Hello,

no, you can configure how often the repo transport of maven should
check for updated snapshots in configured repos. (Not all plugins obey
that). With -U you force an immediate recheck.

updatePolicy    String  The frequency for downloading
updates - can be "always", "daily" (default), "interval:XXX" (in
minutes) or "never" (only if it doesn't exist locally)

It uses the pom.lastUpdated tracking files in the repo cache for that.

Gruss
Bernd

Am Tue, 17 May 2016 11:32:31 -0400
schrieb Eric B <ebenza...@gmail.com>:

> I would suggest that the help documentation is wrong.  To my
> knowledge, Maven always tries to update the snapshots at every
> invocation - precisely the concept of the snapshot.  For full
> releases, however, Maven won't try to re-download releases if they
> are already in the local repo, or if it has already tried to find
> (and failed) a release within a predetermined elapsed time.
> 
> I've always understood the -U parameter to force maven to check for
> different versions than what already exists in the local repo, and to
> force Maven to recheck for the existance of a dependency, even it has
> already tried and failed.
> 
> Thanks,
> 
> Eric
> 
> 
> On Tue, May 17, 2016 at 11:04 AM, Adam Mitchell
> <adam.mitch...@playtech.com> wrote:
> 
> > Whilst that's true of the maven documentation, when you start
> > digging into how it's used during artifact resolution it acts as an
> > override for a repository's update policy.
> >
> > (from 3.3.9 release)
> >
> > It ends up set on
> > org.apache.maven.artifact.repository.RepositoryRequest#isForceUpdate()
> >
> >     /**
> >      * Indicates whether remote repositories should be re-checked
> > for updated artifacts/metadata regardless of their
> >      * configured update policy.
> >      *
> >      * @return {@code true} if remote repositories should be
> > re-checked for updated artifacts/metadata, {@code false}
> >      *         otherwise.
> >      */
> >     boolean isForceUpdate();
> >
> >     /**
> >      * Enables/disabled forced checks for updated
> > artifacts/metadata on remote repositories.
> >      *
> >      * @param forceUpdate {@code true} to forcibly check the remote
> > repositories for updated artifacts/metadata, {@code
> >      *            false} to use the update policy configured on each
> > repository.
> >      * @return This request, never {@code null}.
> >      */
> >     RepositoryRequest setForceUpdate( boolean forceUpdate );
> >
> > Or in the case where you end up in aether, it sets your repository
> > session to always update:
> > org.apache.maven.internal.aether.DefaultRepositorySystemSessionFactory:114
> >         else if ( request.isUpdateSnapshots() )
> >         {
> >             session.setUpdatePolicy( RepositoryPolicy.UPDATE_POLICY_ALWAYS
> > );
> >         }
> >
> > The net result is the same.
> >
> > Though I admit that I wouldn't expect this to necessarily
> > re-download source code unless the metadata was corrupt/missing, it
> > certainly has more meaning that just update snapshots.
> >
> > Quite possibly a bug in maven-core then.
> >
> >
> >
> >
> > | Adam Mitchell | Java Software Architect | Tel: +44 (0)207 633
> > 3570 | Mobile:  | Skype:  | www.playtech.com
> >
> > This communication contains information which is privileged and
> > confidential and is exclusively intended only for the individual or
> > entity named above (recipient(s)). If you are not the intended
> > recipient(s) or the person responsible for delivering it to the
> > intended recipient(s), you are hereby notified that any review,
> > disclosure, dissemination, distribution or reproduction of this
> > communication message in any way or act is prohibited. If you
> > receive this communication by mistake please notify the sender
> > immediately and then destroy any copies of it. Please note that the
> > sender monitors e-mails sent or received. Thank you. -----Original
> > Message----- From: Thomas Broyer [mailto:t.bro...@gmail.com]
> > Sent: 17 May 2016 11:03
> > To: Maven Users List <users@maven.apache.org>
> > Subject: Re: mvn -U dependency:sources re-downloads released
> > sources JARs
> >
> > On Tue, May 17, 2016 at 11:29 AM Adam Mitchell
> > <adam.mitch...@playtech.com
> > >
> > wrote:
> >
> > > -U is force update, it tells maven to ignore locally cached
> > > artifacts and to download them afresh, what behaviour were you
> > > expecting?
> > >
> >
> > -U stands for "update-snapshots" and aims at downloading only
> > "missing releases" (and "updated snapshots", of course).
> >
> > $ mvn -h
> >
> > usage: mvn [options] [<goal(s)>] [<phase(s)>]
> >
> > Options:
> > […]
> >  -U,--update-snapshots                  Forces a check for missing
> >                                         releases and updated
> > snapshots on remote repositories $ mvn -v
> > Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5;
> > 2015-11-10T17:41:47+01:00)
> > Maven home: /mnt/ssd/tbr/tools/maven
> > Java version: 1.8.0_91, vendor: Oracle Corporation Java home:
> > /usr/lib/jvm/java-8-oracle/jre Default locale: fr_FR, platform
> > encoding: UTF-8 OS name: "linux", version: "4.4.0-22-generic",
> > arch: "amd64", family: "unix"
> >
> > ---------------------------------------------------------------------
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> >
> 


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