Difference between maven scope compile and provided for JAR packaging
MavenJarMaven Problem Overview
What is the difference between the maven scope compile and provided when artifact is built as a JAR? If it was WAR, I'd understand - the artifact would be included or not in WEB-INF/lib. But in case of a JAR it doesn't matter - dependencies aren't included. They have to be on classpath when their scope is compile or provided. I know that provided dependencies aren't transitive - but is it only one difference?
Maven Solutions
Solution 1 - Maven
From the Maven Doc:
> - compile > > This is the default scope, used if none is specified. Compile > dependencies are available in all classpaths of a project. > Furthermore, those dependencies are propagated to dependent projects.
> - provided > > This is much like compile, but indicates you expect the JDK or a > container to provide the dependency at runtime. For example, when > building a web application for the Java Enterprise Edition, you would > set the dependency on the Servlet API and related Java EE APIs to > scope provided because the web container provides those classes. This > scope is only available on the compilation and test classpath, and is > not transitive.
Recap:
- dependencies are not transitive (as you mentioned)
- provided scope is only available on the compilation and test classpath, whereas compile scope is available in all classpaths.
- provided dependencies are not packaged
Solution 2 - Maven
>Compile means that you need the JAR for compiling and running the app. For a web application, as an example, the JAR will be placed in the WEB-INF/lib directory. > >Provided means that you need the JAR for compiling, but at run time there is already a JAR provided by the environment so you don't need it packaged with your app. For a web app, this means that the JAR file will not be placed into the WEB-INF/lib directory. > >For a web app, if the app server already provides the JAR (or its functionality), then use "provided" otherwise use "compile".
Solution 3 - Maven
If you're planning to generate a single JAR file with all of its dependencies (the typical xxxx-all.jar), then provided scope matters, because the classes inside this scope won't be package in the resulting JAR.
See maven-assembly-plugin for more information
Solution 4 - Maven
> * compile
Make available into class path, don't add this dependency into final jar if it is normal jar; but add this jar into jar if final jar is a single jar (for example, executable jar)
> * provided
Dependency will be available at run time environment so don't add this dependency in any case; even not in single jar (i.e. executable jar etc)
Solution 5 - Maven
For a jar file, the difference is in the classpath listed in the MANIFEST.MF file included in the jar if addClassPath is set to true in the maven-jar-plugin configuration. 'compile' dependencies will appear in the manifest, 'provided' dependencies won't.
One of my pet peeves is that these two words should have the same tense. Either compiled and provided, or compile and provide.
Solution 6 - Maven
If jar file is like executable spring boot jar file then scope of all dependencies must be compile to include all jar files.
But if jar file used in other packages or applications then it does not need to include all dependencies in jar file because these packages or applications can provide other dependencies themselves.