<!-- Spring Web -->
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- MyBatis -->
<dependency>
	<groupId>org.mybatis.spring.boot</groupId>
	<artifactId>mybatis-spring-boot-starter</artifactId>
	<version>3.0.2</version>
</dependency>
<!-- MySQL連接支持 -->
<dependency>
	<groupId>com.mysql</groupId>
	<artifactId>mysql-connector-j</artifactId>
	<scope>runtime</scope>
</dependency>
<!-- Hutool實(shí)用工具 -->
<dependency>
	<groupId>cn.hutool</groupId>
	<artifactId>hutool-all</artifactId>
	<version>5.8.16</version>
</dependency>
<!-- Lombok注解 -->
<dependency>
	<groupId>org.projectlombok</groupId>
	<artifactId>lombok</artifactId>
	<scope>provided</scope>
</dependency>
<!-- Spring Boot測(cè)試 -->
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-test</artifactId>
	<scope>test</scope>
</dependency>

# 數(shù)據(jù)庫配置
spring:
  datasource:
    url: "jdbc:mysql://127.0.0.1:3306/init_demo?serverTimezone=GMT%2B8"
    username: "swsk33"
    password: "dev-2333"

package com.gitee.swsk33.sqlinitdemo.config;
import cn.hutool.core.io.resource.ClassPathResource;
import jakarta.annotation.PostConstruct;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.jdbc.ScriptRunner;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.StandardCharsets;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
/**
 * 用于第一次啟動(dòng)時(shí)，初始化數(shù)據(jù)庫的配置類
 */
@Slf4j
@Configuration
public class DatabaseInitialize {
	/**
	 * 讀取連接地址
	 */
	@Value("${spring.datasource.url}")
	private String url;
	/**
	 * 讀取用戶名
	 */
	@Value("${spring.datasource.username}")
	private String username;
	/**
	 * 讀取密碼
	 */
	@Value("${spring.datasource.password}")
	private String password;
	/**
	 * 檢測(cè)當(dāng)前連接的庫是否存在（連接URL中的數(shù)據(jù)庫）
	 *
	 * @return 當(dāng)前連接的庫是否存在
	 */
	private boolean currentDatabaseExists() {
		// 嘗試以配置文件中的URL建立連接
		try {
			Connection connection = DriverManager.getConnection(url, username, password);
			connection.close();
		} catch (SQLException e) {
			// 若連接拋出異常則說明連接URL中指定數(shù)據(jù)庫不存在
			return false;
		}
		// 正常情況下說明連接URL中數(shù)據(jù)庫存在
		return true;
	}
	/**
	 * 執(zhí)行SQL腳本
	 *
	 * @param path        SQL腳本文件的路徑
	 * @param isClasspath SQL腳本路徑是否是classpath路徑
	 * @param connection  數(shù)據(jù)庫連接對(duì)象，通過這個(gè)連接執(zhí)行腳本
	 */
	private void runSQLScript(String path, boolean isClasspath, Connection connection) {
		try (InputStream sqlFileStream = isClasspath ? new ClassPathResource(path).getStream() : new FileInputStream(path)) {
			BufferedReader sqlFileStreamReader = new BufferedReader(new InputStreamReader(sqlFileStream, StandardCharsets.UTF_8));
			// 創(chuàng)建SQL腳本執(zhí)行器對(duì)象
			ScriptRunner scriptRunner = new ScriptRunner(connection);
			// 使用SQL腳本執(zhí)行器對(duì)象執(zhí)行腳本
			scriptRunner.runScript(sqlFileStreamReader);
			// 最后關(guān)閉文件讀取器
			sqlFileStreamReader.close();
		} catch (Exception e) {
			log.error("讀取文件或者執(zhí)行腳本失??！");
			e.printStackTrace();
		}
	}
	/**
	 * 執(zhí)行SQL腳本以創(chuàng)建數(shù)據(jù)庫
	 */
	private void createDatabase() {
		try {
			// 修改連接語句，重新建立連接
			// 重新建立的連接不再連接到指定庫，而是直接連接到整個(gè)MySQL
			// 使用URI類解析并拆解連接地址，重新組裝
			URI databaseURI = new URI(url.replace("jdbc:", ""));
			// 得到連接地址中的數(shù)據(jù)庫平臺(tái)名（例如mysql）
			String databasePlatform = databaseURI.getScheme();
			// 得到連接地址和端口
			String hostAndPort = databaseURI.getAuthority();
			// 得到連接地址中的庫名
			String databaseName = databaseURI.getPath().substring(1);
			// 組裝新的連接URL，不連接至指定庫
			String newURL = "jdbc:" + databasePlatform + "://" + hostAndPort + "/";
			// 重新建立連接
			Connection connection = DriverManager.getConnection(newURL, username, password);
			Statement statement = connection.createStatement();
			// 執(zhí)行SQL語句創(chuàng)建數(shù)據(jù)庫
			statement.execute("create database if not exists `" + databaseName + "`");
			// 關(guān)閉會(huì)話和連接
			statement.close();
			connection.close();
			log.info("創(chuàng)建數(shù)據(jù)庫完成！");
		} catch (URISyntaxException e) {
			log.error("數(shù)據(jù)庫連接URL格式錯(cuò)誤！");
			throw new RuntimeException(e);
		} catch (SQLException e) {
			log.error("連接失敗！");
			throw new RuntimeException(e);
		}
	}
	/**
	 * 該方法用于檢測(cè)數(shù)據(jù)庫是否需要初始化，如果是則執(zhí)行SQL腳本進(jìn)行初始化操作
	 */
	@PostConstruct
	private void initDatabase() {
		log.info("開始檢查數(shù)據(jù)庫是否需要初始化...");
		// 檢測(cè)當(dāng)前連接數(shù)據(jù)庫是否存在
		if (currentDatabaseExists()) {
			log.info("數(shù)據(jù)庫存在，不需要初始化！");
			return;
		}
		log.warn("數(shù)據(jù)庫不存在！準(zhǔn)備執(zhí)行初始化步驟...");
		// 先創(chuàng)建數(shù)據(jù)庫
		createDatabase();
		// 然后再次連接，執(zhí)行腳本初始化庫中的表格
		try (Connection connection = DriverManager.getConnection(url, username, password)) {
			runSQLScript("/create-table.sql", true, connection);
			log.info("初始化表格完成！");
		} catch (Exception e) {
			log.error("初始化表格時(shí)，連接數(shù)據(jù)庫失敗！");
			e.printStackTrace();
		}
	}
}

-- 初始化表格前先刪除
drop table if exists `user`;
-- 創(chuàng)建表格
create table `user`
(
	`id`       int unsigned auto_increment,
	`username` varchar(16) not null,
	`password` varchar(32) not null,
	primary key (`id`)
) engine = InnoDB
  default charset = utf8mb4;

// 省略package和import
/**
 * 啟動(dòng)時(shí)需要查詢數(shù)據(jù)庫的Beans
 */
@Slf4j
@Component
public class UserServiceDemo {
	@Autowired
	private UserDAO userDAO;
	@PostConstruct
	private void init() {
		log.info("執(zhí)行數(shù)據(jù)庫測(cè)試訪問...");
		userDAO.add(new User(0, "用戶名", "密碼"));
		List<User> users = userDAO.getAll();
		for (User user : users) {
			System.out.println(user);
		}
	}
}

@Slf4j
@Component
// 使用@DependsOn注解表示當(dāng)前類依賴于名為databaseInitialize的Bean
// 這樣可以使得databaseInitialize這個(gè)Bean（我們的數(shù)據(jù)庫檢查類）先被初始化，并執(zhí)行完成數(shù)據(jù)庫初始化后再初始化本類，以順利訪問數(shù)據(jù)庫
@DependsOn("databaseInitialize")
public class UserServiceDemo {
	// 省略這個(gè)類的內(nèi)容
}