Question

So I have a database with 2 tables – Workflows and WorkflowSteps I want to use the rows stored there to create objects in java BUT the catch is that I want to have my database code separated from my application code. From one point onwards – when Workflow/WorkflowSteps objects are create the rest of the application will not have to worry about DB access. So here is what I have:

public Workflow getPendingWorkflowId() {
    int workflowid = -1;
    Statement statement = null;
    ResultSet rs = null;
    try {
        statement = con.createStatement();

        rs = statement.executeQuery("SELECT id FROM xxx.workflows WHERE status = 'NOT-YET-STARTED' LIMIT 1");

        while (rs.next()) {
            workflowid = rs.getInt("id");
        }

        statement.close();
        rs.close();

    } catch (SQLException ex) {
        Logger.getLogger(DBAccessor.class.getName()).log(Level.SEVERE, null, ex);
        System.out.println("Error fetching workflows id");
    }

    return new Workflow(workflowid);
}

Each workflow object has a List to store the steps that pertain to a particular Workflow and then each WorkflowStep has a Map which is used to store data taken from a 3rd table:

public List<WorkflowStep> getUnworkedStepsByWFId(int id) {

    //can be changed
    ArrayList<WorkflowStep> steps = new ArrayList<WorkflowStep>();
    Statement statement = null;
    ResultSet rs = null;
    try {
        statement = con.createStatement();

        rs = statement.executeQuery("SELECT * FROM `workflow_steps` WHERE `workflow_id` =" + id + " AND status =  'NOT-YET-STARTED'");

        while (rs.next()) {

            steps.add(new WorkflowStep(rs.getInt(1), rs.getInt(3), rs.getInt(4)));

        }

        statement.close();
        rs.close();

    } catch (SQLException ex) {
        Logger.getLogger(DBAccessor.class.getName()).log(Level.SEVERE, null, ex);
        System.out.println("Error fetching workflows id");
    }

    return steps;
} 

And here is the query for the 3rd table:
public Map getParametersForStep(int workflowId, int workstepPos) {

    Statement statement = null;
    ResultSet rs = null;
    Map<String, String> hMap = new HashMap<String, String>();

    try {
        statement = con.createStatement();

        //MIGHT BE WRONG
        rs = statement.executeQuery("SELECT wf.id AS workflowID, ws_steps.id AS workflowStepsID, name, param_value, pathname FROM workflows AS wf INNER JOIN workflow_steps AS ws_steps ON wf.id = ws_steps.workflow_id INNER JOIN ws_parameters ON ws_parameters.ws_id = ws_steps.id INNER JOIN submodule_params ON submodule_params.id = ws_parameters.sp_id AND wf.id =" + workflowId + " AND ws_steps.workflow_position =" + workstepPos);
        String paramName = null;
        String paramValue = null;

        while (rs.next()) {

            paramName = rs.getString("name");

            if (rs.getString("param_value") == null) {
                paramValue = rs.getString("pathname");
            } else {
                paramValue = rs.getString("param_value");
            }

            hMap.put(paramName, paramValue);
        }

        statement.close();
        rs.close();
        return hMap;

    } catch (SQLException ex) {
        Logger.getLogger(DBAccessor.class.getName()).log(Level.SEVERE, null, ex);
        System.out.println("Error fetching workflow step parameters names");
    }

    return Collections.emptyMap();
}

Having this code in mind I end up with the following “procedure” to initialize a Workflow with all its WorkflowSteps and their Parameters:

Workflow wf = db.getPendingWorkflowId();
wf.initSteps(db.getUnworkedStepsByWFId(wf.getId()));
Iterator<WorkflowStep> it = wf.getSteps();

     while(it.hasNext()) {
         WorkflowStep step = it.next();             
         step.setParameters(db.getParametersForStep(wf.getId(), step.getPosInWorkflow()));
     }

I think I have a good level of decoupling but I wonder if this can be refactored somehow – for example probably move the step.setParameters to a method of the WorkflowStep class but then I would have to pass a reference to the database connection (db) to a WorkflowStep object but in my view this will break the decoupling? So how would you people refactor this code?

Answer 1

It seems that you are rolling your own ORM. My suggestion would be to use one of existing ones like Hibernate.