maven pom.xml说明

清疚 2022-09-15 05:59 153阅读 0赞

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## maven pom.xml说明 ##

**官网：**[http://maven.apache.org/pom.html][http_maven.apache.org_pom.html]

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**pom.xml 说明**

**文件格式**

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**parent：继承的父模块**

**示例**

<parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.5.5</version>
            <relativePath/> 
        </parent>

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**packaging：项目打包方式**

When no packaging is declared, Maven assumes the packaging is the default: jar. 
    # 如果packaging没有设置，默认为 jar
    
    The valid types are Plexus role-hints (read more on Plexus for a explanation of roles and 
    role-hints) of the component role org.apache.maven.lifecycle.mapping.LifecycleMapping. The 
    current core packaging values are: pom, jar, maven-plugin, ejb, war, ear, rar
    # 可选打包方式：pom、jar、maven-plugin、ejb、war、ear、rar
    
    The packaging type required to be pom for parent and aggregation (multi-module) projects
    # 多模块项目中，父类项目packaging需要设置为pom

**pom 打包**

# 项目包括含模块user-info、user-service、user-web，打包方式需要设置为pom
        
        <packaging>pom</packaging>
        <modules>
            <module>user-info</module>
            <module>user-service</module>
            <module>user-web</module>
        </modules>

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**dependencies：项目依赖的jar包**

**         **

**可选属性说明**

<dependencies>
        <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.12</version>
          <type>jar</type>
          <scope>test</scope>
          <optional>true</optional>
        </dependency>
    
        <dependency>
          ...
        </dependency>
      </dependencies>
    
    groupId、artifactId、version：项目坐标（组id、标识id、版本）
    type：依赖类型，可选值ejb-client、test-client、jar（默认）
    scope：compile、provided、runtime、test、system
    systemPath：scope为system时，必须设置该值
    optional：依赖可选，即使未导入，也不影响项目启动

**示例**

<dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>
    
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-configuration-processor</artifactId>
                <optional>true</optional>
            </dependency>
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <optional>true</optional>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
        </dependencies>

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**dependencymanagent：管理子项目依赖**

dependencyManagement is used by a POM to help manage dependency information 
    across all of its children. 
    # dependencyManagent用来管理子项目的依赖信息
    
    If the my-parent project uses dependencyManagement to define a dependency on
    junit:junit:4.12, then POMs inheriting from this one can set their dependency 
    giving the groupId=junit and artifactId=junit only and Maven will fill in the
    version set by the parent. The benefits of this method are obvious. Dependency
    details can be set in one central location, which propagates to all inheriting POMs.
    # 如果父项目（my-paret）在dependencyManagement定义了依赖junit:junit:4.12
    # 子项目只使用了groupId=junit、artifactId=junit，没有指定版本，则子项目会使用4.12
    # 好处很明显，父项目可集中管理子项目的依赖版本
    
    Note that the version and scope of artifacts which are incorporated from transitive 
    dependencies are also controlled by version specifications in a dependency 
    management section. This can lead to unexpected consequences. Consider a case in 
    which your project uses two dependences, dep1 and dep2. dep2 in turn also uses 
    dep1, and requires a particular minimum version to function. If you then use 
    dependencyManagement to specify an older version, dep2 will be forced to use the 
    older version, and fail
    # 注意，父项目也会管理子项目的传递依赖
    # 父项目管理依赖dep1、dep2
    # 子项目依赖dep2依赖dep1，并且dep2依赖的dep1有最低版本要求
    # 如果父项目定义的dep1低于最低版本，项目构建失败

**示例**

<dependencyManagement>
        <dependencies>
          <dependency>
            <groupId>org.apache.activemq</groupId>
            <artifactId>activemq-amqp</artifactId>
            <version>${activemq.version}</version>
          </dependency>
          <dependency>
            <groupId>org.apache.activemq</groupId>
            <artifactId>activemq-blueprint</artifactId>
            <version>${activemq.version}</version>
          </dependency>
          <dependency>
            <groupId>org.apache.activemq</groupId>
            <artifactId>activemq-broker</artifactId>
            <version>${activemq.version}</version>
          </dependency>
          ...
      </dependencyManagement>

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**peoperties：项目属性**

<properties>
        <activemq.version>5.16.3</activemq.version>
        ...
      </properties>
    
    key：activemq.version
    value：5.16.3

**属性使用**

# 环境变量 env.X
    Prefixing a variable with "env." will return the shell's environment variable
    变量使用：Path=value ==> ${env.Path}
    
    # java系统变量：java System Properties
    All properties accessible via java.lang.System.getProperties() are available as POM properties
    # 如果java系统变量key可以通过System.getProperty(key)获取，则在pom中可使用${key}引用
    
    
    # settings.xml 属性：setting.key
    A dot (.) notated path in the settings.xml will contain the corresponding element's value
    
    # settings.xml属性使用示例
    <?xml version="1.0" encoding="UTF-8"?>
    <settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
    
      <localRepository>/path/to/local/repo</localRepository>
      <offline>false</offline>
      ...
    </settings>
    ${settings.localRepository}：引用本地仓库地址
    ${settings.offline}：引用offline属性
    
    
    # pom.xml 属性：project.key
    A dot (.) notated path in the POM will contain the corresponding element's value.
    
    # pom.xml属性使用示例
    <?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
      <modelVersion>4.0.0</modelVersion>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-dependencies</artifactId>
      <version>2.5.5</version>
      <packaging>pom</packaging>
    
      ...
    </project>
    ${project.modelVersion}：引用modelVersion
    ${project.groupId}：引用groupId
    ${project.artifactId}：引用artifactId
    ${project.version}：引用version
    ${project.packaging}：引用packaging
    
    
    # pom.xml 自定义属性
      <properties>
        <activemq.version>5.16.3</activemq.version>
        <antlr2.version>2.7.7</antlr2.version>
      </properties>
    ${activemq.version}：引用activemq.version属性
    ${antlr2.version}：引用antlr2.version属性

[http_maven.apache.org_pom.html]: http://maven.apache.org/pom.html