Spring Boot连接MySQL遇DataSource与entityManagerFactory配置错误求助

我正在跟随in28minutes课程，尝试用Spring Boot连接MySQL（不使用H2），但始终遇到配置错误，尝试多种方法都无法解决。

项目代码与配置 #

LearnMySqlDockerApplication.java #

package com.in28min.LearnMySQLDocker;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

@SpringBootApplication(exclude =  {DataSourceAutoConfiguration.class })
@ComponentScan("com.in28min.LearnMySQLDocker.courses")
@Configuration
@EnableJpaRepositories(basePackages = "com.in28min.LearnMySQLDocker.courses.repository")
public class LearnMySqlDockerApplication {

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

}

CourseRepository.java #

package com.in28min.LearnMySQLDocker.courses.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import com.in28min.LearnMySQLDocker.courses.bean.Course;

public interface CourseRepository extends JpaRepository<Course, Long>{

}

CourseController.java #

package com.in28min.LearnMySQLDocker.courses.controller;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.PutMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import com.in28min.LearnMySQLDocker.courses.bean.Course;
import com.in28min.LearnMySQLDocker.courses.repository.CourseRepository;

@RestController
public class CourseController {
    @Autowired
    private CourseRepository repository;
    
    // http://localhost:8080/courses
    @GetMapping("/courses")
    public List<Course> getAllCourses() {       
        return repository.findAll();
    }
    
    // http://localhost:8080/courses/1
    @GetMapping("/courses/{id}")
    public Course getCourseDetails(@PathVariable long id) {
        return repository.findById(id).get();
    }
    
    /*
    POST http://localhost:8080/courses
    {
          "name": "Learn DevOps",
          "author": "in28minutes"
    }*/

    //POST - Create a new resource (/courses)
    @PostMapping("/courses")
    public void createCourse(@RequestBody Course course){
        repository.save(course);        
    }
    
    /*
    PUT - http://localhost:8080/courses/100001
    {
         "id": 100001,
         "name": "Learn Microservices 2",
         "author": "in28minutes"
        }
    */
    
    //PUT - Update/Replace a resource (/courses/1)
    @PutMapping("/courses/{id}")
    public void updateCourse(@PathVariable long id, @RequestBody Course course){
        repository.save(course);        
    }

    
    //DELETE - Delete a resource (/courses/1)
    @DeleteMapping("/courses/{id}")
    public void deleteCourse(@PathVariable long id){
        repository.deleteById(id);
    }
    

//  docker run --detach 
//  --env MYSQL_ROOT_PASSWORD=dummypassword 
//  --env MYSQL_USER=courses-user 
//  --env MYSQL_PASSWORD=dummycourses 
//  --env MYSQL_DATABASE=courses 
//  --name mysql
//  --publish 3306:3306 mysql:5.7
}

Course.java #

package com.in28min.LearnMySQLDocker.courses.bean;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.Id;

@Entity
public class Course {
    @Id
    @GeneratedValue
    private long id;
    
    //@Column(name="course_name")
    private String name;

    private String author;
    
    public Course() {
    }

    public Course(long id, String name, String author) {
        super();
        this.id = id;
        this.name = name;
        this.author = author;
    }

    public long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getAuthor() {
        return author;
    }

    @Override
    public String toString() {
        return "Course [id=" + id + ", name=" + name + ", author=" + author + "]";
    }
}

application.properties #

spring.application.name=Learn-MySQL-Docker
#logging.level.org.springframework=DEBUG
#management.endpoints.web.exposure.include=*
management.endpoints.web.exposure.include=health,metrics
#spring.datasource.url=jdbc:h2:mem:testdb

spring.autoconfigure.exclude=org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration

spring.jpa.hibernate.ddl-auto=update
spring.datasource.url=jdbc:mysql://localhost:3306/courses
spring.datasource.username=courses-user
spring.datasource.password=dummycourses
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL57Dialect



#courses-user@localhost:3306

依赖说明 #

pom.xml已添加以下依赖：spring-boot-starter-data-jpa、mysql-connector-j、hibernate-entitymanager、mysql-connector-java、spring-boot-starter-web

遇到的错误 #

1. Field repository in com.in28min.LearnMySQLDocker.courses.controller.CourseController required a bean named 'entityManagerFactory' that could not be found.
2. Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured.

解决方案 #

核心问题是手动排除了DataSourceAutoConfiguration，打断了Spring Boot自动配置数据源和JPA组件的流程，导致无法初始化entityManagerFactory等必要Bean。

修复步骤： #

1. 移除启动类中的数据源自动配置排除项
   修改后的LearnMySqlDockerApplication.java：

package com.in28min.LearnMySQLDocker;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

@SpringBootApplication
@ComponentScan("com.in28min.LearnMySQLDocker.courses")
@EnableJpaRepositories(basePackages = "com.in28min.LearnMySQLDocker.courses.repository")
public class LearnMySqlDockerApplication {

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

}

2. 移除配置文件中的自动配置排除项
   删除application.properties中这一行：

spring.autoconfigure.exclude=org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration

3. 清理冗余依赖
   mysql-connector-j和mysql-connector-java是同一依赖的不同版本命名，保留mysql-connector-j即可，移除mysql-connector-java避免冲突。

4. 验证MySQL容器状态
   确保MySQL容器正在运行：

docker ps

若未运行，执行启动命令：

docker run --detach \
--env MYSQL_ROOT_PASSWORD=dummypassword \
--env MYSQL_USER=courses-user \
--env MYSQL_PASSWORD=dummycourses \
--env MYSQL_DATABASE=courses \
--name mysql \
--publish 3306:3306 mysql:5.7

原理说明 #

Spring Boot会根据spring-boot-starter-data-jpa和MySQL驱动依赖，自动识别application.properties中的数据源配置，创建DataSource、EntityManagerFactory等核心Bean。排除DataSourceAutoConfiguration会直接中断这个自动配置流程，导致数据库连接相关组件无法初始化，进而触发报错。

内容的提问来源于stack exchange，提问作者Oh Suk