What causes ""Parameter '" + key + "' not found for action '" + action.key() + "'"" in SonarSource/sonarqube?

Declare the parameter in the action's define() via createParam(key).... before reading it with multiParam(key).

SonarSource/sonarqube · error · IllegalArgumentException

"Parameter '" + key + "' not found for action '" +…

Error message

"Parameter '" + key + "' not found for action '" + action.key() + "'"

What it means

ValidatingRequest.multiParam(key) is a typed accessor for multi-valued web service parameters. It first looks up the parameter in the WebService action's definition; if the action does not declare a parameter with that key, it throws IllegalArgumentException. The library throws this to force plugins to declare their parameters so documentation and validation stay consistent.

Solutions

Declare the parameter in the action's define() via createParam(key).... before reading it with multiParam(key).
Fix the key typo so it matches the declared param name.
If reading arbitrary keys is intentional, switch to an untyped read (e.g. request.getMultiParam or the raw request) instead of multiParam.

Example fix

// before
List<String> values = request.multiParam("repositories");

// after (in the action's define())
public void define(WebService.NewAction action) {
  action.createParam("repositories").setMultiple(true);
}
// then in the handler
List<String> values = request.multiParam("repositories");

Defensive patterns

Strategy: validation

Validate before calling

// Java
if (action.param(key) == null) {
  throw new IllegalStateException("Parameter not declared for action: " + key);
}
List<String> values = request.multiParam(key);

Prevention

Declare every parameter you read in the action's define() method as a first step.
Keep parameter keys in constants shared between define() and the handler.
Review new request.read* calls in code review against the define() parameter list.

When it happens

Trigger: Calling request.multiParam("some_key") inside a WebService.SearchRequest implementation where the action never called createParam(...).param("some_key") in define().

Common situations: Plugin code reads a parameter that was added on the client/request side but forgotten in the action's define() method; a typo in the key; a parameter declared under a deprecated key that no longer matches.

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

AI-assisted analysis of SonarSource/sonarqube@184c821202 (2026-09-09). Data as JSON: /api/errors/8022c7db2e942f5c. Report an issue: GitHub.

Appendix: source

Thrown at sonar-plugin-api-impl/src/main/java/org/sonar/api/impl/ws/ValidatingRequest.java:88

    String rawValue = readParam(key, definition);
    String rawValueOrDefault = Objects.toString(rawValue, definition.defaultValue());
    String value = rawValueOrDefault == null ? null : trim(rawValueOrDefault);
    validateRequiredValue(key, definition, rawValue);
    if (value == null) {
      return null;
    }
    validatePossibleValues(key, value, definition);
    validateMaximumLength(key, definition, rawValueOrDefault);
    validateMinimumLength(key, definition, rawValueOrDefault);
    validateMaximumValue(key, definition, value);
    return value;
  }

  @Override
  public List<String> multiParam(String key) {
    WebService.Param definition = action.param(key);
    if (definition == null) {
      throw new IllegalArgumentException("Parameter '" + key + "' not found for action '" + action.key() + "'");
    }
    List<String> values = readMultiParamOrDefaultValue(key, definition);
    return validateValues(values, definition);
  }

  private static String trim(String s) {
    int begin;
    for (begin = 0; begin < s.length(); begin++) {
      if (!Character.isWhitespace(s.charAt(begin))) {
        break;
      }
    }

    int end;
    for (end = s.length(); end > begin; end--) {
      if (!Character.isWhitespace(s.charAt(end - 1))) {
        break;
      }

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