RestClientBeanPostProcessor always mutates underlying RestClient

[lenin-jaganathan]

Describe the bug

The RestClientBeanPostProcessor in the Spring Boot auto-configuration module created a new RestClient bean every time it processed a bean, even when the OpenTelemetry interceptor was already present. This resulted in unnecessary bean creation.

The primary reason I am here is that though this tries to create a mutated bean, it doesn't really go well when the client bean is some kind of proxy/delegates, which hides them and creates a default rest client. Even though the bean is created using an injected RestClient.Builder that would have added RequestInterceptor already.

Steps to reproduce

1. Create a Spring Boot 3.2+ application with OpenTelemetry autoconfiguration
2. Define a RestClient bean with the OTel interceptor already configured
3. Observe that a new RestClient instance is created even though the interceptor is already present and nothing really changed.

Expected behavior

The RestClientBeanPostProcessor should:

• Check if the OTel interceptor is already present in the RestClient
• Return the original bean instance if the interceptor already exists
• Only create a new bean instance when actually adding the interceptor

Actual behavior

The bean post-processor always calls restClient.mutate().build(), creating a new bean instance regardless of whether the interceptor was already present.

Javaagent or library instrumentation version

v2.21.0

Environment

JDK: 25

Additional context

No response

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[lenin-jaganathan]

I think Webclient also suffers from this problem. IMO, having Interceptors/Filters should suffice to add the instrumentation. The BeanPostProcessor approach seems to do too much and plays with the actual client bean instances and this canot be turned off too.

[Arunodoy18]

Hi, I think i got the issue ,it will be a good issue to solve . .take-issue .
ThankYou.