前言：今天在网上无意间看到cas单点登录排除请求的问题，发现很多人在讨论如何通过改写AuthenticationFilter类来实现忽略/排除请求URL的功能；突发奇想搜了一下，还真蛮多人都是这么干的，原谅我是个耿直的boy，当时我笑的饭都喷出来了，只需要一个配置的问题，被你们搞的这么麻烦；虽然很想回复他们“你们这帮人用别人的东西都不看源码的吗？”，转念一想，这也要怪作者不给力，文档里压根没有提到这个配置，在这里用少量篇幅讲解如何配置排除不需要拦截的请求URL,后面用大量篇幅介绍我是如何从源码中得知这个配置的，希望对大家有用！做好自己！--eguid始终坚持原创的开源技术文章分享，博客园与本博客保持同步更新。欢迎大家加群一起交流：608423839

1、cas-client单点登录配置

http://blog.csdn.net/eguid_1/article/details/51278622，cas-client完整配置。

没有实现忽略/排除请求URL的cas-client登录验证过滤器

<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>https://cas.eguid.cc/cas-server/</param-value>
</init-param>
<init-param>
<param-name>serverName</param-name>
<param-value>http://client.eguid.cc/</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>casAuthenticationFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

这个配置依然是可用的，当然我们要实现忽略/排除请求URL的功能，那么我们该怎么做呢？

2、忽略/排除多个请求URL

<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>
<param-name>ignorePattern</param-name>
<param-value>/js/*|/img/*|/view/*|/css/*</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>casAuthenticationFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

如上所见，我们排除了四个请求URL（必须是正则表达式形式，下面会讲为什么要这么配置）

3、cas-client默认登录验证过滤器源码解析

看源码，一定要带着目的去看；我们的目的就是找AuthenticationFilter这个cas-client默认登录验证过滤器是否具有排除登录请求URL的功能。

（1）打开cas-client项目源码

打开github上的cas-client项目，可以把项目导到本地或者直接在github上找到org.jasig.cas.client.authentication.AuthenticationFilter.Java这个类。

（2）登录验证过滤器AuthenticationFilter的doFilter

既然是个过滤器，就直接找到该类的doFilter方法

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;
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;
}
final String serviceUrl = constructServiceUrl(request, response);
final String ticket = retrieveTicketFromRequest(request);
final boolean wasGatewayed = this.gateway && this.gatewayStorage.hasGatewayedAlready(request, serviceUrl);
if (CommonUtils.isNotBlank(ticket) || wasGatewayed) {
filterChain.doFilter(request, response);
return;
}
final String modifiedServiceUrl;
logger.debug("no ticket and no assertion found");
if (this.gateway) {
logger.debug("setting gateway attribute in session");
modifiedServiceUrl = this.gatewayStorage.storeGatewayInformation(request, serviceUrl);
} else {
modifiedServiceUrl = serviceUrl;
}
logger.debug("Constructed service url: {}", modifiedServiceUrl);
final String urlToRedirectTo = CommonUtils.constructRedirectUrl(this.casServerLoginUrl,
getProtocol().getServiceParameterName(), modifiedServiceUrl, this.renew, this.gateway);
logger.debug("redirecting to \"{}\"", urlToRedirectTo);
this.authenticationRedirectStrategy.redirect(request, response, urlToRedirectTo);
}

（3）isRequestUrlExcluded方法

第一眼就看到了上面代码红色标识处的isRequestUrlExcluded,这个意思很直白，判断是不是需要忽略/排除的请求URL。

继续接着找到isRequestUrlExcluded这个方法的实现代码：

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);
}

看红色标识位置的名字，这里用到了UrlPatternMatcherStrategy这个类，意思很简单直白：‘请求url的匹配策略类’，暂时还不知道这里是正则匹配，往后看：

（4）请求URL的匹配策略类UrlPatternMatcherStrategy

private UrlPatternMatcherStrategy ignoreUrlPatternMatcherStrategyClass = null;

发现该类是在初始化方法中进行初始化的：

protected void initInternal(final FilterConfig filterConfig) throws ServletException {
if (!isIgnoreInitConfiguration()) {
super.initInternal(filterConfig);
setCasServerLoginUrl(getString(ConfigurationKeys.CAS_SERVER_LOGIN_URL));
setRenew(getBoolean(ConfigurationKeys.RENEW));
setGateway(getBoolean(ConfigurationKeys.GATEWAY));
final String ignorePattern = getString(ConfigurationKeys.IGNORE_PATTERN);
final String ignoreUrlPatternType = getString(ConfigurationKeys.IGNORE_URL_PATTERN_TYPE);
if (ignorePattern != null) {
final Class<? extends UrlPatternMatcherStrategy> ignoreUrlMatcherClass = PATTERN_MATCHER_TYPES.get(ignoreUrlPatternType);
if (ignoreUrlMatcherClass != null) {
this.ignoreUrlPatternMatcherStrategyClass = ReflectUtils.newInstance(ignoreUrlMatcherClass.getName());
} else {
try {
logger.trace("Assuming {} is a qualified class name...", ignoreUrlPatternType);
this.ignoreUrlPatternMatcherStrategyClass = ReflectUtils.newInstance(ignoreUrlPatternType);
} catch (final IllegalArgumentException e) {
logger.error("Could not instantiate class [{}]", ignoreUrlPatternType, e);
}
}
if (this.ignoreUrlPatternMatcherStrategyClass != null) {
this.ignoreUrlPatternMatcherStrategyClass.setPattern(ignorePattern);
}
}
final Class<? extends GatewayResolver> gatewayStorageClass = getClass(ConfigurationKeys.GATEWAY_STORAGE_CLASS);
if (gatewayStorageClass != null) {
setGatewayStorage(ReflectUtils.newInstance(gatewayStorageClass));
}
final Class<? extends AuthenticationRedirectStrategy> authenticationRedirectStrategyClass = getClass(ConfigurationKeys.AUTHENTICATION_REDIRECT_STRATEGY_CLASS);
if (authenticationRedirectStrategyClass != null) {
this.authenticationRedirectStrategy = ReflectUtils.newInstance(authenticationRedirectStrategyClass);
}
}
}

虽然使用了反射，但是依然不影响我们找到根本所在，找到ConfigurationKeys这个类里面的变量究竟是什么：

ConfigurationKey<String> IGNORE_PATTERN = new ConfigurationKey<String>("ignorePattern", null);
ConfigurationKey<String> IGNORE_URL_PATTERN_TYPE = new ConfigurationKey<String>("ignoreUrlPatternType", "REGEX");

字面上理解这两个常量定义了忽略模式以及忽略模式类型是‘正则’，当然我们还是不确定是不是正则，那么继续往下找

final Class<? extends UrlPatternMatcherStrategy> ignoreUrlMatcherClass = PATTERN_MATCHER_TYPES.get(ignoreUrlPatternType);

我们已经通过ConfigurationKeys类知道ignoreUrlPatternType是个‘REGEX’字符串，那么

PATTERN_MATCHER_TYPES.put("REGEX", RegexUrlPatternMatcherStrategy.class);

那么按照REGEX对应的值找到RegexUrlPatternMatcherStrategy这个类：

（5）确定RegexUrlPatternMatcherStrategy类用于处理正则验证匹配

public final class RegexUrlPatternMatcherStrategy implements UrlPatternMatcherStrategy {
private Pattern pattern;
public RegexUrlPatternMatcherStrategy() {}
public RegexUrlPatternMatcherStrategy(final String pattern) {
this.setPattern(pattern);
}
public boolean matches(final String url) {
return this.pattern.matcher(url).find();
}
public void setPattern(final String pattern) {
this.pattern = Pattern.compile(pattern);
}
}

该类中用到了Pattern来编译和匹配正则表达式

到这里我们终于可以确定可以用ignorePattern来忽略/排除我们不需要拦截的请求URL，当然必须满足正则表达式。

巴特西

关于cas-client单点登录客户端拦截请求和忽略/排除不需要拦截的请求URL的问题（不需要修改任何代码，只需要一个配置）