MySQL 内  Learn数据库中的 student_info表 中的字段信息为：

将字段数据封装，StudentInfo.java

package com.jdbc.model;

/*

* student_info表的实体类

* */

public class StudentInfo {

public StudentInfo() {

}

public StudentInfo(Integer id, String name, String sex, Double score, String birthday) {

this.id = id;

this.name = name;

this.sex = sex;

this.score = score;

this.birthday = birthday;

}

public StudentInfo(String name, String sex, Double score, String birthday) {

this.name = name;

this.sex = sex;

this.score = score;

this.birthday = birthday;

}

private Integer id;

private String name;

private String sex;

private Double score;

private String birthday;

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getSex() {

return sex;

}

public void setSex(String sex) {

this.sex = sex;

}

public Double getScore() {

return score;

}

public void setScore(Double score) {

this.score = score;

}

public String getBirthday() {

return birthday;

}

public void setBirthday(String birthday) {

this.birthday = birthday;

}

//重写显示

@Override

public String toString() {

return "StudentInfo [id=" + id + ", name=" + name + ", sex=" + sex + ", score=" + score + ", birthday="

+ birthday + "]";

}

}

将数据库连接方法封装，为静态方法，可直接类名调用。ConnectionDB.java

package com.jdbc;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.SQLException;

public class ConnectionDB {

private static String url = "jdbc:mysql://localhost:3306/learn?useUnicode=true&characterEncoding=utf-8";

private static String username = "root"; //MySQL账号

private static String password = "123456"; //MySQL密码

private static Connection conn;

/**

* 获取数据库连接

* @return

*/

public static Connection getConn() {

try {

Class.forName("com.mysql.jdbc.Driver");

} catch (ClassNotFoundException e) {

e.printStackTrace();

}

try {

conn = DriverManager.getConnection(url, username, password);

} catch (SQLException e) {

e.printStackTrace();

}

return conn;

}

}

接下来不利用任何框架，封装数据库增删改查方法，并做测试。StudentInfoDao.java

package com.jdbc.dao;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.text.SimpleDateFormat;

import java.util.ArrayList;

import java.util.Date;

import java.util.List;

import com.jdbc.ConnectionDB;

import com.jdbc.model.StudentInfo;

/**

* StudentInfostudent_info

* O(Object)R(Relation)映射 不使用Mybatis,jpa ....框架

*/

public class StudentInfoDao {

/**

* 新增学生

* @param studentInfo

*/

public void add(StudentInfo studentInfo) {

// 连接数据库

Connection conn = ConnectionDB.getConn();

String sql = "insert into student_info(name,sex,birthday,score) values(?,?,?,?)";

try {

// 绑定

PreparedStatement pst = conn.prepareStatement(sql);

// 通过对象往数据库中add数据

// 几个问号几句 (从1开始)

pst.setString(1, studentInfo.getName());

pst.setString(2, studentInfo.getSex());

pst.setString(3, studentInfo.getBirthday());

pst.setDouble(4, studentInfo.getScore());

pst.executeUpdate();

// 关闭数据库

pst.close();

conn.close();

} catch (SQLException e) {

e.printStackTrace();

}

}

/**

* 根据主键删除相应数据库中的数据

* @param id

*/

public void delById(Integer id) {

// 连接数据库

Connection conn = ConnectionDB.getConn();

String sql = "delete from student_info where id=?";

try {

// 绑定

PreparedStatement pst = conn.prepareStatement(sql);

// 几个问号几句(从1开始)

pst.setInt(1, id);

pst.executeUpdate();

// 关闭数据库

pst.close();

conn.close();

} catch (SQLException e) {

e.printStackTrace();

}

}

/**

* 根据主键加载学生

* @param id

* @return

*/

public StudentInfo selById(Integer id) {

// 连接数据库

Connection conn = ConnectionDB.getConn();

// 将查询得的数据存储进对象中，关系到对象的映射

StudentInfo studentInfo = new StudentInfo();

String sql = "select id,name,sex,birthday,score from student_info where id=?";

try {

// 绑定

PreparedStatement pst = conn.prepareStatement(sql);

// 几个问号几句(从1开始)

pst.setInt(1, id);

ResultSet rs = pst.executeQuery(); //rs为查询指针，初始指向要查询对象的前一个位置

if(rs.next()) {

//将查询结果存进对象

studentInfo.setId(rs.getInt("id"));

studentInfo.setName(rs.getString("name"));

studentInfo.setSex(rs.getString("sex"));

studentInfo.setBirthday(rs.getString("birthday"));

studentInfo.setScore(rs.getDouble("score"));

}

// 关闭数据库

pst.close();

conn.close();

} catch (SQLException e) {

e.printStackTrace();

}

return studentInfo;

}

/**

* 修改学生

* @param studentInfo

*/

public void update(StudentInfo studentInfo) {

// 连接数据库

Connection conn = ConnectionDB.getConn();

String sql = "update student_info set name=?,sex=?,birthday=?,score=? where id=?";

try {

// 绑定

PreparedStatement pst = conn.prepareStatement(sql);

// 不修改的保持原数据

// 几个问号几句(从1开始)

pst.setString(1, studentInfo.getName());

pst.setString(2, studentInfo.getSex());

pst.setString(3, studentInfo.getBirthday());

pst.setDouble(4, studentInfo.getScore());

pst.setInt(5, studentInfo.getId());

pst.executeUpdate();

// 关闭数据库

pst.close();

conn.close();

} catch (SQLException e) {

e.printStackTrace();

}

}

/**

* 查询所有学生, 所有则通过list返回全部学生

* @return

*/

public List selAll(){

// 连接数据库

Connection conn = ConnectionDB.getConn();

// 新建list列表存对象

List list = new ArrayList<>();

String sql = "select id,name,sex,birthday,score from student_info";

PreparedStatement pst;

try {

// 绑定

pst = conn.prepareStatement(sql);

ResultSet rs = pst.executeQuery(); //rs指针指向要查询的对象的前一个位置

while(rs.next()) {

// 新建对象

StudentInfo studentInfo = new StudentInfo();

studentInfo.setId(rs.getInt("id"));

studentInfo.setName(rs.getString("name"));

studentInfo.setSex(rs.getString("sex"));

studentInfo.setBirthday(rs.getString("birthday"));

studentInfo.setScore(rs.getDouble("score"));

// 添加进list

list.add(studentInfo);

}

// 关闭数据库

pst.close();

conn.close();

} catch (SQLException e) {

e.printStackTrace();

}

return list;

}

//调用测试

public static void main(String[] args) {

// 日期转字符串

Date date = new Date();

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

String nowDate = sdf.format(date);

StudentInfo si = new StudentInfo("Lily","1",100.0,nowDate);

//new 工具对象

StudentInfoDao studentDao = new StudentInfoDao();

// 直接调用内部方法

studentDao.add(si); // 添加

studentDao.delById(4); // 删除

si = studentDao.selById(17); // 查询

System.out.println("update 前 " + si); //调用内部的toString方法，输出查询到的数据

si.setName("Jim");

si.setSex("0");

studentDao.update(si); // 对上面查询到的数据重新设置值

si = studentDao.selById(17);

System.out.println("update 后 " + si);

List list = studentDao.selAll(); // 查询全部

// 范型输出查询到的列表

System.out.println("输出全部列表：");

for(StudentInfo item:list) {

System.out.println(item);

}

}

}