What's the difference between these Maven dependency scopes: provided/compile/system/import

Question

I have read the documentation and have some understanding.

Please correct or inform me of the truth; as per my understanding:

provided
The dependencies must will be on the machine you run the code on, and must be included in the path
compile
The dependencies will not be on the machine that runs the code, so include them in the build
system
Exactly the same as provided, but you need the dependencies to be present in a jar file strictly
import
Seems like it should import the dependencies from some other POM file but I don't know how/why, so a little elaboration would be appreciated

http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html — jmj, Jun 04 '13 at 00:01
That's where I read from, but somehow I felt I didn't understand that properly, hence the question on SO. Thanks though! — Programming Noob, Jun 04 '13 at 00:04
FYI, for practical example of using `provided` see the Question, [Include a library while programming & compiling, but exclude from build, in NetBeans Maven-based project](https://stackoverflow.com/q/32087445/642706) — Basil Bourque, Jan 22 '18 at 01:31

Daniel Kaplan · Accepted Answer · 2022-03-27T03:12:04.180

Provided means, "This jar should be compiled against locally, but it will be provided on the classpath by something else during runtime, so don't include it in the classpath for me." For example, all web containers (eg: tomcat) include the jars for servlets. You should use provided for the servlet classes so you can compile your code locally, but you don't want to override the servlet classes that tomcat provides for you when you deploy to it.

system means, "These dependencies are on my system and I want to point to them directly". You want to avoid this if you can, because another person on another computer won't necessarily have these dependencies.

The difference between provided is easier to show:

<dependency>
  <groupId>javax.sql</groupId>
  <artifactId>jdbc-stdext</artifactId>
  <version>2.0</version>
  <scope>system</scope>
  <systemPath>${java.home}/lib/rt.jar</systemPath>
</dependency>

See how it has that <systemPath>? That's the difference. You don't specify the path with provided, provided knows how to get the dependency from a repository. system gets it from your file system only.

I've never even heard of import. @JigarJoshi linked to http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html which says

import (only available in Maven 2.0.9 or later)

This scope is only used on a dependency of type pom in the <dependencyManagement> section. It indicates that the specified POM should be replaced with the dependencies in that POM's section. Since they are replaced, dependencies with a scope of import do not actually participate in limiting the transitivity of a dependency.

I think this is saying, "take all the dependencies this project has and inline them in this <dependencyManagement> section." Someone correct me if I'm wrong.

Yes that was ambiguous. What I meant was (for provided) 'I have the dependencies on my machine right now, so currently use them. But when you build the package, don't worry about them because the machine that I will run this code on will have the dependencies and have the classpath appropriately set'. That's the same thing that you are saying, right? — Programming Noob, Jun 04 '13 at 00:03

What's the difference between these Maven dependency scopes: provided/compile/system/import

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