Spring Security 6.x 系列（8）—— 源码分析之配置器SecurityConfigurer接口及其分支实现

一、前言

本章主要内容是关于配置器的接口架构设计，任意找一个配置器一直往上找，就会找到配置器的顶级接口：SecurityConfigurer。

查看SecurityConfigurer接口的实现类情况：

在这里插入图片描述

在 AbstractHttpConfigurer 抽象类的下面可以看到所有用来配置 HttpSecurity 的配置器实现类（也是构造器）。

再通过继承关系图，看看配置器顶层的架构：

在这里插入图片描述

会发现，其中：SecurityConfigurerAdapter和GlobalAuthenticationConfigurerAdapter对SecurityConfigurer接口进行了实现，而WebSecurityConfigurer对SecurityConfigurer接口进行了继承。

查看SecurityConfigurer源码:

源码注释：
Allows for configuring a SecurityBuilder. All SecurityConfigurer first have their init(SecurityBuilder) method invoked. After all init(SecurityBuilder) methods have been invoked, each configure(SecurityBuilder) method is invoked.
允许配置构造器SecurityBuilder。所有SecurityConfigurer首先调用其init(SecurityBuilderr) 方法。在调用了所有init(SecurityBuilderr) 方法之后，将调用每个configure(SecurityBuilderr) 方法。
请参阅:
AbstractConfiguredSecurityBuilder
作者:
Rob Winch
类型形参:
<O> – The object being built by the SecurityBuilder B 由构造器SecurityBuilder构造出最终目的O类型对象
 – The SecurityBuilder that builds objects of type O. This is also the SecurityBuilder that is being configured 构造出O类型对象的构造器SecurityBuilder，也是正在配置的构造器。

特殊说明：
SecurityConfigurer 的所有实现类都是用来配置构造器的。也就是说，泛型中 O 和 B 的关系是，B 用来构造 O。而配置器的作用是配置这个构造器的，从而影响最终构造的结果。

/**
 * Allows for configuring a {@link SecurityBuilder}. All {@link SecurityConfigurer} first
 * have their {@link #init(SecurityBuilder)} method invoked. After all
 * {@link #init(SecurityBuilder)} methods have been invoked, each
 * {@link #configure(SecurityBuilder)} method is invoked.
 *
 * @param <O> The object being built by the {@link SecurityBuilder} B
 * @param <B> The {@link SecurityBuilder} that builds objects of type O. This is also the
 * {@link SecurityBuilder} that is being configured.
 * @author Rob Winch
 * @see AbstractConfiguredSecurityBuilder
 */
public interface SecurityConfigurer<O, B extends SecurityBuilder<O>> {

	/**
	 * Initialize the {@link SecurityBuilder}. Here only shared state should be created
	 * and modified, but not properties on the {@link SecurityBuilder} used for building
	 * the object. This ensures that the {@link #configure(SecurityBuilder)} method uses
	 * the correct shared objects when building. Configurers should be applied here.
	 * 
	 * 初始化构造器B。在这里只应创建和修改共享状态，而不应在用于构造器B上创建和修改属性。
	 * 这确保了configure(SecurityBuilder)方法在构造时使用正确的共享对象。
	 * 应在此处应用配置程序。
	 * 
	 * @param builder
	 * @throws Exception
	 */
	void init(B builder) throws Exception;

	/**
	 * Configure the {@link SecurityBuilder} by setting the necessary properties on the
	 * 
	 * 通过在构造器B上设置必要的属性来配置构造器B。
	 * 
	 * {@link SecurityBuilder}.
	 * @param builder
	 * @throws Exception
	 */
	void configure(B builder) throws Exception;

}

下面我们分别对SecurityConfigurerAdapter、GlobalAuthenticationConfigurerAdapter、WebSecurityConfigurer三个分支进行源码分析。

二、SecurityConfigurerAdapter

源码注释：
A base class for SecurityConfigurer that allows subclasses to only implement the methods they are interested in. It also provides a mechanism for using the SecurityConfigurer and when done gaining access to the SecurityBuilder that is being configured.
SecurityConfigurer的基类，它允许子类仅实现它们感兴趣的方法。它还提供了配置SecurityConfigurer完成后获取正在配置的构造器SecurityBuilder的访问机制。
作者:
Rob Winch, Wallace Wadge
类型形参:
<O> – The Object being built by B 由SecurityBuilder构造器构造出最终目的O类型对象
 – The Builder that is building O and is configured by SecurityConfigurerAdapter 由SecurityConfigurerAdapter配置的构造器SecurityBuilder正在构造O

/**
 * A base class for {@link SecurityConfigurer} that allows subclasses to only implement
 * the methods they are interested in. It also provides a mechanism for using the
 * {@link SecurityConfigurer} and when done gaining access to the {@link SecurityBuilder}
 * that is being configured.
 *
 * @param <O> The Object being built by B
 * @param <B> The Builder that is building O and is configured by
 * {@link SecurityConfigurerAdapter}
 * @author Rob Winch
 * @author Wallace Wadge
 */
public abstract class SecurityConfigurerAdapter<O, B extends SecurityBuilder<O>> implements SecurityConfigurer<O, B> {

	private B securityBuilder;

	private CompositeObjectPostProcessor objectPostProcessor = new CompositeObjectPostProcessor();

	@Override
	public void init(B builder) throws Exception {
	}

	@Override
	public void configure(B builder) throws Exception {
	}

	/**
	 * Return the {@link SecurityBuilder} when done using the {@link SecurityConfigurer}.
	 * This is useful for method chaining.
	 * @return the {@link SecurityBuilder} for further customizations
	 * @deprecated For removal in 7.0. Use the lambda based configuration instead.
	 */
	@Deprecated(since = "6.1", forRemoval = true)
	public B and() {
		return getBuilder();
	}

	/**
	 * Gets the {@link SecurityBuilder}. Cannot be null.
	 * @return the {@link SecurityBuilder}
	 * @throws IllegalStateException if {@link SecurityBuilder} is null
	 */
	protected final B getBuilder() {
		Assert.state(this.securityBuilder != null, "securityBuilder cannot be null");
		return this.securityBuilder;
	}

	/**
	 * Performs post processing of an object. The default is to delegate to the
	 * {@link ObjectPostProcessor}.
	 * @param object the Object to post process
	 * @return the possibly modified Object to use
	 */
	@SuppressWarnings("unchecked")
	protected <T> T postProcess(T object) {
		return (T) this.objectPostProcessor.postProcess(object);
	}

	/**
	 * Adds an {@link ObjectPostProcessor} to be used for this
	 * {@link SecurityConfigurerAdapter}. The default implementation does nothing to the
	 * object.
	 * @param objectPostProcessor the {@link ObjectPostProcessor} to use
	 */
	public void addObjectPostProcessor(ObjectPostProcessor<?> objectPostProcessor) {
		this.objectPostProcessor.addObjectPostProcessor(objectPostProcessor);
	}

	/**
	 * Sets the {@link SecurityBuilder} to be used. This is automatically set when using
	 * {@link AbstractConfiguredSecurityBuilder#apply(SecurityConfigurerAdapter)}
	 * @param builder the {@link SecurityBuilder} to set
	 */
	public void setBuilder(B builder) {
		this.securityBuilder = builder;
	}

	/**
	 * An {@link ObjectPostProcessor} that delegates work to numerous
	 * {@link ObjectPostProcessor} implementations.
	 *
	 * @author Rob Winch
	 */
	private static final class CompositeObjectPostProcessor implements ObjectPostProcessor<Object> {

		private List<ObjectPostProcessor<?>> postProcessors = new ArrayList<>();

		@Override
		@SuppressWarnings({ "rawtypes", "unchecked" })
		public Object postProcess(Object object) {
			for (ObjectPostProcessor opp : this.postProcessors) {
				Class<?> oppClass = opp.getClass();
				Class<?> oppType = GenericTypeResolver.resolveTypeArgument(oppClass, ObjectPostProcessor.class);
				if (oppType == null || oppType.isAssignableFrom(object.getClass())) {
					object = opp.postProcess(object);
				}
			}
			return object;
		}

		/**
		 * Adds an {@link ObjectPostProcessor} to use
		 * @param objectPostProcessor the {@link ObjectPostProcessor} to add
		 * @return true if the {@link ObjectPostProcessor} was added, else false
		 */
		private boolean addObjectPostProcessor(ObjectPostProcessor<?> objectPostProcessor) {
			boolean result = this.postProcessors.add(objectPostProcessor);
			this.postProcessors.sort(AnnotationAwareOrderComparator.INSTANCE);
			return result;
		}

	}

}

内容很简单：

有一个内部类CompositeObjectPostProcessor：复合后置处理器对象类
定义了两个成员变量：
- 将要配置的构造器 securityBuilder
- 复合后置处理器 objectPostProcessor
从接口中实现的方法和自己新加的几个方法
- init 和 configure 是实现接口的方法
- and、getBuilder、postProcess、addObjectPostProcessor、setBuilder 方法是自己加的

2.1 允许子类只实现他们感兴趣的方法

在源码中可以看到，所有的方法都有方法体，包括对接口方法的实现（虽然是空方法体）。所以继承 SecurityConfigurerAdapter 的配置器可以根据自己的需求实现（覆盖）自己感兴趣的方法。

可以自己实现 init ，如果自己不需要初始化，也可以不实现，在构造器调用其 init 方法时什么也不做。

2.2 setBuilder 方法

这个方法有点特别，所以单独说一下，方法内容很简单，就是设置配置器的成员变量private B securityBuilder（即：构造器），但是官网又这样一句注释：

Sets the SecurityBuilder to be used.
This is automatically set when using AbstractConfiguredSecurityBuilder.apply(SecurityConfigurerAdapter)

第一句很好理解：这个方法是来设置要使用的构造器（private B securityBuilder，其B extends SecurityBuilder<O>）。

第二句就是当 AbstractConfiguredSecurityBuilder.apply(SecurityConfigurerAdapter) 调用时被自动设置。

回顾上篇中的4.4.7章节：

/**
 * Applies a {@link SecurityConfigurerAdapter} to this {@link SecurityBuilder} and
 * invokes {@link SecurityConfigurerAdapter#setBuilder(SecurityBuilder)}.
 * @param configurer
 * @return the {@link SecurityConfigurerAdapter} for further customizations
 * @throws Exception
 */
@SuppressWarnings("unchecked")
public <C extends SecurityConfigurerAdapter<O, B>> C apply(C configurer) throws Exception {
	configurer.addObjectPostProcessor(this.objectPostProcessor);
	configurer.setBuilder((B) this);
	add(configurer);
	return configurer;
}

可以看出，configurer在被调用之前是不知道要配置哪个构造器的。在构造器调用 apply 方法时才真正设置配置器的成员变量（即：构造器）。所以官方注释才说 setBuilder 方法时自动调用的，我们不能手动去设置。

只有构造器(B) this应用了这个配置器configurer，这个配置器configurer才会绑定上这个构造器(B) this。

2.3 and 方法

and 方法提供了一种使用完配置器后获得正在配置的构造器SecurityBuilder对象的机制。

有必要说一下为什么是正在配置，因为在这个时候还没有对构造器private B securityBuilder 进行配置。

在上篇文章中讲解Builder设计模式时，提到过构造器的构造时机在调用构造器的 build 方法，在doBuild方法中加入了构造生命周期控制，在里面才开始调用各个配置器的 init 方法和 configure 方法。所以这里获取到的时正在配置的构造器private B securityBuilder对象。

在构造器的构造过程中利用配置器进行配置，从而影响最终构造的结果。

2.4 复合后置处理对象

这个内部类对象很简单，看一下内部类的内容就明白了：它维护的是一个 List 集合

private List<ObjectPostProcessor<?>> postProcessors = new ArrayList<>();

因此称之为：复合后置处理对象（CompositeObjectPostProcessor），就是里面有多个。

2.5 DEBUG 参数跟踪

AbstractConfiguredSecurityBuilder#apply：

在这里插入图片描述
SecurityConfigurerAdapter#setBuilder：

在这里插入图片描述

由上可知： SecurityConfigurerAdapter中设置的构造器为HttpSecurity。

三、GlobalAuthenticationConfigurerAdapter

这个类的类名说明它是一个全局配置相关的类。

/**
 * A {@link SecurityConfigurer} that can be exposed as a bean to configure the global
 * {@link AuthenticationManagerBuilder}. Beans of this type are automatically used by
 * {@link AuthenticationConfiguration} to configure the global
 * {@link AuthenticationManagerBuilder}.
 *
 * @author Rob Winch
 * @since 5.0
 */
@Order(100)
public abstract class GlobalAuthenticationConfigurerAdapter
		implements SecurityConfigurer<AuthenticationManager, AuthenticationManagerBuilder> {

	@Override
	public void init(AuthenticationManagerBuilder auth) throws Exception {
	}

	@Override
	public void configure(AuthenticationManagerBuilder auth) throws Exception {
	}

}

从源码可以看出它实现 SecurityConfigurer 接口，没有具体的实现内容，只是对构造器和构造器将要构造的对象做了限制：

将要配置的构造器：AuthenticationManagerBuilder

可以作为bean公开以配置全局构造器AuthenticationManagerBuilder。
将要构造的对象：AuthenticationManager

将被构造器构造出最终目的类型AuthenticationManager。

四、WebSecurityConfigurer

/**
 * Allows customization to the {@link WebSecurity}. In most instances users will use
 * {@link EnableWebSecurity} and create a {@link Configuration} that exposes a
 * {@link SecurityFilterChain} bean. This will automatically be applied to the
 * {@link WebSecurity} by the {@link EnableWebSecurity} annotation.
 *
 * @author Rob Winch
 * @since 3.2
 * @see SecurityFilterChain
 */
public interface WebSecurityConfigurer<T extends SecurityBuilder<Filter>> extends SecurityConfigurer<Filter, T> {

}

该接口继承SecurityConfigurer接口，从源码中可以看出，它没有定义自己的方法，所有的方法都是从父接口继承，那么它的作用还有配置构造器SecurityBuilder，但是它对类型做了约束：

将要输入WebSecurityConfigurer 的泛型为 T

T继承了SecurityBuilder，所有T表示一个对象构建器 (SecurityBuilder)
传入SecurityBuilder的泛型Filter (javax.servlet.Filter)

表示 SecurityBuilder 将要创建的对象是一个 javax.servet.Filter，也就是说，它约束了T，说明T的作用是构建 Filter
将要传入父接口SecurityConfiqurer的两个泛型：Filter和 T

WebSecurityConfigurer 继承 SecurityConfigurer，从这里可以看出，对SecurityConfigurer做了约束，目前只有T还没有指定具体的类型，至于最终使用什么类型的构造器由实现类活着子接口指定。