JDBC 笔记3 通过PreparedStatement 对数据库进行增删改查

public boolean ChaRu3(User user){
        boolean flag=true;
        Connection conn=null;
        PreparedStatement ps=null;    //创建PreparedStatement 对象
        String sql= "insert into user (name,pwd) values(?,?)";  //sql语句不再采用拼接方式，应用占位符问号的方式写sql语句。
        conn=DBConnUtil.getConn();
        try {
            ps=conn.prepareStatement(sql);
            ps.setString(1, user.getName()); //对占位符设置值，占位符顺序从1开始，第一个参数是占位符的位置，第二个参数是占位符的值。
            ps.setString(2, user.getPwd()); 
            int i=ps.executeUpdate();
            if(i==0){
                flag=false;
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            DBConnUtil.closeAll(null, ps, conn);
        }
        return flag;
        
    }

public boolean XiuGai3(User user){
        boolean flag=true;
        Connection conn=null;
        PreparedStatement ps=null;
        String sql="update user set pwd=? where name=?";
        conn=DBConnUtil.getConn();
        try {
            ps=conn.prepareStatement(sql);
            ps.setString(1, user.getPwd());
            ps.setString(2, user.getName());
            int i= ps.executeUpdate();
            if(i==0){
                flag=false;
            }
            
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            DBConnUtil.closeAll(null, ps, conn);
        }
        return flag;
    }

public boolean ShanChu3(int id){
        boolean flag=true;
        Connection conn=null;
        PreparedStatement ps=null;
        String sql="delete from user where id=?";
        conn=DBConnUtil.getConn();
        try {
            ps=conn.prepareStatement(sql);
            ps.setInt(1, id);
            int i=ps.executeUpdate();
            if(i==0){
                flag=false;
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            DBConnUtil.closeAll(null, ps, conn);
        }
        
        return flag;
    }

public List<User> ChaKan3(){
         List<User> list= new ArrayList<User>();
         Connection conn=null;
         PreparedStatement ps=null;
         ResultSet rs=null;
         String sql="select * from user";
         conn=DBConnUtil.getConn();
         try {
               ps=conn.prepareStatement(sql);
             rs=ps.executeQuery();
             while(rs.next()){
                User user= new User();
                user.setName(rs.getString("name"));
                list.add(user);
             }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            DBConnUtil.closeAll(rs, ps, conn);
        }
        
         return list;
     }