What exactly is a Maven Snapshot and why do we need it?

What exactly is a Maven Snapshot and why do we need it? - java

I am a bit confused about the meaning of a Maven Snapshot and why we build one?

A snapshot version in Maven is one that has not been released.
The idea is that before a 1.0 release (or any other release) is done, there exists a 1.0-SNAPSHOT. That version is what might become 1.0. It's basically "1.0 under development". This might be close to a real 1.0 release, or pretty far (right after the 0.9 release, for example).
The difference between a "real" version and a snapshot version is that snapshots might get updates. That means that downloading 1.0-SNAPSHOT today might give a different file than downloading it yesterday or tomorrow.
Usually, snapshot dependencies should only exist during development and no released version (i.e. no non-snapshot) should have a dependency on a snapshot version.

The three others answers provide you a good vision of what a -SNAPSHOT version is. I just wanted to add some information regarding the behavior of Maven when it finds a SNAPSHOT dependency.
When you build an application, Maven will search for dependencies in the local repository. If a stable version is not found there, it will search the remote repositories (defined in settings.xml or pom.xml) to retrieve this dependency. Then, it will copy it into the local repository, to make it available for the next builds.
For example, a foo-1.0.jar library is considered as a stable version, and if Maven finds it in the local repository, it will use this one for the current build.
Now, if you need a foo-1.0-SNAPSHOT.jar library, Maven will know that this version is not stable and is subject to changes. That's why Maven will try to find a newer version in the remote repositories, even if a version of this library is found on the local repository. However, this check is made only once per day. That means that if you have a foo-1.0-20110506.110000-1.jar (i.e. this library has been generated on 2011/05/06 at 11:00:00) in your local repository, and if you run the Maven build again the same day, Maven will not check the repositories for a newer version.
Maven provides you a way to change this update policy in your repository definition:
<repository>
<id>foo-repository</id>
<url>...</url>
<snapshots>
<enabled>true</enabled>
<updatePolicy>XXX</updatePolicy>
</snapshots>
</repository>
where XXX can be:
always: Maven will check for a newer version on every build;
daily, the default value;
interval:XXX: an interval in minutes (XXX)
never: Maven will never try to retrieve another version. It will do that only if it doesn't exist locally. With the configuration, SNAPSHOT version will be handled as the stable libraries.
(model of the settings.xml can be found here)

The "SNAPSHOT" term means that the build is a snapshot of your code at a given time.
It usually means that this version is still under heavy development.
When the code is ready and it is time to release it, you will want to change the version listed in the POM. Then instead of having a "SNAPSHOT" you would use a label like "1.0".
For some help with versioning, check out the Semantic Versioning specification.

A "release" is the final build for a version which does not change.
A "snapshot" is a build which can be replaced by another build which has the same name. It implies that the build could change at any time and is still under active development.
You have different artifacts for different builds based on the same code. E.g. you might have one with debugging and one without. One for Java 5.0 and one for Java 6. Generally its simpler to have one build which does everything you need. ;)

Maven versions can contain a string literal "SNAPSHOT" to signify that a project is currently under active development.
For example, if your project has a version of “1.0-SNAPSHOT” and you deploy this project’s artifacts to a Maven repository,
Maven would expand this version to “1.0-20080207-230803-1” if you were to
deploy a release at 11:08 PM on February 7th, 2008 UTC. In other words, when you
deploy a snapshot, you are not making a release of a software component; you are
releasing a snapshot of a component at a specific time.
So mainly snapshot versions are used for projects under active development.
If your project depends on a software component that is under active development,
you can depend on a snapshot release, and Maven will periodically attempt
to download the latest snapshot from a repository when you run a build. Similarly, if
the next release of your system is going to have a version “1.8,” your project would
have a “1.8-SNAPSHOT” version until it was formally released.
For example , the following dependency would always download the latest 1.8 development JAR of spring:
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring</artifactId>
<version>1.8-SNAPSHOT”</version>
</dependency>
Maven
An example of maven release process

I'd like to make a point about terminology. The other answers gave good explanations about what a "snapshot" version is in the context of Maven. But does it follow that a non-snapshot version should be termed a "release" version?
There is some tension between the semantic versioning idea of a "release" version, which would seem to be any version that does not have a qualifier such as -SNAPSHOT but also does not have a qualifier such as -beta.4; and Maven's idea idea of a "release" version, which only seems to include the absence of -SNAPSHOT.
In other words, there is a semantic ambiguity of whether "release" means "we can release it to Maven Central" or "the software is in its final release to the public". We could consider -beta.4 to be a "release" version if we release it to the public, but it's not a "final release". Semantic versioning clearly says that something like -beta.4 is a "pre-release" version, so it wouldn't make sense for it to be called a "release" version, even without -SNAPSHOT. In fact by definition even -rc.5 is a release candidate, not an actual release, even though we may allow public access for testing.
So Maven notwithstanding, in my opinion it seems more appropriate only to call a "release" version one that doesn't have any qualifier at all, not even -beta.4. Perhaps a better name for a Maven non-snapshot version would be a "stable" version (inspired by another answer). Thus we would have:
1.2.3-beta.4-SNAPSHOT: A snapshot version of a pre-release version.
1.2.3-SNAPSHOT: A snapshot version of a release version.
1.2.3-beta.4: A stable version of a pre-release version.
1.2.3: A release version (which is a stable, non-snapshot version, obviously).

usually in maven we have two types of builds
1)Snapshot builds
2)Release builds
snapshot builds:SNAPSHOT is the special version that indicate current deployment copy not like a regular version, maven checks the version for every build in the remote repository
so the snapshot builds are nothing but development builds.
Release builds:Release means removing the SNAPSHOT at the version for the build, these are the regular build versions.

A Maven SNAPSHOT is an artifact created by a Maven build and pretends to help developers in the software development cycle.
A SNAPSHOT is an artifact (or project build result ) that is not pretended to be used anywhere, it's only a temporarily .jar, ear, ... created to test the build process or to test new requirements that are not yet ready to go to a production environment.
After you are happy with the SNAPSHOT artifact quality, you can create a RELEASE artifact that can be used by other projects or can be deployed itself.
In your project, you can define a SNAPSHOT using the version element in the pom.xml file of Maven:
<groupId>example.project.maven</groupId>
<artifactId>MavenEclipseExample</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<description>Maven pom example</description>
If you want to understand better Maven you can look into these articles too:
https://connected2know.com/programming/menu-maven-articles/

This is how a snapshot looks like for a repository and in this case is not enabled, which means that the repository referred in here is stable and there's no need for updates.
<project>
...
<repositories>
<repository>
<id>lds-main</id>
<name>LDS Main Repo</name>
<url>http://code.lds.org/nexus/content/groups/main-repo</url>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
</project>
Another case would be for:
<snapshots>
<enabled>true</enabled>
</snapshots>
which means that Maven will look for updates for this repository. You can also specify an interval for the updates with tag.

simply snapshot means it is the version which is not stable one.
when version includes snapshot like 1.0.0 -SNAPSHOT means it is not stable version and look for remote repository to resolve dependencies

Snapshot simply means depending on your configuration Maven will check latest changes on a special dependency. Snapshot is unstable because it is under development but if on a special project needs to has a latest changes you must configure your dependency version to snapshot version. This scenario occurs in big organizations with multiple products that these products related to each other very closely.

understanding the context of SDLC will help understand the difference between snapshot and the release. During the dev process developers all contribute their features to a baseline branch. At some point the lead thinks enough features have accumulated then he will cut a release branch from the baseline branch. Any builds prior to this time point are snapshots. Builds post to this point are releases. Be noted, release builds could change too before going to production if any defect spot during the release testing.

As the name suggests, snapshot refers to a state of project and its dependencies at that moment of time. Whenever maven finds a newer SNAPSHOT of the project, it downloads and replaces the older .jar file of the project in the local repository.
Snapshot versions are used for projects under active development. If your project depends on a software component that is under active development, you can depend on a snapshot release, and Maven will periodically attempt to download the latest snapshot from a repository when you run a build.

In development phase Maven snapshots everyday looks for newer higher version if available in nexus repository n download it locally for next build.
Four option you can set in respository defination
Always,
Daily (default),
Interval,
Never,
Note: In production release we should not have dependency on snapshot version.

The SNAPSHOT value refers to the 'latest' code along a development branch and provides no guarantee the code is stable or unchanging. Conversely, the code in a 'release' version (any version value without the suffix SNAPSHOT) is unchanging.
In other words, a SNAPSHOT version is the 'development' version before the final 'release' version. The SNAPSHOT is "older" than its release.
During the release process, a version of x.y-SNAPSHOT changes to x.y. The release process also increments the development version to x.(y+1)-SNAPSHOT. For example, version 1.0-SNAPSHOT is released as version 1.0, and the new development version is version 1.1-SNAPSHOT.

Related

Ensure Maven pulls latest version of release

This question is a little different than the other "checking for latest dependency version" type questions.
Let's say we have a project, DepProjA, that builds and publishes an artifact for our other Java apps to import as a dependency. For example, AppProj1 lists DepProjA as a dependency in its pom.xml file.
<dependency>
<groupId>com.mycompany.depproj</groupId>
<artifactId>depproja-lib</artifactId>
<version>feature-addthisfeature</version>
</dependency>
As you may notice, DepProjA, publishes "feature" versions of this JAR with the version named after the working branch name. This is so that other teams can test these particular feature updates before they are published as an official version update. If a bug is found and the fix is pushed under the same branch, the "feature" artifact is updated. However,when we rebuild AppProj1 to try and pull and utilize that latest artifact, it seems to be using the previous local version instead.
Is there an option, either in the pom.xml, or the mvn CLI options, so that maven will always pull down the latest artifact instead of using whatever version is cached? I know I can do a "blanket approach" like purging cache and such, but looking for something that targets specific dependencies. Kind of similar with Docker images where the tag itself won't change, but the underlying SHA can be updated when a new version of that tag is published.
An alternate idea I don't even know is possible: When publishing an artifact, is there a way to add custom metadata or labels that I could then reference? For example, I add a "cicdlabel" that could reference the pipeline ID that published the latest version. Then, I could change that in the application's dependency info when I know there is a change:
<dependency>
<groupId>com.mycompany.myproject</groupId>
<artifactId>myproject-lib</artifactId>
<version>feature-addthisfeature</version>
<cicdlabel>12345</cicdlabel>
</dependency>

In Maven by design released artifacts are immutable.
You can not update the same release version of artifact in Maven central.
It ensure that your build is reproducible, when we change content of released artifact the same build can break in the future.
In your case you should use SNAPSHOT versions for your artifact, and SNAPSHOT version can be updated.
You can use updatePolicy for your repository configuration in your settings.xml.
Yo can use mvn -U .. for update SNAPSHOT versions on every build.

How to make Maven evaluating version ranges starting with latest version? [duplicate]

In Maven, dependencies are usually set up like this:
<dependency>
<groupId>wonderful-inc</groupId>
<artifactId>dream-library</artifactId>
<version>1.2.3</version>
</dependency>
Now, if you are working with libraries that have frequent releases, constantly updating the <version> tag can be somewhat annoying. Is there any way to tell Maven to always use the latest available version (from the repository)?

NOTE:
The mentioned LATEST and RELEASE metaversions have been dropped for plugin dependencies in Maven 3 "for the sake of reproducible builds", over 6 years ago.
(They still work perfectly fine for regular dependencies.)
For plugin dependencies please refer to this Maven 3 compliant solution.
If you always want to use the newest version, Maven has two keywords you can use as an alternative to version ranges. You should use these options with care as you are no longer in control of the plugins/dependencies you are using.
When you depend on a plugin or a dependency, you can use the a version value of LATEST or RELEASE. LATEST refers to the latest released or snapshot version of a particular artifact, the most recently deployed artifact in a particular repository. RELEASE refers to the last non-snapshot release in the repository. In general, it is not a best practice to design software which depends on a non-specific version of an artifact. If you are developing software, you might want to use RELEASE or LATEST as a convenience so that you don't have to update version numbers when a new release of a third-party library is released. When you release software, you should always make sure that your project depends on specific versions to reduce the chances of your build or your project being affected by a software release not under your control. Use LATEST and RELEASE with caution, if at all.
See the POM Syntax section of the Maven book for more details. Or see this doc on Dependency Version Ranges, where:
A square bracket ( [ & ] ) means "closed" (inclusive).
A parenthesis ( ( & ) ) means "open" (exclusive).
Here's an example illustrating the various options. In the Maven repository, com.foo:my-foo has the following metadata:
<?xml version="1.0" encoding="UTF-8"?><metadata>
<groupId>com.foo</groupId>
<artifactId>my-foo</artifactId>
<version>2.0.0</version>
<versioning>
<release>1.1.1</release>
<versions>
<version>1.0</version>
<version>1.0.1</version>
<version>1.1</version>
<version>1.1.1</version>
<version>2.0.0</version>
</versions>
<lastUpdated>20090722140000</lastUpdated>
</versioning>
</metadata>
If a dependency on that artifact is required, you have the following options (other version ranges can be specified of course, just showing the relevant ones here):
Declare an exact version (will always resolve to 1.0.1):
<version>[1.0.1]</version>
Declare an explicit version (will always resolve to 1.0.1 unless a collision occurs, when Maven will select a matching version):
<version>1.0.1</version>
Declare a version range for all 1.x (will currently resolve to 1.1.1):
<version>[1.0.0,2.0.0)</version>
Declare an open-ended version range (will resolve to 2.0.0):
<version>[1.0.0,)</version>
Declare the version as LATEST (will resolve to 2.0.0) (removed from maven 3.x)
<version>LATEST</version>
Declare the version as RELEASE (will resolve to 1.1.1) (removed from maven 3.x):
<version>RELEASE</version>
Note that by default your own deployments will update the "latest" entry in the Maven metadata, but to update the "release" entry, you need to activate the "release-profile" from the Maven super POM. You can do this with either "-Prelease-profile" or "-DperformRelease=true"
It's worth emphasising that any approach that allows Maven to pick the dependency versions (LATEST, RELEASE, and version ranges) can leave you open to build time issues, as later versions can have different behaviour (for example the dependency plugin has previously switched a default value from true to false, with confusing results).
It is therefore generally a good idea to define exact versions in releases. As Tim's answer points out, the maven-versions-plugin is a handy tool for updating dependency versions, particularly the versions:use-latest-versions and versions:use-latest-releases goals.

Now I know this topic is old, but reading the question and the OP supplied answer it seems the Maven Versions Plugin might have actually been a better answer to his question:
In particular the following goals could be of use:
versions:use-latest-versions searches the pom for all versions
which have been a newer version and
replaces them with the latest
version.
versions:use-latest-releases searches the pom for all non-SNAPSHOT
versions which have been a newer
release and replaces them with the
latest release version.
versions:update-properties updates properties defined in a
project so that they correspond to
the latest available version of
specific dependencies. This can be
useful if a suite of dependencies
must all be locked to one version.
The following other goals are also provided:
versions:display-dependency-updates scans a project's dependencies and
produces a report of those
dependencies which have newer
versions available.
versions:display-plugin-updates scans a project's plugins and
produces a report of those plugins
which have newer versions available.
versions:update-parent updates the parent section of a project so
that it references the newest
available version. For example, if
you use a corporate root POM, this
goal can be helpful if you need to
ensure you are using the latest
version of the corporate root POM.
versions:update-child-modules updates the parent section of the
child modules of a project so the
version matches the version of the
current project. For example, if you
have an aggregator pom that is also
the parent for the projects that it
aggregates and the children and
parent versions get out of sync, this
mojo can help fix the versions of the
child modules. (Note you may need to
invoke Maven with the -N option in
order to run this goal if your
project is broken so badly that it
cannot build because of the version
mis-match).
versions:lock-snapshots searches the pom for all -SNAPSHOT
versions and replaces them with the
current timestamp version of that
-SNAPSHOT, e.g. -20090327.172306-4
versions:unlock-snapshots searches the pom for all timestamp
locked snapshot versions and replaces
them with -SNAPSHOT.
versions:resolve-ranges finds dependencies using version ranges and
resolves the range to the specific
version being used.
versions:use-releases searches the pom for all -SNAPSHOT versions
which have been released and replaces
them with the corresponding release
version.
versions:use-next-releases searches the pom for all non-SNAPSHOT
versions which have been a newer
release and replaces them with the
next release version.
versions:use-next-versions searches the pom for all versions
which have been a newer version and
replaces them with the next version.
versions:commit removes the pom.xml.versionsBackup files. Forms
one half of the built-in "Poor Man's
SCM".
versions:revert restores the pom.xml files from the
pom.xml.versionsBackup files. Forms
one half of the built-in "Poor Man's
SCM".
Just thought I'd include it for any future reference.

Please take a look at this page (section "Dependency Version Ranges"). What you might want to do is something like
<version>[1.2.3,)</version>
These version ranges are implemented in Maven2.

Unlike others I think there are many reasons why you might always want the latest version. Particularly if you are doing continuous deployment (we sometimes have like 5 releases in a day) and don't want to do a multi-module project.
What I do is make Hudson/Jenkins do the following for every build:
mvn clean versions:use-latest-versions scm:checkin deploy -Dmessage="update versions" -DperformRelease=true
That is I use the versions plugin and scm plugin to update the dependencies and then check it in to source control. Yes I let my CI do SCM checkins (which you have to do anyway for the maven release plugin).
You'll want to setup the versions plugin to only update what you want:
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>versions-maven-plugin</artifactId>
<version>1.2</version>
<configuration>
<includesList>com.snaphop</includesList>
<generateBackupPoms>false</generateBackupPoms>
<allowSnapshots>true</allowSnapshots>
</configuration>
</plugin>
I use the release plugin to do the release which takes care of -SNAPSHOT and validates that there is a release version of -SNAPSHOT (which is important).
If you do what I do you will get the latest version for all snapshot builds and the latest release version for release builds. Your builds will also be reproducible.
Update
I noticed some comments asking some specifics of this workflow. I will say we don't use this method anymore and the big reason why is the maven versions plugin is buggy and in general is inherently flawed.
It is flawed because to run the versions plugin to adjust versions all the existing versions need to exist for the pom to run correctly. That is the versions plugin cannot update to the latest version of anything if it can't find the version referenced in the pom. This is actually rather annoying as we often cleanup old versions for disk space reasons.
Really you need a separate tool from maven to adjust the versions (so you don't depend on the pom file to run correctly). I have written such a tool in the the lowly language that is Bash. The script will update the versions like the version plugin and check the pom back into source control. It also runs like 100x faster than the mvn versions plugin. Unfortunately it isn't written in a manner for public usage but if people are interested I could make it so and put it in a gist or github.
Going back to workflow as some comments asked about that this is what we do:
We have 20 or so projects in their own repositories with their own jenkins jobs
When we release the maven release plugin is used. The workflow of that is covered in the plugin's documentation. The maven release plugin sort of sucks (and I'm being kind) but it does work. One day we plan on replacing this method with something more optimal.
When one of the projects gets released jenkins then runs a special job we will call the update all versions job (how jenkins knows its a release is a complicated manner in part because the maven jenkins release plugin is pretty crappy as well).
The update all versions job knows about all the 20 projects. It is actually an aggregator pom to be specific with all the projects in the modules section in dependency order. Jenkins runs our magic groovy/bash foo that will pull all the projects update the versions to the latest and then checkin the poms (again done in dependency order based on the modules section).
For each project if the pom has changed (because of a version change in some dependency) it is checked in and then we immediately ping jenkins to run the corresponding job for that project (this is to preserve build dependency order otherwise you are at the mercy of the SCM Poll scheduler).
At this point I'm of the opinion it is a good thing to have the release and auto version a separate tool from your general build anyway.
Now you might think maven sort of sucks because of the problems listed above but this actually would be fairly difficult with a build tool that does not have a declarative easy to parse extendable syntax (aka XML).
In fact we add custom XML attributes through namespaces to help hint bash/groovy scripts (e.g. don't update this version).

The dependencies syntax is located at the Dependency Version Requirement Specification documentation. Here it is is for completeness:
Dependencies' version element define version requirements, used to compute effective dependency version. Version requirements have the following syntax:
1.0: "Soft" requirement on 1.0 (just a recommendation, if it matches all other ranges for the dependency)
[1.0]: "Hard" requirement on 1.0
(,1.0]: x <= 1.0
[1.2,1.3]: 1.2 <= x <= 1.3
[1.0,2.0): 1.0 <= x < 2.0
[1.5,): x >= 1.5
(,1.0],[1.2,): x <= 1.0 or x >= 1.2; multiple sets are comma-separated
(,1.1),(1.1,): this excludes 1.1 (for example if it is known not to
work in combination with this library)
In your case, you could do something like <version>[1.2.3,)</version>

Are you possibly depending on development versions that obviously change a lot during development?
Instead of incrementing the version of development releases, you could just use a snapshot version that you overwrite when necessary, which means you wouldn't have to change the version tag on every minor change. Something like 1.0-SNAPSHOT...
But maybe you are trying to achieve something else ;)

Who ever is using LATEST, please make sure you have -U otherwise the latest snapshot won't be pulled.
mvn -U dependency:copy -Dartifact=com.foo:my-foo:LATEST
// pull the latest snapshot for my-foo from all repositories

The truth is even in 3.x it still works, surprisingly the projects builds and deploys. But the LATEST/RELEASE keyword causing problems in m2e and eclipse all over the place, ALSO projects depends on the dependency which deployed through the LATEST/RELEASE fail to recognize the version.
It will also causing problem if you are try to define the version as property, and reference it else where.
So the conclusion is use the versions-maven-plugin if you can.

By the time this question was posed there were some kinks with version ranges in maven, but these have been resolved in newer versions of maven.
This article captures very well how version ranges work and best practices to better understand how maven understands versions: https://docs.oracle.com/middleware/1212/core/MAVEN/maven_version.htm#MAVEN8855

Sometimes you don't want to use version ranges, because it seems that they are "slow" to resolve your dependencies, especially when there is continuous delivery in place and there are tons of versions - mainly during heavy development.
One workaround would be to use the versions-maven-plugin. For example, you can declare a property:
<properties>
<myname.version>1.1.1</myname.version>
</properties>
and add the versions-maven-plugin to your pom file:
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>versions-maven-plugin</artifactId>
<version>2.3</version>
<configuration>
<properties>
<property>
<name>myname.version</name>
<dependencies>
<dependency>
<groupId>group-id</groupId>
<artifactId>artifact-id</artifactId>
<version>latest</version>
</dependency>
</dependencies>
</property>
</properties>
</configuration>
</plugin>
</plugins>
</build>
Then, in order to update the dependency, you have to execute the goals:
mvn versions:update-properties validate
If there is a version newer than 1.1.1, it will tell you:
[INFO] Updated ${myname.version} from 1.1.1 to 1.3.2

If you want Maven should use the latest version of a dependency, then you can use Versions Maven Plugin and how to use this plugin, Tim has already given a good answer, follow his answer.
But as a developer, I will not recommend this type of practices. WHY?
answer to why is already given by Pascal Thivent in the comment of the question
I really don't recommend this practice (nor using version ranges) for
the sake of build reproducibility. A build that starts to suddenly
fail for an unknown reason is way more annoying than updating manually
a version number.
I will recommend this type of practice:
<properties>
<spring.version>3.1.2.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
</dependencies>
it is easy to maintain and easy to debug. You can update your POM in no time.

MY solution in maven 3.5.4 ,use nexus, in eclipse:
<dependency>
<groupId>yilin.sheng</groupId>
<artifactId>webspherecore</artifactId>
<version>LATEST</version>
</dependency>
then in eclipse: atl + F5, and choose the force update of snapshots/release
it works for me.

How to tell Maven to pick the latest minor/revision version for a given major version? [duplicate]

In Maven, dependencies are usually set up like this:
<dependency>
<groupId>wonderful-inc</groupId>
<artifactId>dream-library</artifactId>
<version>1.2.3</version>
</dependency>
Now, if you are working with libraries that have frequent releases, constantly updating the <version> tag can be somewhat annoying. Is there any way to tell Maven to always use the latest available version (from the repository)?

NOTE:
The mentioned LATEST and RELEASE metaversions have been dropped for plugin dependencies in Maven 3 "for the sake of reproducible builds", over 6 years ago.
(They still work perfectly fine for regular dependencies.)
For plugin dependencies please refer to this Maven 3 compliant solution.
If you always want to use the newest version, Maven has two keywords you can use as an alternative to version ranges. You should use these options with care as you are no longer in control of the plugins/dependencies you are using.
When you depend on a plugin or a dependency, you can use the a version value of LATEST or RELEASE. LATEST refers to the latest released or snapshot version of a particular artifact, the most recently deployed artifact in a particular repository. RELEASE refers to the last non-snapshot release in the repository. In general, it is not a best practice to design software which depends on a non-specific version of an artifact. If you are developing software, you might want to use RELEASE or LATEST as a convenience so that you don't have to update version numbers when a new release of a third-party library is released. When you release software, you should always make sure that your project depends on specific versions to reduce the chances of your build or your project being affected by a software release not under your control. Use LATEST and RELEASE with caution, if at all.
See the POM Syntax section of the Maven book for more details. Or see this doc on Dependency Version Ranges, where:
A square bracket ( [ & ] ) means "closed" (inclusive).
A parenthesis ( ( & ) ) means "open" (exclusive).
Here's an example illustrating the various options. In the Maven repository, com.foo:my-foo has the following metadata:
<?xml version="1.0" encoding="UTF-8"?><metadata>
<groupId>com.foo</groupId>
<artifactId>my-foo</artifactId>
<version>2.0.0</version>
<versioning>
<release>1.1.1</release>
<versions>
<version>1.0</version>
<version>1.0.1</version>
<version>1.1</version>
<version>1.1.1</version>
<version>2.0.0</version>
</versions>
<lastUpdated>20090722140000</lastUpdated>
</versioning>
</metadata>
If a dependency on that artifact is required, you have the following options (other version ranges can be specified of course, just showing the relevant ones here):
Declare an exact version (will always resolve to 1.0.1):
<version>[1.0.1]</version>
Declare an explicit version (will always resolve to 1.0.1 unless a collision occurs, when Maven will select a matching version):
<version>1.0.1</version>
Declare a version range for all 1.x (will currently resolve to 1.1.1):
<version>[1.0.0,2.0.0)</version>
Declare an open-ended version range (will resolve to 2.0.0):
<version>[1.0.0,)</version>
Declare the version as LATEST (will resolve to 2.0.0) (removed from maven 3.x)
<version>LATEST</version>
Declare the version as RELEASE (will resolve to 1.1.1) (removed from maven 3.x):
<version>RELEASE</version>
Note that by default your own deployments will update the "latest" entry in the Maven metadata, but to update the "release" entry, you need to activate the "release-profile" from the Maven super POM. You can do this with either "-Prelease-profile" or "-DperformRelease=true"
It's worth emphasising that any approach that allows Maven to pick the dependency versions (LATEST, RELEASE, and version ranges) can leave you open to build time issues, as later versions can have different behaviour (for example the dependency plugin has previously switched a default value from true to false, with confusing results).
It is therefore generally a good idea to define exact versions in releases. As Tim's answer points out, the maven-versions-plugin is a handy tool for updating dependency versions, particularly the versions:use-latest-versions and versions:use-latest-releases goals.

Please take a look at this page (section "Dependency Version Ranges"). What you might want to do is something like
<version>[1.2.3,)</version>
These version ranges are implemented in Maven2.

The dependencies syntax is located at the Dependency Version Requirement Specification documentation. Here it is is for completeness:
Dependencies' version element define version requirements, used to compute effective dependency version. Version requirements have the following syntax:
1.0: "Soft" requirement on 1.0 (just a recommendation, if it matches all other ranges for the dependency)
[1.0]: "Hard" requirement on 1.0
(,1.0]: x <= 1.0
[1.2,1.3]: 1.2 <= x <= 1.3
[1.0,2.0): 1.0 <= x < 2.0
[1.5,): x >= 1.5
(,1.0],[1.2,): x <= 1.0 or x >= 1.2; multiple sets are comma-separated
(,1.1),(1.1,): this excludes 1.1 (for example if it is known not to
work in combination with this library)
In your case, you could do something like <version>[1.2.3,)</version>

Are you possibly depending on development versions that obviously change a lot during development?
Instead of incrementing the version of development releases, you could just use a snapshot version that you overwrite when necessary, which means you wouldn't have to change the version tag on every minor change. Something like 1.0-SNAPSHOT...
But maybe you are trying to achieve something else ;)

Who ever is using LATEST, please make sure you have -U otherwise the latest snapshot won't be pulled.
mvn -U dependency:copy -Dartifact=com.foo:my-foo:LATEST
// pull the latest snapshot for my-foo from all repositories

The truth is even in 3.x it still works, surprisingly the projects builds and deploys. But the LATEST/RELEASE keyword causing problems in m2e and eclipse all over the place, ALSO projects depends on the dependency which deployed through the LATEST/RELEASE fail to recognize the version.
It will also causing problem if you are try to define the version as property, and reference it else where.
So the conclusion is use the versions-maven-plugin if you can.

By the time this question was posed there were some kinks with version ranges in maven, but these have been resolved in newer versions of maven.
This article captures very well how version ranges work and best practices to better understand how maven understands versions: https://docs.oracle.com/middleware/1212/core/MAVEN/maven_version.htm#MAVEN8855

Sometimes you don't want to use version ranges, because it seems that they are "slow" to resolve your dependencies, especially when there is continuous delivery in place and there are tons of versions - mainly during heavy development.
One workaround would be to use the versions-maven-plugin. For example, you can declare a property:
<properties>
<myname.version>1.1.1</myname.version>
</properties>
and add the versions-maven-plugin to your pom file:
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>versions-maven-plugin</artifactId>
<version>2.3</version>
<configuration>
<properties>
<property>
<name>myname.version</name>
<dependencies>
<dependency>
<groupId>group-id</groupId>
<artifactId>artifact-id</artifactId>
<version>latest</version>
</dependency>
</dependencies>
</property>
</properties>
</configuration>
</plugin>
</plugins>
</build>
Then, in order to update the dependency, you have to execute the goals:
mvn versions:update-properties validate
If there is a version newer than 1.1.1, it will tell you:
[INFO] Updated ${myname.version} from 1.1.1 to 1.3.2

If you want Maven should use the latest version of a dependency, then you can use Versions Maven Plugin and how to use this plugin, Tim has already given a good answer, follow his answer.
But as a developer, I will not recommend this type of practices. WHY?
answer to why is already given by Pascal Thivent in the comment of the question
I really don't recommend this practice (nor using version ranges) for
the sake of build reproducibility. A build that starts to suddenly
fail for an unknown reason is way more annoying than updating manually
a version number.
I will recommend this type of practice:
<properties>
<spring.version>3.1.2.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
</dependencies>
it is easy to maintain and easy to debug. You can update your POM in no time.

MY solution in maven 3.5.4 ,use nexus, in eclipse:
<dependency>
<groupId>yilin.sheng</groupId>
<artifactId>webspherecore</artifactId>
<version>LATEST</version>
</dependency>
then in eclipse: atl + F5, and choose the force update of snapshots/release
it works for me.

Maven package versions in final deployment

It is known that whenever a search is done through the Maven repository, one can find dependencies for different versions of a package (e.g. BoneCP Maven Search) depending on the Development Stage.
I would like to know, for any external dependency found in the Maven repository, which version should be included in a final deployment of a project. For instance:
Always the latest RELEASE/RC (Release Candidate)?
Always the latest version even if its an alpha/beta/SNAPSHOT version?
Thanks in advance.

For a release you generally create a tag from stable snapshot version [trunk] and then deploy it to repository.
Generally the highest tag version for the each release is taken for code release and deployment.
Also want to add snapshot version is meant for development and not for release.

How do I tell Maven to use the latest version of a dependency?

In Maven, dependencies are usually set up like this:
<dependency>
<groupId>wonderful-inc</groupId>
<artifactId>dream-library</artifactId>
<version>1.2.3</version>
</dependency>
Now, if you are working with libraries that have frequent releases, constantly updating the <version> tag can be somewhat annoying. Is there any way to tell Maven to always use the latest available version (from the repository)?

NOTE:
The mentioned LATEST and RELEASE metaversions have been dropped for plugin dependencies in Maven 3 "for the sake of reproducible builds", over 6 years ago.
(They still work perfectly fine for regular dependencies.)
For plugin dependencies please refer to this Maven 3 compliant solution.
If you always want to use the newest version, Maven has two keywords you can use as an alternative to version ranges. You should use these options with care as you are no longer in control of the plugins/dependencies you are using.
When you depend on a plugin or a dependency, you can use the a version value of LATEST or RELEASE. LATEST refers to the latest released or snapshot version of a particular artifact, the most recently deployed artifact in a particular repository. RELEASE refers to the last non-snapshot release in the repository. In general, it is not a best practice to design software which depends on a non-specific version of an artifact. If you are developing software, you might want to use RELEASE or LATEST as a convenience so that you don't have to update version numbers when a new release of a third-party library is released. When you release software, you should always make sure that your project depends on specific versions to reduce the chances of your build or your project being affected by a software release not under your control. Use LATEST and RELEASE with caution, if at all.
See the POM Syntax section of the Maven book for more details. Or see this doc on Dependency Version Ranges, where:
A square bracket ( [ & ] ) means "closed" (inclusive).
A parenthesis ( ( & ) ) means "open" (exclusive).
Here's an example illustrating the various options. In the Maven repository, com.foo:my-foo has the following metadata:
<?xml version="1.0" encoding="UTF-8"?><metadata>
<groupId>com.foo</groupId>
<artifactId>my-foo</artifactId>
<version>2.0.0</version>
<versioning>
<release>1.1.1</release>
<versions>
<version>1.0</version>
<version>1.0.1</version>
<version>1.1</version>
<version>1.1.1</version>
<version>2.0.0</version>
</versions>
<lastUpdated>20090722140000</lastUpdated>
</versioning>
</metadata>
If a dependency on that artifact is required, you have the following options (other version ranges can be specified of course, just showing the relevant ones here):
Declare an exact version (will always resolve to 1.0.1):
<version>[1.0.1]</version>
Declare an explicit version (will always resolve to 1.0.1 unless a collision occurs, when Maven will select a matching version):
<version>1.0.1</version>
Declare a version range for all 1.x (will currently resolve to 1.1.1):
<version>[1.0.0,2.0.0)</version>
Declare an open-ended version range (will resolve to 2.0.0):
<version>[1.0.0,)</version>
Declare the version as LATEST (will resolve to 2.0.0) (removed from maven 3.x)
<version>LATEST</version>
Declare the version as RELEASE (will resolve to 1.1.1) (removed from maven 3.x):
<version>RELEASE</version>
Note that by default your own deployments will update the "latest" entry in the Maven metadata, but to update the "release" entry, you need to activate the "release-profile" from the Maven super POM. You can do this with either "-Prelease-profile" or "-DperformRelease=true"
It's worth emphasising that any approach that allows Maven to pick the dependency versions (LATEST, RELEASE, and version ranges) can leave you open to build time issues, as later versions can have different behaviour (for example the dependency plugin has previously switched a default value from true to false, with confusing results).
It is therefore generally a good idea to define exact versions in releases. As Tim's answer points out, the maven-versions-plugin is a handy tool for updating dependency versions, particularly the versions:use-latest-versions and versions:use-latest-releases goals.

Please take a look at this page (section "Dependency Version Ranges"). What you might want to do is something like
<version>[1.2.3,)</version>
These version ranges are implemented in Maven2.

The dependencies syntax is located at the Dependency Version Requirement Specification documentation. Here it is is for completeness:
Dependencies' version element define version requirements, used to compute effective dependency version. Version requirements have the following syntax:
1.0: "Soft" requirement on 1.0 (just a recommendation, if it matches all other ranges for the dependency)
[1.0]: "Hard" requirement on 1.0
(,1.0]: x <= 1.0
[1.2,1.3]: 1.2 <= x <= 1.3
[1.0,2.0): 1.0 <= x < 2.0
[1.5,): x >= 1.5
(,1.0],[1.2,): x <= 1.0 or x >= 1.2; multiple sets are comma-separated
(,1.1),(1.1,): this excludes 1.1 (for example if it is known not to
work in combination with this library)
In your case, you could do something like <version>[1.2.3,)</version>

Are you possibly depending on development versions that obviously change a lot during development?
Instead of incrementing the version of development releases, you could just use a snapshot version that you overwrite when necessary, which means you wouldn't have to change the version tag on every minor change. Something like 1.0-SNAPSHOT...
But maybe you are trying to achieve something else ;)

Who ever is using LATEST, please make sure you have -U otherwise the latest snapshot won't be pulled.
mvn -U dependency:copy -Dartifact=com.foo:my-foo:LATEST
// pull the latest snapshot for my-foo from all repositories

The truth is even in 3.x it still works, surprisingly the projects builds and deploys. But the LATEST/RELEASE keyword causing problems in m2e and eclipse all over the place, ALSO projects depends on the dependency which deployed through the LATEST/RELEASE fail to recognize the version.
It will also causing problem if you are try to define the version as property, and reference it else where.
So the conclusion is use the versions-maven-plugin if you can.

By the time this question was posed there were some kinks with version ranges in maven, but these have been resolved in newer versions of maven.
This article captures very well how version ranges work and best practices to better understand how maven understands versions: https://docs.oracle.com/middleware/1212/core/MAVEN/maven_version.htm#MAVEN8855

Sometimes you don't want to use version ranges, because it seems that they are "slow" to resolve your dependencies, especially when there is continuous delivery in place and there are tons of versions - mainly during heavy development.
One workaround would be to use the versions-maven-plugin. For example, you can declare a property:
<properties>
<myname.version>1.1.1</myname.version>
</properties>
and add the versions-maven-plugin to your pom file:
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>versions-maven-plugin</artifactId>
<version>2.3</version>
<configuration>
<properties>
<property>
<name>myname.version</name>
<dependencies>
<dependency>
<groupId>group-id</groupId>
<artifactId>artifact-id</artifactId>
<version>latest</version>
</dependency>
</dependencies>
</property>
</properties>
</configuration>
</plugin>
</plugins>
</build>
Then, in order to update the dependency, you have to execute the goals:
mvn versions:update-properties validate
If there is a version newer than 1.1.1, it will tell you:
[INFO] Updated ${myname.version} from 1.1.1 to 1.3.2

If you want Maven should use the latest version of a dependency, then you can use Versions Maven Plugin and how to use this plugin, Tim has already given a good answer, follow his answer.
But as a developer, I will not recommend this type of practices. WHY?
answer to why is already given by Pascal Thivent in the comment of the question
I really don't recommend this practice (nor using version ranges) for
the sake of build reproducibility. A build that starts to suddenly
fail for an unknown reason is way more annoying than updating manually
a version number.
I will recommend this type of practice:
<properties>
<spring.version>3.1.2.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
</dependencies>
it is easy to maintain and easy to debug. You can update your POM in no time.

MY solution in maven 3.5.4 ,use nexus, in eclipse:
<dependency>
<groupId>yilin.sheng</groupId>
<artifactId>webspherecore</artifactId>
<version>LATEST</version>
</dependency>
then in eclipse: atl + F5, and choose the force update of snapshots/release
it works for me.

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