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参考b站up主：传送门

前沿: 本章：spring-security 重要的成员 WebSecurity、HttpSecurity、SecurityBuilder、SecurityFilterChain、FilterChainProxy

重点：WebSecurity、HttpSecurity 他们都实现了 SecurityBuilder 接口 用来构建对象

WebSecurity的作用：

首先看下他的结构：

public final class WebSecurity extendsAbstractConfiguredSecurityBuilder<Filter, WebSecurity> implementsSecurityBuilder<Filter>, ApplicationContextAware{}

小插曲：其实WebSecurity继承的AbstractConfiguredSecurityBuilder就已经实现了SecurityBuilder也就是说WebSecurity继承AbstractConfiguredSecurityBuilder就已经能完成工作了，再实现一遍SecurityBuilder什么意思？理解：从看代码的人角度 能够更加清晰的知道WebSecurity它实现了SecurityBuilder，是我们最重要的接口而泛型Filter就已经知道要构建的对象是Filter。

总之：我们一下子在这就能看到WebSecurity最终构建的对象Object是什么？就是Filter。

写不写implements SecurityBuilder 对能完成工作

HttpSecurity的作用

用刚才WebSecurity的方法来理解

public final class HttpSecurity extendsAbstractConfiguredSecurityBuilder<DefaultSecurityFilterChain, HttpSecurity>implements SecurityBuilder<DefaultSecurityFilterChain>,HttpSecurityBuilder<HttpSecurity> {}

HttpSecurity是为了构建DefaultSecurityFilterChain对象的。是默认的SecurityFilterChain

SecurityFilterChain

SecurityFilterChain：是一个接口，默认的实现是DefaultSecurityFilterChain

/**
Defines a filter chain which is capable of being matched against an HttpServletRequest. in order to decide whether it applies to that request.
定义这样的一个过滤器链去匹配一个特定的request，然后决定这个request能不能应用这个List<Filter>
*/
public interface SecurityFilterChain {boolean matches(HttpServletRequest request);List<Filter> getFilters();
}

SecurityFilterChain也是spring-security当中重要的一个成员。两个方法：

1、matches 是否能匹配 request

2、匹配成功 那么就getFilters()方法所有的Filter都应用一遍

SecurityFilterChain的默认实现

DefaultSecurityFilterChain

public final class DefaultSecurityFilterChain implements SecurityFilterChain {// 在matches中判断能不能匹配requestprivate final RequestMatcher requestMatcher;private final List<Filter> filters;public DefaultSecurityFilterChain(RequestMatcher requestMatcher, Filter... filters) {this(requestMatcher, Arrays.asList(filters));}public DefaultSecurityFilterChain(RequestMatcher requestMatcher, List<Filter> filters) {logger.info("Creating filter chain: " + requestMatcher + ", " + filters);this.requestMatcher = requestMatcher;this.filters = new ArrayList<>(filters);}public RequestMatcher getRequestMatcher() {return requestMatcher;}// 匹配成功就把Filter应用一遍public List<Filter> getFilters() {return filters;}// 在matches中判断能不能匹配requestpublic boolean matches(HttpServletRequest request) {return requestMatcher.matches(request);}
}

WebSecurity到底构建了怎样的Filter？

public interface SecurityBuilder<O> {/*** Builds the object and returns it or null.** @return the Object to be built or null if the implementation allows it.* @throws Exception if an error occurred when building the Object*/O build() throws Exception;
}

通过build方法看它的实现：AbstractSecurityBuilder实现了SecurityBuilder接口中的build方法

AbstractSecurityBuilder抽象类中 doBuild方法的构建工作委派给子类实现。

public abstract class AbstractSecurityBuilder<O> implements SecurityBuilder<O>{private AtomicBoolean building = new AtomicBoolean();private O object;//AbstractSecurityBuilder实现了SecurityBuilder接口中的build方法public final O build() throws Exception {if (this.building.compareAndSet(false, true)) {this.object = doBuild();return this.object;}// 解决了重复构建问题 如果再构建一次就抛出异常了throw new AlreadyBuiltException("This object has already been built");}// 构建工作 doBuild 方法protected abstract O doBuild() throws Exception;
}

继续往下走

AbstractConfiguredSecurityBuilder还是一个抽象类。它实现了父类的doBuild方法

public abstract class AbstractConfiguredSecurityBuilder<O, B extends SecurityBuilder<O>>extends AbstractSecurityBuilder<O> {@Overrideprotected final O doBuild() throws Exception {// 加锁 此阶段只能一个线程执行synchronized (configurers) {buildState = BuildState.INITIALIZING;// 留给子类实现的模版方法  不强制子类实现 即不重要的方法beforeInit();init();buildState = BuildState.CONFIGURING;// 留给子类实现的模版方法 不强制子类实现 即不重要的方法beforeConfigure();configure();buildState = BuildState.BUILDING;// 重要方法  有三个类实现它 AuthenticationManagerBuilder HttpSecurity WebSecurityO result = performBuild();buildState = BuildState.BUILT;return result;}} //不强制子类实现protected void beforeInit() throws Exception {}//不强制子类实现protected void beforeConfigure() throws Exception {}// 重要方法protected abstract O performBuild() throws Exception;}

这里通过performBuild();方法构建了我们最终所需要的Object，核心逻辑就在performBuild方法。

有三个类实现它 AuthenticationManagerBuilder、HttpSecurity、 WebSecurity

HttpSecurity的performBuild方法

@Overrideprotected DefaultSecurityFilterChain performBuild() {filters.sort(comparator);return new DefaultSecurityFilterChain(requestMatcher, filters);}

最终返回的就是DefaultSecurityFilterChain 前面说到HttpSecurity所要构建的就是DefaultSecurityFilterChain 那么HttpSecurity的工作完成了。

WebSecurity的performBuild方法

WebSecurity作用：构建一个Filter 显然 构建工作在这

	@Overrideprotected Filter performBuild() throws Exception {Assert.state(!securityFilterChainBuilders.isEmpty(),() -> "At least one SecurityBuilder<? extends SecurityFilterChain> needs to be specified. "+ "Typically this done by adding a @Configuration that extends WebSecurityConfigurerAdapter. "+ "More advanced users can invoke "+ WebSecurity.class.getSimpleName()+ ".addSecurityFilterChainBuilder directly");int chainSize = ignoredRequests.size() + securityFilterChainBuilders.size();List<SecurityFilterChain> securityFilterChains = new ArrayList<>(chainSize);for (RequestMatcher ignoredRequest : ignoredRequests) {securityFilterChains.add(new DefaultSecurityFilterChain(ignoredRequest));}for (SecurityBuilder<? extends SecurityFilterChain> securityFilterChainBuilder : securityFilterChainBuilders) {securityFilterChains.add(securityFilterChainBuilder.build());}// FilterChainProxy 就是Filter的一个变种 最终还是一个FilterFilterChainProxy filterChainProxy = new FilterChainProxy(securityFilterChains);if (httpFirewall != null) {filterChainProxy.setFirewall(httpFirewall);}filterChainProxy.afterPropertiesSet();Filter result = filterChainProxy;//debugEnabled：这个是通过 @EnableWebSecurity(dubug=true)开启的if (debugEnabled) {logger.warn("\n\n"+ "********************************************************************\n"+ "**********        Security debugging is enabled.       *************\n"+ "**********    This may include sensitive information.  *************\n"+ "**********      Do not use in a production system!     *************\n"+ "********************************************************************\n\n");result = new DebugFilter(filterChainProxy);}postBuildAction.run();return result;}

FilterChainProxy

前置知识：

SecurityFilterChain：就是一个过滤器链 前面介绍过了 这个过滤器链能否应用就跟请求能不能匹配。

public class FilterChainProxy extends GenericFilterBean {//传了一堆 SecurityFilterChainpublic FilterChainProxy(List<SecurityFilterChain> filterChains) {this.filterChains = filterChains;}// 　是Filter的一个主要方法  doFilter做过滤的 控制过滤器只能执行一次@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {boolean clearContext = request.getAttribute(FILTER_APPLIED) == null;if (clearContext) {try {request.setAttribute(FILTER_APPLIED, Boolean.TRUE);//核心方法 doFilterInternal(request, response, chain);}finally {SecurityContextHolder.clearContext();request.removeAttribute(FILTER_APPLIED);}}else {doFilterInternal(request, response, chain);}}//FilterChain tomcat下的一个接口 他的最主要实现是 ApplicationFilterChainprivate void doFilterInternal(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {FirewalledRequest fwRequest = firewall.getFirewalledRequest((HttpServletRequest) request);HttpServletResponse fwResponse = firewall.getFirewalledResponse((HttpServletResponse) response);// 拿到一堆Filters  这里是重点List<Filter> filters = getFilters(fwRequest);if (filters == null || filters.size() == 0) {if (logger.isDebugEnabled()) {logger.debug(UrlUtils.buildRequestUrl(fwRequest)+ (filters == null ? " has no matching filters": " has an empty filter list"));}fwRequest.reset();chain.doFilter(fwRequest, fwResponse);return;}// VirtualFilterChain 虚拟的过滤器链  chain 最顶层的过滤器链// VirtualFilterChain最终就是 把 这个参数中的 filters 挨个应用一遍VirtualFilterChain vfc = new VirtualFilterChain(fwRequest, chain, filters);// 虚拟的过滤器链 调用了他的 doFilter方法vfc.doFilter(fwRequest, fwResponse);}// 如果应用中定义了多个SecurityFilterChain 如果想要第一个匹配的去执行 此时需要控制一下顺序 实现Order接口 或者Order注解控制？private List<Filter> getFilters(HttpServletRequest request) {for (SecurityFilterChain chain : filterChains) {// 匹配到第一个即成功if (chain.matches(request)) {return chain.getFilters();}}return null;}@Overridepublic void doFilter(ServletRequest request, ServletResponse response)throws IOException, ServletException {if (currentPosition == size) {if (logger.isDebugEnabled()) {logger.debug(UrlUtils.buildRequestUrl(firewalledRequest)+ " reached end of additional filter chain; proceeding with original chain");}// Deactivate path stripping as we exit the security filter chainthis.firewalledRequest.reset();originalChain.doFilter(request, response);}else {currentPosition++;Filter nextFilter = additionalFilters.get(currentPosition - 1);if (logger.isDebugEnabled()) {logger.debug(UrlUtils.buildRequestUrl(firewalledRequest)+ " at position " + currentPosition + " of " + size+ " in additional filter chain; firing Filter: '"+ nextFilter.getClass().getSimpleName() + "'");}nextFilter.doFilter(request, response, this);}}}
}

最后

至此spring-security流程分析完毕 它最顶层就是一个Filter 这个Filter就是FilterChainProxy。

FilterChainProxy里面有一堆的SecurityFilterChain private List<SecurityFilterChain> filterChains;(这个是FilterChainProxy类中的属性)，这些SecurityFilterChain都有一个匹配器叫做RequestMatcher，这个RequestMatcher是 SecurityFilterChain的默认实现类DefaultSecurityFilterChain中的属性。

RequestMatcher 是一个接口 有若干个实现 它就是用来匹配请求的。

流程总结：

由FilterChainProxy进来通过调用doFilter方法-进去再调用doFilterInternal方法-通过getFilters 根据HttpServletRequest这个对象去匹配第一个能够匹配的SecurityFilterChain 把其中Filters拿出来。

构建成了一个VirtualFilterChain对象 挨个调用他们的doFilter。