记录一下maven子模块依赖父类模块版本报错问题

之前也是经常遇到版本依赖报错问题，由于时间紧就都是把依赖复制了一份到子模块，今天练习项目又遇到了这个问题 

问题重现一下

1.父类模块通过<properties>管理版本，通过<dependencyManagement>管理依赖

<?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>
    <modules>
        <module>common</module>
        <module>infrastructure</module>
        <module>service</module>
    </modules>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.wang</groupId>
    <artifactId>acl_parent</artifactId>
    <packaging>pom</packaging>
    <version>0.0.1-SNAPSHOT</version>
    <name>acl_parent</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <mybatis-plus.version>3.0.5</mybatis-plus.version>
        <velocity.version>2.0</velocity.version>
        <swagger.version>2.7.0</swagger.version>
        <jwt.version>0.7.0</jwt.version>
        <fastjson.version>1.2.28</fastjson.version>
        <gson.version>2.8.2</gson.version>
        <json.version>20170516</json.version>
        <cloud-alibaba.version>0.2.2.RELEASE</cloud-alibaba.version>
    </properties>
    <dependencyManagement>
        <dependencies>
            <!--Spring Cloud-->
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Hoxton.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>

            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>${cloud-alibaba.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <!--mybatis-plus 持久层-->
            <dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>${mybatis-plus.version}</version>
            </dependency>

            <!-- velocity 模板引擎, Mybatis Plus 代码生成器需要 -->
            <dependency>
                <groupId>org.apache.velocity</groupId>
                <artifactId>velocity-engine-core</artifactId>
                <version>${velocity.version}</version>
            </dependency>

            <dependency>
                <groupId>com.google.code.gson</groupId>
                <artifactId>gson</artifactId>
                <version>${gson.version}</version>
            </dependency>
            <!--swagger-->
            <dependency>
                <groupId>io.springfox</groupId>
                <artifactId>springfox-swagger2</artifactId>
                <version>${swagger.version}</version>
            </dependency>
            <!--swagger ui-->
            <dependency>
                <groupId>io.springfox</groupId>
                <artifactId>springfox-swagger-ui</artifactId>
                <version>${swagger.version}</version>
            </dependency>
            <!-- JWT -->
            <dependency>
                <groupId>io.jsonwebtoken</groupId>
                <artifactId>jjwt</artifactId>
                <version>${jwt.version}</version>
            </dependency>
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>fastjson</artifactId>
                <version>${fastjson.version}</version>
            </dependency>
            <dependency>
                <groupId>org.json</groupId>
                <artifactId>json</artifactId>
                <version>${json.version}</version>
            </dependency>
        </dependencies>
    </dependencyManagement>

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

</project>

2.新建子模块 <module>common</module>

引入父类管理的依赖

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>acl_parent</artifactId>
        <groupId>com.wang</groupId>
        <version>0.0.1-SNAPSHOT</version>
        <!--<relativePath></relativePath>-->
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>common</artifactId>
    <packaging>pom</packaging>
    <modules>
        <module>service_base</module>
        <module>spring_security</module>
    </modules>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <scope>provided </scope>
        </dependency>

        <!--mybatis-plus-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <scope>provided </scope>
        </dependency>

        <!--lombok用来简化实体类：需要安装lombok插件-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided </scope>
        </dependency>
        <!--swagger-->
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <scope>provided </scope>
        </dependency>
        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <scope>provided </scope>
        </dependency>
        <!-- redis -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>

        <!-- spring2.X集成redis所需common-pool2-->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-pool2</artifactId>
            <version>2.6.0</version>
        </dependency>
    </dependencies>

</project>

结果子模块版本问题报错

 

 通过查找网上相关问题最终发现是子模块项目没有添加标签<relativePath></relativePath>

 

 加上<relativePath></relativePath>就可以了

 

 

默认值为../pom.xml(但是我加上../pom.xml还是报错 空标签就没有报错了)

点进源码可以看到首先maven从当前项目的父pom查找，然后从文件系统，然后是本地存储库，最后是远程仓库。

Maven looks for the parent pom first in the reactor of currently building projects, then in this location on
the filesystem, then the local repository, and lastly in the remote repo.

查找顺序：relativePath元素中的地址–本地仓库–远程仓库

设定一个空值将始终从仓库中获取，不从本地路径获取。

先这样 还是没有完全搞懂