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标题: 解析查询类型sql自动封装列表数据 [打印本页]

作者: 一秉 时间: 2020-7-12 21:30
标题: 解析查询类型sql自动封装列表数据
1、当一个sql是查询类型时，返回值一般都是列表，这种情况下，我们通过反射模拟mybatis的查询语句封装
2、核心代码：
public static List<Object> buildListDataBySql(String sql, Class<?> clazz) {
      List<Object> resList = new LinkedList<Object>();
      Connection conn = DbUtils.getConnection();
      PreparedStatement ps = null;
      ResultSet rs = null;
      try {
         ps = conn.prepareStatement(sql);
         rs = ps.executeQuery();
         while (rs.next()) {
            Object obj = clazz.newInstance();
            Field[] fields = clazz.getDeclaredFields();
            for (Field field : fields) {
                  String methodName = "set" + field.getName().substring(0,1).toUpperCase() +field.getName().substring(1);
                  Column column = field.getAnnotation(Column.class);
                  if (null != column) {
                     if (column.type() == Integer.class) {
                        Integer value = rs.getInt(field.getName());
                        Method setMethod = clazz.getDeclaredMethod(methodName,
                                 Integer.class);
                        setMethod.invoke(obj, value);
                     } else if (column.type() == String.class) {
                        String value = rs.getString(field.getName());
                        Method setMethod = clazz.getDeclaredMethod(methodName,
                                 String.class);
                        setMethod.invoke(obj, value);
                     }
                  } else {
                     //String类型
                     String value = rs.getString(field.getName());
                     Method setMethod = clazz.getDeclaredMethod(methodName,
                              String.class);
                     setMethod.invoke(obj, value);
                  }
            }
            resList.add(obj);
         }
      } catch (Exception e) {
         e.printStackTrace();
      } finally {
         if (rs != null) {
            try {
                  rs.close();
            } catch (SQLException e) {
            }
         }
         if (conn != null) {
            try {
                  conn.close();
            } catch (SQLException e) {
            }
         }
         if (ps != null) {
            try {
                  ps.close();
            } catch (SQLException e) {
            }
         }
      }

      return resList;
}
3、测试代码：
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
      String sql = "select * from jiudian where 1= 1 ";
      String searchText = request.getParameter("name");
      if (null != searchText && !"".equals(searchText)) {
         sql = sql + " and name like '%" +searchText+ "%'";
      }
      List<Object> res = DaoUtils.buildListDataBySql(sql, Hotel.class);
      response.getWriter().append(res.toString());
}

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