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标题: 模拟mybatis实现sql的解析 [打印本页]

作者: 一秉 时间: 2020-7-12 21:24
标题: 模拟mybatis实现sql的解析
1、通过传入预执行sql和封装好的model，解析sql，实现类似mybatis的半自动化功能
2、代码：
public static boolean updateSql(String sql, Object value) {
      //解析#{xxx}字符串，其中xxx是JavaBean的字段，实现思路是解析里面的属性，通过反射获取value中的值

      int start = sql.indexOf("#{");
      int end = sql.indexOf("}");
      List<Object> vals = new ArrayList<Object>();
      while (start >-1 && end > start) {
         //#{userName} - ? #{userPw}
         //userName -> getUserName
         String wholeProp = sql.substring(start, end+1);
         String subProp = wholeProp.substring(2, wholeProp.length()-1);
         sql = sql.replace(wholeProp, " ? ");
         String methodName = "get" + subProp.substring(0,1).toUpperCase() + subProp.substring(1);
         Method method = null;
         try {
            method = value.getClass().getDeclaredMethod(methodName);
         } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
         }
         try {
            vals.add(method.invoke(value));
         } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
         }
         start = sql.indexOf("#{");
         end = sql.indexOf("}");

      }
      Connection conn = DbUtils.getConnection();
      PreparedStatement ps = null;
      try {
         ps = conn.prepareStatement(sql);
         for (int i = 0 ; i < vals.size(); i++) {
            ps.setObject(i+1, vals.get(i));
         }
         ps.execute();
         return true;
      } catch (SQLException e) {
         return false;
      } finally {
         if (conn != null) {
            try {
                  conn.close();
            } catch (SQLException e) {
            }
         }
         if (ps != null) {
            try {
                  ps.close();
            } catch (SQLException e) {
            }
         }
      }
}
3、测试代码：
String sql = " update news set "
            + " title = #{title},"
            + " info = #{info} "
            + " where id = #{id}";
Object obj = DaoUtils.initEntity(News.class, request);
boolean result = DaoUtils.updateSql(sql, obj);

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