security.config包里定义了该名称：

    /** External alias for FilterChainProxy bean, for use in web.xml files */
    public static final String SPRING_SECURITY_FILTER_CHAIN = "springSecurityFilterChain";

使用springSecurityFilterChain的地方：HttpSecurityBeanDefinitionParser.java 该类建立
Http 安全体系：过滤器栈和受保护的url。

    static void registerFilterChainProxyIfNecessary(ParserContext pc, Object source) {
        if (pc.getRegistry().containsBeanDefinition(BeanIds.FILTER_CHAIN_PROXY)) {
            return;
        }
        // Not already registered, so register the list of filter chains and the FilterChainProxy
        BeanDefinition listFactoryBean = new RootBeanDefinition(ListFactoryBean.class);
        listFactoryBean.getPropertyValues().add("sourceList", new ManagedList());
        pc.registerBeanComponent(new BeanComponentDefinition(listFactoryBean, BeanIds.FILTER_CHAINS));

        BeanDefinitionBuilder fcpBldr = BeanDefinitionBuilder.rootBeanDefinition(FilterChainProxy.class);
        fcpBldr.getRawBeanDefinition().setSource(source);
        fcpBldr.addConstructorArgReference(BeanIds.FILTER_CHAINS);
        fcpBldr.addPropertyValue("filterChainValidator", new RootBeanDefinition(DefaultFilterChainValidator.class));
        BeanDefinition fcpBean = fcpBldr.getBeanDefinition();
        pc.registerBeanComponent(new BeanComponentDefinition(fcpBean, BeanIds.FILTER_CHAIN_PROXY));
        pc.getRegistry().registerAlias(BeanIds.FILTER_CHAIN_PROXY, BeanIds.SPRING_SECURITY_FILTER_CHAIN);
    }

}

从上面的代码可以看出，springSecurityFilterChain是DelegatingFilterProxy的代理对象。

3.FilterChainProxy

代理一组spring管理的filter bean来处理request。从spring security2.0以后，除非你需要对filter chain的内容进行严格的控制，否则你就无需显式的在context中配置一个FilterChainProxy。默认的<security:http />命名空间配置选项可以处理绝大部分应用场景。示例如下：

  <http auto-config="true">
    <remember-me key="xxx" token-validity-seconds="xxx" data-source-ref="dataSource"/>
    <form-login login-page="/login.jsp"/>
    <logout logout-success-url="/login.jsp"/>
    <intercept-url pattern="/*" access="ROLE_USER"/>
  </http>

通过在你的应用中的web.xml中增加一个名为DelegatingFilterProxy标准的spring声明，就可以将FilterChaiProxy链接到servlet 容器的filter chain。

3.1 配置

从spring security 3.1版本，FilterChainProxy通过一组SecurityFilterChain实例来配置，每个SecurityFilterChain实例包含一个RequestMacher和一组匹配request的Filter。

大部分应用只需要包含一个简单的filter chain，若你使用命名空间，你无需显式的设置chain；若你需要一个精确的控制，你可以使用<filter-chain>命名空间元素。它定义了一个urI匹配模式和一组逗号分隔的、应用到request和url匹配的filter。实例如下：

<bean id="myfilterChainProxy" class="org.springframework.security.util.FilterChainProxy">
     <constructor-arg>
         <util:list>
             <security:filter-chain pattern="/do/not/filter*" filters="none"/>
             <security:filter-chain pattern="/**" filters="filter1,filter2,filter3"/>
         </util:list>
     </constructor-arg>
 </bean>

3.2 request处理

　　HttpFirewall实例用来验证接收的request请求，并且创建一个新的包装后的请求，这个新包装的请求提供了和原请求一致的路径值。

　　FilterChainProxy使用firewall实例来获取应用到filter chain的request请求和response响应对象。当request请求通过security filter chain，将调用reset方法，此时将会返回servletPath和pathInfo的原始值，而不是security 模式匹配后的修改值。

3.3 Filter生命周期

注意，servlet容器中的filter生命周期和Ioc容器中的filter生命周期不一致。因此建议你使用Ioc容器而不是servlet容器来管理你增加到应用上下文的filter 的生命周期。

3.4 SecurityFilterChain

定义了一个filter chain，它能够和HttpServletRequest进行匹配，匹配是为了决定是否需要应用到该request请求。

4. filters预览

　　那么spring security有哪些filter呢？

SecurityFilters.java定义了默认的filter及其顺序：

 FIRST (Integer.MIN_VALUE),
    CHANNEL_FILTER,
    SECURITY_CONTEXT_FILTER,
    CONCURRENT_SESSION_FILTER,
    /** {@link WebAsyncManagerIntegrationFilter} */
    WEB_ASYNC_MANAGER_FILTER,
    HEADERS_FILTER,
    CSRF_FILTER,
    LOGOUT_FILTER,
    X509_FILTER,
    PRE_AUTH_FILTER,
    CAS_FILTER,
    FORM_LOGIN_FILTER,
    OPENID_FILTER,
    LOGIN_PAGE_FILTER,
    DIGEST_AUTH_FILTER,
    BASIC_AUTH_FILTER,
    REQUEST_CACHE_FILTER,
    SERVLET_API_SUPPORT_FILTER,
    JAAS_API_SUPPORT_FILTER,
    REMEMBER_ME_FILTER,
    ANONYMOUS_FILTER,
    SESSION_MANAGEMENT_FILTER,
    EXCEPTION_TRANSLATION_FILTER,
    FILTER_SECURITY_INTERCEPTOR,
    SWITCH_USER_FILTER,
    LAST (Integer.MAX_VALUE);

    private static final int INTERVAL = 100;

测试：

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        System.out.println(SecurityFilters.CHANNEL_FILTER.getOrder());
        System.out.println(SecurityFilters.SECURITY_CONTEXT_FILTER.getOrder());
        System.out.println(SecurityFilters.CONCURRENT_SESSION_FILTER.getOrder());
    }

结果如下：

100
200
300

以此类推：

默认的过滤器顺序列表
order 过滤器名称
100 ChannelProcessingFilter
200 ConcurrentSessionFilter
300 SecurityContextPersistenceFilter
400 LogoutFilter
500 X509AuthenticationFilter
600 RequestHeaderAuthenticationFilter
700 CasAuthenticationFilter
800 UsernamePasswordAuthenticationFilter
900 OpenIDAuthenticationFilter
1000 DefaultLoginPageGeneratingFilter
1100 DigestAuthenticationFilter
1200 BasicAuthenticationFilter
1300 RequestCacheAwareFilter
1400 SecurityContextHolderAwareRequestFilter
1500 RememberMeAuthenticationFilter
1600 AnonymousAuthenticationFilter
1700 SessionManagementFilter
1800 ExceptionTranslationFilter
1900 FilterSecurityInterceptor
2000 SwitchUserFilter