HttpSecurity

https://www.jianshu.com/p/6f1b129442a1；
WebSecurityConfigurerAdapter的初始化方法init()中，通过getHttp()方法获取到了HttpSecurity的对象；

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

先构建HttpSecurity对象，然后通过WebSecurity对象的addSecurityFilterChainBuilder()方法添加到securityFilterChainBuilders的List中，最后用来组件过滤器链。

getHttp方法

	protected final HttpSecurity getHttp() throws Exception {
		if (http != null) {
			return http;
		}

		AuthenticationEventPublisher eventPublisher = getAuthenticationEventPublisher();
		localConfigureAuthenticationBldr.authenticationEventPublisher(eventPublisher);

		AuthenticationManager authenticationManager = authenticationManager();
		authenticationBuilder.parentAuthenticationManager(authenticationManager);
		Map<Class<?>, Object> sharedObjects = createSharedObjects();

		http = new HttpSecurity(objectPostProcessor, authenticationBuilder,
				sharedObjects);
		if (!disableDefaults) {
			// @formatter:off
			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();
			// @formatter:on
			ClassLoader classLoader = this.context.getClassLoader();
			List<AbstractHttpConfigurer> defaultHttpConfigurers =
					SpringFactoriesLoader.loadFactories(AbstractHttpConfigurer.class, classLoader);

			for (AbstractHttpConfigurer configurer : defaultHttpConfigurers) {
				http.apply(configurer);
			}
		}
		configure(http);
		return http;
	}

可以从上面的代码中可以知道，因为HttpSecurity构造函数需要AuthenticationManagerBuilder和sharedObjects 对象，上面的代码先创建AuthenticationManagerBuilder的对象，然后填充了共享对象的map，然后调用HttpSecueity的构造函数构造出来一个HttpSecurity的对象，然后configure(http)