Spring Boot应用无法连接数据库，配置后启动失败求助

问题现象 #

启动Spring Boot应用时出现如下错误：

APPLICATION FAILED TO START
***************************

Description:

Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource 
could be configured.

Reason: Failed to determine a suitable driver class


Action:

Consider the following:
    If you want an embedded database (H2, HSQL or Derby), please put it on the classpath.
    If you have database settings to be loaded from a particular profile you may need to activate it (no profiles are currently active).

相关配置与代码 #

application.yml配置 #

server:
  port: 8081
  
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/microservices
    username: root
    password: root
    
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
    properties:
      hibernate:
        dialect: org.hibernate.dialect.MySQL5Dialect

pom.xml依赖 #

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.5</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.lcwd.user.service</groupId>
    <artifactId>UserService</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>UserService</name>
    <description>This is User microservice</description>
    <properties>
        <java.version>11</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.mysql</groupId>
            <artifactId>mysql-connector-j</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

主类代码 #

package com.lcwd.user.service.UserService;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class UserServiceApplication {

    public static void main(String[] args) {
        SpringApplication.run(UserServiceApplication.class, args);
    }

}

解决方案 #

1. 检查配置文件位置与格式 #

• 确认application.yml放在src/main/resources目录下，Spring Boot默认仅加载该目录下的配置文件。
• 严格检查yaml缩进：所有子属性必须用两个空格缩进，禁止使用tab，格式错误会导致配置无法被解析。

2. 验证MySQL驱动依赖与版本匹配 #

• 执行mvn clean install重新拉取依赖，确保mysql-connector-j已正确下载到本地maven仓库。
• 若本地MySQL是5.x版本，需将driver-class-name改为com.mysql.jdbc.Driver；8.x版本则保留com.mysql.cj.jdbc.Driver。

3. 核对数据库连接参数 #

• 确认本地MySQL服务已启动，端口3306未被防火墙或其他程序占用。
• 检查microservices数据库是否已创建，若不存在需先手动创建。
• 验证root账号和密码是否能正常登录本地MySQL，避免账号密码错误。

4. 排查DevTools影响 #

Spring Boot DevTools可能引发配置加载异常，可临时注释掉pom.xml中的devtools依赖，重启应用测试是否恢复正常。

5. 排除自动配置冲突（可选） #

若以上步骤均无效，可尝试在主类中排除数据源自动配置（仅适用于特殊场景，不推荐优先使用）：

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})

内容的提问来源于stack exchange，提问作者Arpit Awasthi