常用過濾器
- org.springframework.security.web.context.SecurityContextPersistenceFilter
首當其沖的一個過濾器，作用之重要，自不必多言。
SecurityContextPersistenceFilter主要是使用SecurityContextRepository在session中保存或更新一個
SecurityContext，並將SecurityContext給以后的過濾器使用，來為后續filter建立所需的上下文。
SecurityContext中存儲了當前用戶的認證以及權限信息。
- org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter
此過濾器用於集成SecurityContext到Spring異步執行機制中的WebAsyncManager
- org.springframework.security.web.header.HeaderWriterFilter
向請求的Header中添加相應的信息,可在http標簽內部使用security:headers來控制
- org.springframework.security.web.csrf.CsrfFilter
csrf又稱跨域請求偽造，SpringSecurity會對所有post請求驗證是否包含系統生成的csrf的token信息，
如果不包含，則報錯。起到防止csrf攻擊的效果。
- org.springframework.security.web.authentication.logout.LogoutFilter
匹配URL為/logout的請求，實現用戶退出,清除認證信息。
- org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter
認證操作全靠這個過濾器，默認匹配URL為/login且必須為POST請求。
- org.springframework.security.web.authentication.ui.DefaultLoginPageGeneratingFilter
如果沒有在配置文件中指定認證頁面，則由該過濾器生成一個默認認證頁面。
- org.springframework.security.web.authentication.ui.DefaultLogoutPageGeneratingFilter
由此過濾器可以生產一個默認的退出登錄頁面
- org.springframework.security.web.authentication.www.BasicAuthenticationFilter
此過濾器會自動解析HTTP請求中頭部名字為Authentication，且以Basic開頭的頭信息。
- org.springframework.security.web.savedrequest.RequestCacheAwareFilter
通過HttpSessionRequestCache內部維護了一個RequestCache，用於緩存HttpServletRequest
- org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter
針對ServletRequest進行了一次包裝，使得request具有更加豐富的API
- org.springframework.security.web.authentication.AnonymousAuthenticationFilter
當SecurityContextHolder中認證信息為空,則會創建一個匿名用戶存入到SecurityContextHolder中。
spring security為了兼容未登錄的訪問，也走了一套認證流程，只不過是一個匿名的身份。
- org.springframework.security.web.session.SessionManagementFilter
SecurityContextRepository限制同一用戶開啟多個會話的數量
- org.springframework.security.web.access.ExceptionTranslationFilter
異常轉換過濾器位於整個springSecurityFilterChain的后方，用來轉換整個鏈路中出現的異常
- org.springframework.security.web.access.intercept.FilterSecurityInterceptor
獲取所配置資源訪問的授權信息，根據SecurityContextHolder中存儲的用戶信息來決定其是否有權
限。
DelegatingFilterProxy
我們在web.xml中配置了一個名稱為springSecurityFilterChain的過濾器DelegatingFilterProxy，接下直接對
DelegatingFilterProxy源碼里重要代碼進行說明，其中刪減掉了一些不重要的代碼。
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：這個過濾器才是真正加載的過濾器
private final Object delegateMonitor;
//注：doFilter才是過濾器的入口，直接從這看！
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，初始化上面私有過濾器屬性delegate
delegateToUse = this.initDelegate(wac);
}
this.delegate = delegateToUse;
}
}
//第三步：執行FilterChainProxy過濾器
this.invokeDelegate(delegateToUse, request, response, filterChain);
}
//第二步：直接看最終加載的過濾器到底是誰
protected Filter initDelegate(WebApplicationContext wac) throws ServletException {
//debug得知targetBeanName為：springSecurityFilterChain
String targetBeanName = this.getTargetBeanName();
Assert.state(targetBeanName != null, "No target bean name set");
//debug得知delegate對象為：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通過springSecurityFilterChain這個名稱，得到了一個FilterChainProxy過濾器，
最終在第三步執行了這個過濾器。
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;
// 可以通過一個叫SecurityFilterChain的對象實例化出一個FilterChainProxy對象
// 這FilterChainProxy又是何方神聖？會不會是真正的過濾器鏈對象呢？先留着這個疑問！
public FilterChainProxy(SecurityFilterChain chain) {
this(Arrays.asList(chain));
}
//又是SecurityFilterChain這家伙！嫌疑更大了！
public FilterChainProxy(List<SecurityFilterChain> filterChains) {
this.filterChainValidator = new FilterChainProxy.NullFilterChainValidator();
this.firewall = new StrictHttpFirewall();
this.filterChains = filterChains;
}
//注：直接從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：具體操作調用下面的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：封裝要執行的過濾器鏈，那么多過濾器就在這里被封裝進去了！
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：加載過濾器鏈
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：封裝過濾器鏈到SecurityFilterChain中！
SecurityFilterChain chain;
do {
if (!var2.hasNext()) {
return null;
}
chain = (SecurityFilterChain) var2.next();
} while (!chain.matches(request));
return chain.getFilters();
}
}
看完上面的代碼，原來這些過濾器都被封裝進SecurityFilterChain中了。
SecurityFilterChain
最后看SecurityFilterChain，這是個接口，實現類也只有一個，這才是web.xml中配置的過濾器鏈對象！
//接口
public interface SecurityFilterChain {
boolean matches(HttpServletRequest var1);
List<Filter> getFilters();
}
//實現類
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 + "]";
}
}