class User{
 private long id;
 private String name;
 private String gender;
 public User(){
 super();
 }
 public User(long id,String name,String gender){
 super();
 this.id = id;
 this.name = name;
 this.gender = gender;
 }
 //get,set方法
 }
 //DAO类
 public class jdbcDao{
 static{
  try{
   Class.forName("com.mysql.jdbc.Driver");
  }catch(Exception e){
  e.printStackTrace();
   }
  }
 private Connection getConn(){
  try{
   return DriverManager.getConnection("jdbc:mysql://localhost:3306:xe","root","password");
   }catch(Exception e){
   e.printStackTrace();
   }
  }
  return null;
 }
 private void release(ResultSet rs,Statement ps,Connection conn){
  if(rs!=null){
   try{
    rs.close();
   }catch(Exception e){
    e.printStackTrace();
   }
  }
  if(ps!=null){
   try{
    ps.close();
   }catch(Exception e){
    e.printStackTrace();
   }
  }
  if(conn!=null){
   try{
    conn.close();
   }catch(Exception e){
    e.printStackTrace();
   }
  }
 }
 //用ID获取用户对象
 public User getUserById(long id){
  ResultSet rs = null;
  PreparedStatement ps = null;
  Connection conn = null;
  String sql = "select * from user where id = ?";
  try{
   conn = this.getConnection();
   ps = conn.prepareStatement(sql);
   ps.setLong(1,id);
   rs = ps.executeQuery();
   if(rs.next()){
    //如果存在，则直接构建并返回用户对象
    User user = new User(rs.getLong("id"),rs.getString("name"),rs.getString("gender"));
    return user;
   }
  }catch(Exception e){
   e.printStackTrace();
  }finally{
   this.release(rs,ps,conn);
  }
  return null;
 }
 //查询所有用户
 public List<User> getAllUsers(){
  List<User> list = new ArrayList<User>();
  ResultSet rs = null;
  PreparedStatement ps = null;
  Connection conn = null;
  String sql = "select * from user ";
  try{
   conn = this.getConnection();
   ps = conn.prepareStatement(sql);
   rs = ps.executeQuery();
   //循环添加用户对象
   while(rs.next()){
    User user = new User(rs.getLong("id"),rs.getString("name"),rs.getString("gender"));
    list.add(user);
   }
  }catch(Exception e){
   e.printStackTrace();
  }finally{
   this.release(rs,ps,conn);
  }
  return list;
 }
 //修改用户数据
 public User updateUser(User user){
  PreparedStatement ps = null;
  Connection conn = null;
  String sql = "update user set id =?,name=?,gender=?";
 try{
   conn = this.getConnection();
   conn.setAutoCommit(false);
   ps = conn.prepareStatement(sql);
   ps.setLong(1,user.getId());
   ps.setString(2,user.getName());
   ps.setString(3,user.getGender());
   int rst = ps.executeUpdate();
   if(rst>0){
    return new User(user.getId(),user.getName(),user.getGender());
   }
   conn.commit();
  }catch(Exception e){
   e.printStackTrace();
   try{
    conn.rollback();
   }catch(Exception e1){
    e1.printStackTrace();
   }
  }finally{
   this.release(null,ps,conn);
  }
  return null;
   }
  }
  //删除用户数据
 public boolean deleteUser(long id){
  PreparedStatement ps = null;
  Connection conn = null;
  String sql = "delete from user where id =?;
 try{
   conn = this.getConnection();
   conn.setAutoCommit(false);
   ps = conn.prepareStatement(sql);
   ps.setLong(1,user.getId());
   ps.setString(2,user.getName());
   ps.setString(3,user.getGender());
   int rst = ps.executeUpdate();
   if(rst>0){
    return user;
   }
   conn.commit();
  }catch(Exception e){
   e.printStackTrace();
   try{
    conn.rollback();
   }catch(Exception e1){
    e1.printStackTrace();
   }
  }finally{
   this.release(null,ps,conn);
  }
  return null;
   }
  }
  //插入用户数据
  public User insertUser(User user){
  PreparedStatement ps = null;
  Connection conn = null;
  String sql = "insert into user values(?,?,?)";
 try{
   conn = this.getConnection();
   conn.setAutoCommit(false);
   ps = conn.prepareStatement(sql);
   ps.setLong(1,user.getId());
   ps.setString(2,user.getName());
   ps.setString(3,user.getGender());
   int rst = ps.executeUpdate();
   if(rst>0){
    return user;
   }
   conn.commit();
  }catch(Exception e){
   e.printStackTrace();
   try{
    conn.rollback();
   }catch(Exception e1){
    e1.printStackTrace();
   }
  }finally{
   this.release(null,ps,conn);
  }
  return null;
   }
  }
 }
 }