flowable/flowable-engine · error · FlowableIllegalArgumentException

The identity link type is required.

Error message

The identity link type is required.

What it means

The identity link body must include a non-null "type" (the identity link type, e.g. 'participant', 'owner', or a custom type). If RestIdentityLink.type is null, FlowableIllegalArgumentException("The identity link type is required.") is thrown.

Source

Thrown at modules/flowable-cmmn-rest/src/main/java/org/flowable/cmmn/rest/service/api/runtime/caze/CaseInstanceIdentityLinkCollectionResource.java:84

            @ApiResponse(code = 400, message = "Indicates the requested body did not contain a userId or a type."),
            @ApiResponse(code = 404, message = "Indicates the requested case instance was not found.")
    })
    @PostMapping(value = "/cmmn-runtime/case-instances/{caseInstanceId}/identitylinks", produces = "application/json")
    @ResponseStatus(HttpStatus.CREATED)
    public RestIdentityLink createIdentityLink(@ApiParam(name = "caseInstanceId") @PathVariable String caseInstanceId, @RequestBody RestIdentityLink identityLink) {

        CaseInstance caseInstance = getCaseInstanceFromRequestWithoutAccessCheck(caseInstanceId);

        if (identityLink.getGroup() == null && identityLink.getUser() == null) {
            throw new FlowableIllegalArgumentException("User or group are required.");
        }
        
        if (StringUtils.isEmpty(identityLink.getGroup()) && StringUtils.isEmpty(identityLink.getUser())) {
            throw new FlowableIllegalArgumentException("Only one value of user or group is supported.");
        }

        if (identityLink.getType() == null) {
            throw new FlowableIllegalArgumentException("The identity link type is required.");
        }

        if (restApiInterceptor != null) {
            restApiInterceptor.createCaseInstanceIdentityLink(caseInstance, identityLink);
        }

        if (StringUtils.isNotEmpty(identityLink.getGroup())) {
            runtimeService.addGroupIdentityLink(caseInstance.getId(), identityLink.getGroup(), identityLink.getType());
            
        } else {
            runtimeService.addUserIdentityLink(caseInstance.getId(), identityLink.getUser(), identityLink.getType());
        }

        return restResponseFactory.createRestIdentityLink(identityLink.getType(), identityLink.getUser(), identityLink.getGroup(), null, null, caseInstance.getId());
    }
}

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Add "type" to the request body, e.g. "participant".
2. Use a known identity link type supported for case instances.
3. Validate that identityLink.type != null before calling the endpoint.

Example fix

// before
{"user": "kermit"}
// after
{"user": "kermit", "type": "participant"}

// Java
if (link.getType() == null || link.getType().isEmpty()) {
    throw new IllegalArgumentException("identity link type is required");
}

When it happens

Trigger: POST /cmmn-runtime/case-instances/{id}/identitylinks with {"user":"kermit"} and no "type" field.

Common situations: Client forgetting the type field; assuming the server defaults the type (it does not); schema drift after upgrading the REST API client model.

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

• User or group are required.
• Variable operation is missing for variable: ${variable.getNa
• Variable value is missing for variable: ${variable.getName()
• Variable operation is missing for variable:
• A group or a user is required to create an identity link.

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/7df3ae114234a53b. Report an issue: GitHub.