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2020Javaweb教程之dao实现查询通用方法

DButils：

public static <T> List<T> select(String sql, RowMapper<T> rm, Object... o){
    List<T> list=new ArrayList<T>();

    try{
        connection=getConnection();
        ps=connection.prepareStatement(sql);
        for(int i=0;i<o.length;i++){
            ps.setObject(i+1,o[i]);
        }
        rs=ps.executeQuery();
       while (rs.next()){
           list.add(rm.select(rs));
       }
       return list;
    }catch (Exception e){}
    return null;
}

映射类接口：RowMapper

public interface RowMapper<T> {
    T select(ResultSet rs);
}

接口实现类：

public class StudentRowMapper implements RowMapper<Student> {
    @Override
    public Student select(ResultSet rs) {
        Student s=new Student();
        try{
            s.setSid(rs.getInt(1));
            s.setSname(rs.getString("sname"));
            s.setSage(rs.getInt("sage"));
            s.setSsex(rs.getString("ssex"));
            s.setBirthday(rs.getDate("birthday"));
            s.setScore(rs.getDouble("score"));
        }catch (Exception e){}
        return s;
    }
}