How to Dynamically Register Spring MVC Handlers in Spring Boot 2.2

Environment: Spring Boot 2.2.10.RELEASE

Write a method prepared for handling requests

<code>@Service
public class UserHandler {
    @ResponseBody
    public Object getUsers(@PathVariable("id") String id, HttpServletRequest request) {
        System.out.println(request);
        return "查询用户ID为：" + id;
    }
}
</code>

The handler does not need to be a container‑managed bean; the Spring MVC annotations work the same as in a @Controller.

Register the interface handler

<code>@Configuration
public class MappingConfig {
    @Autowired
    public void setHandlerMapping(RequestMappingHandlerMapping mapping, UserHandler handler) throws NoSuchMethodException {
        RequestMappingInfo info = RequestMappingInfo.paths("/users/{id}").methods(RequestMethod.GET).build();
        Method method = UserHandler.class.getMethod("getUsers", String.class, HttpServletRequest.class);
        mapping.registerMapping(info, handler, method);
    }
}
</code>

Create a RequestMappingInfo object containing basic request metadata.

Obtain the Method object of the handler.

Register the mapping with RequestMappingHandlerMapping.

During container startup, Spring wraps all @Controller methods into RequestMappingInfo objects and adds them to the RequestMappingHandlerMapping collection.

The container holds many HandlerMapping beans; whether a class is considered a handler is decided by AbstractHandlerMethodMapping#isHandler, which subclasses implement.

<code>public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMapping implements InitializingBean {
    protected abstract boolean isHandler(Class<?> beanType);
}
</code>

RequestMappingHandlerMapping overrides isHandler to check for @Controller or @RequestMapping annotations.

<code>public class RequestMappingHandlerMapping {
    @Override
    protected boolean isHandler(Class<?> beanType) {
        return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
                AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
    }
}
</code>

Thus any bean annotated with @Controller or @RequestMapping is automatically registered as a RequestMappingInfo after the container starts.

When Spring MVC processes a request, it first obtains the appropriate HandlerMapping.

Method parameter handling

Supported parameters include JDK 8 java.util.Optional combined with annotations such as @RequestParam, @RequestHeader, etc., which behave as if required=false.

Method return value handling

End of tutorial.

Public: Spring Boot practical case collection