I'm looking for a way to implement custom endpoints for a reactive application using Spring Boot 2.2.
The endpoints have some subsystems and perform specific resource operations on the subsystems. The URL paths look like:
/actuator/system1/subsystem_a
/actuator/system1/subsystem_b
/actuator/system2/subsystem_c
Furthermore, system1 and system2 are not both always deployed, so I'd like to add dynamically the endpoints of the deployed system only.
I know I can use ReactiveHealthContributorRegistry to add custom health check endpoints dynamically. Is there a similar way for a fully custom endpoint?
Thanks in advance.
It seems there is no way to construct such complex endpoints like what I asked in Spring Boot Actuator.
I finally decided to use RouterFunction and HandlerFunction referring to the following websites.
https://www.baeldung.com/spring-5-functional-web
https://spring.io/blog/2016/09/22/new-in-spring-5-functional-web-framework
I get that Feign is declarative and hence it abstracts out a lot of things for the developer. But, when should one choose one over the other? Though feign is declarative, it has serious problems with oAuth. What are some of the considerations in using RestTemplate over Feign
Feign allows you to abstract the mechanics of calling a REST service. Once you configure and annotate the Feign interface, you can call a REST service by making a simple Java function call. The actual implementation of making a REST call is handled at runtime by Feign. This means that the implementation can be configured without changing your business logic code.
By just changing the Feign configuration in Java or using properties you can add encoding/decoding, logging, and change the REST call implementation library. All this is done through configuration only, while the business logic that calls the service remains unchanged.
Since Feign uses standard Java interfaces, it's also easy to mock them during unit tests.
There are certain advantages.
1.URLs are not hardcoded.
2.you don't have to write unit test cases for feign as there is no code to test however you have to write integration tests.
3.we can use Eureka Client ID instead of the URL.
4.Feign handled the actual code.
5.Feign integrates with Ribbon and Eureka Automatically.
6.Feign provides a very easy way to call RESTful services.
One of the advantages of using Feign over RestTemplate is that, we do not need to write any implementation to call the other services. So there is no
need to write any unit test as there is no code to test in the first place. However, it is advised that we write Integration tests.
Using Feign-clients over rest-templates has number of advantages. I will list down those below.
The developer need not worry about the implementation. Just to create abstract Feign interface and few annotations - declarative
principle. (If you want customized configuration, then it will hold
some code)
With Spring Cloud Eureka, Ribbon client-side load-balancer will be equipped with Feign client.
No need to worry about the unit test, because there is no implementation from you to test. (Arguable)
Supports Feign annotations and JAX-RS annotations.
Highly compatible and easily configurable with Spring Cloud (Specially with Eureka server registry)
Allows Feign client configuration via #Configuration class or application properties.
Allows us to add interceptors. (Add interceptors via #Configuration or application properties. Alternatively can use
Spring Cloud provided interceptors as well. Example -
BasicAuthRequestInterceptor)
Hystrix support for fall-back mechanism.
Logging
Error handling
Feign is a good choice, If you are fascinated with JPA and the way how it resolves your queries, then Feign is the tool for you. Feign will handle your server requests perfectly fine.
RestTemplate is used for making the synchronous call. When using RestTemplate, the URL parameter is constructed programmatically, and data is sent across to the other service. In more complex scenarios, we will have to get to the details of the HTTP APIs provided by RestTemplate or even to APIs at a much lower level.
Feign is a Spring Cloud Netflix library for providing a higher level of abstraction over REST-based service calls. Spring Cloud Feign works on a declarative principle. When using Feign, we write declarative REST service interfaces at the client, and use those interfaces to program the client. The developer need not worry about the implementation ...
Advantages of using Feign over RestTemplate:
Declarative approach: Feign provides a more declarative approach to define and use REST API clients, which can make the code more readable and easier to maintain.
Integrated with Eureka: Feign is integrated with Netflix Eureka for service discovery, making it easier to build and consume APIs in a microservices architecture.
Better error handling: Feign provides better error handling, including support for custom error handling and retries.
Support for multiple encodings: Feign supports multiple encoding types, including JSON, XML, and form data, while RestTemplate only supports JSON and XML.
Disadvantages of using Feign over RestTemplate:
Limited flexibility: Feign provides a more opinionated approach to defining and using REST API clients, which may limit flexibility in certain situations.
Limited control over HTTP request and response: Feign abstracts away some of the low-level details of the HTTP request and response, which can make it harder to control and customize these details if needed.
Lack of official support: Feign is not an officially supported library from Spring, which may be a consideration for some developers or organizations.
I have a spring mvc application which runs correctly,now another colleague wants to call the same functions from another application but he needs REST URL of my functions.
how is it possible to provide the same functionality through spring REST?
is it just with new annotations .please provide some resource to show me how to do it.
when server has a service, only legal clients which had any contracts with server can access it. And clients can use service by the way such as: use RestTemplate to get/post request to URL of service, and clients can get data as JSON, or XML type if you have an equivalent object as this image:
Also, a service can be support as a interface, ex: google search is a service supported by google, but it's not rest service.
If you know each other URL address you can consume each other REST API from java code by using RestTemplate object.
I would advise you to go over the Spring starter guide which deals with that issue, here is the link (Consuming a RESTful Web Service):
https://spring.io/guides/gs/consuming-rest/
I'm splitting up a monolith web service into several microservices using spring boot. To reduce duplicated code I extracted shared parts in a maven module that is used in the different microservices.
The monolith application had a healthcheck page that showed various information about the state of the service and some debbuging infos. It is implemented with Spring MVC and jsp.
I'd like to use this view in each of the microservices. Whats the best way to do this without duplicating the view/controller?
I was thinking of adding a web module to the shared maven project that contains the controller, view, spring mvc settings,...
But I'm not sure if it is good to have two web modules in one microservice.
Have you considered using spring boot actuator to retrieve health (and more) application information?
http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#production-ready
You could then have another microservice that retrieves that information from each of your services, or just simply check it on then hitting the different endpoints (/health, /env, etc.).
UPDATE:
If you have you custom health logic you can even implement your own actuator endpoint for it. Furthermore, you can create your own library to reuse it in all your microservices:
http://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#production-ready-customizing-endpoints-programmatically
46.4 Adding custom endpoints
If you add a #Bean of type Endpoint then it will automatically be exposed over JMX and HTTP (if there is an
server available). An HTTP endpoints can be customized further by
creating a bean of type MvcEndpoint. Your MvcEndpoint is not a
#Controller but it can use #RequestMapping (and #Managed*) to expose
resources.
[Tip]
If you are doing this as a library feature consider adding a
configuration class annotated with #ManagementContextConfiguration to
/META-INF/spring.factories under the key
org.springframework.boot.actuate.autoconfigure.ManagementContextConfiguration.
If you do that then the endpoint will move to a child context with all
the other MVC endpoints if your users ask for a separate management
port or address. A configuration declared this way can be a
WebConfigurerAdapter if it wants to add static resources (for
instance) to the management endpoints.
My application exposes a RESTful API which when called calls out to a mailbox server and fetches data. I want to be able disable the service during application runtime in the event of some outage on the mailbox server. I wanted to do this in a way that the logic of deciding whether or not to call the mailbox server was abstracted from the actual code that calls the mailbox server. Two options which seem to fit this scenario are filters and interceptors however I'm looking for advice on which one best suits this requirement and what are the difference between each?
Thanks
If you are using Spring MVC then you can use an interceptor, which is like a filter but that has access to the Spring context. If you are using Jersey then you can't use interceptors.