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Allow Type reference instead of Class reference in RestTemplate's convenience methods. #35301

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Allow Type reference instead of Class reference in RestTemplate's convenience methods. #35301

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sam-hieken
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@sam-hieken sam-hieken commented Aug 9, 2025 •
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Issue

The convenience methods *ForEntity and *ForObject in RestTemplate don't allow generic types to be specified in the result body. For example:

public class Main {
	static class ExampleType {
		...
	}

	public static void main(String[] args) {
		RestTemplate restTemplate = ...;
		URI url = ...;
		
                // Type mismatch: cannot convert from ResponseEntity<List> to ResponseEntity<List<Main.ExampleType>>
		ResponseEntity<List<ExampleType>> result = restTemplate.getForEntity(url, List.class);
        }
}

Using Type as the type of the responseType parameters instead of Class<T> in these methods would allow generic types to be used as well (and since Class extends Type, changing it wouldn't be a breaking change):

public class Main {
	static class ExampleType {
		...
	}
	
	public static void main(String[] args) {
		RestTemplate restTemplate = ...;
		URI url = ...;
		
		// Example of how we can now allow generic types using com.fasterxml.jackson.core.type.TypeReference
		ResponseEntity<List<ExampleType>> result = restTemplate.getForEntity(url, new TypeReference<List<ExampleType>>() {}.getType());
}

@spring-projects-issues spring-projects-issues added the status: waiting-for-triage An issue we've not yet triaged or decided on label Aug 9, 2025
@sam-hieken sam-hieken force-pushed the resttemplate-allow-generic-types branch from b0cd03d to 6b1a55b Compare August 9, 2025 22:26
@bclozel
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bclozel commented Aug 10, 2025

Thanks for the proposal but this is well supported already with ParameterizedTypeReference, see https://docs.spring.io/spring-framework/reference/integration/rest-clients.html#rest-resttemplate

Also I don't think this change would have the desired behavior as the generic type information is probably not handled by messages readers in this way.

Thanks!

@bclozel bclozel closed this Aug 10, 2025
@bclozel bclozel added status: declined A suggestion or change that we don't feel we should currently apply and removed status: waiting-for-triage An issue we've not yet triaged or decided on labels Aug 10, 2025
@sam-hieken
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Thanks for taking a look Brian

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