This question is about Maven. My project has spring-boot-starter-parent as its parent. Mvn Repository's link, shows that through all parent hierarchies, spring-boot-starter-parent has 273 dependencies in total.
However, when I run the goal dependency:copy-dependencies, I get only a handful of jars, and in particular, I notice that javassist is not one of the jars. Why aren't the jars for all 273 dependencies copied by dependency:copy-dependencies? Can Maven somehow tell if some of these dependencies are not needed by my project?
There are 273 managed dependencies in spring-boot-starter-parent. Managed dependencies are just there to give maven details about libraries your project uses when it needs it. They are not actually included in your project when it gets built. The dependencies included are those in your project's <dependencies> section and their transitive dependencies. Hence the difference you see.
Related
I a maven rookie and am wondering how to get a binary jar file if it is not already in the repo. Specifically i'm in need of: jackson-dataformats-text-2.13.0.jar. Do I need to build it myself? I'm used to creating a project and marking a library as a dependency and seeing the jar downloaded into my .m2 cache but all i see in my cache is:
jchan#jchan-Z170N:~/.m2/repository/com/fasterxml/jackson/dataformat/jackson-dataformats-text/2.13.0$ ls
jackson-dataformats-text-2.13.0.jar.lastUpdated jackson-dataformats-text-2.13.0.pom.sha1
jackson-dataformats-text-2.13.0.pom _remote.repositories
Can someone advise how I am to get a built version of the jar from maven central?
We are still maintaining our ant build and I need the jar file for this. (i know i know, ancient stuff but team is not ready to port just yet).
parent pom don't contain jar file
This is the reason why no bundle link is present on the official public maven repository https://mvnrepository.com
The maven dependency is not a jar, is a parent. So the extension is: .pom which is just a plain pom.xml
Parent dependencies don't contain compiled class like .jar.
In your specific case, there are another dependencies who contains jars:
https://repo1.maven.org/maven2/com/fasterxml/jackson/dataformat/jackson-dataformat-yaml/2.13.0/
https://repo1.maven.org/maven2/com/fasterxml/jackson/dataformat/jackson-dataformat-xml/2.13.0/
advice
Check what classes do you need on your ant project and search if exist a jar (with the classes you need) on https://mvnrepository.com
Another option is to get all the dependencies from pom :
https://repo1.maven.org/maven2/com/fasterxml/jackson/dataformat/jackson-dataformats-text/2.9.0/jackson-dataformats-text-2.9.0.pom and download them into your ant project. In theory is the same of add the parent pom in a maven project
In the maven repository, there is a pom.xml corresponding to every jar. What is the use of that pom.xml.
How important is that pom.xml and will the execution work without that pom.xml ? Thanks in advance.
Each of those jars is a project (somewhere) that was built using Maven - hence the need for a pom. Also, the pom describes all the transitive dependencies for any jar that your project needs. Those files are important, and your project cannot build without them.
I have a parent project(has its own pom.xml) in which I import the child project as a jar with its own pom.xml.
In the parent pom.xml I have specified my child jar as a dependency - this gets resolved, but i want maven to resolve the dependencies required by my child jar.
My Use case to replicate :
When I include spring-web-mvc.jar the transitive dependencies are resolved automatically.
I have a similar requirement where I include my child.jar into a main framework project and expect the transitive dependencies to get resolved (Notw: the child.jar is not hosted it is packaged as jar and present on the local file system)
Current Structure:
Child Project:
|----/src/main/java
|----/src/main/resources
|----child-pom.xml
>This child project will be a jar as dependency in the parent project
Parent Project
|----/src/main/java
|----/src/main/resources
|----/src/main/webapp/WEB-INF/lib/child.jar
|---- parent-pom.xml
The problem:
When i create a war from parent project i want all the dependecy including transitive ones to show in WEB-INF lib.
Currently this is not happening.
First when talking of parent/ child Maven projects normaly you have your"childs" specified as modules in a common parent project which itself is beeing packed with the packaging type pom rather than make them a dependency of the parent project.
When it comes to the dependencies of your "childs" or generally "dependencies of your dependencies" those are called transitive dependencies and are pretty well explained in the official documentation found here: http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html
The resolving of those transitive dependencies is one of Mavens core strenghts and guaranteed by default unless they lead to conflicts that make the build fail.
Two things to help here are having a closer look into the enforcer plugin (http://maven.apache.org/enforcer/maven-enforcer-plugin/) and the shader plugin (http://maven.apache.org/plugins/maven-shade-plugin/) .... well and the official documentation of corse (reading the whole thing takes less than a day - then supports you further for specific topics whereas we gladly further support you too if you already have pom.xml files and you are stuck somewhere.
While the enforcer-plugin covers certain conflicts regarding different versions of the same artefacts the shader plugin will just pack everything you specified to a single jar for reverseengineering (its not the normal use case but i sometimes use it that way if i am not absolutly sure what ends in my final archives).
Also worth a look at is the dependency-plugin already available in the maven distributions - mvn dependency:tree -Dverbose will give you pretty detailed information on the resolved dependencies (and probably version conflicts).
On mvnrepositry, when you search for a certain module, there's a link to download the binary. For some versions it has a pom.xml file available for download instead of the jar. What are you supposed to do with that pom.xml? It seems like if I specify a version that does not have a downloadable jar, but instead downloadable pom.xml, my maven build will fail. Is what I'm seeing correct?
Modules that only have pom files are maven modules with pom packaging. They are used to aggregate multiple modules into one unit. You can use such a module as a dependency for your maven project. Maven will download the pom file, analyze the dependencies included in that pom file and download those & add it to your automatically.
Even modules that have jars (jar packaging) have a pom file associated with them. This pom file defines the other dependencies that are required for using it. Maven will automatically process and fetch those dependencies (transitive dependencies).
This makes specifying and managing dependency for any project. You will specify the top level modules that your projects directly depends on and other things required will automatically figured out and downloaded. It also makes it easier when you have upgrade to a new version - all the transitive dependencies will get upgraded automatically.
One of the reason that cause this is because of licensing issue.
License for such JARs prohibit public redistribution in such approach. So someone provide only the POM so that you can get the JAR yourself and install it to your local maven repo/ internal repo, together with the POM provided.
I've spent a lot of time and my head is blowing up already so I'll be very thankful for any help.
I'm migrating Netbeans Platform application from ant to maven, and so I'm changing all the jars in my version control repo to maven dependencies. I've found needed artifact in main maven repo and I've added it as a dependency with a help of Netbeans, but it's of type POM and was placed in Non-classpath Dependencies and I have no idea how to use it as it wasn't added to classpath etc…
Can someone explain what are these POM dependencies and how to use them?
Thank you in advance!!
EDIT
here is dependency definition in pom.xml
<dependency>
<groupId>com.kitfox.svg</groupId>
<artifactId>svg-salamander</artifactId>
<version>1.0</version>
<type>pom</type>
</dependency>
Adding a pom dependency only pulls down transitive dependencies, that is jar dependencies defined as dependencies in the pom. The pom does not get added on the classpath for obvious reasons, but the transitive dependencies reachable from pom will be added to classpath.
What you ideally need to do is have dependencies of type jar Default dependency type is jar and you can simply define dependencies without any type element in the dependency section.
If you have located the jar files you need in Maven Cental, then you simply need to provide groupId artifactId and version for each one of those in dependencies section.
Personally I cannot think of any case when one would need to add pom type dependency. I usually use pom packaging for parent module in a project (specify common project configuration like plugin versions, common dependencies, like log4j for example, repositories, properties etc.) and for utility package module (the one that assembles the project and does some other necessary things).
Judging from my experience (I did it several times), when migrating project from ant to maven you should take all the jar files that your project used to depend on and convert them into maven dependencies (groupId:artifactId:version). Most probably all of these dependencies will not have any <type> (e.g. be jars).