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jdbc书

    RegistrationPK primaryKey = new RegistrationPK();
    primaryKey.theuser = theuser;
    return primaryKey;
    } catch (CreateException ce) {
      throw ce;
    } catch (SQLException sqe) {
      throw new CreateException (sqe.getMessage());
    } finally {
      try {
         ps.close();
      } catch (Exception ignore) {}
      try {
         con.close();
      } catch (Exception ignore) {}
    }
}
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

<A NAME="load"></A>
<H3>Load Method</H3>

This method gets the primary key from the entity context
and passes it to the <CODE>refresh</CODE> method which loads the
data.

</FONT>

<PRE>
  public void ejbLoad() throws RemoteException {
    try {
      refresh((RegistrationPK) ctx.getPrimaryKey());
    }
    catch (FinderException fe) {
      throw new RemoteException (fe.getMessage());
    }
  }
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

<A NAME="refresh"></A>
<H3>Refresh Method</H3>

<P>
The <CODE>refresh</CODE> method is programmer-supplied code
to load the data from the database. It checks the primary key 
value, gets a connection to the database, and creates a
<CODE>PreparedStatement</CODE> object for querying
the database for the user specified in the primary key.

<P>
Data is read from the database into a <CODE>ResultSet</CODE>
and assigned to the global member variables so the 
<CODE>RegistrationBean</CODE> has the most up-to-date information
for the user.

</FONT>

<PRE>
private void refresh(RegistrationPK pk)
             throws FinderException, RemoteException {

  if (pk == null) {
    throw new RemoteException ("primary key 
				cannot be null");
  }
  Connection con = null;
  PreparedStatement ps = null;
  try {
     con=getConnection();
     ps=con.prepareStatement("select password, 
		emailaddress, creditcard, 
		balance from registration 
		where theuser = ?");
     ps.setString(1, pk.theuser);
     ps.executeQuery();
     ResultSet rs = ps.getResultSet();
     if (rs.next()) {
       theuser = pk.theuser;
       password = rs.getString(1);
       emailaddress = rs.getString(2);
       creditcard = rs.getString(3);
       balance = rs.getDouble(4);
     }
     else {
        throw new FinderException (
                    "Refresh: Registration ("
                    + pk.theuser + ") not found");
     }
  }
  catch (SQLException sqe) {
     throw new RemoteException (sqe.getMessage());
  }
  finally {
     try {
        ps.close();
     }
     catch (Exception ignore) {}
     try {
        con.close();
     }
     catch (Exception ignore) {}
  }
}
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">

<A NAME="store"></A>
<H3>Store Method</H3>

This method gets a database connection and creates a 
<CODE>PreparedStatement</CODE> to update the database. 

</FONT>

<PRE>
public void ejbStore() throws RemoteException {
  Connection con = null;
  PreparedStatement ps = null;
  try {
     con = getConnection();
     ps = con.prepareStatement("update registration 
				set password = ?, 
				emailaddress = ?, 
				creditcard = ?, 
				balance = ? 
				where theuser = ?");
     ps.setString(1, password);
     ps.setString(2, emailaddress);
     ps.setString(3, creditcard);
     ps.setDouble(4, balance);
     ps.setString(5, theuser);
     int i = ps.executeUpdate();
     if (i == 0) {
       throw new RemoteException (
                   "ejbStore: Registration (
		   " + theuser + ") not updated");
     }
  } catch (RemoteException re) {
       throw re;
  } catch (SQLException sqe) {
       throw new RemoteException (sqe.getMessage());
  } finally {
    try {
       ps.close();
    } catch (Exception ignore) {}
     try {
        con.close();
     }
     catch (Exception ignore) {}
  }
}
</PRE>

<FONT FACE="Verdana, Arial, Helvetica, sans-serif">


<A NAME="find"></A>
<H3>Find Method</H3>

The <CODE>ejbFindByPrimaryKey</CODE> method matches the signature
of the <CODE>FindByPrimaryKey</CODE> method in the
<A HREF="./Code/registration/RegistrationHome.java">RegistrationHome</A>
interface. It calls the <CODE>refresh</CODE> method to get or
refresh the user data for the user specified by the primary key.

<P>
The container-managed persistence version of <CODE>RegistrationBean</CODE> 
does not implement this method because the container handles getting
and refreshing the user data.

</FONT>

<PRE>
public RegistrationPK ejbFindByPrimaryKey(
		RegistrationPK pk)
           	throws FinderException, 
           	RemoteException {

  if ((pk == null) || (pk.theuser == null)) {
     throw new FinderException ("primary key 
				 cannot be null");
  }
  refresh(pk);
  return pk;
}
</PRE>

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