jdbc查詢 返回對象結合

JDBC查詢是根據遊標返回具體某一列的值

 while(rs.next()){

  rs.getObject(0);

  rs.getObject(1);

}

下面藉助反射，來實現類與表之間的映射

/**
 * version 1.0
 * 根據輸入的SQL返回對象
 * @param sql
 * @param cls
 * @return
 */

public static Object query(String sql, Class<?> cls) {
    Map<String, Object> map = new HashMap<>();
    List<Object> list = new ArrayList<>();
    Field[] fields = cls.getDeclaredFields();
    try {
        Connection conn = getConnection();
        Statement statement = conn.createStatement();
        ResultSet rs = statement.executeQuery(sql);
        ResultSetMetaData data = rs.getMetaData();
        while (rs.next()) {
            Object obj= cls.newInstance();
            for (int i = 1; i <= data.getColumnCount(); i++) {
                String columnName = data.getColumnName(i);
                map.put(columnName, rs.getObject(i));
            }
            for (Field field : fields) {
                String name = field.getName();
                field.setAccessible(true);
                Object value = map.get(name);
                field.set(obj, value);
            }
            list.add(obj);
        }
        return list;
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}