I thought I understood Maven as I've worked on a few projects using it, but I seem to be having trouble creating my own project with it, so can someone correct me wherever I may be wrong?
Assuming I create a new Maven project (we'll say I did it through Eclipse or IntelliJ):
If I add a dependency to my POM file, assuming I add a public repository where that dependency can be found, shouldn't the IDE download the specified JAR and make it so that it is recognized when I use it in my code? Currently, my projects do not recognize any classes that should be found in JARs via my POM dependencies.
Assuming #1 does work, how can I determine via maven which transient dependencies I have? For example, I'm using classes from Pentaho Data Integration, and some of the plugins for it reference things like org.mozilla.javascript.*. Could maven automatically tell me that without me having to run the code, see it fail, and manually fix the dependency? There will be hundreds of those instances here, so manual fixing really isn't viable.
Here are my IntelliJ two cents:
1 - Adding a dependency in pom.xml of your project
Should indeed download the depended jar(s). You may need to approve "Import Changes" dialog if it pops in, or enable auto import.
2 - Seeing transitive dependencies
It can be achieved via Maven Dependencies Diagram - unfortunately only in IntelliJ Ultimate edition. You can use Maven Dependencies Plugin to see the dependencies tree in your favorite CLI.
Question 1: Adding a dependency
In Eclipse, depending on how you created the project, you should be able to add dependencies that are automatically recognized using the maven context menu.
Note that you should have created the project using the eclipse maven plugin so that it has maven nature.
To add dependencies/plugins from a remote repository, you can search in the resulting UI for a dependency if you know the artifactId or groupId. The plugin will pull up the deps whether the repo url is specified in the pom.xml or not.
After adding a dependency to the POM, the IDE will start downloading it and all transient dependencies as soon as you save the file.
If something goes wrong, you can try to "Update Project" from the context menu.
Question 2: Determining transitive dependencies
Transient dependencies are visible in the "Dependency Hierarchy" tab of the POM editor.
I usually default to the command line because it allows much more flexibility and functionality when tracking the dependency graph.
I am sorry but I have not worked with IntelliJ
Related
I’m using Eclipse Mars with Maven (v 3.3). When I update a dependency in my pom (change the version), my Eclipse-Maven project doesn’t pick it up, even when I right click my project, and select “Maven” -> “Update Project.” I know this because I do not see compilation errors in the Eclipse Java editor that I see when I build the project on the command line using
mvn clean install
When I remove the project from the workspace and re-import it, then things get back to normal. However this is a cumbersome process. How do I get my Maven-Eclipse project to automatically detect changes in my pom and update the project libraries appropriately?
And yes, in the “Project” menu, “Build Automatically” is checked.
When you import the project into Eclipse, use Eclipse's own built-in Maven support (aka, m2e). I recommend against using mvn eclipse:eclipse as it doesn't give the best results (as you're seeing). Maven is a build and dependency management tool, not an IDE; expecting it to manage IDE-specific stuff is silly, in my opinion (I realize the Maven team thinks differently, that Maven should be responsible for managing your IDE, but that's nonsense).
So if you have the project available on your system, delete any Eclipse-specific files (typically just .classpath, .project, and folder .settings), they were generated by mvn eclipse:eclipse and you don't want them interfering with the "proper" import process described here. Then inside Eclipse, use File > Import > Maven > Existing Maven Projects to import the project. That should result in better integration between Eclipse and maven, including automatically updating the Eclipse build path when the pom is changed.
As a quick check, after doing the import that way, you should see a group called Maven Dependencies in the Libraries tab of the project's Build Path (in Properties dialog). Like this:
If you want the Eclipse project configuration to be automatically updated every time the pom is changed, there's a (experimental) setting for that under Preferences > Maven. Be aware that doing so might not be desirable, though - as mentioned in this feature request, it's a somewhat lengthy process that touches a bunch of stuff in the Eclipse Project; doing that automatically on every pom.xml change could end up being more trouble than it's worth.
Three Mandatory checks you should do for automatic update in your classpath
Your Repository is not in-sync with your Eclipse IDE, Please check the below settings in your IDE.
Right Click your any POM.xml from your IDE and check for the Maven profile which should be auto-activated. Also offline and Force update check box shouldn't be enabled. Please refer the below image.
Always check for your user settings which should reflect your local maven settings.xml, as shown in the below figure.
After performing all these checks, refresh your Eclipse Work-space to get these changes reflected.
Eclipse should be updating your classpath. If it's not, that implies something is going wrong.
It's hard to say what the problem could be exactly without knowing more about your project's pom.xml. More information might be necessary to solve the issue, but I'll just make a stab in the dark:
Open the .project file in your project's root folder and check the ordering of builders and natures there. It might be possible that some other nature on the project is also causing maven2Nature to fail. Move maven nature up and see if that helps any.
Alternatively you might be thinking that Eclipse does not update your dependencies because it does not add some some error indicators in the project that should be there with new dependencies. If that's the case try cleaning the current project (project>clean...). Maven in Eclipse does not necessarily trigger a full rebuild when dependencies are updated.
If none of this works, closing/opening the project might solve the issue quicker than re-importing.
What you wrote, should work. Did you check this:
does "pure" mvn install from terminal see your changes in POM?
maybe some Maybe plugin is buggy, cached some dependencies in target, and mvn clean install is needed
you can run Eclipse in a new workspace, and import your project there, sometimes it helps in case of such strange problems
instead of importing Maven project to Eclipse via m2eclipse, you can try to create Eclipse files via the old mvn eclipse:eclipse and see what happens then
does it work well when you try to import your Maven project to other IDE, the free IntelliJ Community Edition for example?
As a last resort, you can delete your current Eclipse installation and install a new version. When you add several plugins, they might interfere with one another and create weird behavior. After you do that, do not import your Maven project into your workspace, but rather create a new one and copy and paste the files that you had.
I'm working one an Eclipse RCP project. Currently we create a dependencies plug-in project and put all jars libraries into that project and export all packages. This method will give a huge repo, thus we want to use Tycho/Maven and let it figure out the dependencies for us.
The first approach is removing dependenciec project and use p2-maven-pluging to transform existing jars libraries to p2 format repo. Install all libraries from p2 repos and add required bundle in Require-Bundle section in each MANIFEST.MF. This is a little bit tedious since in every project having dependencies in Require-Bundle, I have to manually replace it to corresponding bundle names. And in the end, the project build using Tycho could successfully run, but in Eclipse it gives me java.lan.NoClassDefFoundError: Could not initialize class X.
I think there are few configuration files, where Tycho depends on some of them and Eclipse depends on the rest, but I'm not sure what it is.
The second approach is removing all jars in dependencies project but adding them in Require-Bundle or Import-Package. However, both won't work since in Export-Package section Eclipse will complain these packages are not existed. Thus other projects depends on this dependencies project won't find those packages they need, which causing more errors in Eclipse.
Does anyone know the best practice to deal with this issue?
Update:
I'm using basically the first approach, but add dependencies in Import-Package in each project instead of Require-Bundle. This would eliminate the need to specify the specific bundle version, as long as they provide the same API and they are compatible, your application would work. So everytimes I update private p2 repository, I don't need to change MANIFEST.MF in each project.
The only MANIFEST.MF I need to manually add dependencies in Require-Bundle is a library developed by our self. Without it, Tycho won't fetch required dependencies from private p2 repository. If still get NoClassDefFoundError, try adding all plugins in Run -> Run Configuration .. -> plug-ins, it may help.
I definitely not apply your approach 1, with the mega-plugin of exports. There's a related discussion here: Handling non-OSGi dependencies when integrating Maven, Tycho and Eclipse
As a rule, use Import-Package instead of Require-Bundle.
To get bundles will appear in the Export-Package section Eclipse:
if they are non-Eclipse (maven libraries), then build the project and reference the libraries in the Eclipse runtime section.
if they are Eclipse dependences, they should be in your workspace or Target Platform.
More generally, it may help for you to define a Target Platform. You can build/deploy all of your locally created plugins into a local p2 repository (see http://www.sonatype.org/nexus/). Then add that p2 site to your Target Platform.
I have an existing eclipse project with standard dependencies in the classpath. I need to add a new dependency through maven but the rest of the dependencies need to stay there as jars bundled with the project.
I am using m2e, if I right click on the project --> maven --> enable maven, a pom file is created. At this stage I can add my new dependency through the pom file but all the existing dependencies seem to be gone from the classpath.
Hence the question: Is there a way to create a hybrid project that has both standard dependencies and maven dependencies?
You could add your legacy dependencies by using the scope "system" (and the tag "systemPath") ?
See http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html.
I don't think you should even attempt to create such a thing, and I don't know why you would want to.
If you want to use Maven, then you should define all your dependencies in your pom so that a maven build will actually work. If all your dependencies aren't defined, how do you expect maven to build your project?
You need to decide which means of dependency resolution you want to use instead of trying to mix two together.
With the maven-eclipse-plugin, using mvn eclipse:eclipse, you can specifiy eclipse project natures and builders that will automatically be added to the eclipse project.
Earlier versions of m2eclipse used the configuration block of the maven-eclipse-plugin and also let you activate natures and builders using the same mechanisms. This seems to no longer be the case because a) I can't find any reference to maven-eclipse-plugin in the m2eclipse sources and b) it just doesn't work :-)
So this is my question: is there any way to configure the eclipse project generated by m2eclipse from the pom.xml? Specifically: project builders and natures, but I'd be interested in other options as well.
The following thread summarizes almost everything. First, it explains that m2eclipse doesn't and won't support anything from the Maven Eclipse Plugin anymore because:
Sonatype doesn't maintain it.
It causes them too much troubles.
Second, it states that the m2eclipse way to handle additional project natures and builders is to write project configurators:
(...) we encourage writing configurators to add the natures and builders you want based on what it available in the POM.
See this link for a guide and this project for some existing configurators for checkstyle, findbugs, pmd.
I have now implemented this as a maven plugin I call maven-eclipseconf-plugin.
Unfortunately it's proprietary work for a client, so I can't share it. But let me describe what I do:
Tied to the lifecycle verify, I check for the existence of an eclipse .project file. If it's there, I check it for the presence of the builders and natures I want to automatically add (and you can deactivate this behavior by using a maven property or a stop file with a configurable name). You can also define configuration files that will be written (like .pmd, which is related to this other question of mine). The contents of the Configuration files can be specified inline, it can come from an external file, or from a URL. I also tried to introduce variable substitution in the config files where a special placeholder would be replaced with a multi-moduke-project's root folder, but I had to give up on that approach.
Anyway, the plugin gives me pretty much all the functionality of the maven-eclipse-plugin I ever used (of course there is a lot more though) and I'm happy with that. Perhaps I will build something similar once more in open source when this contract is finished.
Project configurators are the proposed approach. But the latest version of m2e-extensions is from early 2010 and developed against m2eclipse 0.10.x. There is a successor project called m2e-code-quality which is more recent and active and developed against m2eclipse 0.12.x.
But neither m2e-extensions nor m2e-code-quality do support FindBugs at the moment. And there are some other limitations with header files, exclusions and modified JARs.
I have successfully used a universal approach with AntRun, Ant and XMLTask to automatically add project natures, builders and configuration files for Eclipse plugins from pom.xml.
I'm a beginner at Maven and I've played with it from a command line point of view a little, so now I was trying to use it in Eclipse; I installed the m2eclipse plugin to do so.
But I'm stumped from the very beginning! Apparently I've missed a bit of terminology somewhere along the line. I can't keep track of all these new Maven terms... What is a Maven Project, and what is a Maven Module? These are my options when creating a new project in the Maven category in Eclipse.
They are basically the same thing, but with one difference.
When you create a module, you must specify a parent project.
When you specify the parent project, it adds a <modules> section to the parent projects pom.xml.
That section basically says to the parent project:
run every command I get against all of my modules first
So for example, if you run, mvn package on the top-level project, it will run mvn package against all its module projects first.
Hint:
Make sure all modules have high cohesion and related to each other, otherwise you will have a huge messy project without applying SRP (Single Responsibility Principle)
Found it! My searches were returning tons of hits for creating a "multi-module project", but once I added "-multi" to my query, the answer was on the first page.
According to Creating and Importing Projects:
m2eclipse provides the ability to create a Maven module. Creating a Maven module is almost identical to creating a Maven project as it also creates a new Maven project using a Maven archetype. However, a Maven module is a subproject of another Maven project typically known as a parent project.