Nexus同步下载maven中央仓库里的包到本地

最近发现公司的Jenkins打包时需要通过https://maven.aliyun.com/repository/public 去下载一些依赖包，但是局域网里之前搭建了Nexus的，登录到nexus上一看，全是公司内部开发的基础包和第三方合作机构的包，感觉这种模式有问题，自己百度上网看了下，发现标准模式是：开发人员全部通过Nexus下载依赖包，如果Nexus本地找不到，就通过代理下载Maven中央仓库的文件到Nexus本地，然后开发人员再从Nexus上拉到自己的电脑上(鄙人见识短浅，非专业配置管理)。以下为我这边调整后的拓扑图：

这种情况下，Nexus上不存在相关的jar时，只要从Maven中央仓库同步了1次就永久存在本地了。以后不管来了多少开发人员，只要本地settings指向Nexus私服后，就可以从私服上下载文件，内网下载速度快而且稳定。之前那种开发人员电脑直接访问互联网maven仓会带来很多问题：1、多个人同时下载jar依赖会消耗大量互联网带宽资源，2、下载资源的会话可能会不稳定，3、依赖jar可能还有很多依赖，建立很多会话数，消耗公司互联网网络设备的性能。

以下为主要的设置步骤，在修改设置之前我先看了这篇文章受到一点启发，文章的链接：https://www.cnblogs.com/zhangzimo/p/13931917.html

1、进入nexus的管理界面，将Central的远程地址改为阿里云的地址：https://maven.aliyun.com/repository/public/ ，按照下图改下配置

2、改下apache-snapshots的配置，我感觉这个用不到，算了统一改了吧,https://maven.aliyun.com/repository/apache-snapshots/

3、将相关仓库加到组中

好了，接下来到jenkins上修改apache-maven-3.5.4/conf下的配置文件，主要的内容如下

<localRepository>/app/repository</localRepository>


  <pluginGroups>

  </pluginGroups>


  <proxies>


  </proxies>

  <servers>

    <server>
      <id>releases</id>
      <username>admin</username>
      <password>k123456K</password>
    </server>

    <server>
      <id>snapshots</id>
      <username>admin</username>
      <password>k123456K</password>
    </server>

  </servers>
    <mirrors>    
      <mirror>
      <id>nexus</id>
      <name>nexus</name>
      <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>
      <mirrorOf>*</mirrorOf>        
      </mirror>
    </mirrors>
  
    <profiles>

    <profile>
      
      <activation>
        <activeByDefault>true</activeByDefault>
      </activation>
      
      <repositories>
        <repository>
          <id>release</id>
          <name>release</name>
          <releases>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </releases>
          <snapshots>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </snapshots>

          <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>
        </repository>
  
        <repository>
          <id>thirdparty</id>
          <name>thirdparty</name>
          <releases>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </releases>
          <snapshots>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </snapshots>

          <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>
        </repository>
                               <repository>  
                                        <id>snapshots</id>
                                        <name>snapshots</name>
                                        <releases>
                                                <enabled>true</enabled>
                                                <updatePolicy>always</updatePolicy>
                                                <checksumPolicy>warn</checksumPolicy>
                                        </releases>
                                        <snapshots>
                                                <enabled>true</enabled>
                                                <updatePolicy>always</updatePolicy>
                                                <checksumPolicy>warn</checksumPolicy>
                                        </snapshots>

                                        <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>

                               </repository>
      </repositories>
      
      <pluginRepositories>
        <pluginRepository>
          <id>snapshots</id>
          <name>snapshots</name>
          <releases>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </releases>
          <snapshots>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </snapshots>

          <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>
        </pluginRepository>
      </pluginRepositories>
      
    </profile>

  </profiles>

</settings>

好了，所有的步骤完成了。结果jenkins打包的时候，提示本地私服上没有相关的依赖包，但是不去阿里云Maven中央库上下载文件。百度了都没有类似的问题，头疼得很，后来从nexus上的日志下手，发现提示远端仓库不可达(后来可以下载中央仓库文件这个日志还是一直在，好像和这个问题没关系)。

jvm 1    | 2022-11-10 10:41:43,455+0800 WARN  [proxy-3-thread-18732] admin org.sonatype.nexus.proxy.maven.maven2.M2Repository - Remote peer of proxy repository "Apache Snapshots" [id=apache-snapshots] threw a org.sonatype.nexus.proxy.ItemNotFoundException exception. - Cause(s): Remote peer of repository M2Repository(id=apache-snapshots) detected as unavailable.

jvm 1    | 2022-11-10 10:42:32,979+0800 INFO  [ar-4-thread-3] admin org.sonatype.nexus.proxy.maven.routing.internal.RemoteScrapeStrategy - Not possible remote scrape of M2Repository(id=apache-snapshots), no scraper succeeded.

jvm 1    | 2022-11-10 10:46:39,488+0800 WARN  [proxy-3-thread-18734] admin org.sonatype.nexus.proxy.maven.maven2.M2Repository - Remote peer of proxy repository "Central" [id=central] threw a org.sonatype.nexus.proxy.ItemNotFoundException exception. - Cause(s): Remote peer of repository M2Repository(id=central) detected as unavailable.

再去看了下nexus上的状态，发现Central和Apache Snapshots的代理功能被自动禁用了 (下图)：

估计问题就和这个有关，后面改了下Central和Apache Snapshots的设置

分别启用Central和Apache Snapshots的代理功能 

然后无意中点到仓库组Public repositories的‘Rebuild Metadata’，之前好像还点到了Central的‘Expire Cache’和Public repositories的‘Expire Cache’，发现Nexus可以同步下载阿里云Maven中央仓库的文件了。汗，终于搞定了。

以下为jenkins上apache-maven-3.5.4/conf/settings的所有内容，这个settings的文件要替换所有的jenkins服务器上maven配置文件和开发人员的电脑上maven程序的配置文件。

<?xml versinotallow="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:schemaLocatinotallow="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
  
  <!-- TIPS: modify local repository -->
  <localRepository>/app/comm/repository</localRepository>


  <pluginGroups>

  </pluginGroups>


  <proxies>


  </proxies>

  <!-- servers | This is a list of authentication profiles, keyed by the server-id 
    used within the system. | Authentication profiles can be used whenever maven 
    must make a connection to a remote server. | -->
  <servers>

    <server>
      <id>releases</id>
      <username>admin</username>
      <password>k2244444u1K</password>
    </server>

    <server>
      <id>snapshots</id>
      <username>admin</username>
      <password>k2244444u1K</password>
    </server>

  </servers>

  <!-- mirrors | This is a list of mirrors to be used in downloading artifacts 
    from remote repositories. | | It works like this: a POM may declare a repository 
    to use in resolving certain artifacts. | However, this repository may have 
    problems with heavy traffic at times, so people have mirrored | it to several 
    places. | | That repository definition will have a unique id, so we can create 
    a mirror reference for that | repository, to be used as an alternate download 
    site. The mirror site will be the preferred | server for that repository. 
    | -->
  <mirrors>

    <!--<mirror>
      <id>repo2</id>
      <mirrorOf>central</mirrorOf>
      <name>Human Readable Name for this Mirror.</name>
      <url>http://repo2.maven.org/maven2/</url>
    </mirror> -->
    
    

    <!--<mirror>
      <id>net-cn</id>
      <mirrorOf>central</mirrorOf>
      <name>Human Readable Name for this Mirror.</name>
      <url>http://maven.net.cn/content/groups/public/</url>
    </mirror>

    <mirror>
      <id>ui</id>
      <mirrorOf>central</mirrorOf>
      <name>Human Readable Name for this Mirror.</name>
      <url>http://uk.maven.org/maven2/</url>
    </mirror>-->
    
     <!--<mirror>
      <id>nexus-aliyun</id>
      <mirrorOf>nexus-aliyun</mirrorOf>
      <name>Nexus aliyun</name>
      <url>http://maven.aliyun.com/nexus/content/groups/public</url>
    </mirror>

    <mirror>
      <id>ibiblio</id>
      <mirrorOf>central</mirrorOf>
      <name>Human Readable Name for this Mirror.</name>
      <url>http://mirrors.ibiblio.org/pub/mirrors/maven2/</url>
    </mirror>

    <mirror>
      <id>jboss-public-repository-group</id>
      <mirrorOf>central</mirrorOf>
      <name>JBoss Public Repository Group</name>
      <url>http://repository.jboss.org/nexus/content/groups/public</url>
    </mirror>-->
    
    <mirror>
      <id>nexus</id>
      <name>nexus</name>
      <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>
      <mirrorOf>*</mirrorOf>        
      </mirror>



  </mirrors>

  <!-- profiles | This is a list of profiles which can be activated in a variety 
    of ways, and which can modify | the build process. Profiles provided in the 
    settings.xml are intended to provide local machine- | specific paths and 
    repository locations which allow the build to work in the local environment. 
    | | For example, if you have an integration testing plugin - like cactus 
    - that needs to know where | your Tomcat instance is installed, you can provide 
    a variable here such that the variable is | dereferenced during the build 
    process to configure the cactus plugin. | | As noted above, profiles can 
    be activated in a variety of ways. One way - the activeProfiles | section 
    of this document (settings.xml) - will be discussed later. Another way essentially 
    | relies on the detection of a system property, either matching a particular 
    value for the property, | or merely testing its existence. Profiles can also 
    be activated by JDK version prefix, where a | value of '1.4' might activate 
    a profile when the build is executed on a JDK version of '1.4.2_07'. | Finally, 
    the list of active profiles can be specified directly from the command line. 
    | | NOTE: For profiles defined in the settings.xml, you are restricted to 
    specifying only artifact | repositories, plugin repositories, and free-form 
    properties to be used as configuration | variables for plugins in the POM. 
    | | -->
  <profiles>

    <profile>
      
      <activation>
        <activeByDefault>true</activeByDefault>
      </activation>
      
      <repositories>
        <repository>
          <id>release</id>
          <name>release</name>
          <releases>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </releases>
          <snapshots>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </snapshots>

          <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>
        </repository>
  
        <repository>
          <id>thirdparty</id>
          <name>thirdparty</name>
          <releases>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </releases>
          <snapshots>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </snapshots>

          <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>
        </repository>
                               <repository>  
                                        <id>snapshots</id>
                                        <name>snapshots</name>
                                        <releases>
                                                <enabled>true</enabled>
                                                <updatePolicy>always</updatePolicy>
                                                <checksumPolicy>warn</checksumPolicy>
                                        </releases>
                                        <snapshots>
                                                <enabled>true</enabled>
                                                <updatePolicy>always</updatePolicy>
                                                <checksumPolicy>warn</checksumPolicy>
                                        </snapshots>

                                        <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>

                               </repository>
      </repositories>
      
      <pluginRepositories>
        <pluginRepository>
          <id>snapshots</id>
          <name>snapshots</name>
          <releases>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </releases>
          <snapshots>
            <enabled>true</enabled>
            <updatePolicy>always</updatePolicy>
            <checksumPolicy>warn</checksumPolicy>
          </snapshots>

          <url>http://10.50.11.15:8081/nexus/content/groups/public/</url>
        </pluginRepository>
      </pluginRepositories>
      
    </profile>

  </profiles>

</settings>