Invalid ＜url-pattern＞ [sso.action] in filter mapping

Tomcat 8.5.86版本启动web项目报错Caused by: java.lang.IllegalArgumentException: Invalid <url-pattern> [sso.action] in filter mapping

查看项目的web.xml文件相关片段

 <filter-mapping><filter-name>SSOFilter</filter-name><url-pattern>sso.action</url-pattern></filter-mapping>

这里的url-pattern取值可能不符合标准。首先查看servlet 3.1规范

Java Servlet Specifications
Servlet 4.0 specification is JSR 369.
Servlet 3.1 specification is JSR 340.
Servlet 3.0 specification is JSR 315.
Servlet 2.5 is a maintenance release of Servlet 2.4. Both are JSR 154.

相关的内容如下图所示

再查看Tomcat的源码org.apache.catalina.core.StandardContext#validateURLPattern

 /*** Validate the syntax of a proposed <code>&lt;url-pattern&gt;</code> for conformance with specification* requirements.** @param urlPattern URL pattern to be validated** @return <code>true</code> if the URL pattern is conformant*/private boolean validateURLPattern(String urlPattern) {// 不能为空if (urlPattern == null) {return false;}// 不能包含换行 制表符if (urlPattern.indexOf('\n') >= 0 || urlPattern.indexOf('\r') >= 0) {return false;}// 空字符串代表匹配所有if (urlPattern.equals("")) {return true;}// 以 * 开头if (urlPattern.startsWith("*.")) {if (urlPattern.indexOf('/') < 0) {checkUnusualURLPattern(urlPattern);return true;} else {return false;}}// 以/开头不包含*if (urlPattern.startsWith("/") && !urlPattern.contains("*.")) {checkUnusualURLPattern(urlPattern);return true;} else {return false;}}

可以看到urlPattern可以为空字符串、至少以*.开头不包含/或者以/开头不不包含*.。
checkUnusualURLPattern仅仅是打印日志，不会导致报错

    /*** Check for unusual but valid <code>&lt;url-pattern&gt;</code>s. See Bugzilla 34805, 43079 & 43080*/private void checkUnusualURLPattern(String urlPattern) {if (log.isInfoEnabled()) {// First group checks for '*' or '/foo*' style patterns// Second group checks for *.foo.bar style patternsif ((urlPattern.endsWith("*") &&(urlPattern.length() < 2 || urlPattern.charAt(urlPattern.length() - 2) != '/')) ||urlPattern.startsWith("*.") && urlPattern.length() > 2 && urlPattern.lastIndexOf('.') > 1) {log.info("Suspicious url pattern: \"" + urlPattern + "\"" + " in context [" + getName() + "] - see" +" sections 12.1 and 12.2 of the Servlet specification");}}}

以上实现在Tomcat 9.0.55中没有变化

综合分析，修改web.xml中配置如下(在url-pattern前面添加一个/)

<filter-mapping><filter-name>SSOFilter</filter-name><url-pattern>/sso.action</url-pattern>
</filter-mapping>