Is it possible to define a custom rest template? - spring-boot

Question

I'm trying to define a common bean to be used for all my application so to add inside a logger and other logic. My idea would be:
public class MyRestTemplate extends RestTemplate{
Then:
#Configuration
public class RestTemplateConfig {
#Bean
public MyRestTemplate myRestTemplate(RestTemplateBuilder builder){
return (MyRestTemplate) builder.build(); //throws classcast exception!
}
}
What am I doing wrong? Is there another way? I want to be sure that people will have to use my customized class.

Answer 1

If you want some customizations in your restTemplate you could define a class that implements RestTemplateCustomizer and add a custom interceptor to it.
public class CustomRestTemplateCustomizer implements RestTemplateCustomizer {
#Override
public void customize(RestTemplate restTemplate) {
restTemplate.getInterceptors().add(new CustomClientHttpRequestInterceptor());
}
}
Then you have to define that custom interceptor for all the requests going out of this restTemplate with
public class CustomClientHttpRequestInterceptor implements ClientHttpRequestInterceptor {
#Override
public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
// This is where you can do a lot of thing with this request like logging
return execution.execute(request, body);
}
}
And finally, just define a bean for the custom restTemplate you have written
#Bean
public CustomRestTemplateCustomizer customRestTemplateCustomizer() {
return new CustomRestTemplateCustomizer();
}

Answer 2

builder.build() returns a RestTemplate, not a MyRestTemplate.
If you change your code as shown below you would create a bean named myRestTemplate. Spring use the name of the method as bean name if you don't override it in the #Bean annotation.
#Configuration
public class RestTemplateConfig {
#Bean
public RestTemplate myRestTemplate(RestTemplateBuilder builder){
return builder.build(); //throws classcast exception!
}
}
Please also see https://docs.spring.io/spring-boot/docs/1.5.x/reference/html/boot-features-restclient.html