Validation

The engine provides a WorkflowValidator that checks workflow definitions for structural and semantic problems before execution. The same rules are implemented in TypeScript for real-time validation in the visual editor.

Usage

Java

WorkflowValidator validator = new WorkflowValidator();
List<ValidationProblem> problems = validator.validate(workflow);

boolean hasErrors = validator.hasErrors(problems);

TypeScript

import { validateWorkflow } from '@apitomy/flow-ui';

const problems = validateWorkflow(workflow);
const hasErrors = problems.some(p => p.severity === 'error');

Severity Levels

Severity	Meaning
ERROR	The workflow cannot execute. Must be fixed.
WARNING	The workflow can execute but the definition is likely wrong.

startWorkflow automatically validates the definition and rejects workflows with ERROR-level problems.

Validation Rules

Structural (ERROR)

Code	Rule
`EMPTY_WORKFLOW`	Workflow has no nodes at all
`MISSING_WORKFLOW_ID`	Workflow has no ID (null or blank)
`MISSING_WORKFLOW_NAME`	Workflow has no name (null or blank)
`MISSING_NODE_ID`	Node has no ID (null or blank)
`MISSING_EDGE_ID`	Edge has no ID (null or blank)
`NO_START_NODE`	Exactly one start node is required
`MULTIPLE_START_NODES`	More than one start node found
`NO_END_NODE`	At least one end node is required
`INVALID_EDGE_SOURCE`	Edge references a source node ID that doesn't exist
`INVALID_EDGE_TARGET`	Edge references a target node ID that doesn't exist
`DUPLICATE_NODE_ID`	Two or more nodes share the same ID
`DUPLICATE_EDGE_ID`	Two or more edges share the same ID
`START_HAS_INCOMING`	Start node must not have incoming edges
`END_HAS_OUTGOING`	End node must not have outgoing edges
`MISSING_ACTION_TYPE`	Action node has no `actionType` in its config
`INVALID_ACTION_TYPE_VALUE`	Action node `actionType` is present but not a non-blank string
`INVALID_WAIT_DURATION`	Wait node `duration` is present but not a valid ISO 8601 duration

Structural (WARNING)

Code	Rule
`MISSING_NODE_NAME`	Node has no name (null or blank)

Connectivity (ERROR / WARNING)

Code	Severity	Rule
`DISCONNECTED_NODE`	ERROR	Node has no incoming or outgoing edges (completely isolated)
`NO_OUTGOING_EDGES`	ERROR	Non-end node has no outgoing edges (execution would stall)
`NO_INCOMING_EDGES`	WARNING	Non-start node has no incoming edges (unreachable)
`UNREACHABLE_NODE`	WARNING	Node cannot be reached from the start node
`NO_PATH_TO_END`	WARNING	Node has no path to any end node

Edge / Condition (WARNING)

Code	Rule
`SELF_LOOP_EDGE`	Edge connects a node to itself
`DUPLICATE_EDGE`	Multiple edges share the same source and target
`DEFAULT_EDGE_WITH_CONDITION`	Default edge has a condition that will never be evaluated
`SINGLE_CONDITIONAL_EDGE`	Node has a single outgoing edge with a condition but no fallback
`NO_DEFAULT_EDGE`	Node has multiple conditional edges but no default fallback
`MULTIPLE_DEFAULT_EDGES`	Node has more than one default edge
`INVALID_CONDITION`	Edge condition is not syntactically valid EL (Java only)
`DUPLICATE_EDGE_PRIORITY`	Multiple edges from the same node share the same priority

Semantic (WARNING)

Code	Rule
`DUPLICATE_EVENT_RECEIVER`	Multiple receive-event nodes match the same events
`MISSING_EVENT_TYPE`	Receive-event node has no `eventType` configured
`INVALID_EVENT_TYPE_VALUE`	Receive-event node `eventType` is not a non-blank string
`UNCONDITIONAL_MULTIPLE_EDGES`	Node has multiple outgoing edges with no conditions
`AUTOMATED_CYCLE`	Cycle containing only action nodes (could cause infinite execution)
`MISSING_START_INPUTS`	Start node has no inputs defined
`INVALID_INPUT_DEFINITION`	Start node input entry is missing a name
`DUPLICATE_INPUT_NAME`	Start node has multiple inputs with the same name
`MISSING_ACTION_INPUTS`	Action node has no inputs defined
`INVALID_INPUTS_TYPE`	Action node `inputs` is present but not a Map
`MISSING_ACTION_OUTPUTS`	Action node has no outputs defined
`INVALID_OUTPUTS_TYPE`	Action node `outputs` is present but not a List
`DUPLICATE_OUTPUT_NAME`	Action or human-task node has duplicate output names
`EMPTY_ACTION_INPUT_EXPRESSION`	Action node input has an empty or blank EL expression
`MISSING_TASK_DESCRIPTION`	Human task node has no description
`MISSING_TASK_OUTPUTS`	Human task node has no outputs defined
`EMPTY_TASK_INPUT_EXPRESSION`	Human task input has an empty or blank EL expression
`MISSING_WAIT_DURATION`	Wait node has no duration configured

ValidationProblem

public record ValidationProblem(
    ValidationSeverity severity,  // ERROR or WARNING
    String code,                  // machine-readable code (e.g. "NO_START_NODE")
    String message,               // human-readable description
    String nodeId,                // affected node (optional)
    String edgeId                 // affected edge (optional)
) {}

TypeScript Validator Notes

The TypeScript implementation covers all rules except INVALID_CONDITION, which requires parsing Jakarta EL expressions (a Java library). All other rules are structural or semantic checks that work identically in both languages.