Store the results of ResultSet in a list - mysql

Question

My goal is to centralize all the interactions with my MySql database in a single class (e.g. SqlUtils). I basically want to maintain access to ResultSet or a similar class even after the connection is closed. The following way doesn't work as after my business method receives the ResultSet, an exception is thrown because the underlying connection is already closed. I want to emphasize that opening and closing a connection to the database has to take place inside getResultSet().
public ResultSet getResultSet(String sql) {
try (Connection conn = getConnection();){
return conn.createStatement().executeQuery(sql);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
What I'm now thinking to do is something like this:
public List<ResultHolder> getResultSet(String sql) {
List<ResultHolder> list = new LinkedList<>();
try (Connection conn = getConnection();
ResultSet res = conn.createStatement().executeQuery(sql);) {
while(res.next()) {
list.add(res.convertToResultHolder());
}
} catch (Exception e) {
e.printStackTrace();
}
return list;
}
Is there any class that does what I need, which I expressed as ResultHolder.

Answer 1

If you want to have access to all the resultset data even after connection is closed then I would suggest following:
public List<Map<String, Object>> getResultSet(String sql) {
// this list will hold all the data returned from resultset
List<Map<String, Object>> rows = new ArrayList<Map<String, Object>>();
try (Connection conn = getConnection();
ResultSet rs = conn.createStatement().executeQuery(sql);) {
while(rs.next()) {
// this map corresponds to each row of the resultset
// key: column-name, value: column-value
Map<String, Object> row = new LinkedHashMap<String, Object>();
// populate each row using resultset's Meta data
ResultSetMetaData meta = rs.getMetaData();
for (int i=1; i<=meta.getColumnCount(); i++)
row.put(meta.getColumnName(i), rs.getObject(i));
rows.add(row);
}
} catch (Exception e) {
e.printStackTrace();
}
return rows;
}