spring-security的过滤器执行

1.众所周知spring-security是一个过滤器链形成的安全web架构，那么这些过滤器链都是如何执行的呢？下面就讲解执行过程。

@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {

		// Lazily initialize the delegate if necessary.
		Filter delegateToUse = this.delegate;
		if (delegateToUse == null) {
			synchronized (this.delegateMonitor) {
				if (this.delegate == null) {
					WebApplicationContext wac = findWebApplicationContext();
					if (wac == null) {
						throw new IllegalStateException("No WebApplicationContext found: no ContextLoaderListener registered?");
					}
					this.delegate = initDelegate(wac);
				}
				delegateToUse = this.delegate;
			}
		}

		// Let the delegate perform the actual doFilter operation.
		invokeDelegate(delegateToUse, request, response, filterChain);
	}

invokeDelegate就是执行过滤器链FilterChainProxy,然后执行配置的过滤器链。其中UsernamePasswordAuthenticationFilter就是账号密码校验过滤器，

public Authentication attemptAuthentication(HttpServletRequest request, HttpServletResponse response) throws AuthenticationException {
        if(this.postOnly && !request.getMethod().equals("POST")) {
            throw new AuthenticationServiceException("Authentication method not supported: " + request.getMethod());
        } else {
            String username = this.obtainUsername(request);
            String password = this.obtainPassword(request);
            if(username == null) {
                username = "";
            }

            if(password == null) {
                password = "";
            }

            username = username.trim();
            UsernamePasswordAuthenticationToken authRequest = new UsernamePasswordAuthenticationToken(username, password);
            this.setDetails(request, authRequest);
            return this.getAuthenticationManager().authenticate(authRequest);
        }
    }

this.getAuthenticationManager()就是providerManager，最终由providerManager提供校验。