Populate Array from Oracle Database

Question

I am trying to create this from a DB Connection and populate the Array with the results. I just need help with populating "DestinationItem[]" from the SQL below.

//DestinationBean.java
//  Manual Array works but I need this to be populated from DB using the below Query and DB Connection info.
    private DestinationItem[] destinationResults = new DestinationItem[]{
            new DestinationItem("58285", "Dodge Grand Caravan"),
            new DestinationItem("57605", "Dodge SX 2.0"),
            new DestinationItem("58265", "Chrysler 300 Touring")
    };

    public DestinationItem[] getdestinationResults() {
        return destinationResults;
    }

    public class DestinationItem {
        String destid;
        String commdefid;

        public DestinationItem(String destid, String commdefid) {
            this.destid = destid;
            this.commdefid = commdefid;
        }
// Getter/Setter below

// END

I need to take this DB Connection Logic and populate the "DestinationItem[]" Array above and I need help.

//DBConnection
public static ArrayList<CustomerBean> getCustomer() {
    try {
        Class.forName("oracle.jdbc.OracleDriver").newInstance();

        Connection con = DriverManager.getConnection("jdbc:oracle:thin:", "BLAH", "BLAH");
        PreparedStatement ps = con.prepareStatement("select destination_id, commdef_id from BLAH.destination");

        ArrayList<CustomerBean> al = new ArrayList<CustomerBean>();

        ResultSet rs = ps.executeQuery();

        boolean found = false;

        while (rs.next()) {
            CustomerBean e = new CustomerBean();
            e.setDestId(rs.getString("destination_id"));
            e.setDestId(rs.getString("commdef_id"));
            al.add(e);
            found = true;
        }

        rs.close();
        if (found) {
            return al;
        } else {
            return null; // no entires found
        }
    } catch (Exception e) {
        System.out.println("Error In getCustomer() -->" + .getMessage());
        return (null);
    }
}

Answer 1

Here's a snippet that should do what you need:

List<DestinationItem> destinationsList = new ArrayList<DestinationItem>();

while (rs.next()) {
    destinationsList.add(new DestinationItem(
        rs.getString("destination_id"), rs.getString("commdef_id")));
}
rs.close();

// if you need to convert the list into an array, you can do it like this:
DestinationItem[] destinationsArray = destinationsList.toArray(
                                          new DestinationItem[destinationsList.size()]);

Some considerations:

It is easiest to use a dynamic data structure such as a List for retrieving data from the ResultSet , because that way you don't need to care about the number of rows returned from the DB before the iteration.

It is considered a best practise to never return null from methods that return List s (like your getCustomer() method). If no data is found, simply return an empty List . This will make client code simpler when null checks are not needed.

You should close the Connection con and PreparedStatement ps resources you open in the method. A common idiom for this is to have a structure like this in data-accessing methods:

Connection con = null;
PreparedStatement ps = null;
try {
    // initialize and use 'con' and 'ps'
} finally {
    if (ps != null) {
        ps.close();
    }
    if (con != null) {
        con.close();
    }
}

If you are on Java 7 or above, you can do the same in a more elegant way with the try-with-resources statement .

Finally, instead of catch (Exception e) , you should consider either throwing a possible (checked) SQLException from the method, or if you do not want to change the method signature, wrapping the SQLException into a RuntimeException . In general, you should not catch Exception s you cannot (or do not) handle in your method. In these cases, it's better to let the problem bubble up to the client code instead of silently ignoring it.