I know there are lot of questions created for Thymeleaf: Could not parse as expression error. But I could not find reason for the error I am facing, hence created this question.
I am creating a Spring Boot app using the steps here.
The expression that returns error in console is:
<a th:href="/@{'/edit/' + ${product.id}}">Edit</a>
Console:
2021-04-03 11:00:16.907 ERROR 5864 --- [nio-8080-exec-1] org.thymeleaf.TemplateEngine : [THYMELEAF][http-nio-8080-exec-1] Exception processing template "index": Could not parse as expression: "/@{'/edit/' + ${product.id}}" (template: "index" - line 32, col 25)
org.thymeleaf.exceptions.TemplateProcessingException: Could not parse as expression: "/@{'/edit/' + ${product.id}}" (template: "index" - line 32, col 25)
at org.thymeleaf.standard.expression.StandardExpressionParser.parseExpression(StandardExpressionParser.java:131) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.standard.expression.StandardExpressionParser.parseExpression(StandardExpressionParser.java:62) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.standard.expression.StandardExpressionParser.parseExpression(StandardExpressionParser.java:44) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.EngineEventUtils.parseAttributeExpression(EngineEventUtils.java:220) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.EngineEventUtils.computeAttributeExpression(EngineEventUtils.java:207) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.standard.processor.AbstractStandardExpressionAttributeTagProcessor.doProcess(AbstractStandardExpressionAttributeTagProcessor.java:125) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess(AbstractAttributeTagProcessor.java:74) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.processor.element.AbstractElementTagProcessor.process(AbstractElementTagProcessor.java:95) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.util.ProcessorConfigurationUtils$ElementTagProcessorWrapper.process(ProcessorConfigurationUtils.java:633) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.ProcessorTemplateHandler.handleOpenElement(ProcessorTemplateHandler.java:1314) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.OpenElementTag.beHandled(OpenElementTag.java:205) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.Model.process(Model.java:282) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.Model.process(Model.java:290) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.IteratedGatheringModelProcessable.processIterationModel(IteratedGatheringModelProcessable.java:367) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.IteratedGatheringModelProcessable.process(IteratedGatheringModelProcessable.java:221) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.ProcessorTemplateHandler.handleCloseElement(ProcessorTemplateHandler.java:1640) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.CloseElementTag.beHandled(CloseElementTag.java:139) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.TemplateModel.process(TemplateModel.java:136) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.engine.TemplateManager.parseAndProcess(TemplateManager.java:661) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1098) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.TemplateEngine.process(TemplateEngine.java:1072) ~[thymeleaf-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.spring5.view.ThymeleafView.renderFragment(ThymeleafView.java:366) ~[thymeleaf-spring5-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.thymeleaf.spring5.view.ThymeleafView.render(ThymeleafView.java:190) ~[thymeleaf-spring5-3.0.12.RELEASE.jar:3.0.12.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1393) ~[spring-webmvc-5.3.5.jar:5.3.5]
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1138) ~[spring-webmvc-5.3.5.jar:5.3.5]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1077) ~[spring-webmvc-5.3.5.jar:5.3.5]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962) ~[spring-webmvc-5.3.5.jar:5.3.5]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.5.jar:5.3.5]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.5.jar:5.3.5]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) ~[tomcat-embed-core-9.0.44.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.5.jar:5.3.5]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.44.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.44.jar:9.0.44]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.5.jar:5.3.5]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.5.jar:5.3.5]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.5.jar:5.3.5]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.5.jar:5.3.5]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.5.jar:5.3.5]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.5.jar:5.3.5]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:189) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:162) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1707) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) ~[na:na]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.44.jar:9.0.44]
at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]
Removing the slash before @ in th:href expression resolves error
<a th:href="@{'/edit/' + ${product.id}}">Edit</a>
To pass the path variable we can use double underscore around path variable.
<a th:href="@{/edit/__${product.id}__}">Edit</a>