对5月13号中BaseDao方法进行优化改造，更接近于框架的编写

/*
* 通用查询、更新升级版
* */
public class BaseDao2 {
    static {
        try {
            Class.forName(ConfigUtil.getValue("driver"));
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public Connection getConn(){
        try {
            return DriverManager.getConnection(ConfigUtil.getValue("url"),
                    ConfigUtil.getValue("username"),
                    ConfigUtil.getValue("password"));
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }
    }

    public void close(ResultSet rs, PreparedStatement ps, Connection conn){
        try {
            if(rs != null) {
                rs.close();
            }
            if(ps != null){
                ps.close();
            }
            if(conn != null){
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    /*
    * 返回一条查询记录
    * 输入参数Object[] obj中存放sql语句中变量的值
    * */
    public Object search(String sql, Object[] obj, Class<?> clz){
        Connection conn = getConn();
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            ps = conn.prepareStatement(sql);
            if(obj != null && obj.length>0){
                for(int i=0; i<obj.length; i++) {
                    ps.setObject(i + 1, obj[i]);
                }
            }
            rs = ps.executeQuery();
            if(!rs.next()){
                return null;
            }
            /*
            * 在此处应该要给对象赋值，但遇到了以下问题
            * 如何确定列数？
            * 如何确定列名？
            * 如何确定查询的是哪个对象？
            * */
            return doResultSet(rs,clz);
        } catch (SQLException e) {
            throw new RuntimeException();
        }finally {
            close(null, ps, conn);
        }
    }

/*
    * 运用java反射机制，编写通用类，Class<?>表示不知道传入的会是什么类型的数据，因此用？代替
    * */
    public Object doResultSet(ResultSet rs, Class<?> clz){
        Object bean = null;
        try {
            bean = clz.newInstance();   //对象实例化
            ResultSetMetaData metaData = rs.getMetaData();  //获取元数据
            int colCount = metaData.getColumnCount();   //获取列数
            for(int i=0; i<colCount; i++){
                Object colValue = rs.getObject(i+1);    //获取列的值
                String colName = metaData.getColumnName(i+1);
                Field f = clz.getDeclaredField(colName);
                f.setAccessible(true);  //取消某些检测
                f.set(bean,colValue);   //将从数据库获取的值传递给bean对象
            }

        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
        return bean;
    }

    /*
    * 查询对象为List，即有多条查询记录
    * */
    public Object searchList(String sql,Object[] obj,Class<?> clz){
        PreparedStatement ps = null;
        ResultSet rs = null;
        Connection conn = getConn();
        try {
            ps = conn.prepareStatement(sql);
            if(obj != null && obj.length>0) {
                for (int i = 0; i < obj.length; i++) {
                    ps.setObject(i + 1, obj[i+1]);
                }
            }
            rs = ps.executeQuery();
            if(!rs.next()){
                return null;
            }
            return doResultSetList(rs, clz);
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }finally {
            close(rs,ps,conn);
        }
    }

    public List<Object> doResultSetList(ResultSet rs,Class<?> clz){
        List<Object> list = new ArrayList<Object>();
        try {
            while(rs.next()) {
                Object bean = clz.newInstance();
                ResultSetMetaData metaData = rs.getMetaData();
                int colCount = metaData.getColumnCount();
                for (int i = 0; i < colCount; i++) {
                    String colName = metaData.getColumnName(i + 1);
                    Object colValue = rs.getObject(i + 1);
                    Field f = clz.getDeclaredField(colName);
                    f.setAccessible(true);
                    f.set(bean, colValue);
                }
                list.add(bean);
            }
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
        return list;
    }

    public int update(String sql, Object[] obj){
        Connection conn = getConn();
        PreparedStatement ps = null;
        try {
            ps = conn.prepareStatement(sql);
            if(obj != null && obj.length>0) {
                for (int i = 0; i < obj.length; i++) {
                    ps.setObject(i+1,obj[i]);
                }
            }
            return ps.executeUpdate();
        } catch (SQLException e) {
            throw new RuntimeException();
        }finally {
            close(null,ps,conn);
        }
    }
}