Invoking REST services from Spring is much easier if you use Spring Open Feign.
It allows you to invoke REST services declaratively and saves a lot of code.
Here is the post explaining the basic concept of Open Feign:
How to call a REST service declaratively using Open Feign?
It is a very simple example with no authentication involved.
I went on to protect the REST service I invoked using Open Feign, with Basic Authentication.
And then when I tried to hit a REST service which internally used Open Feign to invoke the now protected REST service, I got the below error:
That is because I didn’t customize Open Feign to deal with authentication.
Below is the FeignClient code as explained in the above link:
package com.springboot.openfeign;
import java.util.List;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@FeignClient(name = "personclient", url = "http://localhost:8090/")
public interface PersonClient {
@RequestMapping(method = RequestMethod.GET, value = "/persons")
List<Person> getPersons();
}
To enable authentication , add authorization header as a parameter to the above getPersons() method. Here is the updated code:
package com.springboot.openfeign;
import java.util.List;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@FeignClient(name = "personclient", url = "http://localhost:8090/")
public interface PersonClient {
@RequestMapping(method = RequestMethod.GET, value = "/persons")
List<Person> getPersons(@RequestHeader("Authorization") String header);
}
I have added a @RequestHeader annotation with ‘Authorization’ as a parameter to it.
To pass this authorization header while invoking the above rest service , build the basic authentication header as below:
package com.springboot.openfeign;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.util.Base64Utils;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class RestConsumer {
@Autowired
private PersonClient client;
@GetMapping("/getAllPersons")
public List<Person> getAllPersons() {
String username = "admin";
String password = "admin";
byte[] encodedBytes = Base64Utils.encode((username + ":" + password).getBytes());
String authHeader = "Basic " + new String(encodedBytes);
return client.getPersons(authHeader);
}
}
After making the above changes , I hit the service again:
I got the response!
Here is the github url for the entire code of feign client:
The Full Stack Developer 
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