We need to create validators for each status. The validator will check if transition from current state is allowed or not. All validators are injected into WorkflowExecutionValidator. private List<Validator> validators WorkflowExecutionValidator will pick up an appropriate validator from a list and check if transition is allowed. Validators are implemented for each workflow execution status Validators are applied in production code

public class WorkflowExecutionValidator {
    
    private List<Validator> validators;
    
    public WorkflowExecutionValidator(List<Validator> validators) {
        this.validators = validators;
    }

    public void validate(WorkflowExecution execution) {
        // pick up an appropriate validator from a list and check if transition is allowed
    }
}