How to get SpringDoc OpenAPI to work with Servlets? - spring

Question

In my actual project, I exclude a couple packages with endpoints from the main ComponentScan. Instead, each one gets its own ServletRegistrationBean. This way they can all have their own JSON serialization configuration beans.
But if I do this, then SpringDoc does not detect any of my endpoints.
I'm using spring-boot 2.6.4 and springdoc-openapi-ui 1.6.6
package com.example;
#SpringBootApplication(scanBasePackages = "com.example")
#ComponentScan(basePackages = "com.example", excludeFilters = {
#ComponentScan.Filter(type = FilterType.REGEX, pattern = "com.example.demo.*")
})
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
#Bean
public ServletRegistrationBean<DispatcherServlet> api(ApplicationContext parent) {
return createChildServlet(
Arrays.asList("/api/*"),
DemoApiConfig.class,
"api",
parent);
}
private ServletRegistrationBean<DispatcherServlet> createChildServlet(List<String> urlMappings,
Class<?> configuration, String servletRegistrationBeanName, ApplicationContext parent) {
var applicationContext = new AnnotationConfigWebApplicationContext();
applicationContext.register(configuration);
applicationContext.setParent(parent);
var dispatcherServlet = new DispatcherServlet(applicationContext);
var servletRegistrationBean = new ServletRegistrationBean<>(dispatcherServlet,
urlMappings.toArray(new String[] {}));
servletRegistrationBean.setName(servletRegistrationBeanName);
servletRegistrationBean.setLoadOnStartup(1);
return servletRegistrationBean;
}
}
I've verified that this bean does get created, it just doesn't seem to be used.
package com.example.demo;
#EnableWebMvc
#Configuration
#ComponentScan
public class DemoApiConfig {
}
package com.example.demo;
#RestController
#RequestMapping("/demo/v1")
public class DemoController {
#Operation(summary = "Demo documentation")
#GetMapping("/test")
public ResponseEntity<String> test() {
return ResponseEntity.ok("Test");
}
}
If I remove the ComponentScan filter, then the endpoint exists twice as /api/demo/v1/test and /demo/v1/test, and springdoc only detects /demo/v1/test).
With the ComponentScan filter, only /api/demo/v1/test exists and springdoc does not detect it.
How do I get SpringDoc to detect endpoints that exist only inside Servlets?