Spring Security源码（九）：过滤器链上的过滤器是如何排序的？

文章目录

• 一、框架原理
• • 概述
• 过滤器链实战示例
• 二、FilterComparator
• • 源码
• 说明
• 自定义过滤器顺序设置
• 三、如何排序
• • 实际排序
• FilterSecurityInterceptor
• 四、系列文章
• • Spring Security 系列
• Spring Security OAuth 系列

---

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 FilterChainProxy 的 doFilter() 上，自行走一下代码，会发现请求需要经过如下过滤器：

>
> 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 UserAuthenticationFilter、JwtAuthenticationFilter

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;
	}
}