maven--pom.xml--＜scope＞为import的作用

末蓝、 2023-09-29 13:02 23阅读 0赞

原文网址：[maven--pom.xml--<scope>为import的作用\_IT利刃出鞘的博客-CSDN博客][maven--pom.xml--_scope_import_IT_-CSDN]

## 简介 ##

**说明**

本文介绍maven中<scope>的值为import时的含义。

<scope>import</scope>

**用法说明**

import这个<scope>只能用在dependencyManagement里面，且仅用于<type>为pom的<dependency>。

它的作用就是引入了某个pom文件。被标记为scope=import的这个<dependency>会被替换为一系列的<dependency>。

因为它们是被替换的，所以这些scope=import的<dependency>不会遵循依赖继承。

官网解释：

> This scope is only supported on a dependency of type pom in the <dependencyManagement> section. It indicates the dependency is to be replaced with the effective list of dependencies in the specified POM's <dependencyManagement> section. Since they are replaced, dependencies with a scope of import do not actually participate in limiting the transitivity of a dependency.

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## 示例 ##

项目A和项目B的pom.xml文件中都定义了<dependencyManagement>，同时在B的<dependencyManagement>中定义<dependency>指向A，且<scope>为import：

project-B的pom.xml

<dependencyManagement>
      <dependencies>
        <dependency>
          <groupId>project-A</groupId>
          <artifactId>project-A</artifactId>
          <version>1.0</version>
          <scope>import</scope>
        </dependency>
        ...
      </dependencies>
    </dependencyManagement>

这就相当于项目B将项目A中定义的所有<dependencies>全部复制粘贴到了项目B的pom.xml中。由于是“复制粘贴”，所以没有继承关系。

## 项目实例 ##

Maven是单继承机制，也就是parent标签只能有一个。而POM文件的parent标签一般是继承spring-boot-starter-parent。如果想继承其他的父类（比如：spring-cloud-dependencies）怎么办？

import这个scope可以解决这个单继承的问题。

**解决方案如下：**

在项目中的pom.xml中做如下操作：

1.  指定parent为spring-boot-starter-parent
2.  在dependencyManagement中指定Spring Cloud依赖，scope设置为import

**自己的pom.xml**

<?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>2.4.13</version>
            <relativePath/> 
        </parent>
        <groupId>com.knife</groupId>
        <artifactId>router4j-client-feign-boot-starter</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>router4j-client-feign-boot-starter</name>
        <description>Demo project for Spring Boot</description>
    
        <properties>
            <java.version>1.8</java.version>
        </properties>
    
        <dependencyManagement>
            <dependencies>
                <dependency>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-dependencies</artifactId>
                    <version>2020.0.1</version>
                    <type>pom</type>
                    <scope>import</scope>
                </dependency>
            </dependencies>
        </dependencyManagement>
    
        <dependencies>
        </dependencies>
    
    </project>

**Spring Cloud的pom.xml**

spring-cloud-dependencies-2020.0.1.pom.xml

<?xml version="1.0" encoding="UTF-8"?>
    <project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
      <modelVersion>4.0.0</modelVersion>
      <parent>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies-parent</artifactId>
        <version>3.0.1</version>
        <relativePath></relativePath>
      </parent>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-dependencies</artifactId>
      <version>2020.0.1</version>
      <packaging>pom</packaging>
      <name>spring-cloud-dependencies</name>
      <description>Spring Cloud Dependencies</description>
      
      <properties>
        
        <spring-cloud-openfeign.version>3.0.1</spring-cloud-openfeign.version>
        <spring-cloud-gateway.version>3.0.1</spring-cloud-gateway.version>
        <main.basedir>${basedir}/../..</main.basedir>
      </properties>
      
      <dependencyManagement>
        <dependencies>
          
          <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-openfeign-dependencies</artifactId>
            <version>${spring-cloud-openfeign.version}</version>
            <type>pom</type>
            <scope>import</scope>
          </dependency>
          
          <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-gateway-dependencies</artifactId>
            <version>${spring-cloud-gateway.version}</version>
            <type>pom</type>
            <scope>import</scope>
          </dependency>
        </dependencies>
      </dependencyManagement>
    </project>

## import用法总结 ##

**情景1：解决单继承问题**

通过import pom文件达到依赖的目的（典型的非继承模式），从而不用从父类中引用依赖

**情景2：单一职责原则**

根据依赖的分类，细化每个单一职责的pom.xml文件。可以将不同种类的依赖放到不同pom.xml，然后通过<scope> import引入

[maven--pom.xml--_scope_import_IT_-CSDN]: https://knife.blog.csdn.net/article/details/124556648
[Link 1]: https://app.yinxiang.com/fx/d2ac6ff4-94c5-4e5f-9d4f-f5dfc344ede6