14 . org.springframework.security.web.access.ExceptionTranslationFilter
异常转换过滤器位于整个springSecurityFilterChain的后方，用来转换整个链路中出现的异常
15 . org.springframework.security.web.access.intercept.FilterSecurityInterceptor
获取所配置资源访问的授权信息，根据SecurityContextHolder中存储的用户信息来决定其是否有权限。
那么，是不是spring security一共就这么多过滤器呢？答案是否定的！随着spring-security.xml配置的添加，还
会出现新的过滤器。
那么，是不是spring security每次都会加载这些过滤器呢？答案也是否定的！随着spring-security.xml配置的修
改，有些过滤器可能会被去掉。
spring security 过滤器链加载原理
public class DelegatingFilterProxy extends GenericFilterBean {
@Nullable
private String contextAttribute;
@Nullable
private WebApplicationContext webApplicationContext;
@Nullable
private String targetBeanName;
private boolean targetFilterLifecycle;
@Nullable
private volatile Filter delegate;//注：这个过滤器才是真正加载的过滤器
private final Object delegateMonitor;
//注：doFilter才是过滤器的入口，直接从这看！
public void doFilter(ServletRequest request, ServletResponse response, FilterChain
filterChain) throws ServletException, IOException {
Filter delegateToUse = this.delegate;
if (delegateToUse == null) {
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?");
}
//第一步：doFilter中最重要的一步，初始化上面私有过滤器属性delegate
delegateToUse = this.initDelegate(wac);
}
this.delegate = delegateToUse;
}
}
//第三步：执行FilterChainProxy过滤器
this.invokeDelegate(delegateToUse, request, response, filterChain);
}
//第二步：直接看最终加载的过滤器到底是谁
protected Filter initDelegate(WebApplicationContext wac) throws ServletException {
//debug得知targetBeanName为：springSecurityFilterChain
String targetBeanName = this.getTargetBeanName();
Assert.state(targetBeanName != null, "No target bean name set");
//debug得知delegate对象为：FilterChainProxy
Filter delegate = (Filter)wac.getBean(targetBeanName, Filter.class);
if (this.isTargetFilterLifecycle()) {
delegate.init(this.getFilterConfig());
}
return delegate;
}
protected void invokeDelegate(Filter delegate, ServletRequest request, ServletResponse
response, FilterChain filterChain) throws ServletException, IOException {
delegate.doFilter(request, response, filterChain);
}
}
第二步debug结果如下：
