常用过滤器
- org.springframework.security.web.context.SecurityContextPersistenceFilter
首当其冲的一个过滤器，作用之重要，自不必多言。
SecurityContextPersistenceFilter主要是使用SecurityContextRepository在session中保存或更新一个
SecurityContext，并将SecurityContext给以后的过滤器使用，来为后续filter建立所需的上下文。
SecurityContext中存储了当前用户的认证以及权限信息。
- org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter
此过滤器用于集成SecurityContext到Spring异步执行机制中的WebAsyncManager
- org.springframework.security.web.header.HeaderWriterFilter
向请求的Header中添加相应的信息,可在http标签内部使用security:headers来控制
- org.springframework.security.web.csrf.CsrfFilter
csrf又称跨域请求伪造，SpringSecurity会对所有post请求验证是否包含系统生成的csrf的token信息，
如果不包含，则报错。起到防止csrf攻击的效果。
- org.springframework.security.web.authentication.logout.LogoutFilter
匹配URL为/logout的请求，实现用户退出,清除认证信息。
- org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter
认证操作全靠这个过滤器，默认匹配URL为/login且必须为POST请求。
- org.springframework.security.web.authentication.ui.DefaultLoginPageGeneratingFilter
如果没有在配置文件中指定认证页面，则由该过滤器生成一个默认认证页面。
- org.springframework.security.web.authentication.ui.DefaultLogoutPageGeneratingFilter
由此过滤器可以生产一个默认的退出登录页面
- org.springframework.security.web.authentication.www.BasicAuthenticationFilter
此过滤器会自动解析HTTP请求中头部名字为Authentication，且以Basic开头的头信息。
- org.springframework.security.web.savedrequest.RequestCacheAwareFilter
通过HttpSessionRequestCache内部维护了一个RequestCache，用于缓存HttpServletRequest
- org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter
针对ServletRequest进行了一次包装，使得request具有更加丰富的API
- org.springframework.security.web.authentication.AnonymousAuthenticationFilter
当SecurityContextHolder中认证信息为空,则会创建一个匿名用户存入到SecurityContextHolder中。
spring security为了兼容未登录的访问，也走了一套认证流程，只不过是一个匿名的身份。
- org.springframework.security.web.session.SessionManagementFilter
SecurityContextRepository限制同一用户开启多个会话的数量
- 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
- 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。
DelegatingFilterProxy
我们在web.xml中配置了一个名称为springSecurityFilterChain的过滤器DelegatingFilterProxy，接下直接对
DelegatingFilterProxy源码里重要代码进行说明，其中删减掉了一些不重要的代码。
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);
}
}
由此可知，DelegatingFilterProxy通过springSecurityFilterChain这个名称，得到了一个FilterChainProxy过滤器，
最终在第三步执行了这个过滤器。
FilterChainProxy
public class FilterChainProxy extends GenericFilterBean {
private static final Log logger = LogFactory.getLog(FilterChainProxy.class);
private static final String FILTER_APPLIED = FilterChainProxy.class.getName().concat(".APPLIED");
private List<SecurityFilterChain> filterChains;
private FilterChainProxy.FilterChainValidator filterChainValidator;
private HttpFirewall firewall;
// 可以通过一个叫SecurityFilterChain的对象实例化出一个FilterChainProxy对象
// 这FilterChainProxy又是何方神圣？会不会是真正的过滤器链对象呢？先留着这个疑问！
public FilterChainProxy(SecurityFilterChain chain) {
this(Arrays.asList(chain));
}
//又是SecurityFilterChain这家伙！嫌疑更大了！
public FilterChainProxy(List<SecurityFilterChain> filterChains) {
this.filterChainValidator = new FilterChainProxy.NullFilterChainValidator();
this.firewall = new StrictHttpFirewall();
this.filterChains = filterChains;
}
//注：直接从doFilter看
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
boolean clearContext = request.getAttribute(FILTER_APPLIED) == null;
if (clearContext) {
try {
request.setAttribute(FILTER_APPLIED, Boolean.TRUE);
this.doFilterInternal(request, response, chain);
} finally {
SecurityContextHolder.clearContext();
request.removeAttribute(FILTER_APPLIED);
}
} else {
//第一步：具体操作调用下面的doFilterInternal方法了
this.doFilterInternal(request, response, chain);
}
}
private void doFilterInternal(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
FirewalledRequest fwRequest = this.firewall.getFirewalledRequest((HttpServletRequest) request);
HttpServletResponse fwResponse = this.firewall.getFirewalledResponse((HttpServletResponse) response);
//第二步：封装要执行的过滤器链，那么多过滤器就在这里被封装进去了！
List<Filter> filters = this.getFilters((HttpServletRequest) fwRequest);
if (filters != null && filters.size() != 0) {
FilterChainProxy.VirtualFilterChain vfc = new FilterChainProxy.VirtualFilterChain(fwRequest, chain, filters);
//第四步：加载过滤器链
vfc.doFilter(fwRequest, fwResponse);
} else {
if (logger.isDebugEnabled()) {
logger.debug(UrlUtils.buildRequestUrl(fwRequest) + (filters == null ? " has no matching filters" : " has an empty filter list"));
}
fwRequest.reset();
chain.doFilter(fwRequest, fwResponse);
}
}
private List<Filter> getFilters(HttpServletRequest request) {
Iterator var2 = this.filterChains.iterator();
//第三步：封装过滤器链到SecurityFilterChain中！
SecurityFilterChain chain;
do {
if (!var2.hasNext()) {
return null;
}
chain = (SecurityFilterChain) var2.next();
} while (!chain.matches(request));
return chain.getFilters();
}
}
看完上面的代码，原来这些过滤器都被封装进SecurityFilterChain中了。
SecurityFilterChain
最后看SecurityFilterChain，这是个接口，实现类也只有一个，这才是web.xml中配置的过滤器链对象！
//接口
public interface SecurityFilterChain {
boolean matches(HttpServletRequest var1);
List<Filter> getFilters();
}
//实现类
public final class DefaultSecurityFilterChain implements SecurityFilterChain {
private static final Log logger = LogFactory.getLog(DefaultSecurityFilterChain.class);
private final RequestMatcher requestMatcher;
private final List<Filter> filters;
public DefaultSecurityFilterChain(RequestMatcher requestMatcher, Filter... filters) {
this(requestMatcher, Arrays.asList(filters));
}
public DefaultSecurityFilterChain(RequestMatcher requestMatcher, List<Filter> filters) {
logger.info("Creating filter chain: " + requestMatcher + ", " + filters);
this.requestMatcher = requestMatcher;
this.filters = new ArrayList(filters);
}
public RequestMatcher getRequestMatcher() {
return this.requestMatcher;
}
public List<Filter> getFilters() {
return this.filters;
}
public boolean matches(HttpServletRequest request) {
return this.requestMatcher.matches(request);
}
public String toString() {
return "[ " + this.requestMatcher + ", " + this.filters + "]";
}
}