Maven Repository Configuration: settings.xml in Detail

settings.xml is Maven’s global configuration file; it controls repository addresses, authentication information, mirrors and so on. Understanding it matters a great deal for team collaboration and CI/CD.

Location of settings.xml

The user level takes precedence, but it is recommended to use the user-level configuration to avoid affecting others.

Configuring the Local Repository Path

<settings>
    <localRepository>D:/maven-repo</localRepository>
</settings>

The default is ~/.m2/repository/. Putting it on a non-system drive avoids downloading everything again after reinstalling the system.

Configuring a Remote Repository

<profiles>
    <profile>
        <id>aliyun</id>
        <repositories>
            <repository>
                <id>aliyun-central</id>
                <name>阿里云公共仓库</name>
                <url>https://maven.aliyun.com/repository/public</url>
                <releases><enabled>true</enabled></releases>
                <snapshots><enabled>false</enabled></snapshots>
            </repository>
        </repositories>
    </profile>
</profiles>

<activeProfiles>
    <activeProfile>aliyun</activeProfile>
</activeProfiles>

Configuring Private Repository Authentication

Configure it in settings.xml (do not put it in pom.xml):

<servers>
    <server>
        <id>company-releases</id>
        <username>deployer</username>
        <password>${env.NEXUS_PASSWORD}</password>
    </server>
</servers>

The id of <server> must match the id of <distributionManagement> in pom.xml.

In CI/CD it is recommended to use an environment variable for the password:

<password>${env.NEXUS_PASSWORD}</password>

Configuring a Mirror

Redirect all requests to the private repository:

<mirrors>
    <mirror>
        <id>nexus</id>
        <mirrorOf>*</mirrorOf>
        <url>https://nexus.company.com/repository/maven-public/</url>
    </mirror>
</mirrors>

Values of mirrorOf:

• * — intercept everything
• central — intercept Maven Central only
• *,!company-repo — intercept everything but exclude company-repo

Configuring a Proxy

When the corporate network requires a proxy:

<proxies>
    <proxy>
        <id>company-proxy</id>
        <active>true</active>
        <protocol>http</protocol>
        <host>proxy.company.com</host>
        <port>8080</port>
        <nonProxyHosts>localhost|*.company.com</nonProxyHosts>
    </proxy>
</proxies>

Encrypting Passwords

Do not write passwords in plain text; use Maven encryption:

# create a master password
mvn --encrypt-master-password

# encrypt the server password
mvn --encrypt-password

Write the encryption results into settings-security.xml and settings.xml.

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