If I run mvn deploy does it build new artifacts or it just deploy the already existing artifacts in to the remote server?

Question

Note: This question has been originally posted by Lahiru Gunathilake as an answer to another question. I'm moving it here as a separated question for the sake of clarity.

When we are doing a release we just build in our local machine and do the QA and then we host it in to repository. If we run mvn deploy does it create new artifacts, this cause having different artifact in the repository and in binary distribution because we are creating the binary distribution from our local repository. But if someone get the source code and do the build they'll get a different one. But if mvn deploy doesn't build but only deploy it's fine.

Answer 1

As explained in Build Lifecycle Basics:

A Build Lifecycle is Made Up of Phases

Each of these build lifecycles is defined by a different list of build phases, wherein a build phase represents a stage in the lifecycle.

For example, the default lifecycle has the following build phases (for a complete list of the build phases, refer to the Lifecycle Reference):

• validate - validate the project is correct and all necessary information is available
• compile - compile the source code of the project
• test - test the compiled source code using a suitable unit testing framework. These tests should not require the code be packaged or deployed
• package - take the compiled code and package it in its distributable format, such as a JAR.
• integration-test - process and deploy the package if necessary into an environment where integration tests can be run
• verify - run any checks to verify the package is valid and meets quality criteria
• install - install the package into the local repository, for use as a dependency in other projects locally
• deploy - done in an integration or release environment, copies the final package to the remote repository for sharing with other developers and projects.

These build phases (plus the other build phases not shown here) are executed sequentially to complete the default lifecycle. Given the build phases above, this means that when the default lifecycle is used, Maven will first validate the project, then will try to compile the sources, run those against the tests, package the binaries (e.g. jar), run integration tests against that package, verify the package, install the verifed package to the local repository, then deploy the installed package in a specified environment.

To do all those, you only need to call the last build phase to be executed, in this case, deploy:

mvn deploy

That is because if you call a build phase, it will execute not only that build phase, but also every build phase prior to the called build phase.

So, the answer is yes, mvn deploy will execute install and build the project artifacts. But if you don't change anything, this will produce exactly the same artifact.