How to handle HTTP OPTIONS requests in Spring Boot?

Question

First off, I've read "How to handle HTTP OPTIONS with Spring MVC?" but the answers do not seem directly applicable to Spring Boot.

It looks like I should do this:

configure the dispatcherServlet by setting its dispatchOptionsRequest to true

But how to do that, given that I have no XML configs, or any variety of DispatcherServlet initializer class in my code (mentioned by this answer)?

In a @RestController class, I have a method like this, which currently does not get invoked.

@RequestMapping(value = "/foo", method = RequestMethod.OPTIONS)
public ResponseEntity options(HttpServletResponse response) {
    log.info("OPTIONS /foo called");
    response.setHeader("Allow", "HEAD,GET,PUT,OPTIONS");
    return new ResponseEntity(HttpStatus.OK);
}

Spring Boot 1.2.7.RELEASE; a simple setup not very different from that in Spring REST guide.

Answer 1

Option 1: Spring Boot properties (Spring Boot 1.3.0+ only)

Starting with Spring Boot 1.3.0 this behavior can be configured using following property:

spring.mvc.dispatch-options-request=true

Option 2: Custom DispatcherServlet

DispatcherServlet in Spring Boot is defined by DispatcherServletAutoConfiguration. You can create your own DispatcherServlet bean somewhere in your configuration classes, which will be used instead of the one in auto configuration:

@Bean(name = DispatcherServletAutoConfiguration.DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
public DispatcherServlet dispatcherServlet() {
    DispatcherServlet dispatcherServlet = new DispatcherServlet();
    dispatcherServlet.setDispatchOptionsRequest(true);
    return dispatcherServlet;
}

But be aware that defining your DispatcherServlet bean will disable the auto configuration, so you should manually define other beans declared in the autoconfiguration class, namely the ServletRegistrationBean for DispatcherServlet.

Option 3: BeanPostProcessor

You can create BeanPostProcessor implementation which will set the dispatchOptionsRequest attribute to true before the bean is initialized. Yoy can put this somewhere in your configuration classes:

@Bean
public DispatcherServletBeanPostProcessor dispatcherServletBeanPostProcessor() {
    return new DispatcherServletBeanPostProcessor();
}

public static class DispatcherServletBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        if (bean instanceof DispatcherServlet) {
            ((DispatcherServlet) bean).setDispatchOptionsRequest(true);
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }
}

Option 4: SpringBootServletInitializer

If you had SpringBootServletInitializer in your application you could do something like this to enable OPTIONS dispatch:

public class ServletInitializer extends SpringBootServletInitializer {
    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(Application.class);
    }

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        super.onStartup(servletContext);
        servletContext.getServletRegistration(DispatcherServletAutoConfiguration.DEFAULT_DISPATCHER_SERVLET_BEAN_NAME)
                .setInitParameter("dispatchOptionsRequest", "true");
    }
}

That would however only work if you deployed your app as a WAR into Servlet container, as the SpringBootServletInitializer code is not executed when running your Spring Boot app using main method.