> For the complete documentation index, see [llms.txt](https://moluo.gitbook.io/notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://moluo.gitbook.io/notes/gong-ju-shi-yong/maven/1.0.maven-jian-jie.md).

# 1.0.Maven简介

## 为什么要使用Maven？

举个例子，公司要做一个web项目，作为程序员的你，第一步要做的就是各个框架的jar包下载，而这会带来什么？

* jar包太多，一个个去官网下载jar包麻烦。
* jar包有用的，没用的，版本兼容问题

为了解决以上问题，于是开源大神提出了项目管理工具：Maven、Ant、Gradle

## Maven项目的目录结构

```java
src                                            源代码目录
 ├─main                                         ├─main
 │  ├─java                                     │  ├─功能代码
 │  │  └─package                             │  │  └─自定义的包
 │  └─resources                                 │  └─功能代码资源目录
 └─test                                         └─test
     ├─java                                        ├─测试代码
     │  └─package                                │  └─自定义的包
     └─resources                                └─测试代码资源目录
pom.xml                                     Maven的配置文件
```

## Maven配置文件----pom.xml解析

### pom.xml模板

```markup
<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">
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.domain-name.project-name</groupId>
   <artifactId>module-name</artifactId>
   <version>0.0.1-SNAPSHOT</version>

   <dependencies>
      <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>
         <version>3.8.1</version>
         <scope>test</scope>
      </dependency>
   </dependencies>
</project>
```

### pom.xml详解

[史上最全的Maven Pom文件标签详解](https://www.cnblogs.com/sharpest/p/7738444.html)

```markup
<?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">

    <!--maven的版本-->
    <modelVersion>4.0.0</modelVersion>

    <!--项目的包名：公司网址反写+项目名-->
    <groupId>com.moluo</groupId>
    <!--模块名，建议项目名+模块名-->
    <artifactId>girl</artifactId>
    <!--项目版本：snapshot快照、release稳定、beta公测、GA正式发布-->
    <version>0.0.1-SNAPSHOT</version>

    <!--maven打包方式war、zip、pom-->
    <packaging>jar</packaging>

    <!--项目的描述名-->
    <name>girl</name>
    <!--项目描述-->
    <description>Demo project for Spring Boot</description>
    <url>项目地址</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <parent>
        <!--继承父模块的pom-->
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
        <relativePath/>
    </parent>

    <dependencyManagement>
        <!--不会在项目中运行，用于给子pom依赖-->
        <dependencies>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <!--依赖的项目-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.0.3.RELEASE</version>
        </dependency>
    </dependencies>


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

    <modules>
        <!--模块聚合,同时编译多个maven项目-->
        <module></module>
    </modules>

</project>
```

## Maven命令

* **mvn compile** //编译项目，会在项目根目录下生成target目录且编译后的class文件存放在target/classes目录下
* **mvn test**  //测试，会在target/surefire-reports目录下生成测试报告
* **mvn package** //打包，会在target目录下生成项目的jar
* **mvn clean** //删除target目录
* **mvn install** //安装jar包到本地仓库中

> Maven插件 mvn archetype:genarate //maven自动建立目录骨架

## Maven相关知识

### Maven是怎么找到我们需要的构件的呢？

**通过仓库+坐标**

> * 坐标 groupId: artifactId: version:
> * 仓库 本地仓库和远程仓库 镜像仓库

### 为中央仓库配置镜像仓库

maven安装目录/conf/setttings.xml

```markup
<mirror>
      <id>maven.net.cn  (镜像仓库的id)</id>
      <mirrorOf>central(为那个仓库配置镜像仓库)</mirrorOf>
      <name>central mirror in china</name>
      <url>http://maven.aliyun.com/nexus/content/groups/public（镜像仓库的url）</url>
</mirror>
```

### 更改本地仓库路径

maven安装目录/conf/settings.xml

```bash
  <localRepository>/path/to/local/repo(本地仓库路径)</localRepository>
```

## Maven生命周期


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