How do I use Maven through a proxy?

Question

Hi dear community,

I wanna share with you my experience of using maven through proxy.

You would most likely face exceptions and messages like:

repository metadata for: 'org.apache.maven.plugins' could not be retrieved from repository: central due to an error: Error transferring file: Connection refused: connect

See my answer below.

All the best. Thanks

Answer 1

For details of setting up a proxy for Maven, see the mini guide.

Essentially you need to ensure the proxies section in either the global settings [maven install]/conf/settings.xml) or user settings (${user.home}/.m2/settings.xml) is configured correctly. It is better to do this in your user settings to avoid storing the password in plain text in a public location.

Maven 2.1 introduced password encryption, but I've not got round to checking if the encryption applies for the proxy settings as well as repository passwords (don't see why it wouldn't though).

For info, there is a commented-out proxy configuration in your settings.xml and instructions on how to modify it.

From the mini-guide, your settings should look something like this:

<proxies>
  <proxy>
    <active>true</active>
    <protocol>http</protocol>
    <host>proxy.somewhere.com</host>
    <port>8080</port>
    <username>proxyuser</username>
    <password>somepassword</password>
    <nonProxyHosts>www.google.com|*.somewhere.com</nonProxyHosts>
  </proxy>
</proxies>

Answer 2

Those are caused most likely by 2 issues:

1. You need to add proxy configuration to your settings.xml. Here's a trick in your username field. Make sure it looks like domain\username. Setting domain there and putting this exact slash is important '\'. You might want to use <![CDATA[]]> tag if your password contains non xml-friendly characters.
2. I've noticed maven 2.2.0 does not work sometimes through a proxy at all, where 2.2.1 works perfectly fine.

If some of those are omitted - maven could fail with random error messages.

Just hope I've saved somebody from googling around this issue for 6 hours, like I did.

Answer 3

I know this is not really an answer to the question, but it might be worth knowing for someone searching this post. It is also possible to install a Maven repository proxy like nexus.

Your maven would be configured to contact the local Nexus proxy, and Nexus would then retrieve (and cache) the artifacts. It can be configured through a web interface and has support for (http) proxies).

This can be an advantage, especially in a company setting, as artefacts are locally available and can be downloaded fast, and you are not that dependent on the availability of external Maven repositories anymore.

To link back to the question; with Nexus there is a nice GUI for the proxy configuration, and it needs to be done on one place only, and not for every developer.

Answer 4

I've set up a SOCKS5 proxy and I'd like maven to use it. However there seems to be no documentation available on how to do this. No example in settings.xml either. Is it possible?