In my Vaadin application (I am using Vaadin v24.3.8) I am trying to define me a “help”-link that should serve a static HTML help-page.
The file help.html to be served is placed in folder <resources>/help/.
To make spring-boot serve that static file I added a configuration class providing access to a resource folder "help" using the URL-path "help/...":
... package and imports omitted ...
@Configuration
public class StaticConfig implements WebMvcConfigurer
{
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
registry
.addResourceHandler("/help/*.*") // URL-path: …/help/…
.addResourceLocations("classpath:/help/") // → serves content from …/src/main/resources/help
;
}
}
If I enter the URL "https://localhost:8085/help/help.html" that file gets properly served - as expected.
Next I defined myself a link (i.e. a Vaadin "anchor") in my application’s main-view like so:
Anchor help = new Anchor("help/help.html", "Help");
...
addToNavBar(help);
The link is displayed fine. The URL that is shown when I hover with the mouse over it is: "https://localhost:8085/help/help.html".
If I inspect the element in the browser's development tools it shows:
<a class="help-link" href="help/help.html">Help</a>
again: everything as expected.
However, when I click onto that link I get the error:
Could not navigate to 'help/help.html'
Available routes:
<root>
login
logout
This detailed message is only shown when running in development mode.
The URL shown in the browser's address field at that point is "https://localhost:8085/help/help.html".
If I then trigger a refresh in the browser, i.e. if I reload that page it loads the help-page without problem.
?!? Why is that page not loaded immediately when I click the link in the application? Why do I first get an error and only on reload the page loads fine? What am I missing here???
If you don't specifically need a Spring resource handler for this file, you can just put it in /src/main/resources/META-INF/resources/help/help.html (see https://vaadin.com/docs/latest/flow/advanced/loading-resources#flow.resource-cheat-sheet) and have Vaadin serve it as a static resource instead.
By default, the static resource is available for authenticated users; use HttpSecurity to specify different rules: https://vaadin.com/docs/latest/flow/security/enabling-security#security-configuration-class