Information and doclink on routes not found error about known Spring …

…Boot Devtools issue (#655)

Spring Boot Devtools issue (spring-projects/spring-boot#19543)

vaadin-spring/src/main/java/com/vaadin/flow/spring/VaadinServletContextInitializer.java

@@ -86,6 +86,7 @@
 import com.vaadin.flow.server.startup.WebComponentExporterAwareValidator;
 import com.vaadin.flow.server.webcomponent.WebComponentConfigurationRegistry;
 import com.vaadin.flow.spring.VaadinScanPackagesRegistrar.VaadinScanPackages;
+import com.vaadin.flow.spring.router.SpringRouteNotFoundError;
 import com.vaadin.flow.theme.Theme;
 
 /**
@@ -630,11 +631,10 @@ private Collection<String> getWebComponentPackages() {
     }
 
     private Collection<String> getErrorParameterPackages() {
-        return Stream
-                .concat(Stream
-                        .of(HasErrorParameter.class.getPackage().getName()),
-                        getDefaultPackages().stream())
-                .collect(Collectors.toSet());
+        return Stream.concat(
+                Stream.of(HasErrorParameter.class.getPackage().getName(),
+                        SpringRouteNotFoundError.class.getPackage().getName()),
+                getDefaultPackages().stream()).collect(Collectors.toSet());
     }
 
     private List<String> getDefaultPackages() {

vaadin-spring/src/main/java/com/vaadin/flow/spring/router/SpringRouteNotFoundError.java

@@ -0,0 +1,28 @@
+package com.vaadin.flow.spring.router;
+
+import com.vaadin.flow.component.Html;
+import com.vaadin.flow.router.BeforeEnterEvent;
+import com.vaadin.flow.router.ErrorParameter;
+import com.vaadin.flow.router.NotFoundException;
+import com.vaadin.flow.router.RouteNotFoundError;
+
+public class SpringRouteNotFoundError extends RouteNotFoundError {
+    @Override
+    public int setErrorParameter(BeforeEnterEvent event,
+            ErrorParameter<NotFoundException> parameter) {
+        int retval = super.setErrorParameter(event, parameter);
+
+        // Alert user about potential issue with Spring Boot Devtools losing
+        // routes https://github.com/spring-projects/spring-boot/issues/19543
+        String customMessage = "<span>When using Spring Boot Devtools with "
+                + "automatic reload, please note that routes can sometimes be "
+                + "lost due to a <a href ='https://github.com/spring-projects/spring-boot/issues/19543'>"
+                + "compilation race condition</a>. See "
+                + "<a href='https://vaadin.com/docs/flow/workflow/setup-live-reload-springboot.html'>"
+                + "the documentation</a> for further workarounds and other "
+                + "live reload alternatives.";
+        getElement().appendChild(new Html(customMessage).getElement());
+
+        return retval;
+    }
+}