Spring Security源码:过滤器链上的过滤器是如何排序的?

Posted 木兮同学

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一、框架原理

概述

前面源码篇文章(篇尾附上链接)提到,整个框架的核心就是一个过滤器 FilterChainProxy,这个过滤器维护了一组过滤器链,真正起作用的其实是这个过滤器里的过滤器链。我们知道过滤器链可是有执行顺序的,关于它是如何排序的,本篇来聊聊。

过滤器链实战示例

先来看看一个请求进来需要走过的过滤器链有哪些,以下为前面实战篇(篇尾附上链接)中过滤器链debug截图,断点打在核心过滤器 FilterChainProxydoFilter() 上,自行走一下代码,会发现请求需要经过如下过滤器:
过滤器链
可以看到很多熟悉的过滤器,包括我们自己定义的两个过滤器 UserAuthenticationFilterJwtAuthenticationFilter

二、FilterComparator

内部其实是使用这个类来对Filter的实例进行排序,以确保它们的顺序正确。

源码

final class FilterComparator implements Comparator<Filter>, Serializable {
	private static final int STEP = 100;
	private Map<String, Integer> filterToOrder = new HashMap<String, Integer>();

	FilterComparator() {
		int order = 100;
		put(ChannelProcessingFilter.class, order);
		order += STEP;
		put(ConcurrentSessionFilter.class, order);
		order += STEP;
		put(WebAsyncManagerIntegrationFilter.class, order);
		order += STEP;
		put(SecurityContextPersistenceFilter.class, order);
		order += STEP;
		put(HeaderWriterFilter.class, order);
		order += STEP;
		put(CorsFilter.class, order);
		order += STEP;
		put(CsrfFilter.class, order);
		order += STEP;
		put(LogoutFilter.class, order);
		order += STEP;
		put(X509AuthenticationFilter.class, order);
		order += STEP;
		put(AbstractPreAuthenticatedProcessingFilter.class, order);
		order += STEP;
		filterToOrder.put("org.springframework.security.cas.web.CasAuthenticationFilter",
				order);
		order += STEP;
		put(UsernamePasswordAuthenticationFilter.class, order);
		order += STEP;
		put(ConcurrentSessionFilter.class, order);
		order += STEP;
		filterToOrder.put(
				"org.springframework.security.openid.OpenIDAuthenticationFilter", order);
		order += STEP;
		put(DefaultLoginPageGeneratingFilter.class, order);
		order += STEP;
		put(ConcurrentSessionFilter.class, order);
		order += STEP;
		put(DigestAuthenticationFilter.class, order);
		order += STEP;
		put(BasicAuthenticationFilter.class, order);
		order += STEP;
		put(RequestCacheAwareFilter.class, order);
		order += STEP;
		put(SecurityContextHolderAwareRequestFilter.class, order);
		order += STEP;
		put(JaasApiIntegrationFilter.class, order);
		order += STEP;
		put(RememberMeAuthenticationFilter.class, order);
		order += STEP;
		put(AnonymousAuthenticationFilter.class, order);
		order += STEP;
		put(SessionManagementFilter.class, order);
		order += STEP;
		put(ExceptionTranslationFilter.class, order);
		order += STEP;
		put(FilterSecurityInterceptor.class, order);
		order += STEP;
		put(SwitchUserFilter.class, order);
	}

	public int compare(Filter lhs, Filter rhs) {
		Integer left = getOrder(lhs.getClass());
		Integer right = getOrder(rhs.getClass());
		return left - right;
	}

	/**
	 * Determines if a particular {@link Filter} is registered to be sorted
	 *
	 * @param filter
	 * @return
	 */
	public boolean isRegistered(Class<? extends Filter> filter) {
		return getOrder(filter) != null;
	}

	/**
	 * Registers a {@link Filter} to exist after a particular {@link Filter} that is
	 * already registered.
	 * @param filter the {@link Filter} to register
	 * @param afterFilter the {@link Filter} that is already registered and that
	 * {@code filter} should be placed after.
	 */
	public void registerAfter(Class<? extends Filter> filter,
			Class<? extends Filter> afterFilter) {
		Integer position = getOrder(afterFilter);
		if (position == null) {
			throw new IllegalArgumentException(
					"Cannot register after unregistered Filter " + afterFilter);
		}

		put(filter, position + 1);
	}

	/**
	 * Registers a {@link Filter} to exist at a particular {@link Filter} position
	 * @param filter the {@link Filter} to register
	 * @param atFilter the {@link Filter} that is already registered and that
	 * {@code filter} should be placed at.
	 */
	public void registerAt(Class<? extends Filter> filter,
			Class<? extends Filter> atFilter) {
		Integer position = getOrder(atFilter);
		if (position == null) {
			throw new IllegalArgumentException(
					"Cannot register after unregistered Filter " + atFilter);
		}

		put(filter, position);
	}

	/**
	 * Registers a {@link Filter} to exist before a particular {@link Filter} that is
	 * already registered.
	 * @param filter the {@link Filter} to register
	 * @param beforeFilter the {@link Filter} that is already registered and that
	 * {@code filter} should be placed before.
	 */
	public void registerBefore(Class<? extends Filter> filter,
			Class<? extends Filter> beforeFilter) {
		Integer position = getOrder(beforeFilter);
		if (position == null) {
			throw new IllegalArgumentException(
					"Cannot register after unregistered Filter " + beforeFilter);
		}

		put(filter, position - 1);
	}

	private void put(Class<? extends Filter> filter, int position) {
		String className = filter.getName();
		filterToOrder.put(className, position);
	}

	/**
	 * Gets the order of a particular {@link Filter} class taking into consideration
	 * superclasses.
	 *
	 * @param clazz the {@link Filter} class to determine the sort order
	 * @return the sort order or null if not defined
	 */
	private Integer getOrder(Class<?> clazz) {
		while (clazz != null) {
			Integer result = filterToOrder.get(clazz.getName());
			if (result != null) {
				return result;
			}
			clazz = clazz.getSuperclass();
		}
		return null;
	}
}

说明

  • 可以看到该类被实例化的时候,就将框架中存在的过滤器都设置了一个顺序值,保存在 filterToOrder
  • 该类还实现了Comparator接口,实现了它的 compare() 方法,里面是根据过滤器的顺序值进行排序的。
  • 类中提供了一些给外部添加过滤器的接口,比如:
    • registerBefore(Filter filter, Filter beforeFilter):在beforeFilter过滤器之前添加过滤器。
    • registerAfter(Filter filter, Filter afterFilter):在afterFilter过滤器之后添加过滤器。
    • registerAt(Filter filter, Filter atFilter):加入和atFilter过滤器相同顺序的过滤器。

自定义过滤器顺序设置

  • 在登录过滤器配置UserLoginConfigurer 中配置 UserAuthenticationFilter 过滤器顺序:
	@Override
	public void configure(B http) throws Exception {

		UserAuthenticationFilter authFilter = new UserAuthenticationFilter();

		authFilter.setAuthenticationManager(http.getSharedObject(AuthenticationManager.class));
		authFilter.setSessionAuthenticationStrategy(new NullAuthenticatedSessionStrategy());

		// 登录成功处理器
		authFilter.setAuthenticationSuccessHandler(new UserLoginSuccessHandler(securityConfig));
		// 登录失败处理器
		authFilter.setAuthenticationFailureHandler(new HttpStatusLoginFailureHandler());

		// 拦截器位置
		UserAuthenticationFilter filter = postProcess(authFilter);
		http.addFilterAfter(filter, LogoutFilter.class);
	}
  • 点进 addFilterAfter() 方法查看,其实调用的就是 FilterComparator 中的方法:
	public HttpSecurity addFilterAfter(Filter filter, Class<? extends Filter> afterFilter) {
		comparator.registerAfter(filter.getClass(), afterFilter);
		return addFilter(filter);
	}

三、如何排序

上面小节只是给过滤器加上一个顺序,而对于我们的过滤器链并没有排序,实际上过滤器链还没生成呢,在启动项目的时候才开始创建过滤器,来看看创建过程中是如何对过滤器进行排序的。

实际排序

  • 还记得实际上过滤器是在哪创建的吗,在《Spring Security源码(五):FilterChainProxy是如何创建的?》一章中提到过,过滤器是在 HttpSecurity 中的 performBuild()方法中创建的,可以看到在这里会把已经创建好保存到 filters 中的过滤器进行排序,其实就是每创建一个过滤器都对过滤器链进行一个排序。
	@Override
	protected DefaultSecurityFilterChain performBuild() throws Exception {
		Collections.sort(filters, comparator);
		return new DefaultSecurityFilterChain(requestMatcher, filters);
	}

FilterSecurityInterceptor

这是一个特殊的过滤器,特殊在每条过滤器链都是以这个过滤器结尾,这个过滤器是Spring Security框架做权限访问控制的核心过滤器,请求最后能否通过是否有权限访问后台资源都是由它决定,关于这个过滤器咱们下一篇详细讲解,链接在篇尾。


四、系列文章

实战篇

源码篇

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