错误信息如下:
21-Sep-2020 09:52:59.280 SEVERE [Thread-16] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [springDispatcherServlet] in context with path [] threw exception [Handler dispatch failed; nested exception is java.lang.InternalError: java.lang.reflect.InvocationTargetException] with root cause java.lang.NullPointerException at java.desktop/sun.awt.FontConfiguration.getVersion(FontConfiguration.java:1262) at java.desktop/sun.awt.FontConfiguration.readFontConfigFile(FontConfiguration.java:225) at java.desktop/sun.awt.FontConfiguration.init(FontConfiguration.java:107) at java.desktop/sun.awt.X11FontManager.createFontConfiguration(X11FontManager.java:719) at java.desktop/sun.font.SunFontManager$2.run(SunFontManager.java:367) at java.base/java.security.AccessController.doPrivileged(Native Method) at java.desktop/sun.font.SunFontManager.<init>(SunFontManager.java:312) at java.desktop/sun.awt.FcFontManager.<init>(FcFontManager.java:35) at java.desktop/sun.awt.X11FontManager.<init>(X11FontManager.java:56) at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490) at java.desktop/sun.font.FontManagerFactory$1.run(FontManagerFactory.java:84) at java.base/java.security.AccessController.doPrivileged(Native Method) at java.desktop/sun.font.FontManagerFactory.getInstance(FontManagerFactory.java:74) at java.desktop/java.awt.Font.getFont2D(Font.java:497) at java.desktop/java.awt.Font$FontAccessImpl.getFont2D(Font.java:237) at java.desktop/sun.font.FontUtilities.getFont2D(FontUtilities.java:139) at java.desktop/sun.java2d.SunGraphics2D.checkFontInfo(SunGraphics2D.java:670) at java.desktop/sun.java2d.SunGraphics2D.getFontInfo(SunGraphics2D.java:831) at java.desktop/sun.java2d.pipe.GlyphListPipe.drawString(GlyphListPipe.java:46) at java.desktop/sun.java2d.SunGraphics2D.drawString(SunGraphics2D.java:2929) at com.xrh.extend.imageCode.ImageCode.createImage(ImageCode.java:41) at com.xrh.base.user.CTR_User.getVerifyByImage(CTR_User.java:483) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:220) at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134) at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at com.xrh.web.DomainFilter.doFilter(DomainFilter.java:39) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at com.xrh.core.PowerFilter.doFilter(PowerFilter.java:60) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:528) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:798) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:810) at org.apache.tomcat.util.net.Nio2Endpoint$SocketProcessor.doRun(Nio2Endpoint.java:1777) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at org.apache.tomcat.util.net.AbstractEndpoint.processSocket(AbstractEndpoint.java:1082) at org.apache.tomcat.util.net.Nio2Endpoint$Nio2SocketWrapper$2.completed(Nio2Endpoint.java:569) at org.apache.tomcat.util.net.Nio2Endpoint$Nio2SocketWrapper$2.completed(Nio2Endpoint.java:547) at java.base/sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:127) at java.base/sun.nio.ch.Invoker$2.run(Invoker.java:219) at java.base/sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at java.base/java.lang.Thread.run(Thread.java:834)
解决办法：图形验证码依赖了系统组件，只需安装依赖即可解决
Centos 7+系统执行以下两条命令后重启应用服务即可：
yum install fontconfig fc-cache --force