What means a "correct project" and "all necessary information available" in the "validate phase" in Maven

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I am learning about Maven and its whole lifecycle process. I think I understand most of its phases quite well, it is explained on their website and quite easy to follow, but there is one of the phases that I don't understand very well.

The validate phase, according to the specifications of Maven, says the following:

validate - validate the project is correct and all necessary information is available

I've been googling a lot about what means a "correct project", or what it refers to "all necessary information available". I tried to find examples about what Maven understands as a "correct project", and trying to figure out what necessary information is referring. The only one example I found is the one that is explained in this forum: Maven Build Lifecycle: validate

They are saying here that an example of a correct project may be

that the styling of the code meets some criteria, so say we add the maven-checkstyle-plugin

First, what means style? If I set as a coding requirement that the methods must start with capital letter, or that it must check that all the objects must be checked if they are null before use them or something like that? What means styling here and what type of criteria fits here? And second, can you provide to me more examples about what can I check in order to have a "correct project" in this phase of the lifecycle and plugins that can be used? I've been searching through the Maven repository, but I wasn't able to find something clear to me.

And about the "all necessary information available", in that link they say as an example that the phase must validate that all the config files needed to compile and run the project are present and properly built. But, what more information could be necessary to be checked in this validate phase before going to the compile phase? Can you give me more examples about it and some plugins that could be interesting?

1 Answers

When it comes to what a correct project and all necessary information available means for the validate phase, the forum link provided by you answers that question: it is up to developers to actually decide what kind of validation they want to perform.

For example, you mentioned the "code style" - some developers might decide that their project files must be formatted in some special way. This could be enforced by using the formatter-maven-plugin. One of its goal, the one called validate, is bound by default to the validate maven phase and fails the build if the code is not formatted as expected.

Regarding the "correct project information", some developers might decide that their project should contain some specific files (maybe a license file) or maybe there should be some specific properties set with correct values which can be enforced by using the maven-enforcer-plugin. Its description says:

The Enforcer plugin provides goals to control certain environmental constraints such as Maven version, JDK version and OS family along with many more built-in rules and user created rules.

Similarly to the formatter plugin, one of the enforcer's goals (the one called enforce) is by default bound to the validate phase, allowing developers to check if project follows many different rules.

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