JavaWeb上机实验1 数据库访问（一）

package LWL01; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.ArrayList; public class StudentDao{//添加 student public boolean insert(Student student) { boolean flag=false ; PreparedStatement pstat=null; Connection conn=JDBCUtils.getConnection(); String sql ="insert into student (sid,sname,age,course) values (?,?,?,?) "; try { pstat =conn.prepareStatement(sql); pstat.setInt(1, student.getSid()); pstat.setString(2, student.getSname()); pstat.setString(3, student.getAge()); pstat.setString(4, student.getCourse()); int num=pstat.executeUpdate(); if(num>0) { flag =true; } } catch (SQLException e) { e.printStackTrace(); }finally{ JDBCUtils.release(conn, pstat);} return flag; } //更新student public boolean update(Student student){ boolean flag=false ; PreparedStatement pstat = null; Connection conn=JDBCUtils.getConnection(); String sql ="update student set sname=?,age=?, course=? where sid=?"; try { pstat=conn.prepareStatement(sql); pstat.setInt(4, student.getSid()); pstat.setString(1, student.getSname()); pstat.setString(2, student.getAge()); pstat.setString(3,student.getCourse()); int num=pstat.executeUpdate(); if (num>0) { flag =true;} } catch (SQLException e){ e.printStackTrace(); }finally{ JDBCUtils.release(conn,pstat); } return flag; } //删除 student public boolean delete(Student student){ boolean flag=false ; PreparedStatement pstat=null; Connection conn=JDBCUtils.getConnection(); String sql ="delete from student where sid=?"; try { pstat=conn.prepareStatement(sql); pstat.setInt(1, student.getSid()); int num=pstat.executeUpdate(); if(num>0){ flag=true;} } catch (SQLException e){ e.printStackTrace(); }finally { JDBCUtils.release(conn,pstat); } return flag; } //查询所有student public ArrayList<Student> selectAll(){ PreparedStatement pstat = null; Connection conn=JDBCUtils.getConnection(); String sql ="select * from student"; ArrayList<Student> list = new ArrayList<>(); try{ pstat = conn.prepareStatement(sql); ResultSet rs=pstat.executeQuery(sql); while (rs.next()) { Student newStudent = new Student(); newStudent.setSid(rs.getInt("sid")); newStudent.setSname( rs.getString("sname")); newStudent.setAge(rs.getString("age")); newStudent.setCourse(rs.getString("course")); list.add(newStudent);} } catch (SQLException e) { e.printStackTrace(); }finally { JDBCUtils.release(conn,pstat); } return list; } //查询单个Student public Student SelectOne(Student student){ PreparedStatement pstat=null; Connection conn=JDBCUtils.getConnection(); String sql ="select * from student where sid= ? "; Student newStudent= new Student(); try { pstat=conn.prepareStatement(sql); pstat.setInt(1, student.getSid()); ResultSet rs=pstat.executeQuery(); while (rs.next()) { newStudent.setSid(rs.getInt("sid")); newStudent.setSname(rs.getString("sname")); newStudent.setAge(rs.getString("age")); newStudent.setCourse(rs.getString("course")); } } catch (SQLException e) { e.printStackTrace(); }finally { JDBCUtils.release(conn, pstat);} return newStudent; } }