OpenFeign/feign · error · IllegalArgumentException

Invalid HTTP Method

Error message

Invalid HTTP Method: ${method}

What it means

RequestTemplate.method(String) parses the given string into an HttpMethod enum via HttpMethod.valueOf. If the string is not a valid HTTP method name, the resulting IllegalArgumentException is rethrown with 'Invalid HTTP Method: <method>'.

Solutions

1. Pass a standard uppercase HTTP method name, e.g. method("GET")
2. Trim and normalize case: HttpMethod.valueOf(method.trim().toUpperCase()) before calling
3. Fix the annotation or config value supplying the method string
4. Prefer the typed method(HttpMethod) overload to get compile-time safety

Example fix

// before
template.method("Get");
// after
template.method("GET"); // or template.method(HttpMethod.GET)

if (java.net.http.HttpMethod.includes == null) { /* Java 8-safe check */ }
java.util.Set<String> VALID = java.util.Set.of("GET","POST","PUT","DELETE","PATCH","HEAD","OPTIONS","TRACE");
if (!VALID.contains(method.trim().toUpperCase())) {
  throw new IllegalArgumentException("Unsupported method: " + method);
}

try {
  template.method(name);
} catch (IllegalArgumentException e) {
  if (e.getMessage() != null && e.getMessage().startsWith("Invalid HTTP Method")) {
    LOGGER.warn("Falling back to GET; invalid method {}", name);
    template.method("GET");
  } else { throw e; }
}

When it happens

Trigger: Calling RequestTemplate.method("GETS") or any string that is not a standard HTTP method token (GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS, TRACE) when building a template programmatically or via a misconfigured contract.

Common situations: Typo in a custom Contract/annotation parser, reading the HTTP verb from configuration or an annotation value with a typo, lowercasing methods before passing them in.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• url values must be not be absolute.
• name is required.
• Method return type is not parameterized
• Wildcards are not supported for return-type parameters
• template has not been resolved.

AI-assisted analysis of OpenFeign/feign@e2a1e27560 (2026-09-10). Data as JSON: /api/errors/a51b0e720bf542e1. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/feign/RequestTemplate.java:307

      throw new IllegalStateException("template has not been resolved.");
    }
    return Request.create(this.method, this.url(), this.headers(), this.body, this);
  }

  /**
   * Set the Http Method.
   *
   * @param method to use.
   * @return a RequestTemplate for chaining.
   * @deprecated see {@link RequestTemplate#method(HttpMethod)}
   */
  @Deprecated
  public RequestTemplate method(String method) {
    checkNotNull(method, "method");
    try {
      this.method = HttpMethod.valueOf(method);
    } catch (IllegalArgumentException iae) {
      throw new IllegalArgumentException("Invalid HTTP Method: " + method);
    }
    return this;
  }

  /**
   * Set the Http Method.
   *
   * @param method to use.
   * @return a RequestTemplate for chaining.
   */
  public RequestTemplate method(HttpMethod method) {
    checkNotNull(method, "method");
    this.method = method;
    return this;
  }

  /**
   * The Request Http Method.

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