Spring Security常用過濾器介紹

Spring Security常見的15個攔截器
1 . 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。
2 . 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
3 . 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
4 . 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。
5. 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。
6 . 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。
7 . 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。
8 . 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
9 . 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。
10 . org.springframework.security.web.savedrequest.RequestCacheAwareFilter
    通過HttpSessionRequestCache內部維護了一個RequestCache，用於緩存HttpServletRequest
11 . 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
12 . 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。
13 . org.springframework.security.web.session.SessionManagementFilter
   SecurityContextRepository限制同一用戶開啟多個會話的數量
14 . 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
15 . 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。

那么，是不是spring security一共就這么多過濾器呢？答案是否定的！隨着spring-security.xml配置的添加，還
會出現新的過濾器。
那么，是不是spring security每次都會加載這些過濾器呢？答案也是否定的！隨着spring-security.xml配置的修
改，有些過濾器可能會被去掉。
spring security 過濾器鏈加載原理

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：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);
}
}

 

第二步debug結果如下：

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;
//咿！？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();
}
}

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！

public interface SecurityFilterChain {

    boolean matches(HttpServletRequest request);

    List<Filter> getFilters();
}

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 requestMatcher;
    }

    public List<Filter> getFilters() {
        return filters;
    }

    public boolean matches(HttpServletRequest request) {
        return requestMatcher.matches(request);
    }

    @Override
    public String toString() {
        return "[ " + requestMatcher + ", " + filters + "]";
    }
}