public class UserDaoImpl implements UserDao {

	@Override

	public List<User> getUserByPage(PageInfo pif,User user){

		List<User> lu = new ArrayList<User>();

		Connection conn = DButil.getconn();

//		注意拼接式字符串之间要有空格 userinfo u "

		String sql = "SELECT u.uname,u.uaddr from userinfo u ";

//		!"".equals(user.getUname()) 如果前段搜索用户名不填写，传到后端的是空值

		boolean contactAnd = false;

		String myWhere = "where";

		String myAnd = "and";

		List<String> params = new ArrayList<>();

		if(user.getUname()!=null&&!"".equals(user.getUname())) {

			if(contactAnd) {

//		" 空格 uname = ?空格 "

				sql += myAnd + " uname = ? ";

			}else {

				sql += myWhere + " uname = ? ";

				contactAnd = true;

			}

			params.add(user.getUname());

		}

		if(user.getUaddr()!=null&&!"".equals(user.getUaddr())) {

			if(contactAnd) {

				sql += myAnd + " uaddr like ? ";

			}else {

				sql += myWhere + " uaddr like ? ";

				contactAnd = true;

			}

			params.add("%"+user.getUaddr()+"%");

		}

//		拼接分页查询的limit

		sql+= " Limit "+(pif.getPage()-1)*pif.getPageSize() +","+pif.getPageSize();

		try {

			PreparedStatement ps = conn.prepareStatement(sql);

//			占位符个数不确定，所以不能直接.所以需要对是否有占位符有几个进行判断

//			如果有拼接占位符号？，则在循环中对占位符进行赋值

			for(int i = 0;i<params.size();i++) {

				ps.setString(i+1,params.get(i));

			}

			ResultSet rs = ps.executeQuery();

			while(rs.next()) {

				User user1 = new User();

				user1.setUname(rs.getString("uname"));

				user1.setUaddr(rs.getString("uaddr"));

				lu.add(user1);

			}

			System.out.println(lu);

		} catch (SQLException e) {

			e.printStackTrace();

		}

		return lu;

	}