perwendel/spark · error · IllegalArgumentException

httpMethod cannot be null or blank

Error message

httpMethod cannot be null or blank

What it means

Routes.remove(String path, String httpMethod) validates that the HTTP method string is non-null and non-blank before converting it via HttpMethod.valueOf. An empty or null httpMethod cannot map to a route, so Spark throws IllegalArgumentException.

Solutions

  1. Pass a valid HTTP method string: "GET", "POST", "PUT", "DELETE", "PATCH", "HEAD", "TRACE", "CONNECT", "OPTIONS".
  2. Guard the call against null/blank before invoking remove.
  3. Note the adjacent check: after this validation, HttpMethod.valueOf will also throw IllegalArgumentException for a non-blank but invalid method name, so use an exact uppercase method name.

Example fix

// before
routes.remove("/users", method); // method may be null/blank

// after
if (method != null && !method.trim().isEmpty()) {
    routes.remove("/users", method.toUpperCase());
}
Defensive patterns

Strategy: validation

Validate before calling

if (httpMethod == null || httpMethod.trim().isEmpty()) throw new IllegalArgumentException("httpMethod must be non-blank");
routes.remove(path, httpMethod.toUpperCase());

Try / catch

try {
    routes.remove(path, httpMethod);
} catch (IllegalArgumentException e) {
    log.error("Invalid httpMethod for route removal: {}", e.getMessage());
}

Prevention

When it happens

Trigger: Calling routes.remove("/path", null), routes.remove("/path", ""), or routes.remove("/path", " ").

Common situations: HTTP method read from a variable/config/request that is unset; uppercase/lowercase mishandling leaving an empty string after trimming; a switch statement building the method name incorrectly.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of perwendel/spark@1973e402f5 (2026-09-10). Data as JSON: /api/errors/6945eaba87eb3ff1. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/spark/route/Routes.java:155

    /**
     * Removes a particular route from the collection of those that have been previously routed.
     * Search for a previously established routes using the given path and HTTP method, removing
     * any matches that are found.
     *
     * @param path       the route path
     * @param httpMethod the http method
     * @return <tt>true</tt> if this a matching route has been previously routed
     * @throws IllegalArgumentException if <tt>path</tt> is null or blank or if <tt>httpMethod</tt> is null, blank
     *                                  or an invalid HTTP method
     * @since 2.2
     */
    public boolean remove(String path, String httpMethod) {
        if (StringUtils.isEmpty(path)) {
            throw new IllegalArgumentException("path cannot be null or blank");
        }

        if (StringUtils.isEmpty(httpMethod)) {
            throw new IllegalArgumentException("httpMethod cannot be null or blank");
        }

        // Catches invalid input and throws IllegalArgumentException
        HttpMethod method = HttpMethod.valueOf(httpMethod);

        return removeRoute(method, path);
    }

    /**
     * Removes a particular route from the collection of those that have been previously routed.
     * Search for a previously established routes using the given path and removes any matches that are found.
     *
     * @param path the route path
     * @return <tt>true</tt> if this a matching route has been previously routed
     * @throws java.lang.IllegalArgumentException if <tt>path</tt> is null or blank
     * @since 2.2
     */
    public boolean remove(String path) {

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