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This article will explain in detail how to implement the service gateway filter in springcloud. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

Filter function

The interface provided by our microservice application can be accessed by the client through a unified API gateway portal. However, when each client user requests the interface provided by the micro-service application, their access rights often need to be limited, and the system will not open all the micro-service interfaces to them. However, the current service routing does not have the function of restricting permissions, and all requests will be forwarded to specific applications without reservation and return results. In order to achieve secure checksum access control of client requests, the simplest and roughest way is to implement a set of filters or interceptors for verifying signatures and authentication permissions for each microservice application.

However, this approach is not desirable, it will increase the difficulty of system maintenance in the future, because in many cases, all kinds of verification logic in the same system are roughly the same or similar. this implementation will cause similar verification logic code to be scattered among various micro-services, and the emergence of redundant code is something we do not want to see. Therefore, it is better to separate these verification logic and build an independent authentication service. After the divestiture, many developers will directly implement verification by calling authentication services in micro-service applications, but this only solves the separation of authentication logic. In essence, this part of the logic that is not amateur will be split into the original micro-service applications, redundant interceptors or filters will still exist.

For such problems, it is better to complete these non-business checks through front-end gateway services. Due to the addition of the gateway service, external clients have a unified access to our system. Since these verifications have nothing to do with the specific business, why not complete the checksum filtering when the request arrives? instead of forwarding and filtering, resulting in a longer request delay. At the same time, by completing checksum filtering in the gateway, micro-service applications can remove a variety of complex filters and interceptors, which reduces the complexity of interface development and testing of micro-service applications.

In order to implement the verification of client requests in the API gateway, we will need to use another core function of Spring Cloud Zuul: filters.

Zuul allows developers to intercept and filter requests by defining filters on API gateways. The implementation method is very simple. We only need to inherit the ZuulFilter abstract class and implement the four abstract functions defined by it to complete the interception and filtering of requests.

Realization of filter

For example, in the following code, we define a simple Zuul filter that checks whether there is an accessToken parameter in the HttpServletRequest before the request is routed, routes it, denies access if not, and returns a 401 Unauthorized error.

Public class AccessFilter extends ZuulFilter {private static Logger log = LoggerFactory.getLogger (AccessFilter.class); @ Overridepublic String filterType () {return "pre";} @ Overridepublic int filterOrder () {return 0;} @ Overridepublic boolean shouldFilter () {return true;} @ Overridepublic Object run () {RequestContext ctx = RequestContext.getCurrentContext (); HttpServletRequest request = ctx.getRequest (); log.info ("send {} request to {}", request.getMethod (), request.getRequestURL (). ToString ()); Object accessToken = request.getParameter ("accessToken") If (accessToken = = null) {log.warn ("access token is empty"); ctx.setSendZuulResponse (false); ctx.setResponseStatusCode (401); return null;} log.info ("access token ok"); return null;}}

In the filter code implemented above, we implement a custom filter by inheriting the ZuulFilter abstract class and overriding the following four methods. These four methods define:

FilterType: the type of filter that determines the lifecycle in which the filter is executed. This is defined as pre, which is executed before the request is routed.

FilterOrder: the order in which the filter is executed. When a request has multiple filters in a phase, it needs to be executed sequentially according to the values returned by the method.

ShouldFilter: determines whether the filter needs to be executed. Here we return true directly, so the filter takes effect on all requests. In practical application, we can use this function to specify the effective range of the filter.

Run: the specific logic of the filter. Here we use ctx.setSendZuulResponse (false) to make zuul filter the request without routing it, and then set the error code returned by ctx.setResponseStatusCode (401). Of course, we can also further optimize our return, for example, editing the returned body content through ctx.setResponseBody (body).

After implementing the custom filter, it will not take effect directly. We also need to create a specific Bean for it to start the filter. For example, add the following to the application main class:

@ EnableZuulProxy@SpringCloudApplicationpublic class Application {public static void main (String [] args) {new SpringApplicationBuilder (Application.class) .web (true) .run (args);} @ Beanpublic AccessFilter accessFilter () {return new AccessFilter () }} this is the end of the article on "how to implement Service Gateway filter in springcloud". I hope the above content can be helpful to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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