protected boolean entityExists(Object pk) throws CreateException 
{
      return false;
}

Assume MySQL won't generate duplicate keys

 public Object execute(Method m,
    Object[] args,
    EntityEnterpriseContext ctx) throws CreateException 
{
      // primary key to return
      Object pk = null;
      if(!createAllowed) {
         throw new CreateException("Creation is not allowed because a " +
               "primary key field is read only.");
      }
      // the key is generated by the database
      insertEntity(ctx);
      pk = entity.extractPrimaryKeyFromInstance(ctx);
      log.debug("Created: pk="+pk);
      return pk;
}

 protected List getInsertFields() 
{
      List fields = entity.getFields();
      List insertFields = new ArrayList(fields.size());
      for(Iterator iter = fields.iterator(); iter.hasNext(); ) {
         JDBCFieldBridge field = (JDBCFieldBridge)iter.next();
         if(!field.isReadOnly() && !field.isPrimaryKeyMember()) {
            insertFields.add(field);
         } 
      }
      return insertFields;
}

This method includes only non primary key fields

 protected  void insertEntity(EntityEnterpriseContext ctx) throws CreateException 
{
      Connection con = null;
      PreparedStatement ps = null;
      int rowsAffected  = 0;
      try {
         // get the connection
         DataSource dataSource = entity.getDataSource();
         con = dataSource.getConnection();
         // create the statement
         log.debug("Executing SQL: " + insertEntitySQL);
         ps = con.prepareStatement(insertEntitySQL);
         // set the parameters
         int index = 1;
         for(Iterator iter = insertFields.iterator(); iter.hasNext(); ) {
            JDBCFieldBridge field = (JDBCFieldBridge)iter.next();
            index = field.setInstanceParameters(ps, index, ctx);
         }
         // execute statement
         rowsAffected = ps.executeUpdate();
         // cast to the wrapped statement
         org.jboss.ejb.plugins.cmp.jdbc.WrappedStatement ws =
            (org.jboss.ejb.plugins.cmp.jdbc.WrappedStatement) ps;
         // fetch underlying statement and cast it to MySQL native
         com.mysql.jdbc.PreparedStatement mySqlStmt =
            (com.mysql.jdbc.PreparedStatement) ws.getUnderlyingStatement();
         ResultSet rs = mySqlStmt.getGeneratedKeys();
         Object pk = null;
         if( rs.next() ) {
            pk = rs.getObject( 1 );
         }
         if( pk == null ) {
            throw new Exception( "Primary key isn't generated." );
         }
         // write pk fields to the context
         for( Iterator iter = entity.getPrimaryKeyFields().iterator();
            iter.hasNext(); ) {
            JDBCCMPFieldBridge cmpField = (JDBCCMPFieldBridge) iter.next();
            cmpField.setInstanceValue( ctx, pk );
            break;
         }
      } catch(Exception e) {
         log.error("Could not create entity", e);
         throw new CreateException("Could not create entity:" + e);
      } finally {
         JDBCUtil.safeClose(ps);
         JDBCUtil.safeClose(con);
      }
      // check results
      if(rowsAffected != 1) {
         throw new CreateException("Insertion failed. Expected one " +
               "affected row: rowsAffected=" + rowsAffected +
               "id=" + ctx.getId());
      }
      log.debug("Rows affected = " + rowsAffected);
      // Mark the inserted fields as clean.
      for(Iterator iter = insertFields.iterator(); iter.hasNext(); ) {
         JDBCFieldBridge field = (JDBCFieldBridge)iter.next();
         field.setClean(ctx);
      }
}

This method executes MySQL specific code