javaweb-数据库

Posted 2022-01-15 可能自洽

javaweb-数据库

一、mysql

1.下载

MySQL :: Download MySQL Community Server (Archived Versions)

2.配置

2.1 环境变量

C:\\Users\\leo\\Downloads\\mysql-5.7.24-winx64

2.2 my.ini

[mysql]
default-character-set=utf8
[mysqld]
character-set-server=utf8
default-storage-engine=INNODB
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

2.3 以管理员方式运行cmd

(1) 创建data文件夹

mysqld --initialize-insecure

(2) 注册mysql服务

mysqld -install

(3) 启动mysql

net start mysql

停止服务

net stop mysql

(4) 改个密码

mysqladmin -u root password 0000

(5) 连接好，就可以开始敲mysql了

mysql -uroot -p0000

3.使用navicat

3.1 新建连接

点测试连接，成功的话就确定

3.2 新建数据库

二、JDBC

1.下载jar

https://downloads.mysql.com/archives/c-j/

2.粘贴到idea里，然后add

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

public class test 
    public static void main(String[] args) throws Exception 
        // 注册驱动
        Class.forName("com.mysql.jdbc.Driver");
        // 获取连接
        String url = "jdbc:mysql://127.0.0.1:3306/db1";
        String user = "root";
        String password = "0000";
        Connection connection = DriverManager.getConnection(url, user, password);
        // 定义sql语句
        String sql = "update stu set name = 123 where id = 1";
        // 获取执行sql的对象
        Statement statement = connection.createStatement();
        // 执行
        int count = statement.executeUpdate(sql);
        System.out.println(count);
        // 关闭
        statement.close();
        connection.close();
    

3.JDBC API

3.1DriverManager

注册驱动

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

MySQL5之后的驱动jar包，可以省略注册驱动步骤

获取数据库连接

3.2 Connection

获取执行SQL的对象
管理事务

3.3 ResultSet 结果集对象

执行DQL语句返回ResultSet对象

import java.sql.*;

public class test 
    public static void main(String[] args) throws Exception 
        String url = "jdbc:mysql://127.0.0.1:3306/db1?useSSL=true";
        String user = "root";
        String password = "0000";
        Connection connection = DriverManager.getConnection(url, user, password);
        String sql = "select * from stu";
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery(sql);
        while (resultSet.next()) 
        	// 这里可以写列的名称也可以写编号（从1开始）
            int id = resultSet.getInt(1);
            String name = resultSet.getString(2);
            int gender = resultSet.getInt(3);
            Date birthday = resultSet.getDate(4);
            System.out.println(id);
            System.out.println(name);
            System.out.println(gender);
            System.out.println(birthday);
            System.out.println("----------------------");
        
        resultSet.close();
        statement.close();
        connection.close();
    

查询stu表里的数据，封装为Stu对象，并存储到ArrayList集合中
定义实体类 Stu

import java.sql.Date;

public class Stu 
    private int id;
    private String name;
    private int gender;
    private Date birthday;

    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 getGender() 
        return gender;
    

    public void setGender(int gender) 
        this.gender = gender;
    

    public Date getBirthday() 
        return birthday;
    

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

    @Override
    public String toString() 
        return "Stu" +
                "id=" + id +
                ", name='" + name + '\\'' +
                ", gender=" + gender +
                ", birthday=" + birthday +
                '';
    

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

public class test 
    public static void main(String[] args) throws Exception 
        String url = "jdbc:mysql://127.0.0.1:3306/db1?useSSL=true";
        String user = "root";
        String password = "0000";
        Connection connection = DriverManager.getConnection(url, user, password);
        String sql = "select * from stu";
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery(sql);
        List<Stu> stuList = new ArrayList<>();
        while (resultSet.next()) 
            Stu stu = new Stu();
            int id = resultSet.getInt(1);
            String name = resultSet.getString(2);
            int gender = resultSet.getInt(3);
            Date birthday = resultSet.getDate(4);
            stu.setId(id);
            stu.setName(name);
            stu.setGender(gender);
            stu.setBirthday(birthday);
            stuList.add(stu);
        
        System.out.println(stuList);
        resultSet.close();
        statement.close();
        connection.close();
    

3.4 PreparedStatement

预编译SQL语句并执行:预防SQL注入问题
SQL注入是通过操作输入来修改事先定义好的SQL语句，用以达到执行代码对服务器进行攻击的方法。

(1) 创建表

DROP TABLE IF EXISTS tb_user;
CREATE TABLE tb_user (
id INT,
input_username VARCHAR (20),
input_password VARCHAR (20)
);
INSERT INTO tb_user VALUES(1,"giao1","1"),(2,"giao2","2");

SELECT * FROM tb_user;

(2) 体会sql注入

import java.sql.*;

public class test 
    public static void main(String[] args) throws Exception 
        String url = "jdbc:mysql://127.0.0.1:3306/db1?useSSL=true";
        String user = "root";
        String password = "0000";
        Connection connection = DriverManager.getConnection(url, user, password);
//        String input_name = "giao1";
//        String input_password = "1";
        String input_name = "asdfasf";
        String input_password = "' or '1'='1";
        String sql = "select * from tb_user where input_username='" + input_name + "' and input_password='" + input_password + "'";
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery(sql);
        if (resultSet.next()) 
            System.out.println("ok");
         else 
            System.out.println("no");
        
        resultSet.close();
        statement.close();
        connection.close();
    

(3) 解决sql注入问题

import java.sql.*;

public class test 
    public static void main(String[] args) throws Exception 
        String url = "jdbc:mysql://127.0.0.1:3306/db1?useSSL=true";
        String user = "root";
        String password = "0000";
        Connection connection = DriverManager.getConnection(url, user, password);
        String input_name = "giao1";
        String input_password = "1";
//        String input_name = "asdfasf";
//        String input_password = "' or '1'='1";
        String sql = "select * from tb_user where input_username= ? and input_password=?";
        PreparedStatement prepareStatement = connection.prepareStatement(sql);
        prepareStatement.setString(1, input_name);
        prepareStatement.setString(2, input_password);
        ResultSet resultSet = prepareStatement.executeQuery();
        if (resultSet.next()) 
            System.out.println("ok");
         else 
            System.out.println("no");
        
        resultSet.close();
        prepareStatement.close();
        connection.close();
    

（4）其原理

url后边加这句话useServerPrepStmts=true
my.ini后面加一些命令

[mysql]
default-character-set=utf8
[mysqld]
character-set-server=utf8
default-storage-engine=INNODB
sql_mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

log-output=FILE
general-log=1
general_log_file="D:\\mysql.log"
slow-query-log=1
slow_query_log_file="D:\\mysql_slow.log"
long_query_time=2

然后打开cmd，输入services.msc打开服务窗口，点击重新启动，然后D盘就有log文件啦

String url = "jdbc:mysql://127.0.0.1:3306/db1?useSSL=true&useServerPrepStmts=true";

如果把&useServerPrepStmts=true去掉，就没有预编译了

如果 prepareStatement.executeQuery() 执行两次，日志文件只预编译一次，所以性能更高

import java.sql.*;

public class test 
    public static void main(String[] args) throws Exception 
        String url = "jdbc:mysql://127.0.0.1:3306/db1?useSSL=true&useServerPrepStmts=true";
        String user = "root";
        String password = "0000";
        Connection connection = DriverManager.getConnection(url, user, password);
//        String input_name = "giao1";
//        String input_password = "1";
        String input_name = "asdfasf";
        String input_password = "' or '1'='1";
        String sql = "select * from tb_user where input_username= ? and input_password=?";
        PreparedStatement prepareStatement = connection.prepareStatement(sql);
        prepareStatement.setString(1, input_name);
        prepareStatement.setString(2, input_password);
        prepareStatement.executeQuery();
        prepareStatement.setString(1, "input_name");
        prepareStatement.setString(2, "input_password");
        prepareStatement.executeQuery();
        prepareStatement.close();
        connection.close();
    

3.5 数据库连接池

数据库连接池是个容器，负责分配、管理数据库连接(Connection)
它允许应用程序重复使用一个现有的数据库连接，而不是再重新建立一个
释放空闲时间超过最大空闲时间的数据库连接来避免因为没有释放数据库连接而引|起的数据库连接遗漏
好处：资源重用，提升系统响应速度，避免数据库连接遗漏

(1) 下载jar包，然后导入idea

https://repo1.maven.org/maven2/com/alibaba/druid/1.2.8/

(2) 练习

新建 druid.properties 文件并写入配置

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/db1?useSSL=true&useServerPrepStmts=true
username=root
password=0000
# 初始化连接数
initialSize=5
# 连接池中最大的活跃连接数
maxActive=10
maxWait=3000

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.FileInputStream;
import java.sql.*;
import java.util.Properties;

public class test 
    public static void main(String[] args) throws Exception 
        Properties properties = new Properties();
        properties.load(new FileInputStream("D:\\\\Codes\\\\IdeaProjects\\\\test\\\\src\\\\druid.properties"));
        DataSource dataSource = DruidDataSourceFactory.createDataSource(properties);
        Connection connection = dataSource.getConnection();
        System.out.println(connection);
    

4.JDBC 练习

4.1 新建表并填入数据

drop table if exists tb_brand;

create table tb_brand(
id int primary key auto_increment,
brand_name varchar(20),
company_name varchar(20),
ordered int,
description varchar(100),
status int
);

insert into tb_brand (brand_name, company_name, ordered, description, status)
values ('三只松鼠','三只松鼠股份有限公司',5,'好吃不上火',0),
('华为','华为技术有限公司',100, '华为致力于把数字世界带入每个人、每个家庭、每个组织，构建万物互联的智能世界',1),
('小米','小米科技有限公司',50, 'are you ok', 1);

SELECT * FROM tb_brand;

4.2 实体类 Brand

public class Brand 
    private Integer id;
    private String brand_name;
    private String company_name;
    private Integer ordered;
    private String description;
    private Integer status;

    public Integer getId() 
        return id;
    

    public void setId(Integer id) 
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