同事提了一個要求，要求對外提供的接口不需要經過單點登錄驗證，我剛開始想，這簡單，提供不需要攔截的url數組，在AuthenticationFilter里面對url進行檢查，在此數組內，就不需要攔截。
下面是AuthenticationFilter類的doFilter方法的部分源碼：
public final void doFilter(final ServletRequest servletRequest, final ServletResponse servletResponse, final FilterChain filterChain) throws IOException, ServletException { final HttpServletRequest request = (HttpServletRequest) servletRequest; final HttpServletResponse response = (HttpServletResponse) servletResponse;
//在此寫驗證url if (isRequestUrlExcluded(request)) { logger.debug("Request is ignored."); filterChain.doFilter(request, response); return; } final HttpSession session = request.getSession(false); final Assertion assertion = session != null ? (Assertion) session.getAttribute(CONST_CAS_ASSERTION) : null; if (assertion != null) { filterChain.doFilter(request, response); return; }
以上是部分源碼，本來我想在注釋的地方，對url進行檢查，但是下面一行的 isRequestUrlExcluded(request)，這不正是檢查URL排除的地方嗎？原來cas-client已經實現了此功能。下面我們一步步的梳理代碼。
isRequestUrlExcluded的方法如下：
private boolean isRequestUrlExcluded(final HttpServletRequest request) { if (this.ignoreUrlPatternMatcherStrategyClass == null) { return false; } final StringBuffer urlBuffer = request.getRequestURL(); if (request.getQueryString() != null) { urlBuffer.append("?").append(request.getQueryString()); } final String requestUri = urlBuffer.toString(); return this.ignoreUrlPatternMatcherStrategyClass.matches(requestUri); }
我們可以看到這里的關鍵是ignoreUrlPatternMatcherStrategyClass，忽略Url模式驗證策略類。
1 protected void initInternal(final FilterConfig filterConfig) throws ServletException { 2 if (!isIgnoreInitConfiguration()) { 3 super.initInternal(filterConfig); 4 setCasServerLoginUrl(getString(ConfigurationKeys.CAS_SERVER_LOGIN_URL)); 5 setRenew(getBoolean(ConfigurationKeys.RENEW)); 6 setGateway(getBoolean(ConfigurationKeys.GATEWAY)); 7
8 final String ignorePattern = getString(ConfigurationKeys.IGNORE_PATTERN); 9 final String ignoreUrlPatternType = getString(ConfigurationKeys.IGNORE_URL_PATTERN_TYPE); 10
11 if (ignorePattern != null) { 12 final Class<? extends UrlPatternMatcherStrategy> ignoreUrlMatcherClass = PATTERN_MATCHER_TYPES.get(ignoreUrlPatternType); 13 if (ignoreUrlMatcherClass != null) { 14 this.ignoreUrlPatternMatcherStrategyClass = ReflectUtils.newInstance(ignoreUrlMatcherClass.getName()); 15 } else { 16 try { 17 logger.trace("Assuming {} is a qualified class name...", ignoreUrlPatternType); 18 this.ignoreUrlPatternMatcherStrategyClass = ReflectUtils.newInstance(ignoreUrlPatternType); 19 } catch (final IllegalArgumentException e) { 20 logger.error("Could not instantiate class [{}]", ignoreUrlPatternType, e); 21 } 22 }
紅色部分是實例化，是關鍵。我們從第八行開始看起，分別是獲取ignorePattern和ignoreUrlPatternType參數，兩者的意思分別是忽略的url和忽略的模式。
ConfigurationKey<String> IGNORE_PATTERN = new ConfigurationKey<String>("ignorePattern", null); ConfigurationKey<String> IGNORE_URL_PATTERN_TYPE = new ConfigurationKey<String>("ignoreUrlPatternType", "REGEX");
可以看到代碼默認的識別url的方式是正則表達式。而識別方式一共有三種，我們看一下PATTERN_MATCHER_TYPES，分別是包含、正則和精確。
1 private static final Map<String, Class<? extends UrlPatternMatcherStrategy>> PATTERN_MATCHER_TYPES =
2 new HashMap<String, Class<? extends UrlPatternMatcherStrategy>>(); 3
4 static { 5 PATTERN_MATCHER_TYPES.put("CONTAINS", ContainsPatternUrlPatternMatcherStrategy.class); 6 PATTERN_MATCHER_TYPES.put("REGEX", RegexUrlPatternMatcherStrategy.class); 7 PATTERN_MATCHER_TYPES.put("EXACT", ExactUrlPatternMatcherStrategy.class); 8 }
因此，我們只需在web.xml中的過濾器上添加參數來配置不需要單點登錄攔截url（例子是如果url中包含/service/，則不需要經過單點登錄驗證）。
<filter>
<filter-name>casAuthenticationFilter</filter-name>
<filter-class>org.jasig.cas.client.authentication.AuthenticationFilter</filter-class>
<init-param>
<param-name>casServerLoginUrl</param-name>
<param-value>http://cas.eguid.cc/cas-server/</param-value>
</init-param>
<init-param>
<param-name>serverName</param-name>
<param-value>http://cilent.eguid.cc/</param-value>
</init-param>
<init-param> <description>不攔截的請求</description> <param-name>ignorePattern</param-name> <param-value>/service/</param-value> </init-param> <init-param> <description>識別模式</description> <param-name>ignoreUrlPatternType</param-name> <param-value>CONTAINS</param-value> </init-param>
</filter>
<filter-mapping>
<filter-name>casAuthenticationFilter</filter-name>
<url-pattern>/*</url-pattern>