JDBC code

import java.sql.*;
import java.util.ArrayList;
import java.util.List;
class Student {
 private int id;
 private String name;
 private int age;
 public Student(int id, String name, int age) {
  super();
  this.id = id;
  this.name = name;
  this.age = age;
 }
 public Student() {
 }
 public int getId() {
  return id;
 }
 public void setId(int id) {
  this.id = id;
 }
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 public int getAge() {
  return age;
 }
 public void setAge(int age) {
  this.age = age;
 }
 @Override
 public String toString() {
  return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
 }
 
}
 


class StudentDao {
 Connection con;
 PreparedStatement pst;
 ResultSet rs;
 
 public Connection getConn() throws ClassNotFoundException, SQLException
 {
  // 1 加载驱动
  Class.forName("com.mysql.jdbc.Driver");
  // 2 获得数据库的连接
  Connection con =
    DriverManager.getConnection
    ("jdbc:mysql://localhost:3306/rot?useUnicode=true&characterEncoding=utf-8", "root", "");
  return con;
 }
 public void closeAll() throws SQLException
 {
if(rs!=null)
{
rs.close();
}
if(pst!=null)
{
pst.close();
}
 }
 //增加
 public int addStudent(Student student) throws ClassNotFoundException, SQLException
 {
  con=getConn();
  String insertSQL="insert into student values(null,?,?)";
  pst = con.prepareStatement(insertSQL);
  pst.setString(1,student.getName());
  pst.setInt(2, student.getAge());
  
  int result=pst.executeUpdate();
  closeAll();
  return result;  
 }
 
 //删除
 public int delStudent(int id) throws ClassNotFoundException, SQLException
 {
  con=getConn();
  String sql="delete from student where id=?";
  pst = con.prepareStatement(sql);
  pst.setInt(1,id);
  
  int result=pst.executeUpdate();
  pst.close();
  con.close();
  return result;  
 }
 
 //修改
 public int updateStudent(Student student) throws ClassNotFoundException, SQLException
 {
  con=getConn();
  String sql="update student set name=?,age=? where id=?";
  pst = con.prepareStatement(sql);
  pst.setString(1,student.getName());
  pst.setInt(2, student.getAge());
  pst.setInt(3,student.getId());
  
  int result=pst.executeUpdate();
  pst.close();
  con.close();
  return result; 
  
 }
 
 //查询所有记录
 public List<Student> queryAll() throws ClassNotFoundException, SQLException
 {
  con=getConn();
  String sql="select * from student";
  pst=con.prepareStatement(sql);
  rs = pst.executeQuery();
  
  List<Student> stuList=new ArrayList<Student>();
  while(rs.next())
  {
   Student stu=new Student();
   stu.setId(rs.getInt(1));
   stu.setName(rs.getString(2));
   stu.setAge(rs.getInt(3));
   stuList.add(stu);
  }
  return stuList;
 }
 
 //根据主键查询记录
 public Student queryById(int id) throws ClassNotFoundException, SQLException
 {
  con=getConn();
  String sql="select * from student where id=?";
  pst=con.prepareStatement(sql);
  pst.setInt(1, id);
  rs = pst.executeQuery();
  Student stu=null;
  if(rs.next())
  {
   stu=new Student(rs.getInt(1),rs.getString(2),rs.getInt(3));
  }  
  return stu;
 }
}
public class Main {
 public static void main(String[] args) throws ClassNotFoundException, SQLException  {
  StudentDao dao=new StudentDao();
  
  Student stu1=new Student(1,"系统",22);
 int result = dao.addStudent(stu1);
  if(result==1)
  {
   System.out.println("插入记录成功！");
  }
  
int result2 = dao.delStudent(1);
  if(result2==1)
  {
   System.out.println("删除记录成功！");
  }
  
  Student stu2=new Student(3,"李四",32);
  int result3 = dao.updateStudent(stu2);
  if(result3==1)
  {
   System.out.println("修改记录成功！");
  }
  
  List<Student> stuList=dao.queryAll();
  for(Student stu:stuList)
  {
   System.out.println(stu);
  }
  System.out.println("=======");
  
  Student stu = dao.queryById(100);
  System.out.println(stu);
 
 }
}