How to Fix DNS Resolution Error in Spring Boot

Stumped by a DNS Resolution Error in Spring Boot? This error is more common than you'd think, and the fix is usually simple.

Why This Happens

DNS resolution errors in Spring Boot occur when the runtime can't resolve a hostname to an IP address. This may be caused by misconfigured DNS servers, IPv6/IPv4 issues, network connectivity problems, or transient DNS cache failures.

How to Fix It

The key is to configure connect and read timeouts on your RestTemplate bean:

// RestTemplate with timeout configuration
@Bean
public RestTemplate restTemplate() {
    var factory = new SimpleClientHttpRequestFactory();
    factory.setConnectTimeout(Duration.ofSeconds(5));
    factory.setReadTimeout(Duration.ofSeconds(10));
    return new RestTemplate(factory);
}

Common Pitfall

When debugging this, start by reproducing the exact error message. Slight variations in the error text can point to completely different root causes in Spring Boot. If you're using Docker or a containerized setup, make sure the fix is reflected in both your local and production Dockerfiles.

Testing Your Changes

Run your test suite to make sure the fix doesn't introduce regressions. If you don't have tests covering this area, now is a good time to add a simple integration test. A quick manual smoke test across different browsers or environments can also catch edge cases your tests might miss.

Monitoring

To prevent this from recurring unnoticed, set up [Bugsly](https://bugsly.dev) for your Spring Boot project — it monitors errors and gives you actionable alerts.