Java-MySql：JDBC

JDBC概述

JDBC搭建

1、导入mysql开发商提供的jar包

2、注册驱动

3、与数据库连接

注解：

Statement：

代码

运行

PreparedStatement：

代码

运行

PreparedStatement和Statement

Statement

增

代码

运行

删

代码

运行

改

代码

运行

PreparedStatement

增

代码

运行

删

代码

运行

改

代码

运行

PreparedStatement和Statement 区别

结果集处理

代码

运行

代码

运行

编辑代码

运行

JDBC概述

jdbc(Java DataBase Connectivity)java语言连接数据库
本模块中，java提供了一组用来连接数据库的类和接口
java语言开发者，本身没有提供如何具体连接数据库的功能，只是定义了一组java程序连接数据库的访问接口。

1、连接到数据库

2、向数据库发送增删改这一类的sql

3、发送查询sql

java语言只需要定义连接数据库的接口，具体的实现交给了不同的数据库开发商

java只需要定义一套接口，就可以连接不同的接口

JDBC搭建

1、导入mysql开发商提供的jar包

2、注册驱动

两种方式：

1、反射方式加载驱动类
Class.forName("com.mysql.cj.jdbc.Driver");

2 、DriverManager.registerDriver(new Driver());

3、与数据库连接

获得Satement执行sql语句

发送sql语句

关闭与数据库的连接

注解：

url: jdbc:mysql://127.0.0.1:3306：（端口（3306））

/schooldb（数据库名）

?serverTimezone=Asia/Shanghai"

user:用户名（root）

password:密码

Statement：

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class Demo1 {
    public static void main(String[] args) throws ClassNotFoundException, SQLException {

        //2、注册驱动 
        DriverManager.registerDriver(new Driver());

        //3、建立与数据库的连接
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        //个人数据库密码
        String password = "root";
        Connection connection = DriverManager.getConnection(url, user, password);
        System.out.println(connection);//com.mysql.cj.jdbc.ConnectionImpl@25359ed8

        //发送sql
        Statement statement = connection.createStatement();
        System.out.println(statement);//com.mysql.cj.jdbc.StatementImpl@6166e06f
        statement.executeUpdate("insert into major(name)value ('数学')");

        //关闭与数据库的连接
        statement.close();
        connection.close();
    }
}

运行

PreparedStatement：

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.*;

public class Demo3 {
    public static void main(String[] args) throws ClassNotFoundException, SQLException {

        //2、注册驱动
        //反射方式加载驱动类
        //Class.forName("com.mysql.cj.jdbc.Driver");
        DriverManager.registerDriver(new Driver());

        //3、建立与数据库的连接
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        //个人数据库密码
        String password = "root";
        Connection connection = DriverManager.getConnection(url, user, password);

        //发送sql
        //？ 占位符 表示要插入一个参数
        PreparedStatement ps = connection.prepareStatement("insert into major(name)value (?)");
        //1向第一个占位符的位置插入数据
        ps.setObject(1, "智能");
        ps.executeUpdate();
        //关闭与数据库的连接
        ps.close();
        connection.close();
    }
}

运行

PreparedStatement和Statement

Statement

增

代码

 package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class Demo2 {
    public static void main(String[] args) throws SQLException {
        Demo2.insert("元神启","动", "2018-8-23", "12345678910", 1.4);
    }

    public static void insert(String name,String gender,String birthday,String phone,double height) throws SQLException {
        //注册驱动
        DriverManager.registerDriver(new Driver());
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        //个人数据库密码
        String password = "root";
        //建立与数据库的连接
        Connection connection = DriverManager.getConnection(url, user, password);
        //发送sql
        Statement statement = connection.createStatement();
        statement.executeUpdate("insert into student(name,gender,birthday,phone,height)value('"+name+"','"+gender+"','"+birthday+"','"+phone+"',"+height+")");
        //关闭与数据库的连接
        statement.close();
        connection.close();
    }
}

运行

删

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class Demo2 {
    public static void main(String[] args) throws SQLException {
        Demo2.delete(6);
    }

    public static void delete(int number) throws SQLException {
        //注册驱动
        DriverManager.registerDriver(new Driver());
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        //个人数据库密码
        String password = "root";
        //建立与数据库的连接
        Connection connection = DriverManager.getConnection(url, user, password);
        //发送sql
        Statement statement = connection.createStatement();
        //直接将字符串拼接到sql中，不能防止sql注入攻击"or 1=1"
        statement.executeUpdate("delete from student where number = "+number);
        //关闭与数据库的连接
        statement.close();
        connection.close();
    }
}

运行

改

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class Demo2 {
    public static void main(String[] args) throws SQLException {
        Demo2.update(3,"爱丽西娅","女", "2024-4-14", "123456789", 1.72);
    }

    public static void update(int number,String name,String gender,String birthday,String phone,double height) throws SQLException {
        //注册驱动
        DriverManager.registerDriver(new Driver());
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        //个人数据库密码
        String password = "root";
        //建立与数据库的连接
        Connection connection = DriverManager.getConnection(url, user, password);
        //发送sql
        Statement statement = connection.createStatement();
        statement.executeUpdate("update student set name='"+name+"',gender='"+gender+"',birthday='"+birthday+"',phone='"+phone+"',height="+height+" where number ="+number);
        //关闭与数据库的连接
        statement.close();
        connection.close();
    }
}

运行

PreparedStatement

增

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.*;

public class Demo4 {
    public static void main(String[] args) throws SQLException {
        Demo4.insert("小姨","鹤", "2018-8-23", "123456789", 1.4);
    }

    public static void insert(String name,String gender,String birthday,String phone,double height) throws SQLException {
        //注册驱动
        DriverManager.registerDriver(new Driver());
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        //个人数据库密码
        String password = "root";
        //建立与数据库的连接
        Connection connection = DriverManager.getConnection(url, user, password);
        //发送sql
        PreparedStatement ps = connection.prepareStatement("insert into student(name,gender,birthday,phone,height)value(?,?,?,?,?)");
        ps.setObject(1,name);
        ps.setObject(2,gender);
        ps.setObject(3,birthday);
        ps.setObject(4,phone);
        ps.setObject(5,height);
        ps.executeUpdate();
        //关闭与数据库的连接
        ps.close();
        connection.close();
    }
}

运行

删

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.*;

public class Demo4 {
    public static void main(String[] args) throws SQLException {
        Demo4.delete(15);
    }

    public static void delete(int number) throws SQLException {
        //注册驱动
        DriverManager.registerDriver(new Driver());
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        //个人数据库密码
        String password = "root";
        //建立与数据库的连接
        Connection connection = DriverManager.getConnection(url, user, password);
        //发送sql
        //封装sql
        PreparedStatement ps = connection.prepareStatement("delete from student where number = ?");
        //向sql中传参 传参时会进行验证，防止sql注入攻击，更安全
        ps.setObject(1, number);
        ps.executeUpdate();
        //关闭与数据库的连接
        ps.close();
        connection.close();
    }
}

运行

改

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.*;

public class Demo4 {
    public static void main(String[] args) throws SQLException {
        Demo4.update(3,"申鹤","女", "2024-4-14", "12345678910", 1.72);
    }

    public static void update(int number,String name,String gender,String birthday,String phone,double height) throws SQLException {
        //注册驱动
        DriverManager.registerDriver(new Driver());
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        //个人数据库密码
        String password = "root";
        //建立与数据库的连接
        Connection connection = DriverManager.getConnection(url, user, password);
        //发送sql
        PreparedStatement ps = connection.prepareStatement("update student set name=?,gender=?,birthday=?,phone=?,height=? where number =?");
        ps.setObject(1, name);
        ps.setObject(2, gender);
        ps.setObject(3, birthday);
        ps.setObject(4, phone);
        ps.setObject(5, height);
        ps.setObject(6, number);
        ps.executeUpdate();
        //关闭与数据库的连接
        ps.close();
        connection.close();
    }
}

运行

PreparedStatement和Statement 区别

1、代码的可读性和可维护性. 虽然用PreparedStatement来代替Statement会使代码多出几行,但这样的代码无论从可读性还是可维护性上来说.都比直接用Statement的代码高很多档次。

2、最重要的一点是极大地提高了安全性.

防止sql注入　

Stringsql= “ delete from user where id = ”+num; 　　

如果我们把[or 1=1]作为id传入进来? 　　

delete from tb_name where id = 1 or 1 = 1; 　　

因为‘1’ = ‘1’肯定成立　　

而如果你使用预编译语句.你传入的任何内容就不会和原来的语句发生任何匹配的关系.

预编译模式中每个占位符处,只能插入一个值,而会过滤其他语句。

结果集处理

PreparedStatement和Statement中的executeQuery()方法中会返回一个ResultSet对象,查询结果就封装在此对象中.

使用ResultSet中的next()方法获得下一行数据

使用getXXX(String name)方法获得值

package com.ffyc.jdbcpro;

import java.util.Date;

public class Student {
    private int number;
    private String name;
    private String gender;
    private Date birthday;
    private String phone;
    private double height;
    private Date ref_time;

    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public double getHeight() {
        return height;
    }

    public void setHeight(double height) {
        this.height = height;
    }

    public Date getRef_time() {
        return ref_time;
    }

    public void setRef_time(Date ref_time) {
        this.ref_time = ref_time;
    }

    @Override
    public String toString() {
        return "Student{" +
                "number=" + number +
                ", name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", birthday=" + birthday +
                ", phone='" + phone + '\'' +
                ", height=" + height +
                ", ref_time=" + ref_time +
                '}';
    }
}

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.*;

public class Demo5 {
    public static void main(String[] args) throws SQLException {
        Student student = Demo5.findStudentByNumber(16);
        System.out.println(student);
    }

    public static Student findStudentByNumber(int number) throws SQLException {
        DriverManager.registerDriver(new Driver());
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        String password = "root";
        Connection connection = DriverManager.getConnection(url, user, password);
        PreparedStatement ps = connection.prepareStatement("select number,name,gender,birthday,height,phone,reg_time from student where number = ?");
        ps.setObject(1, number);
        //执行查询后，mysql将数据封装到一个ResultSet对象中
        ResultSet rs = ps.executeQuery();
        System.out.println(rs);//com.mysql.cj.jdbc.result.ResultSetImpl@64d2d351
        //将ResultSet中的数据包装到自己的对象中，这样用起来更加方便
        //结果集中有没有数据 如果有返回true,否则返回false
        Student stu = new Student();
        while (rs.next()){
            stu.setNumber(rs.getInt("number"));
            stu.setName(rs.getString("name"));
            stu.setGender(rs.getString("gender"));
            stu.setBirthday(rs.getDate("birthday"));
            stu.setHeight(rs.getDouble("height"));
            stu.setPhone(rs.getString("phone"));
            stu.setRef_time(rs.getTimestamp("reg_time"));

        }
        return stu;
    }
}

运行

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

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

public class Demo6 {
    public static void main(String[] args) throws SQLException {
        ArrayList<Student> students = findStudent();
        System.out.println(students);
    }
    public static ArrayList<Student> findStudent() throws SQLException {
        DriverManager.registerDriver(new Driver());
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        String password = "root";
        Connection connection = DriverManager.getConnection(url, user, password);
        PreparedStatement ps = connection.prepareStatement("select number,name,gender,birthday,height,phone,reg_time from student");
        ResultSet rs = ps.executeQuery();
        //创建一个集合对象用来封装多个学生对象
        ArrayList<Student> students = new ArrayList<>();
        while (rs.next()){
            //每循环一次，创建一个学生对象
            Student stu = new Student();
            stu.setNumber(rs.getInt("number"));
            stu.setName(rs.getString("name"));
            stu.setGender(rs.getString("gender"));
            stu.setBirthday(rs.getDate("birthday"));
            stu.setHeight(rs.getDouble("height"));
            stu.setPhone(rs.getString("phone"));
            stu.setRef_time(rs.getTimestamp("reg_time"));
            //把当前学生对象返回到集合中
            students.add(stu);
        }
        return students;
    }
}

运行

代码

package com.ffyc.jdbcpro;

import com.mysql.cj.jdbc.Driver;

import java.sql.*;

public class Demo7 {
    public static void main(String[] args) throws SQLException {
        int res = checkNum(16);
        System.out.println(res);

    }

    public static int checkNum(int number) throws SQLException {
        DriverManager.registerDriver(new Driver());
        String url = "jdbc:mysql://127.0.0.1:3306/schooldb?serverTimezone=Asia/Shanghai";
        String user = "root";
        String password = "root";
        Connection connection = DriverManager.getConnection(url, user, password);
        PreparedStatement ps = connection.prepareStatement("select count(*) c from student where number = ?");
        ps.setObject(1, number);
        ResultSet resultSet = ps.executeQuery();
        if(resultSet.next()){
            return resultSet.getInt("c");
        }else{
            return 0;
        }
    }
}