Question

First of all, I’m new to Java.

I’m trying to figure out what would be a good/handy way to work with DB from Java. I’m using c3p0 for connection pooling. Hibernate or other ORM is not an option this time, we decided to stick with “plain SQL” for now.

Currently basic retrieval of data looks like this:

private int getUserID(int sessionID, String userIP) {
 int result = 0;
 Connection conn = null;
 PreparedStatement st = null;
 ResultSet rs = null;
 try {
  // Application.cpds is an instance of c3p0's ComboPooledDataSource
  conn = Application.cpds.getConnection();
  st = conn.prepareStatement("SELECT user_id, user_ip, is_timed_out FROM g_user.user_session WHERE id = ?");
  st.setInt(1, sessionID);
  rs = st.executeQuery();
  if ( rs.next() ) {
   if ( !rs.getBoolean("is_timed_out") && userIP.equals(rs.getString("user_ip")) ) {
    result = rs.getInt("user_id");
   }
  }
 }
 catch (SQLException e) {
  e.printStackTrace();
 }
 finally {
  if ( rs != null ) {
   try { rs.close(); } catch (SQLException e) { e.printStackTrace(); }
  }
  if ( st != null ) {
   try { st.close(); } catch (SQLException e) { e.printStackTrace(); }
  }
  if ( conn != null ) {
   try { conn.close(); } catch (SQLException e) { e.printStackTrace(); }
  }
 }
 return result;
}

The code looks very long for such a basic operation. Another problem is that most of the code would have to be repeated in many places (declaring Connection, PreparedStatement, ResultSet, closing them, catching exceptions). Though, this is what I see in most examples when googling.

In PHP I would create a wrapper class that would have method select() that accepts 2 arguments (string)sqlQuery and (array)parameters and would return simple array of data. Wrapper class would also have few more specific methods, like:

• selectValue() for single value (e.g., select count(*) from user)
• selectRow() for single row (e.g., select name, surname from user where id = :user_id)
• selectColumn for single column (e.g., select distinct remote_address from user)

Is anything like this practiced in Java? Or is there anything better / handier? Or should I use same style as in getUserID() example above? As I said, ORM is not an option this time.

Thanks in advance 🙂

---

edit: Currently DBConnection class is written. It gets connection from c3p0 connection pool in constructor. It has few public methods for working with DB: select() for tabular data, selectValue() for single value, selectRow() and selectColumn() for single row or column, as well as insert(), update(), delete() and ddl(). Methods accept String query, Object[] params arguments, with params being optional. insert(), update() and delete() return Integer which is result of PreparedStatement.executeUpdate(). select methods return different results:

• ArrayCollection<HashMap<String, Object>> select()
• Object selectValue()
• HashMap<String, Object> selectRow()
• ArrayCollection<Object> selectColumn()

The last problem is with compiler warnings – "warning: [unchecked] unchecked cast". This is because all methods call single private method that returns Object and cast its result to mentioned types. As I am new to Java, I’m also not sure if I have chosen appropriate types for selects. Other than that, everything seems to work as expected.

Answer 1

If the an ORM is no option, you could still use Spring’s JDBC helper classes:
http://docs.spring.io/spring-framework/docs/4.1.0.RELEASE/spring-framework-reference/html/jdbc.html

Or you could simply write some helper methods on your own. Maybe a DBUtil.close(conn, st, rs); would be nice.

And by the way, you really should use a logging framework instead of “e.printStackTrace()“

EDIT:
One more thing: I think it’s kind of hard to add ORM afterwards, when you have all the SQL already written in plain JDBC. You can’t refactor that stuff, you have to throw it away and do it again.

EDIT:
You don’t have to close the resultSet if you are closing the statement anyway. The Java ResultSet API reads:

A ResultSet object is automatically
closed when the Statement object that
generated it is closed, re-executed,
or used to retrieve the next result
from a sequence of multiple results.

Beside that, C3P0 does resource management as well and and closes Statements when you return a connection. You might to look that up too.