Hi,
your viewer doesn’t work with Vaadin 14.
I’ve got the following error message:
2020-05-01 18:34:37.092 ERROR 48628 --- [nio-8080-exec-2]
c.v.f.s.DefaultErrorHandler :
java.lang.IllegalStateException: Couldn't find the definition of the element with tag 'gallery-viewer' in any template file declared using '@JsModule' annotations. Check the availability of the template files in your WAR file or provide alternative implementation of the method getTemplateContent() which should return an element representing the content of the template file
at com.vaadin.flow.component.polymertemplate.NpmTemplateParser.getTemplateContent(NpmTemplateParser.java:140) ~[flow-server-2.1.8.jar:2.1.8]
at com.vaadin.flow.component.polymertemplate.TemplateDataAnalyzer.parseTemplate(TemplateDataAnalyzer.java:200) ~[flow-server-2.1.8.jar:2.1.8]
at com.vaadin.flow.component.polymertemplate.TemplateInitializer.lambda$null$23ee5b4f$1(TemplateInitializer.java:86) ~[flow-server-2.1.8.jar:2.1.8]
at com.vaadin.flow.internal.ReflectionCache.lambda$wrapValueProvider$d0062d93$1(ReflectionCache.java:84) ~[flow-server-2.1.8.jar:2.1.8]
at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(Unknown Source) ~[?:1.8.0_121]
It seems that your html template was not inside the package.