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Version: 2.0

Feign starter

Purpose​

This starters enables Feign client discovery and use. Feign clients are REST clients used for synchronous HTTP communications between microservices. Requests are automatically load balanced.

Configuration​

Add starter dependency to your POM (version depends on the REGARDS BOM)

<dependency>
  <groupId>fr.cnes.regards.framework</groupId>
  <artifactId>feign-regards-starter</artifactId>
</dependency>

Dependency :

# See multitenant starter properties
# Security utils needs JWT secret

Autoconfiguration​

Starter autoconfigures:

  • FeignSecurityManager to manage security token injection into request headers.
  • Enable automatic client discovery in package fr.cnes.regards (unless test profile is activated)

How to​

How to create a client​

Create a Spring MVC interface annotated with RestClient :

@RestClient(name = "targetMicroserviceName")
@RequestMapping(produces = MediaType.APPLICATION_JSON_UTF8_VALUE, consumes = MediaType.APPLICATION_JSON_UTF8_VALUE)
public interface IHelloClient {

    @RequestMapping(method = RequestMethod.GET, value = "/hello")
    ResponseEntity<Hello> getHello();
}
danger

When using request or path parameters, you have to explicitly declare expected names (e.g. @PathVariable("param_name"))!

danger

Produce and consume format has to be set to JSON in @RequestMapping.

How to use a client​

Importing Feign starter in your pom.xml, all classes annotated with RestClient are automatically discovered in package fr.cnes.regards. So, you can @Autowired it in your service.

If client is in a different package, use @EnableFeignClients in a configuration class to declare this package.

How to make a system (i.e. internal) call​

By default, FeignSecurityManager propagates user token in Feign request from security holder.

To call an endpoint as system, you must inform FeignSecurityManager before process request.

If you act as a daemon and you have to manage tenant in system client call, use IRuntimeTenantResolver to force the right tenant.

try {
  // Optionnaly specify working tenant (thread safe action)
  runtimeTenantResolver.forceTenant("tenant");
  // Enable system call as follow (thread safe action)
  FeignSecurityManager.asSystem();
  // Process client request ...
} finally {
  // We advice you to clean context
  runtimeTenantResolver.clearTenant();
  FeignSecurityManager.reset();
}

How to create a client programmatically​

Use FeignClientBuilder, TokenClientProvider and FeignSecurityManager to init one :

MyClient client = FeignClientBuilder.build(new TokenClientProvider<>(MyClient.class,
        "url", feignSecurityManager));

How to mock Feign​

Feign starter allows to disable client discovery. To do so, run the tests in a test profile (use @ActiveProfiles) and mock your clients as you wish (using stub, Mockito, etc.).

If you set your own annotation on a configuration class, we recommend to add profile annotation as follow to be able to mock client in test profile :

@Profile("!test")
@Configuration
@EnableFeignClients("your.package")