Spring Boot RestTemplate Basic Authentication using RestTemplateBuilder - spring

Question

In Spring Boot I'm trying to create a RestTemplate which will use basic authentication using
#Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
builder.basicAuthorization("username", "password");
RestTemplate template = builder.build();
return template;
}
I then inject the RestTemplate in my service class as
#Autowired
private RestTemplate restTemplate;
However, my requests fail with a 401 unauthorized exception:
Caused by: org.springframework.web.client.HttpClientErrorException: 401 Unauthorized
Using another REST Client (Postman) the requests to the same URL succeeds so I assume the basic authentication is not working correctly. From the debug output it looks as if the authentication header is not being set. What will make this work?

Answer 1

The problem is that you are using the RestTemplateBuilder in a wrong way. The RestTemplateBuilder is immutable. So when doing builder.basicAuthorization("username", "password") you actually get a new instance, with a BasicAuthorizationInterceptor added and configured, of the RestTemplateBuilder. (this applies to all configuration methods of the RestTemplateBuilder they all create a fresh copied instance).
However your code is discarding that specifically configured instance and you are basically using the non secured default RestTemplateBuilder.
#Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
builder.basicAuthorization("username", "password");
RestTemplate template = builder.build();
return template;
}
This code should be replaced with something like this.
#Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
return builder.basicAuthorization("username", "password").build();
}
Which will use the specifically configured instance.

Answer 2

One solution is to create the RestTemplate as follows:
#Bean
public RestTemplate restTemplate(RestTemplateBuilder builder) {
RestTemplate template = builder.build();
template.setMessageConverters(
Arrays.asList(
new FormHttpMessageConverter(),
new StringHttpMessageConverter()
)
);
template.getInterceptors().add(new BasicAuthorizationInterceptor("username", "password"));
return template;
}