pom中更換阿里雲倉庫時不要忽略了pluginRepositories

用maven也大幾年了，也一直在用阿里雲的中央倉庫。
不喜歡在maven的settings.xml裏改，更喜歡直接在pom.xml裏改，因爲受git管理，小夥伴們拉下來即可。

然而網上的大部分技術文章都只會指導你這麼配置：

<repositories>
    <repository>
        <id>aliyun</id>
        <url>https://maven.aliyun.com/repository/public</url>
        <releases>
            <enabled>true</enabled>
        </releases>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </repository>
</repositories>

如果你只是配置了repositories，那麼你會發現在mvn在下載依賴的時候，一部分從阿里雲下載，一部分還是從默認的倉庫（https://repo.maven.apache.org ）下載。

# mvn clean install
[INFO] Scanning for projects...
Downloading from aliyun: http://maven.aliyun.com/nexus/content/groups/public/org/springframework/boot/spring-boot-starter-parent/2.0.2.RELEASE/spring-boot-s
tarter-parent-2.0.2.RELEASE.pom
Downloaded from aliyun: http://maven.aliyun.com/nexus/content/groups/public/org/springframework/boot/spring-boot-starter-parent/2.0.2.RELEASE/spring-boot-st
arter-parent-2.0.2.RELEASE.pom (12 kB at 3.1 kB/s)
...
...
...
[INFO]
[INFO] --------------------------< com.zy:zy-parent >--------------------------
[INFO] Building zy-parent 1.0.0-SNAPSHOT
[INFO] --------------------------------[ pom ]---------------------------------
Downloading from central: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-clean-plugin/3.0.0/maven-clean-plugin-3.0.0.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/apache/maven/plugins/maven-clean-plugin/3.0.0/maven-clean-plugin-3.0.0.pom (4.8 kB at 2.2 k
B/s)
...
...
...
[INFO]
[INFO] --- maven-clean-plugin:3.0.0:clean (default-clean) @ zy-parent ---
Downloading from central: https://repo.maven.apache.org/maven2/org/apache/maven/maven-plugin-api/3.0/maven-plugin-api-3.0.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/apache/maven/maven-plugin-api/3.0/maven-plugin-api-3.0.pom (2.3 kB at 1.5 kB/s)
...
...
...
[INFO]
[INFO] --- maven-install-plugin:2.5.2:install (default-install) @ zy-parent ---
Downloading from central: https://repo.maven.apache.org/maven2/org/apache/maven/maven-plugin-api/2.2.1/maven-plugin-api-2.2.1.pom
Downloaded from central: https://repo.maven.apache.org/maven2/org/apache/maven/maven-plugin-api/2.2.1/maven-plugin-api-2.2.1.pom (1.5 kB at 1.2 kB/s)
...
...
...
[INFO] Installing E:\work\scratch\lily\src\zy-parent\pom.xml to D:\tools\maven\repo\com\zy\zy-parent\1.0.0-SNAPSHOT\zy-parent-1.0.0-SNAPSHOT.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 04:25 min
[INFO] Finished at: 2019-11-14T10:13:53+08:00
[INFO] ------------------------------------------------------------------------

原來，只有項目本身的依賴，走了aliyun這個repository，maven命令需要的插件（比如clean、install都是maven的插件），走的還是默認的repository。

查看maven的官方文檔（http://maven.apache.org/pom.html#Plugin_Repositories ），可以看到pom中除了repositories節點之外，還有一個關於倉庫的節點是pluginRepositories：

Repositories are home to two major types of artifacts. The first are artifacts that are used as dependencies of other artifacts. These are the majority of plugins that reside within central. The other type of artifact is plugins. Maven plugins are themselves a special type of artifact. Because of this, plugin repositories may be separated from other repositories (although, I have yet to hear a convincing argument for doing so). In any case, the structure of the pluginRepositories element block is similar to the repositories element. The pluginRepository elements each specify a remote location of where Maven can find new plugins.

所以我們還需要再pom中增加pluginRepositories纔可以。
這也是網上大部分文章裏忽略掉的內容。。。。。

最終的pom文件如下：

<repositories>
    <repository>
        <id>aliyun</id>
        <url>https://maven.aliyun.com/repository/public</url>
        <releases>
            <enabled>true</enabled>
        </releases>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </repository>
</repositories>
<pluginRepositories>
    <pluginRepository>
        <id>aliyun-plugin</id>
        <url>https://maven.aliyun.com/repository/public</url>
        <releases>
            <enabled>true</enabled>
        </releases>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </pluginRepository>
</pluginRepositories>

現在，你可以清空本地maven倉庫中的包，然後再次執一下mvn clean install，看看是不是都走了阿里雲的倉庫了。