如何使用Java为Web服务中的每个API调用特定方法？

Question

I have a web-service which provides dozens of APIs. I want to let each of them do something once they've be invoked automatically, like checking the authorization, without invoking manually.

For example, I got 3 APIs like described below :

@POST
public Response postSome() {
   checkAuthorization();
   ...
}

@GET
public Response getSome() {
   checkAuthorization();
   ...
}

@DELETE
public Response deleteSome() {
   checkAuthorization();
   ...
}

Of course, I could invoke checkAuthorization() method in each of my APIs, but it was quiet troublesome, redundant, and unsafe, because me or other writer might forget doing this.

Is there any method(eg inheritance ) or other way could achieve this, so I don't have to call checkAuthorization() every time I created a new API? Thanks.

Answer 1

You could achieve this using Interceptor.

Spring allow you to intercept web request through handler interceptors. The handler interceptor have to implement the HandlerInterceptor interface, which contains three methods :

preHandle() – Called before the handler execution, returns a boolean value, “true” : continue the handler execution chain; “false”, stop the execution chain and return it.

postHandle() – Called after the handler execution, allow manipulate the ModelAndView object before render it to view page.

afterCompletion() – Called after the complete request has finished. Seldom use, cant find any use case.

public class AuthenticationInterceptor extends HandlerInterceptorAdapter {

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception exception)
    throws Exception {
    // TODO Auto-generated method stub

    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
    throws Exception {
    // TODO Auto-generated method stub

    }

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
     checkAuthorization()
    }


}

Implement an AppConfig class or add the addInterceptors in one of the existing Configuration class.

@Configuration  
public class AppConfig extends WebMvcConfigurerAdapter  {  

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
       registry.addInterceptor(new AuthenticationInterceptor ());
    }
} 

Write your checkAuthorization() logic in preHandle() . Hope this helps.

Answer 2

You can check authorization on different levels

You can create a method level annotation calling the checkAuthorization method, then you just annotate every method. It may result in cleaner code, but the same way you need not to forget annotate your methods.

You can create a web service interceptor - a piece of code executed for each incoming request, but the implementation will depend on a used framework