Question

So I am making a simple java project to play around with JDBC in glassfish and see how it works. The program just shows you a list of surveys and a list of questions for the survey you select. However i cant seem to display the list of questions for the survey I selected. I keep getting empty values. These are the methods I have created:

convert the resultset to object model data values

public JHAKSurvey findSurvey(long id) {
    System.out.println("JDBC: FIND SURVEY");
    Connection connection = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    JHAKSurvey survey = null;
    try {
        connection = openConnection();
        String query = "SELECT * FROM APP.SURVEY WHERE ID=?";
        ps = connection.prepareStatement(query);
        ps.setLong(1, id);
        rs = ps.executeQuery();
        while (rs.next()) {
            survey = createSurveyFromResultSet(rs);             
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        closeConnection(connection);
    }
    return survey;
}

private method to query the list of questions from the QUESTION table for a survey id

private void findQuestionsBySurvey(JHAKSurvey survey){
    System.out.println("JDBC: FIND QUESTIONS BY SURVEY");
    Connection connection = null;
    PreparedStatement ps = null;

    try {
        connection = openConnection();
        String query = "SELECT * FROM APP.QUESTION WHERE SURVEYID=?";
        ps = connection.prepareStatement(query);
        ps.setLong(1, survey.getId());
        ps.executeQuery(query);
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        closeConnection(connection);
    }

}

private method to convert the find the resultset list to an question object and add it to the survey object

private void createQuestionFromResultSet(ResultSet rs, JHAKSurvey survey){
    ArrayList<JHAKQuestion> qList = new ArrayList<JHAKQuestion>();      
    JHAKQuestion question = new JHAKQuestion();
    JHAKSurvey ss = new JHAKSurvey();
    //qList.add(survey.getQuestions());

    try {
        while (rs.next()) {
            //question.setDescription(qList.toString());
            question.setId(rs.getLong("ID"));
            question.setDescription(rs.getString("DESCRIPTION"));
            qList.add(question);
            survey.setQuestions(qList);
        }               
        System.out.println("createQuestionFromResultSet : JDBC : successful");
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        System.out.println("createQuestionFromResultSet : JDBC : fail");
        e.printStackTrace();
    }
}

private method to convert a resultset to an survey object.

    private JHAKSurvey createSurveyFromResultSet(ResultSet rs){
    JHAKSurvey survey = new JHAKSurvey();
    Boolean active = false;
    String yes;
    try {
        yes = rs.getString("ACTIVE");
        survey.setId(rs.getLong("ID"));
        survey.setTitle(rs.getString("TITLE"));
        if (yes.equals(Character.toString('Y'))) {
            survey.setActive(true);
        } else {
            survey.setActive(false);
        }   
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }


    return survey;
}

What am I missing? I also seem to get error:

cannot convert from void to JHAKQuestion

When I try the method: createQuestionFromResultSet();

Thank You

Answer 1

Look at your method:

private void findQuestionsBySurvey(JHAKSurvey survey){

You want to get the questions of a survey, but the method returns void. Make it return a List<Question>. And in the body of the method, iterate through the resultset, transform each row into a question, add the question to a List<Question>, and return this list.

Or, if the goal of the method is to add questions to the survey passed as argument, then rename the method to

private void addQuestionsToSurvey(JHAKSurvey survey) {

and, inside the method body, call the method createQuestionFromResultSet (which should be named createQuestionsFromResultSetAndAddThemToSurvey), with the resultset and the survey as argument:

private void findQuestionsBySurvey(JHAKSurvey survey){
    System.out.println("JDBC: FIND QUESTIONS BY SURVEY");
    Connection connection = null;
    PreparedStatement ps = null;

    try {
        connection = openConnection();
        String query = "SELECT * FROM APP.QUESTION WHERE SURVEYID=?";
        ps = connection.prepareStatement(query);
        ps.setLong(1, survey.getId());
        ResultSet rs = ps.executeQuery(query);
        createQuestionFromResultSet(survey); 
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        closeConnection(connection);
    }

}