Question

Is this good style of java data access code, or is it too much try finally ?

public List<Item> getItems() throws ItemException {
    ArrayList<Item> items = new ArrayList<Item>();
    try {
        Connection con = ds.getConnection();
        try {
            PreparedStatement pStmt = con.prepareStatement("SELECT ....");
            try {
                ResultSet rs = pStmt.executeQuery();
                try {
                    while (rs.next()) {
                        Item item = new Item();
                        item.setItemNo(rs.getString("item_id"));
                        // ...
                        items.add(item);
                    }
                } finally {
                    rs.close();
                }
            } finally {
                pStmt.close();
            }
        } finally {
            con.close();
        }
    } catch (SQLException e) {
        throw new ItemException(e);
    }
    return items;
}

Answer 1

Compare it to my code:

Connection con = null;
PreparedStatement pStmt = null;
ResultSet rs = null;
try
{
    con = ds.getConnection();
    pStmt = con.prepareStatement("SELECT ....");
    rs = pStmt.executeQuery();
    while (rs.next()) {
        Item item = new Item();

        item.setItemNo(rs.getString("item_id"));
        ...

        items.add(item);
    }
}
finally {
    rs = DBUtil.close (rs);
    pStmt = DBUtil.close (rs);
    con = DBUtil.close (rs);
}

Here is what close() looks like:

public static ResultSet close (ResultSet rs) {
    try {
        if (rs != null)
            rs.close ();
    } catch (SQLException e) {
        e.printStackTrace (); 
        // Or use your favorite logging framework.
        // DO NOT THROW THIS EXCEPTION OR IT WILL
        // HIDE EXCEPTIONS IN THE CALLING METHOD!!
    }
    return null; // Make sure no one uses this anymore
}

[EDIT] You’ll need to copy this code for the other types.

I also moved all this into a helper class called DBOp so I just have to override processRow(ResultSet row) to do the actual processing and I can omit all that boilerplate code. In Java 5, the constructor of DBOp reads:

public DBOp (Logger log, DataSource ds, String sql, Object... param)

I’m passing in the logger so I can show which instance is actually polling data.