Class to connect, manage and disconnect a DDBB

Question

Hi I had posted this Topic in Java Programming forum, buit I have seen here is the correct.
I have a doubt about how to do this class:
I have a java class witch I use from jps pages to make differents querys throw Data Base.
In this class, I have a constructor method where I have the connection to the DDBB, So I hava difrents methods to make que differnts querys, and so I have a method to do disconnect form the DDBB
So I have something like:
public class SrvGestUsersService {
     Connection dbconn;
//CONTRUCTOR METHOD
public SrvGestUsersService() {
          try
               Class.forName("org.gjt.mm.mysql.Driver");
               try{
                    dbconn = DriverManager.getConnection("jdbc:mysql://localhost/paleodbTemp?user=XXXX&password=YYYY");
                                   }catch (SQLException s)
                    System.out.println("SQL Error "+s+"\n");
                    s.printStackTrace();
               }finally{
dbconn.close();
          }catch (ClassNotFoundException err)
               System.out.println("Class loading error "+err+"\n");
               err.printStackTrace();
         }finally{
dbconn.close();
          System.out.println("\nConexi�n a la DB conseguida.\n");
//METHOD TO DISCONNECT
public void desconnectDB() {
          try {
               dbconn.close();
          } catch (SQLException e) {
               System.out.println("ERROR dbconn.close(): "+e);
               e.printStackTrace();
//DIFFERNET METHODS
public FileVO[] getFilesVOfromUSER(Long idUser) throws IllegalAccessException, InvocationTargetException, NoSuchMethodException{
          FileDaoImpl fileDaoImpl = new FileDaoImpl();
          FileCriteria criterio = new FileCriteria();
          criterio.setIdUser(idUser);
          List lFilesE = fileDaoImpl.buscar(dbconn, criterio); // devuelve List de Entities
          return aFilesVO;
     }Now in my jsp pages, I do:
//to create an instance of the class:
SrvGestUsersService instac = new SrvGestUsersService();
//I have create the connection to the DDBB, have not?
//to call a method to get information of the DDBB:
FileVO[] aFileVO = instac.getFilesVOfromUSER(22);
//to DISCONNECT
instac.desconnectDB();
Is correct this way to work??
The connectio to the DDBB is really closed?
Thanks very much

Answer 1

Hi duffymo,
If you're using Tomcat, wouldn't you be so much better off with a connection pool? Yes I use Tomcat. To make a connection pool, I must to have the server.xml (localed in CATALINA/conf/) like this, no?
<?xml version='1.0' encoding='utf-8'?>
<Server>
  <Listener className="org.apache.catalina.mbeans.ServerLifecycleListener"/>
  <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener"/>
  <GlobalNamingResources>
    <Environment name="simpleValue" type="java.lang.Integer" value="30"/>
    <Resource name="jdbc/defaultDS" type="javax.sql.DataSource"/>
    <Resource auth="Container" description="User database that can be updated and saved" name="UserDatabase" type="org.apache.
catalina.UserDatabase"/>
    <ResourceParams name="jdbc/defaultDS">
      <parameter>
        <name>maxWait</name>
        <value>5000</value>
      </parameter>
      <parameter>
        <name>maxActive</name>
        <value>4</value>
      </parameter>
      <parameter>
        <name>password</name>
        <value>MYPASSWORDTOCONNECT</value>
      </parameter>
      <parameter>
        <name>url</name>
        <value>jdbc:mysql://localhost/DDBBNAMETOCONNECT</value>
      </parameter>
      <parameter>
        <name>driverClassName</name>
        <value>com.mysql.jdbc.Driver</value>
      </parameter>
      <parameter>
        <name>maxIdle</name>
        <value>2</value>
      </parameter>
      <parameter>
        <name>username</name>
        <value>USERNAMETOCONNECT</value>
      </parameter>
    </ResourceParams>
    <ResourceParams name="UserDatabase">
      <parameter>
        <name>factory</name>
        <value>org.apache.catalina.users.MemoryUserDatabaseFactory</value>
      </parameter>
      <parameter>
        <name>pathname</name>
        <value>conf/tomcat-users.xml</value>
      </parameter>
    </ResourceParams>
  </GlobalNamingResources>
  <Service name="Catalina">
    <Connector acceptCount="100" connectionTimeout="20000" disableUploadTimeout="true" port="8080" redirectPort="8443" maxSpar
eThreads="75" maxThreads="150" minSpareThreads="25">
    </Connector>
    <Connector port="8009" protocol="AJP/1.3" protocolHandlerClassName="org.apache.jk.server.JkCoyoteHandler" redirectPort="84
43">
    </Connector>
    <Engine defaultHost="localhost" name="Catalina">
      <Host appBase="webapps" name="localhost">
        <Logger className="org.apache.catalina.logger.FileLogger" prefix="localhost_log." suffix=".txt" timestamp="true"/>
      </Host>
      <Logger className="org.apache.catalina.logger.FileLogger" prefix="catalina_log." suffix=".txt" timestamp="true"/>
      <Realm className="org.apache.catalina.realm.UserDatabaseRealm"/>
    </Engine>
  </Service>
</Server>where I must configure:
<parameter>
        <name>password</name>
        <value>MYPASSWORDTOCONNECT</value>
</parameter>
<parameter>
        <name>url</name>
        <value>jdbc:mysql://localhost/DDBBNAMETOCONNECT</value>
</parameter>
<parameter>
        <name>username</name>
        <value>USERNAMETOCONNECT</value>
</parameter>no?
My problem now is that I have not permits to write server.xml, because only root has (the server is in my Faculty and I have to ask it to the administrator)
When I will have this file configurated like I have post up, I�ll create a *java class to create the conecction*, some like:
public class ConenectionBD{
    private static DataSource src = null;
    private ConnectionBD()
    public static Connection connect() throws Exception
        Connection con = null;
        try{
            if(src == null){
                Context ctx = new InitialContext();
                src = (DataSource)ctx.lookup("java:comp/env/jdbc/defaultDS");
            con = src.getConnection();
            if(con == null)
                throw new Exception("Problemas con la conexion");
        }catch(NamingException ne){
            throw new Exception("Impossible to get java:comp/env/jdbc/defaultDS", ne);
        }catch(SQLException e){
            throw new Exception("Impossible get connection", e);
        return con;
    public static void disconnect(Connection con) throws SQLException
        if(con != null)
            con.close();
}Now, woth this class, I'll be able to get information of the DDBB from a Servlet or other java class, doing:
String userAux = "paul";
String pswAux = "paul2007";
boolean existAux;
existe = false;
Connection con = null;
        try
            con = ConnectionBD.connect();
            StringBuffer sql = new StringBuffer("SELECT * FROM USERSTABLE WHERE USERNAME = ? AND PASSWORD = ?");
            PreparedStatement pstmt = con.prepareStatement(sql.toString());
            pstmt.setString(1, userAux);
            pstmt.setString(2, pswAux);
            ResultSet resultQuery = pstmt.executeQuery();
            if(resultQuery.next())
                existAux = true;
                System.out.println("Loof for OK, user: " + userAux);
        catch(Exception e) {
            e.printStackTrace();
            throw e;
        }finally{
            ConnectionBD.disconnect(con);
...Now It�s rigth??
Thanks.
Edited by: jesusmgmarin on Dec 29, 2007 8:19 PM
Edited by: jesusmgmarin on Dec 29, 2007 8:21 PM