Spring Boot+Gradle项目数据库连接报错：Could not obtain connection to query metadata

问题背景 #

使用Spring Boot 2.7.3、Gradle、Lombok开发Java 17应用，配置MySQL数据库连接时启动报错：Could not obtain connection to query metadata。相关配置如下：

1. resources/db.migration 建表SQL #

CREATE TABLE users
(
    id        int                                NOT NULL AUTO_INCREMENT,
    role      enum('CUSTOMER','TRAINER','ADMINISTRATION') NOT NULL,
    email     varchar(45)                        NOT NULL,
    password  varchar(200)                       NOT NULL,
    firstName varchar(45)                        NOT NULL,
    lastName  varchar(45)                        NOT NULL,
    PRIMARY KEY (id),
    UNIQUE(email)
);

2. application.properties 配置 #

spring.datasource.url=jdbc:mysql://localhost:3306/hiddenName
spring.datasource.username=hiddenUsername
spring.datasource.password=hiddenPassword

3. build.gradle 依赖配置 #

plugins {
    id 'org.springframework.boot' version '2.7.3'
    id 'io.spring.dependency-management' version '1.0.13.RELEASE'
    id 'java'
}

group = 'HiddenName'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'

configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-validation'
    implementation 'ch.qos.logback:logback-classic:1.2.11'
    testImplementation 'org.projectlombok:lombok:1.18.22'
    compileOnly 'org.projectlombok:lombok'
    annotationProcessor 'org.projectlombok:lombok'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
    testImplementation 'junit:junit:4.13.2'
    testImplementation 'org.assertj:assertj-core:3.20.2'
    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.1'
    testImplementation 'org.junit.jupiter:junit-jupiter-engine:5.8.1'
    testImplementation 'junit:junit:4.13.2'
    testImplementation 'org.assertj:assertj-core:3.20.2'

    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-validation'

    implementation 'mysql:mysql-connector-java:8.0.30'
    implementation 'ch.qos.logback:logback-classic:1.2.11'
    implementation 'org.springdoc:springdoc-openapi-ui:1.6.10'
    compileOnly 'org.projectlombok:lombok'
    annotationProcessor 'org.projectlombok:lombok'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
    testRuntimeOnly 'com.h2database:h2'
}

test {
    useJUnitPlatform()
}

问题排查与修复步骤 #

1. 验证基础数据库连接 #

首先排除最基础的连接问题：

• 确认MySQL服务正在本地3306端口运行，可通过命令行测试连接：

  mysql -h localhost -P 3306 -u hiddenUsername -p
  

  输入密码后，若能成功登录，再检查hiddenName数据库是否存在，不存在则执行：

  CREATE DATABASE hiddenName;
  

• 若连接失败，检查账号密码是否正确、数据库权限是否开放（比如本地账号是否允许localhost连接）。

2. 修正数据库连接配置 #

MySQL 8.0+需要指定时区、SSL等参数，更新application.properties：

spring.datasource.url=jdbc:mysql://localhost:3306/hiddenName?useSSL=false&serverTimezone=UTC&allowPublicKeyRetrieval=true
spring.datasource.username=hiddenUsername
spring.datasource.password=hiddenPassword
# 显式指定MySQL 8.0驱动类，避免自动适配问题
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
# 禁用JPA自动建表，避免与Flyway迁移冲突
spring.jpa.hibernate.ddl-auto=none
# 可选：开启SQL日志便于排查
spring.jpa.show-sql=true

3. 清理Gradle重复依赖 #

原build.gradle存在大量重复依赖（如spring-boot-starter-web、lombok、junit等），易导致类冲突，整理后的依赖如下：

plugins {
    id 'org.springframework.boot' version '2.7.3'
    id 'io.spring.dependency-management' version '1.0.13.RELEASE'
    id 'java'
}

group = 'HiddenName'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'

configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}

repositories {
    mavenCentral()
}

dependencies {
    // 核心Web、JPA、Validation依赖
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    implementation 'org.springframework.boot:spring-boot-starter-validation'

    // MySQL驱动
    implementation 'mysql:mysql-connector-java:8.0.30'

    // Lombok支持
    compileOnly 'org.projectlombok:lombok'
    annotationProcessor 'org.projectlombok:lombok'

    // 日志框架
    implementation 'ch.qos.logback:logback-classic:1.2.11'

    // OpenAPI文档支持
    implementation 'org.springdoc:springdoc-openapi-ui:1.6.10'

    // 测试依赖
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.1'
    testImplementation 'org.junit.jupiter:junit-jupiter-engine:5.8.1'
    testImplementation 'org.assertj:assertj-core:3.20.2'
    testRuntimeOnly 'com.h2database:h2'

    // 添加Flyway数据库迁移依赖（因存在db.migration目录）
    implementation 'org.springframework.boot:spring-boot-starter-flyway'
}

test {
    useJUnitPlatform()
}

关键调整：

• 移除所有重复依赖，避免版本冲突
• 将Lombok依赖移至compileOnly和annotationProcessor（主代码也需使用Lombok）
• 添加spring-boot-starter-flyway依赖，匹配db.migration目录的迁移需求

4. 配置Flyway（可选） #

若首次使用Flyway且数据库已有表，需添加以下配置到application.properties，避免基线检查报错：

spring.flyway.baseline-on-migrate=true

验证修复 #

1. 执行Gradle清理编译：

   ./gradlew clean build
   

2. 启动MySQL服务，确认hiddenName数据库存在
3. 启动Spring Boot应用，查看日志：
   • 应出现Successfully connected to database相关日志
   • Flyway会自动执行db.migration目录下的建表SQL

内容的提问来源于stack exchange，提问作者Stoyan Grozdev