ORM原理

   static List<Object> getObjects(String sql, Class clazz)
       throws SQLException, Exception, IllegalAccessException,
      InvocationTargetException {
    Connection conn =  null;
    PreparedStatement ps =  null;
    ResultSet rs =  null;
     try {
      conn = JdbcUtils.getConnection();
      ps = conn.prepareStatement(sql);
      rs = ps.executeQuery();
      String[] colNames = getColNames(rs);

      List<Object> objects =  new ArrayList<Object>();
      Method[] ms = clazz.getMethods();
       while (rs.next()) {
        Object object = clazz.newInstance();
         for ( int i = 0; i < colNames.length; i++) {
          String colName = colNames[i];
          String methodName =  "set" + colName;
           // Object value = rs.getObject(colName);
           // try {
           // Method m = clazz
           // .getMethod(methodName, value.getClass());
           // if (m != null)
           // m.invoke(object, value);
           // } catch (NoSuchMethodException e) {
           // e.printStackTrace();
           // //
           // }
           for (Method m : ms) {
             if (methodName.equals(m.getName())) {
              m.invoke(object, rs.getObject(colName));
               break;
            }
          }
          objects.add(object);
        }
      }
       return objects;
    }  finally {
      JdbcUtils.free(rs, ps, conn);
    }
  }

   private  static String[] getColNames(ResultSet rs)  throws SQLException {
    ResultSetMetaData rsmd = rs.getMetaData();
     int count = rsmd.getColumnCount();
    String[] colNames =  new String[count];
     for ( int i = 1; i <= count; i++) {
      colNames[i - 1] = rsmd.getColumnLabel(i);
    }
     return colNames;
  }