Attempted to call method length on null context object和“arrays.length(tag.blogs)“ (template: “tags“）
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使用thymeelaf和springboot出现的bug，报错信息如下
org.thymeleaf.exceptions.TemplateInputException: An error happened during template parsing (template: "class path resource [templates/tags.html]")
at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parse(AbstractMarkupTemplateParser.java:241) ~[thymeleaf-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parseStandalone(AbstractMarkupTemplateParser.java:100) ~[thymeleaf-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.thymeleaf.engine.TemplateManager.parseAndProcess(TemplateManager.java:667) ~[thymeleaf-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1087) [thymeleaf-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1061) [thymeleaf-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.thymeleaf.spring4.view.ThymeleafView.renderFragment(ThymeleafView.java:335) [thymeleaf-spring4-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.thymeleaf.spring4.view.ThymeleafView.render(ThymeleafView.java:189) [thymeleaf-spring4-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1286) [spring-webmvc-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1041) [spring-webmvc-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:984) [spring-webmvc-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) [spring-webmvc-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) [spring-webmvc-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) [spring-webmvc-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-embed-websocket-8.5.20.jar:8.5.20]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) [spring-web-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:108) [spring-web-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) [spring-web-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) [spring-web-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.11.RELEASE.jar:4.3.11.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:799) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1457) [tomcat-embed-core-8.5.20.jar:8.5.20]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.20.jar:8.5.20]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_162]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_162]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.20.jar:8.5.20]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_162]
Caused by: org.attoparser.ParseException: Exception evaluating SpringEL expression: "arrays.length(tag.blogs)" (template: "tags" - line 63, col 41)
at org.attoparser.MarkupParser.parseDocument(MarkupParser.java:393) ~[attoparser-2.0.1.RELEASE.jar:2.0.1.RELEASE]
at org.attoparser.MarkupParser.parse(MarkupParser.java:257) ~[attoparser-2.0.1.RELEASE.jar:2.0.1.RELEASE]
at org.thymeleaf.templateparser.markup.AbstractMarkupTemplateParser.parse(AbstractMarkupTemplateParser.java:230) ~[thymeleaf-3.0.2.RELEASE.jar:3.0.2.RELEASE]
... 52 common frames omitted
Caused by: org.thymeleaf.exceptions.TemplateProcessingException: Exception evaluating SpringEL expression: "arrays.length(tag.blogs)" (template: "tags" - line 63, col 41)
at org.thymeleaf.spring4.expression.SPELVariableExpressionEvaluator.evaluate(SPELVariableExpressionEvaluator.java:290) ~[thymeleaf-spring4-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.thymeleaf.standard.expression.VariableExpression.executeVariableExpression(VariableExpression.java:165) ~[thymeleaf-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.thymeleaf.standard.expression.SimpleExpression.executeSimple(SimpleExpression.java:66) ~[thymeleaf-3.0.2.RELEASE.jar:3.0.2.RELEASE]
at org.thymeleaf.standard