springSecurity安全框架的学习和原理解读

一个可以为基于Spring的企业应用系统提供声明式的安全訪问控制解决方式的安全框架（简单说是对访问权限进行控制嘛），应用的安全性包括用户认证（Authentication）和用户受权（Authorization）两个部分。用户认证指的是验证某个用户是否为系统中的合法主体，也就是说用户可否访问该系统。用户认证通常要求用户提供用户名和密码。系统经过校验用户名和密码来完成认证过程。用户受权指的是验证某个用户是否有权限执行某个操做。在一个系统中，不一样用户所具备的权限是不一样的。好比对一个文件来讲，有的用户只能进行读取，而有的用户能够进行修改。通常来讲，系统会为不一样的用户分配不一样的角色，而每一个角色则对应一系列的权限。 spring security的主要核心功能为认证和受权，全部的架构也是基于这两个核心功能去实现的。

二、框架原理

众所周知想要对对Web资源进行保护，最好的办法莫过于Filter，要想对方法调用进行保护，最好的办法莫过于AOP。因此springSecurity在咱们进行用户认证以及授予权限的时候，经过各类各样的拦截器来控制权限的访问，从而实现安全。
以下为其主要过滤器

WebAsyncManagerIntegrationFilter
SecurityContextPersistenceFilter
HeaderWriterFilter
CorsFilter
LogoutFilter
RequestCacheAwareFilter
SecurityContextHolderAwareRequestFilter
AnonymousAuthenticationFilter
SessionManagementFilter
ExceptionTranslationFilter
FilterSecurityInterceptor
UsernamePasswordAuthenticationFilter
BasicAuthenticationFilter

三、框架的核心组件

SecurityContextHolder：提供对SecurityContext的访问
SecurityContext,：持有Authentication对象和其余可能须要的信息
AuthenticationManager 其中能够包含多个AuthenticationProvider
ProviderManager对象为AuthenticationManager接口的实现类
AuthenticationProvider 主要用来进行认证操做的类调用其中的authenticate()方法去进行认证操做
Authentication：Spring Security方式的认证主体
GrantedAuthority：对认证主题的应用层面的受权，含当前用户的权限信息，一般使用角色表示
UserDetails：构建Authentication对象必须的信息，能够自定义，可能须要访问DB获得
UserDetailsService：经过username构建UserDetails对象，经过loadUserByUsername根据userName获取UserDetail对象（能够在这里基于自身业务进行自定义的实现如经过数据库，xml,缓存获取等）

2、自定义安全配置的加载机制

一、前提基于自身业务须要

有关springSecrity安全框架的理解参考：springSecurity安全框架介绍

自定义了一个springSecurity安全框架的配置类继承WebSecurityConfigurerAdapter，重写其中的方法configure，可是并不清楚自定义的类是如何被加载并起到做用，这里一步步经过debug来了解其中的加载原理。

其实在咱们实现该类后，在web容器启动的过程当中该类实例对象会被WebSecurityConfiguration类处理。

@Configuration
public class SpringSecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private AccessDeniedHandler accessDeniedHandler;

    @Autowired
    private CustAuthenticationProvider custAuthenticationProvider;

    // roles admin allow to access /admin/**
    // roles user allow to access /user/**
    // custom 403 access denied handler
    //重写了其中的configure（）方法设置了不一样url的不一样访问权限
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.csrf().disable()
                .authorizeRequests()
                .antMatchers("/home", "/about","/img/*").permitAll()
                .antMatchers("/admin/**","/upload/**").hasAnyRole("ADMIN")
                .antMatchers("/order/**").hasAnyRole("USER","ADMIN")
                .antMatchers("/room/**").hasAnyRole("USER","ADMIN")
                .anyRequest().authenticated()
                .and()
                .formLogin()
                .loginPage("/login")
                .permitAll()
                .and()
                .logout()
                .permitAll()
                .and()
                .exceptionHandling().accessDeniedHandler(accessDeniedHandler);
    }

    // create two users, admin and user
    @Autowired
    public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {

// auth.inMemoryAuthentication()
// .withUser("user").password("user").roles("USER")
// .and()
// .withUser("admin").password("admin").roles("ADMIN");

// auth.jdbcAuthentication()

        auth.authenticationProvider(custAuthenticationProvider);
    }

二、WebSecurityConfiguration类

@Configuration
public class WebSecurityConfiguration implements ImportAware, BeanClassLoaderAware {
    private WebSecurity webSecurity;
    private Boolean debugEnabled;
    private List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers;
    private ClassLoader beanClassLoader;
   
   ...省略部分代码

    @Bean(
        name = {"springSecurityFilterChain"}
    )
    public Filter springSecurityFilterChain() throws Exception {
        boolean hasConfigurers = this.webSecurityConfigurers != null
         && !this.webSecurityConfigurers.isEmpty();
        if(!hasConfigurers) {
            WebSecurityConfigurerAdapter adapter = (WebSecurityConfigurerAdapter)
            this.objectObjectPostProcessor
              .postProcess(new WebSecurityConfigurerAdapter() {
            });
            this.webSecurity.apply(adapter);
        }

        return (Filter)this.webSecurity.build();
    }

  
    
    /*一、先执行该方法将咱们自定义springSecurity配置实例 （可能还有系统默认的有关安全的配置实例 ） 配置实例中含有咱们自定义业务的权限控制配置信息 放入到该对象的list数组中webSecurityConfigurers中 使用@Value注解来将实例对象做为形参注入 */   
 @Autowired(
        required = false
    )
    public void setFilterChainProxySecurityConfigurer(ObjectPostProcessor<Object> objectPostProcessor, @Value("#{@autowiredWebSecurityConfigurersIgnoreParents.getWebSecurityConfigurers()}") List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers) throws Exception {
    
    //建立一个webSecurity对象 
    this.webSecurity = (WebSecurity)objectPostProcessor.postProcess(new WebSecurity(objectPostProcessor));
        if(this.debugEnabled != null) {
            this.webSecurity.debug(this.debugEnabled.booleanValue());
        }

        //对全部配置类的实例进行排序
        Collections.sort(webSecurityConfigurers, WebSecurityConfiguration.AnnotationAwareOrderComparator.INSTANCE);
        Integer previousOrder = null;
        Object previousConfig = null;


        //迭代全部配置类的实例 判断其order必须惟一
        Iterator var5;
        SecurityConfigurer config;
        for(var5 = webSecurityConfigurers.iterator(); var5.hasNext(); previousConfig = config) {
            config = (SecurityConfigurer)var5.next();
            Integer order = Integer.valueOf(WebSecurityConfiguration.AnnotationAwareOrderComparator.lookupOrder(config));
            if(previousOrder != null && previousOrder.equals(order)) {
                throw new IllegalStateException("@Order on WebSecurityConfigurers must be unique. Order of " + order + " was already used on " + previousConfig + ", so it cannot be used on " + config + " too.");
            }

            previousOrder = order;
        }


        //将全部的配置实例添加到建立的webSecutity对象中
        var5 = webSecurityConfigurers.iterator();

        while(var5.hasNext()) {
            config = (SecurityConfigurer)var5.next();
            this.webSecurity.apply(config);
        }
        //将webSercurityConfigures 实例放入该对象的webSecurityConfigurers属性中
        this.webSecurityConfigurers = webSecurityConfigurers;
    }

   
}

2.一、 setFilterChainProxySecurityConfigurer（）方法

@Value("#{@autowiredWebSecurityConfigurersIgnoreParents.getWebSecurityConfigurers()}") List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers

该参数webSecurityConfigurers会将全部的配置实例放入该形参中

该方法中主要执行以下

一、建立webSecurity对象

二、主要检验了配置实例的order顺序（order惟一不然会报错）

三、将全部的配置实例存放进入到webSecurity对象中，其中配置实例中含有咱们自定义业务的权限控制配置信息

2.二、springSecurityFilterChain()方法

调用springSecurityFilterChain()方法，这个方法会判断咱们上一个方法中有没有获取到webSecurityConfigurers，没有的话这边会建立一个WebSecurityConfigurerAdapter实例，并追加到websecurity中。接着调用websecurity的build方法。实际调用的是websecurity的父类AbstractSecurityBuilder的build方法，最终返回一个名称为springSecurityFilterChain的过滤器链。里面有众多Filter(springSecurity其实就是依靠不少的Filter来拦截url从而实现权限的控制的安全框架)

三、AbstractSecurityBuilder类

public abstract class AbstractSecurityBuilder<O> implements SecurityBuilder<O> {
    private AtomicBoolean building = new AtomicBoolean();
    private O object;

  

    //调用build方法来返回过滤器链，仍是调用SecurityBuilder的dobuild()方法

    public final O build() throws Exception {
        if(this.building.compareAndSet(false, true)) {
            this.object = this.doBuild();
            return this.object;
        } else {
            throw new AlreadyBuiltException("This object has already been built");
        }
    }

   //...省略部分代码
}

3.1 调用子类的doBuild()方法

public abstract class AbstractConfiguredSecurityBuilder<O, B extends SecurityBuilder<O>> extends AbstractSecurityBuilder<O> {
    private final Log logger;
    private final LinkedHashMap<Class<? extends SecurityConfigurer<O, B>>, List<SecurityConfigurer<O, B>>> configurers;
    private final List<SecurityConfigurer<O, B>> configurersAddedInInitializing;
    private final Map<Class<? extends Object>, Object> sharedObjects;
    private final boolean allowConfigurersOfSameType;
    private AbstractConfiguredSecurityBuilder.BuildState buildState;
    private ObjectPostProcessor<Object> objectPostProcessor;


    //doBuild()核心方法 init(),configure(),perFormBuild()
    protected final O doBuild() throws Exception {
        LinkedHashMap var1 = this.configurers;
        synchronized(this.configurers) {
            this.buildState = AbstractConfiguredSecurityBuilder.BuildState.INITIALIZING;
            this.beforeInit();
            this.init();
            this.buildState = AbstractConfiguredSecurityBuilder.BuildState.CONFIGURING;
            this.beforeConfigure();
            this.configure();
            this.buildState = AbstractConfiguredSecurityBuilder.BuildState.BUILDING;
            O result = this.performBuild();
            this.buildState = AbstractConfiguredSecurityBuilder.BuildState.BUILT;
            return result;
        }
    }

    protected abstract O performBuild() throws Exception;
    
    //调用init方法 调用配置类WebSecurityConfigurerAdapter的init()方法
    private void init() throws Exception {
        Collection<SecurityConfigurer<O, B>> configurers = this.getConfigurers();
        Iterator var2 = configurers.iterator();

        SecurityConfigurer configurer;
        while(var2.hasNext()) {
            configurer = (SecurityConfigurer)var2.next();
            configurer.init(this);
        }

        var2 = this.configurersAddedInInitializing.iterator();

        while(var2.hasNext()) {
            configurer = (SecurityConfigurer)var2.next();
            configurer.init(this);
        }

    }

    private void configure() throws Exception {
        Collection<SecurityConfigurer<O, B>> configurers = this.getConfigurers();
        Iterator var2 = configurers.iterator();

        while(var2.hasNext()) {
            SecurityConfigurer<O, B> configurer = (SecurityConfigurer)var2.next();
            configurer.configure(this);
        }

    }

    private Collection<SecurityConfigurer<O, B>> getConfigurers() {
        List<SecurityConfigurer<O, B>> result = new ArrayList();
        Iterator var2 = this.configurers.values().iterator();

        while(var2.hasNext()) {
            List<SecurityConfigurer<O, B>> configs = (List)var2.next();
            result.addAll(configs);
        }

        return result;
    }

    //...省略部分代码
}

3.2 先调用本类的init()方法

build过程主要分三步，init->configure->peformBuild

1 init方法作了两件事，一个就是调用getHttp()方法获取一个http实例，并经过web.addSecurityFilterChainBuilder方法把获取到的实例赋值给WebSecurity的securityFilterChainBuilders属性，这个属性在咱们执行build的时候会用到，第二个就是为WebSecurity追加了一个postBuildAction，在build都完成后从http中拿出FilterSecurityInterceptor对象并赋值给WebSecurity。
2 getHttp()方法，这个方法在当咱们使用默认配置时（大多数状况下）会为咱们追加各类SecurityConfigurer的具体实现类到httpSecurity中，如exceptionHandling()方法会追加一个ExceptionHandlingConfigurer，sessionManagement()方法会追加一个SessionManagementConfigurer,securityContext()方法会追加一个SecurityContextConfigurer对象，这些SecurityConfigurer的具体实现类最终会为咱们配置各类具体的filter。
3 另外getHttp()方法的最后会调用configure(http)，这个方法也是咱们继承WebSecurityConfigurerAdapter类后最可能会重写的方法。
4 configure(HttpSecurity http)方法，默认的configure(HttpSecurity http)方法继续向httpSecurity类中追加SecurityConfigurer的具体实现类，如authorizeRequests()方法追加一个ExpressionUrlAuthorizationConfigurer，formLogin()方法追加一个FormLoginConfigurer。其中ExpressionUrlAuthorizationConfigurer这个实现类比较重要，由于他会给咱们建立一个很是重要的对象FilterSecurityInterceptor对象，FormLoginConfigurer对象比较简单，可是也会为咱们提供一个在安全认证过程当中常常用到会用的一个Filter：UsernamePasswordAuthenticationFilter。

以上三个方法就是WebSecurityConfigurerAdapter类中init方法的主要逻辑，

public abstract class WebSecurityConfigurerAdapter implements WebSecurityConfigurer<WebSecurity> {

    public void init(final WebSecurity web) throws Exception {
        final HttpSecurity http = this.getHttp();
        web.addSecurityFilterChainBuilder(http).postBuildAction(new Runnable() {
            public void run() {
                FilterSecurityInterceptor securityInterceptor = (FilterSecurityInterceptor)http.getSharedObject(FilterSecurityInterceptor.class);
                web.securityInterceptor(securityInterceptor);
            }
        });
    }


 protected final HttpSecurity getHttp() throws Exception {
        if(this.http != null) {
            return this.http;
        } else {
            DefaultAuthenticationEventPublisher eventPublisher = (DefaultAuthenticationEventPublisher)this.objectPostProcessor.postProcess(new DefaultAuthenticationEventPublisher());
       

//添加认证的事件的发布者
this.localConfigureAuthenticationBldr.authenticationEventPublisher(eventPublisher);
//获取AuthenticationManager对象其中一至多个进行认证处理的对象实例，后面会进行讲解 
AuthenticationManager authenticationManager = this.authenticationManager();
            this.authenticationBuilder.parentAuthenticationManager(authenticationManager);
            Map<Class<? extends Object>, Object> sharedObjects = this.createSharedObjects();
            this.http = new HttpSecurity(this.objectPostProcessor, this.authenticationBuilder, sharedObjects);
            if(!this.disableDefaults) {
                ((HttpSecurity)((DefaultLoginPageConfigurer)((HttpSecurity)((HttpSecurity)((HttpSecurity)((HttpSecurity)((HttpSecurity)((HttpSecurity)((HttpSecurity)((HttpSecurity)this.http.csrf().and()).addFilter(new WebAsyncManagerIntegrationFilter()).exceptionHandling().and()).headers().and()).sessionManagement().and()).securityContext().and()).requestCache().and()).anonymous().and()).servletApi().and()).apply(new DefaultLoginPageConfigurer())).and()).logout();
                ClassLoader classLoader = this.context.getClassLoader();
                List<AbstractHttpConfigurer> defaultHttpConfigurers = SpringFactoriesLoader.loadFactories(AbstractHttpConfigurer.class, classLoader);
                Iterator var6 = defaultHttpConfigurers.iterator();

                while(var6.hasNext()) {
                    AbstractHttpConfigurer configurer = (AbstractHttpConfigurer)var6.next();
                    this.http.apply(configurer);
                }
            }

            //最终调用咱们的继承的WebSecurityConfigurerAdapter中重写的configure()
            //将咱们业务相关的权限配置规则信息进行初始化操做
            this.configure(this.http);
            return this.http;
        }
    }


 protected AuthenticationManager authenticationManager() throws Exception {
        if(!this.authenticationManagerInitialized) {
            this.configure(this.localConfigureAuthenticationBldr);
            if(this.disableLocalConfigureAuthenticationBldr) {
                this.authenticationManager = this.authenticationConfiguration.getAuthenticationManager();
            } else {
                this.authenticationManager = (AuthenticationManager)this.localConfigureAuthenticationBldr.build();
            }

            this.authenticationManagerInitialized = true;
        }

        return this.authenticationManager;
    }



}

3.三、第二步configure

configure方法最终也调用到了WebSecurityConfigurerAdapter的configure(WebSecurity web)方法，默认实现中这个是一个空方法，具体应用中也常常重写这个方法来实现特定需求。

3.四、第三步 peformBuild

具体的实现逻辑在WebSecurity类中
这个方法中最主要的任务就是遍历securityFilterChainBuilders属性中的SecurityBuilder对象，并调用他的build方法。
这个securityFilterChainBuilders属性咱们前面也有提到过，就是在WebSecurityConfigurerAdapter类的init方法中获取http后赋值给了WebSecurity。所以这个地方就是调用httpSecurity的build方法。
httpSecurity的build方式向其中追加一个个过滤器

public final class WebSecurity extends AbstractConfiguredSecurityBuilder<Filter, WebSecurity> implements SecurityBuilder<Filter>, ApplicationContextAware {
    
  ...省略部分代码

    //调用该方法经过securityFilterChainBuilder.build()方法来建立securityFilter过滤器
    //并添加到securityFilterChains对象中，包装成FilterChainProxy 返回
    protected Filter performBuild() throws Exception {
        Assert.state(!this.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 = this.ignoredRequests.size() + this.securityFilterChainBuilders.size();
        List<SecurityFilterChain> securityFilterChains = new ArrayList(chainSize);
        Iterator var3 = this.ignoredRequests.iterator();

        while(var3.hasNext()) {
            RequestMatcher ignoredRequest = (RequestMatcher)var3.next();
            securityFilterChains.add(new DefaultSecurityFilterChain(ignoredRequest, new Filter[0]));
        }

        var3 = this.securityFilterChainBuilders.iterator();

        while(var3.hasNext()) {
            SecurityBuilder<? extends SecurityFilterChain> securityFilterChainBuilder = (SecurityBuilder)var3.next();
            securityFilterChains.add(securityFilterChainBuilder.build());
        }

        FilterChainProxy filterChainProxy = new FilterChainProxy(securityFilterChains);
        if(this.httpFirewall != null) {
            filterChainProxy.setFirewall(this.httpFirewall);
        }

        filterChainProxy.afterPropertiesSet();
        Filter result = filterChainProxy;
        if(this.debugEnabled) {
            this.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);
        }

        this.postBuildAction.run();
        return (Filter)result;
    }

   
}

四、举例说明如何将一个Configurer转换为filter

ExpressionUrlAuthorizationConfigurer的继承关系
ExpressionUrlAuthorizationConfigurer->AbstractInterceptUrlConfigurer->AbstractHttpConfigurer->SecurityConfigurerAdapter->SecurityConfigurer
对应的init方法在SecurityConfigurerAdapter类中，是个空实现，什么也没有作，configure方法在SecurityConfigurerAdapter类中也有一个空实现，在AbstractInterceptUrlConfigurer类中进行了重写

Abstractintercepturlconfigurer.java代码

@Override  
    public void configure(H http) throws Exception {  
        FilterInvocationSecurityMetadataSource metadataSource = createMetadataSource(http);  
        if (metadataSource == null) {  
            return;  
        }  
        FilterSecurityInterceptor securityInterceptor = createFilterSecurityInterceptor(  
                http, metadataSource, http.getSharedObject(AuthenticationManager.class));  
        if (filterSecurityInterceptorOncePerRequest != null) {  
            securityInterceptor  
                    .setObserveOncePerRequest(filterSecurityInterceptorOncePerRequest);  
        }  
        securityInterceptor = postProcess(securityInterceptor);  
        http.addFilter(securityInterceptor);  
        http.setSharedObject(FilterSecurityInterceptor.class, securityInterceptor);  
    }  
...  
private AccessDecisionManager createDefaultAccessDecisionManager(H http) {  
        AffirmativeBased result = new AffirmativeBased(getDecisionVoters(http));  
        return postProcess(result);  
    }  
...  
private FilterSecurityInterceptor createFilterSecurityInterceptor(H http,               FilterInvocationSecurityMetadataSource metadataSource,               AuthenticationManager authenticationManager) throws Exception {  
        FilterSecurityInterceptor securityInterceptor = new FilterSecurityInterceptor();  
        securityInterceptor.setSecurityMetadataSource(metadataSource);  
        securityInterceptor.setAccessDecisionManager(getAccessDecisionManager(http));  
        securityInterceptor.setAuthenticationManager(authenticationManager);  
        securityInterceptor.afterPropertiesSet();  
        return securityInterceptor;  
    }

4.一、在这个类的configure中建立了一个FilterSecurityInterceptor，而且也能够明确看到spring security默认给咱们建立的AccessDecisionManager是AffirmativeBased。

4.二、.最后再看下HttpSecurity类执行build的最后一步 performBuild，这个方法就是在HttpSecurity中实现的

Httpsecurity.java代码

@Override  
    protected DefaultSecurityFilterChain performBuild() throws Exception {  
        Collections.sort(filters, comparator);  
        return new DefaultSecurityFilterChain(requestMatcher, filters);  
    }

能够看到，这个类只是把咱们追加到HttpSecurity中的security进行了排序，用的排序类是FilterComparator，从而保证咱们的filter按照正确的顺序执行。接着将filters构建成filterChian返回。在前面WebSecurity的performBuild方法中，这个返回值会被包装成FilterChainProxy，并做为WebSecurity的build方法的放回值。从而以springSecurityFilterChain这个名称注册到springContext中（在WebSecurityConfiguration中作的）

4.3.在WebSecurity的performBuild方法的最后一步还执行了一个postBuildAction.run，这个方法也是spring security给咱们提供的一个hooks，能够在build完成后再作一些事情，好比咱们在WebSecurityConfigurerAdapter类的init方法中咱们利用这个hook在构建完成后将FilterSecurityInterceptor赋值给了webSecurity类的filterSecurityInterceptor属性

3、用户登陆的验证和受权过程

一、用户一次完整的登陆验证和受权，是一个请求通过层层拦截器从而实现权限控制，整个web端配置为DelegatingFilterProxy（springSecurity的委托过滤其代理类），它并不实现真正的过滤，而是全部过滤器链的代理类，真正执行拦截处理的是由spring 容器管理的个个filter bean组成的filterChain.

调用实际的FilterChainProxy 的doFilterInternal()方法去获取全部的拦截器并进行过滤处理以下是DelegatingFilterProxy的doFilter（）方法

public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        Filter delegateToUse = this.delegate;
        if(delegateToUse == null) {
            Object var5 = this.delegateMonitor;
            synchronized(this.delegateMonitor) {
                delegateToUse = this.delegate;
                if(delegateToUse == null) {
                    WebApplicationContext wac = this.findWebApplicationContext();
                    if(wac == null) {
                        throw new IllegalStateException("No WebApplicationContext found: no ContextLoaderListener or DispatcherServlet registered?");
                    }

                    delegateToUse = this.initDelegate(wac);
                }

                this.delegate = delegateToUse;
            }
        }

//调用实际的FilterChainProxy 的doFilterInternal()方法 去获取全部的拦截器并进行过滤处理
        this.invokeDelegate(delegateToUse, request, response, filterChain);
    }

调用实际的FilterChainProxy 的doFilter()方法去获取全部的拦截器并进行过滤处理。

二、FilterChainProxy类

最终调用FilterChainProxy 的doFilterInternal()方法，获取全部的过滤器实例

public 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);
                //doFilter 调用doFilterInternal方法
                this.doFilterInternal(request, response, chain);
            } finally {
                SecurityContextHolder.clearContext();
                request.removeAttribute(FILTER_APPLIED);
            }
        } else {
            this.doFilterInternal(request, response, chain);
        }

    }

    private void doFilterInternal(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        FirewalledRequest fwRequest = this.firewall.getFirewalledRequest((HttpServletRequest)request);
        HttpServletResponse fwResponse = this.firewall.getFirewalledResponse((HttpServletResponse)response);
         //过去全部的过滤器
        List<Filter> filters = this.getFilters((HttpServletRequest)fwRequest);
        if(filters != null && filters.size() != 0) {
            FilterChainProxy.VirtualFilterChain vfc = new FilterChainProxy.VirtualFilterChain(fwRequest, chain, filters);
            vfc.doFilter(fwRequest, fwResponse);
        } else {
            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);
        }
    }


  private List<Filter> getFilters(HttpServletRequest request) {
       //遍历全部的matcher类 若是支持就继续获取
        Iterator var2 = this.filterChains.iterator();

        SecurityFilterChain chain;
        do {
            if(!var2.hasNext()) {
                return null;
            }

            chain = (SecurityFilterChain)var2.next();
        } while(!chain.matches(request));
        //后去匹配中的全部过滤器
        return chain.getFilters();
    }