Browsers are generally restricted when client-side web applications running from one origin request data from another origin. Enabling cross-origin access is generally termed as CORS (Cross-Origin Resource Sharing).

This example shows how to enable cross-origin requests. With microservices, as each service runs with its own origin, it will easily get into the issue of a client-side web application consuming data from multiple origins. For instance, a scenario where a browser client accessing Customer from the Customer microservice and Order History from the Order microservices is very common in the microservices world.

Spring Boot provides a simple declarative approach to enabling cross-origin requests. The following example shows how to enable a microservice to enable cross-origin requests:

@RestController
class GreetingController{
  @CrossOrigin
  @RequestMapping("/")
  Greet greet(){
    return new Greet("Hello World!");
  }
}

By default, all the origins and headers are accepted. We can further customize the cross-origin annotations by giving access to specific origins, as follows. The @CrossOrigin annotation enables a method or class to accept cross-origin requests:

@CrossOrigin("http://mytrustedorigin.com")

Global CORS can be enabled using the WebMvcConfigurer bean and customizing the addCorsMappings(CorsRegistry registry) method.