Spring Boot项目添加spring-boot-starter-mail依赖失败求助

问题背景 #

原本运行正常的Spring Boot应用，添加spring-boot-starter-mail依赖后无法下载，IDEA中标红，需要使用JavaMailSender实现邮件发送功能。

环境信息 #

• Java版本：1.8
• Spring Boot版本：2.1.6.RELEASE
• IDE：IntelliJ IDEA 2021.2

报错信息 #

Dependency 'org.springframework.boot:spring-boot-starter-mail:2.1.6.RELEASE' not found

完整pom.xml代码 #

<?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>2.1.6.RELEASE</version>
        <relativePath/>
    </parent>
    <groupId>com.demo</groupId>
    <artifactId>MyWebApp</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>MyWebApp</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-data-version>2.1.9.RELEASE</spring-data-version>
        <hibernate-version>5.3.6.Final</hibernate-version>
        <mysql.version>8.0.16</mysql.version>
        <spring-session-bom.version>Bean-SR6</spring-session-bom.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>

        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-jasper</artifactId>
            <version>${tomcat.version}</version>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.20</version>
            <scope>compile</scope>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>${hibernate-version}</version>
            <type>jar</type>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.hibernate.validator</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>6.0.17.Final</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>${hibernate-version}</version>
            <type>jar</type>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>${mysql.version}</version>
            <exclusions>
                <exclusion>
                    <artifactId>protobuf-java</artifactId>
                    <groupId>com.google.protobuf</groupId>
                </exclusion>
            </exclusions>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
            <version>2.1.6.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>

        <dependency>
            <groupId>com.sun.mail</groupId>
            <artifactId>javax.mail</artifactId>
            <version>${sun-mail.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-jpa</artifactId>
        </dependency>

        <dependency>
            <groupId>org.hsqldb</groupId>
            <artifactId>hsqldb</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.session</groupId>
            <artifactId>spring-session-bom</artifactId>
            <version>${spring-session-bom.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-test</artifactId>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

解决方案 #

1. 清理本地Maven缓存 #

• 删除本地Maven仓库中org/springframework/boot/spring-boot-starter-mail/2.1.6.RELEASE目录，执行mvn clean install命令重新下载依赖。
• 检查settings.xml镜像配置，确保使用的镜像（如阿里云镜像）包含该版本依赖，网络连接正常。

2. 修复pom.xml冗余依赖 #

• 移除com.sun.mail:javax.mail依赖：spring-boot-starter-mail已内置JavaMail相关依赖，手动添加会导致版本冲突，且${sun-mail.version}未定义，属于无效配置。
• 移除tomcat-embed-jasper的version标签：${tomcat.version}未在properties中定义，让Spring Boot父工程自动管理版本即可。

修改后的邮件依赖片段：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-mail</artifactId>
</dependency>

3. 刷新IDE缓存 #

• 在IDEA中执行File -> Invalidate Caches... -> Invalidate and Restart，清除缓存后重启。
• 右键pom.xml选择Maven -> Reload Project，强制重新加载依赖。

4. 确认版本有效性 #

Spring Boot 2.1.6.RELEASE对应的spring-boot-starter-mail版本确实存在，检查依赖groupId、artifactId和版本号是否拼写错误。

内容的提问来源于stack exchange，提问作者Jdslk