spring security 源码学习（三）WebSecurityConfiguration

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本篇目标是解析WebSecurityConfiguration是如何初始化的

首先，看下他的源码。

/**
 * Uses a {@link WebSecurity} to create the {@link FilterChainProxy} that performs the web
 * based security for Spring Security. It then exports the necessary beans. Customizations
 * can be made to {@link WebSecurity} by extending {@link WebSecurityConfigurerAdapter}
 * and exposing it as a {@link Configuration} or implementing
 * {@link WebSecurityConfigurer} and exposing it as a {@link Configuration}. This
 * configuration is imported when using {@link EnableWebSecurity}.
 *
 * @see EnableWebSecurity
 * @see WebSecurity
 *
 * @author Rob Winch
 * @author Keesun Baik
 * @since 3.2
 */
@Configuration
public class WebSecurityConfiguration implements ImportAware, BeanClassLoaderAware {
	private WebSecurity webSecurity;

	private Boolean debugEnabled;

	private List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers;

	private ClassLoader beanClassLoader;

	@Autowired(required = false)
	private ObjectPostProcessor<Object> objectObjectPostProcessor;

	@Bean
	public static DelegatingApplicationListener delegatingApplicationListener() {
		return new DelegatingApplicationListener();
	}

	@Bean
	@DependsOn(AbstractSecurityWebApplicationInitializer.DEFAULT_FILTER_NAME)
	public SecurityExpressionHandler<FilterInvocation> webSecurityExpressionHandler() {
		return webSecurity.getExpressionHandler();
	}

	/**
	 * Creates the Spring Security Filter Chain
	 * @return
	 * @throws Exception
	 */
	@Bean(name = AbstractSecurityWebApplicationInitializer.DEFAULT_FILTER_NAME)
	public Filter springSecurityFilterChain() throws Exception {
		boolean hasConfigurers = webSecurityConfigurers != null
				&& !webSecurityConfigurers.isEmpty();
		if (!hasConfigurers) {
			WebSecurityConfigurerAdapter adapter = objectObjectPostProcessor
					.postProcess(new WebSecurityConfigurerAdapter() {
					});
			webSecurity.apply(adapter);
		}
		return webSecurity.build();
	}

	/**
	 * Creates the {@link WebInvocationPrivilegeEvaluator} that is necessary for the JSP
	 * tag support.
	 * @return the {@link WebInvocationPrivilegeEvaluator}
	 * @throws Exception
	 */
	@Bean
	@DependsOn(AbstractSecurityWebApplicationInitializer.DEFAULT_FILTER_NAME)
	public WebInvocationPrivilegeEvaluator privilegeEvaluator() throws Exception {
		return webSecurity.getPrivilegeEvaluator();
	}

	/**
	 * Sets the {@code <SecurityConfigurer<FilterChainProxy, WebSecurityBuilder>}
	 * instances used to create the web configuration.
	 *
	 * @param objectPostProcessor the {@link ObjectPostProcessor} used to create a
	 * {@link WebSecurity} instance
	 * @param webSecurityConfigurers the
	 * {@code <SecurityConfigurer<FilterChainProxy, WebSecurityBuilder>} instances used to
	 * create the web configuration
	 * @throws Exception
	 */
	@Autowired(required = false)
	public void setFilterChainProxySecurityConfigurer(
			ObjectPostProcessor<Object> objectPostProcessor,
			@Value("#{@autowiredWebSecurityConfigurersIgnoreParents.getWebSecurityConfigurers()}") List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers)
			throws Exception {
		webSecurity = objectPostProcessor
				.postProcess(new WebSecurity(objectPostProcessor));
		if (debugEnabled != null) {
			webSecurity.debug(debugEnabled);
		}

		Collections.sort(webSecurityConfigurers, AnnotationAwareOrderComparator.INSTANCE);

		Integer previousOrder = null;
		Object previousConfig = null;
		for (SecurityConfigurer<Filter, WebSecurity> config : webSecurityConfigurers) {
			Integer order = 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;
			previousConfig = config;
		}
		for (SecurityConfigurer<Filter, WebSecurity> webSecurityConfigurer : webSecurityConfigurers) {
			webSecurity.apply(webSecurityConfigurer);
		}
		this.webSecurityConfigurers = webSecurityConfigurers;
	}

	@Bean
	public AutowiredWebSecurityConfigurersIgnoreParents autowiredWebSecurityConfigurersIgnoreParents(
			ConfigurableListableBeanFactory beanFactory) {
		return new AutowiredWebSecurityConfigurersIgnoreParents(beanFactory);
	}

	/**
	 * A custom verision of the Spring provided AnnotationAwareOrderComparator that uses
	 * {@link AnnotationUtils#findAnnotation(Class, Class)} to look on super class
	 * instances for the {@link Order} annotation.
	 *
	 * @author Rob Winch
	 * @since 3.2
	 */
	private static class AnnotationAwareOrderComparator extends OrderComparator {
		private static final AnnotationAwareOrderComparator INSTANCE = new AnnotationAwareOrderComparator();

		@Override
		protected int getOrder(Object obj) {
			return lookupOrder(obj);
		}

		private static int lookupOrder(Object obj) {
			if (obj instanceof Ordered) {
				return ((Ordered) obj).getOrder();
			}
			if (obj != null) {
				Class<?> clazz = (obj instanceof Class ? (Class<?>) obj : obj.getClass());
				Order order = AnnotationUtils.findAnnotation(clazz, Order.class);
				if (order != null) {
					return order.value();
				}
			}
			return Ordered.LOWEST_PRECEDENCE;
		}
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see org.springframework.context.annotation.ImportAware#setImportMetadata(org.
	 * springframework.core.type.AnnotationMetadata)
	 */
	public void setImportMetadata(AnnotationMetadata importMetadata) {
		Map<String, Object> enableWebSecurityAttrMap = importMetadata
				.getAnnotationAttributes(EnableWebSecurity.class.getName());
		AnnotationAttributes enableWebSecurityAttrs = AnnotationAttributes
				.fromMap(enableWebSecurityAttrMap);
		debugEnabled = enableWebSecurityAttrs.getBoolean("debug");
		if (webSecurity != null) {
			webSecurity.debug(debugEnabled);
		}
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see
	 * org.springframework.beans.factory.BeanClassLoaderAware#setBeanClassLoader(java.
	 * lang.ClassLoader)
	 */
	public void setBeanClassLoader(ClassLoader classLoader) {
		this.beanClassLoader = classLoader;
	}
}

　　如这个类开头的注释写的一样，这个类的最后会生成一个FilterChainProxy类（一个Fliter），作为过滤器（链）来处理一个请求进入spring后进行的认证操作。我们挑着这里面比较重要的步骤进行分析下。

（一）AutowiredWebSecurityConfigurersIgnoreParents初始化

	@Bean
	public AutowiredWebSecurityConfigurersIgnoreParents autowiredWebSecurityConfigurersIgnoreParents(
			ConfigurableListableBeanFactory beanFactory) {
		return new AutowiredWebSecurityConfigurersIgnoreParents(beanFactory);
	}

　这个类有一个获取所有WebSecurityConfigurer子类实例的方法

	public List<SecurityConfigurer<Filter, WebSecurity>> getWebSecurityConfigurers() {
		List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers = new ArrayList<SecurityConfigurer<Filter, WebSecurity>>();
		Map<String, WebSecurityConfigurer> beansOfType = beanFactory
				.getBeansOfType(WebSecurityConfigurer.class);
		for (Entry<String, WebSecurityConfigurer> entry : beansOfType.entrySet()) {
			webSecurityConfigurers.add(entry.getValue());
		}
		return webSecurityConfigurers;
	}

　这个类的用途在下面

（二）WebSecurity实例化以及基本配置的设置

	@Autowired(required = false)
	public void setFilterChainProxySecurityConfigurer(
			ObjectPostProcessor<Object> objectPostProcessor,
　　　　　　　　　　　　　　　//利用上面的初始化的AutowiredWebSecurityConfigurersIgnoreParents的getWebSecurityConfigurers方法获取我们的Spring security的配置
			@Value("#{@autowiredWebSecurityConfigurersIgnoreParents.getWebSecurityConfigurers()}") List<SecurityConfigurer<Filter, WebSecurity>> webSecurityConfigurers)
			throws Exception {
　　　　　　　　　　//创建WebSecurity实例
		webSecurity = objectPostProcessor
				.postProcess(new WebSecurity(objectPostProcessor));
		if (debugEnabled != null) {
			webSecurity.debug(debugEnabled);
		}

		Collections.sort(webSecurityConfigurers, AnnotationAwareOrderComparator.INSTANCE);

		Integer previousOrder = null;
		Object previousConfig = null;
		for (SecurityConfigurer<Filter, WebSecurity> config : webSecurityConfigurers) {
			Integer order = 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;
			previousConfig = config;
		}
		for (SecurityConfigurer<Filter, WebSecurity> webSecurityConfigurer : webSecurityConfigurers) {
			webSecurity.apply(webSecurityConfigurer);
		}
		this.webSecurityConfigurers = webSecurityConfigurers;
	}

　　这个方法主要的操作是实例化WebSecurity，并将Spring security的配置设置为他的webSecurityConfigurers属性的值

 　  这边为了方便查看之前的配置，我们把配置类的代码也插入到这边

@Configuration
@EnableWebSecurity
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {
	@Override
	protected void configure(HttpSecurity http) throws Exception {
		http
			.authorizeRequests()
				.antMatchers("/", "/home").permitAll()
				.anyRequest().authenticated()
				.and()
			.formLogin()
				.loginPage("/login")
				.permitAll()
				.and()
			.logout()
				.permitAll();
	}

	@Bean
	@Override
	public UserDetailsService userDetailsService() {
		UserDetails user =
			 User.withDefaultPasswordEncoder()
				.username("user")
				.password("password")
				.roles("USER")
				.build();

		return new InMemoryUserDetailsManager(user);
	}
}

　　（三）springSecurityFilterChain初始化

	@Bean(name = AbstractSecurityWebApplicationInitializer.DEFAULT_FILTER_NAME)
	public Filter springSecurityFilterChain() throws Exception {
　　　　　　　　　　//step 1 
		boolean hasConfigurers = webSecurityConfigurers != null
				&& !webSecurityConfigurers.isEmpty();
		if (!hasConfigurers) {
			WebSecurityConfigurerAdapter adapter = objectObjectPostProcessor
					.postProcess(new WebSecurityConfigurerAdapter() {
					});
			webSecurity.apply(adapter);
		}
　　　　　　　　　　//step 2
		return webSecurity.build();
	}

　　就是这个方法，将最核心的Spring security的过滤器（链）初始化了。

　　这个方法的第一步就是判断当前是否配置了webSecurityConfigurers，如果没有，则会生成一个默认的：new WebSecurityConfigurerAdapter()，这个也就可以解释我刚接触Spring security时的困惑（为什么引入了Spring security的依赖后，我基本的配置类没写，我的接口就不能调用了？答：这边给了个默认的配置）

　　第二步就会对webSecurity进行构建：webSecurity.build()；

　　首先调用的是AbstractSecurityBuilder的build()方法

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

　　然后调用doBuild()方法，doBuild()是在AbstractSecurityBuilder的子类AbstractConfiguredSecurityBuilder中实现的

	@Override
	protected final O doBuild() throws Exception {
		synchronized (configurers) {
			buildState = BuildState.INITIALIZING;

			beforeInit();
			init();

			buildState = BuildState.CONFIGURING;

			beforeConfigure();
			configure();

			buildState = BuildState.BUILDING;

			O result = performBuild();

			buildState = BuildState.BUILT;

			return result;
		}
	}

　　这是一个很典型的模版方法模式，其中的beforeInit()和beforeConfigure()皆为钩子方法，这里默认也没有任何实现，我们暂时不用关注，主要需要注意的是init()、configure()和performBuild()方法。下面我们一个个分析这几个方法

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