Clarify how to to customize the TestRestTemplate

The documentation is pretty silent on how to customize TestRestTemplate (e.g. register additional HttpMessageConverters). I’ve discovered RestTemplateCustomizer but declaring a Spring bean for that doesn’t seem to have any effect. Declaring a bean of type RestTemplate and customizing that through a RestTemplateBuilder doesn’t either.

I finally tried this:

@Bean
TestRestTemplate template(RestTemplateBuilder builder) {
    return new TestRestTemplate(
            builder.additionalMessageConverters(new ProjectingJackson2HttpMessageConverter()).build());
}

But that lets the bootstrap fail as I now end up with two TestRestTemplate instances. Making the manually declared one @Primary makes the context bootstrap, but the RestTemplate created then doesn’t seem to support non-absolute URIs.

I am aware that in my particular example I can declare HttpMessageConverter beans but they then get registered with both the server side MVC setup and the client.

[FrontierPsychiatrist]

Ok, it was (luckily 😃) my error. I didn’t see that the RestTemplateBuilder is immutable and the methods will always return a new instance. So I set an additional message converter and wondered why it was never used - but in fact it wasn’t even in the builder.

I misinterpreted the lazy bean initiliazition via applicationContext.getBean(...) as being too late while it was actually calling my bean producer method.

So if anyone ever has a similar problem, don’t do this

@Bean
public RestTemplateBuilder restTemplateBuilder() {
  RestTemplateBuilder builder = new RestTemplateBuilder();
  builder.additionalMessageConverters(...);
  return builder;
}

it won’t work.

Instead do this

@Bean
public RestTemplateBuilder restTemplateBuilder() {
  return new RestTemplateBuilder().additionalMessageConverters(...);
}

[kartoffelsup]

I think you would need to add this to a @Configuration class. And also, ask on stack overflow next time :p