OpenFeign/feign · error · IllegalStateException

Cannot find any suitable constructor in class

Error message

Cannot find any suitable constructor in class [${exceptionClass}] - did you forget to mark one with @FeignExceptionConstructor or at least have a public default constructor?

What it means

Thrown by ExceptionGenerator.getConstructor when the exception class has no constructor marked with @FeignExceptionConstructor and also no public no-arg constructor accessible via getConstructor(). Feign needs an invokable constructor to instantiate the configured exception type.

Solutions

1. Annotate one suitable constructor with @FeignExceptionConstructor
2. Add a public no-arg constructor to the exception class
3. Make the existing no-arg constructor public

Example fix

// before
public class ApiError extends RuntimeException {
  public ApiError(int status, String body) { ... } // no default ctor, none annotated
}
// after
public class ApiError extends RuntimeException {
  @FeignExceptionConstructor
  public ApiError(int status, String body) { ... }
}

boolean ok = Arrays.stream(ApiError.class.getConstructors())
    .anyMatch(c -> c.isAnnotationPresent(FeignExceptionConstructor.class))
  || Arrays.stream(ApiError.class.getConstructors())
    .anyMatch(c -> c.getParameterCount() == 0);
if (!ok) throw new IllegalStateException("Needs @FeignExceptionConstructor or public default ctor");

try { Feign.builder().build(); }
catch (IllegalStateException e) { if (e.getMessage().startsWith("Cannot find any suitable constructor")) { ... } }

When it happens

Trigger: Configuring a custom exception class that has only constructors with parameters, none annotated with @FeignExceptionConstructor; or a no-arg constructor that is private/protected/package-private.

Common situations: Using Lombok @Builder or a convenience multi-arg constructor which removes the implicit default constructor; exception class written for a different framework; non-public constructor added for encapsulation.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• Cannot generate exception - check constructor parameter…
• Too many constructors marked with @FeignExceptionConstructor
• Cannot access constructor
• Cannot instantiate exception with constructor
• Cannot invoke constructor

AI-assisted analysis of OpenFeign/feign@e2a1e27560 (2026-09-10). Data as JSON: /api/errors/317a21dc7717a841. Report an issue: GitHub.

Appendix: source

Thrown at annotation-error-decoder/src/main/java/feign/error/ExceptionGenerator.java:232

          continue;
        }
        Class<?>[] parameterTypes = constructor.getParameterTypes();
        if (parameterTypes.length == 0) {
          continue;
        }
        if (preferredConstructor == null) {
          preferredConstructor = (Constructor<? extends Exception>) constructor;
        } else {
          throw new IllegalStateException(
              "Too many constructors marked with @FeignExceptionConstructor");
        }
      }

      if (preferredConstructor == null) {
        try {
          return exceptionClass.getConstructor();
        } catch (NoSuchMethodException e) {
          throw new IllegalStateException(
              "Cannot find any suitable constructor in class ["
                  + exceptionClass.getName()
                  + "] - did you forget to mark one with @FeignExceptionConstructor or at least"
                  + " have a public default constructor?",
              e);
        }
      }
      return preferredConstructor;
    }
  }
}

View on GitHub (pinned to e2a1e27560)