JDBC的基本操作

连接数据库
• 增 删 改 查
• 关闭资源

一、 什么是JDBC?(直接上图嘿嘿嘿…）
二、命名规范

1.黄色的是包名，黑色的是类名
2.公司域名倒写.模块名称
3.Domain代表具体的类与要操作的数据表有映射关系，即成员属性对应列名，拥有get,set方法。
4.impl意思是实现类，I是接口。

三、具体操作

package edu.xxxx.jdbc.dao.impl;

import edu.xxxx.jdbc.dao.IStudentDao;
import edu.xxxx.jdbc.domain.Student;

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class StudentDaoImpl implements IStudentDao {

private final String url="jdbc:mysql://localhost:3306/test";//最后一个为数据库名（已经建好）
private final String user="root";
private final String password="123456";

private Connection connection=null;
private PreparedStatement preparedStatement=null;
private ResultSet resultSet=null;

//连接
@Override
public void init() {
try {
Class.forName("com.mysql.cj.jdbc.Driver");//加载驱动
connection= DriverManager.getConnection(url,user,password);//获取连接对象
System.out.println("do init");
} catch (Exception e) {
e.printStackTrace();
}
}

//关闭资源
public  void close(){
if(resultSet!=null){
try {
resultSet.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if(preparedStatement!=null){
try {
preparedStatement.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (connection!=null){
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
System.out.println("do close");
}

//添加
@Override
public void save(Student student) {
init();
String sql="insert into student(id,name,age) values(?,?,?)";
try {
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setInt(1,student.getId());
preparedStatement.setString(2,student.getName());
preparedStatement.setInt(3,student.getAge());
preparedStatement.executeUpdate();
System.out.println("do save");
} catch (SQLException e) {
e.printStackTrace();
}finally{
this.close();
}

}

//获取
@Override
public Student get(int id) {
init();
String sql="select * from student where id=?";
try {
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setInt(1,id);
resultSet=preparedStatement.executeQuery();
Student student = new Student();
if(resultSet.next()) {
student.setId(resultSet.getInt("id"));
student.setName(resultSet.getString("name"));
student.setAge(resultSet.getInt("age"));
}
System.out.println("do get");
return student;
} catch (SQLException e) {
e.printStackTrace();
}finally {
this.close();
}
return null;
}

//获取全部
@Override
public List<Student> getall() {
init();
String sql="select * from student";
try {
preparedStatement=connection.prepareStatement(sql);
resultSet=preparedStatement.executeQuery();

List<Student> studentList=new ArrayList<Student>();
while(resultSet.next()){
Student student=new Student();
student.setId(resultSet.getInt("id"));
student.setName(resultSet.getString("name"));
student.setAge(resultSet.getInt("age"));
studentList.add(student);

}
return studentList;
} catch (SQLException e) {
e.printStackTrace();
}finally {
this.close();
}

return null;
}

//删除
@Override
public void del(int id) {
init();
String sql="delete from student where id=?";
try {
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setInt(1,id);
preparedStatement.execute();
System.out.println("do delete");
} catch (SQLException e) {
e.printStackTrace();
}finally {
this.close();
}

}

//更改
@Override
public void update(int id, Student student) {
init();
String sql="update student set name=?,age=? where id=?";
try {
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setString(1,student.getName());
preparedStatement.setInt(2,student.getAge());
preparedStatement.setInt(3,id);
preparedStatement.executeUpdate();
System.out.println("do Update");
} catch (SQLException e) {
e.printStackTrace();
}finally {
this.close();
}

}
}