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Maven: How to stop using old version of dependency?

In my Java Maven Project I can see the following 2 versions of the one dependency (apache httpcomponents):
How can I ensure that only the newest version (4.5.2) is used in my project?
I cannot even find 4.2.1 declared anywhere within my pom.xml files to remove it.

There should never be two versions of the same dependency for a given project.
So either your IDE shows something wrong here or you did not mvn clean before the build so that old and new dependencies mixed.
Maven will always take only one version. Unfortunately, you cannot tell Maven to take the latest one, but it will always take the nearest one in the dependency tree.
If you want to set the version for a specific dependency, use <dependencyManagement>.

Based on your screenshot you're using IntelliJ. And I have to agree that this view is kind of confusing. In the Project-tab you'll External Libraries which contain all dependencies of all projects in this tab. For that reason dependencies might appear with different versions.
In the Maven-tab (right hand side) you can see the dependency-tree per project. First you'll see the direct dependencies, which you can expand to see the next level of dependencies. AFAIK there's no complete dependency list available in IntelliJ, as one would see with Eclipse.

That's the view of IDE, it shows all the using or used library in your project. Once you point your pom.xml to the new version and rebuild your project, the new version will be used.
In Intellj, you can select: Menu -> File -> Invalidate Caches/Restart to update it. If that won't help, start new project from your existing pom.xml file

Maven m2eclipse detect changes in dependecy in workspace and automatically install

I found an annoying issue working with m2eclipse in Eclipse.
My workspace contains 2 projects, an application A and a library B. The application A POM has B as a dependency and everything works correctly. (The project dependecy is found and used when I build the application)
But if I change some code in project B and I forgot to mvn:install it, when I build the application it uses the last built version of the library and it loses my last changes.
Is there a way to force Maven / M2Eclipse to check if the source code of the dependecy is newer than the last version built, and to install it when installing/ deploying the main application?
Or maybe my approach is wrong or is something obvious that I'm missing?

You can tell m2eclipse to use resolve dependencies from the workspace rather than through the normal mechanisms. In your project properties (NOT workspace properties), select Maven->Resolve dependencies from Workspace projects.
This will mean that when you change B and subsequently build A, the changes should be picked up automatically.
If, however, you build outside Eclipse, you'll have to do the normal mvn install to get the correct dependencies.

I don't know of a way to tell maven to build the library first, then build your project. You could put two maven commands into a script and run the script.
Alternatively, you could put both projects inside a maven parent project, and then build the parent. This causes all child project to be built too (so in your case the library, and the application).

I think you have couple of options here
If you can change the maven project set up, I would suggest you to use maven multimodule
Option two might solve your problem but still involves a manual stop when you change your dependent project B, Do this on for your dependent project in eclipse
Select Library B ==> Properties ==> Maven ==> in the input box under Goals to invoke after project clean: ==> enter : install
To deploy any change that you made to Project B in eclipse to maven local/remote repo, You have to run Clean build in eclipse, This will deploy the latest Library B to the maven repository
Also make sure your Library B version is a SnapShot during the development

If you are looking to run the latest snapshots on your local machine you should try to set things up to launch directly from Eclipse.
Apart from avoiding the problem you originally posted about, it also has other advantages.
It will save you a lot of time by not having to perform intermediate build steps.
You can start and stop servers without having to leave your IDE.
The Eclipse console has extra features that you don't get from the system console.
You don't have to modify your start scripts to attach a debugger.

Adding custom maven project as dependency

I'm using eclipse with the m2eclipse plugin now I just want to resolve a - imho - easy problem: I've got two maven projects, I want to add project A as dependency to project B.
Well how do I achieve this in a manner way? If I add the project A to the build path of project B eclipse recognizes the classes but this project isn't resolved by eclipse on build time.
I got it working by installing project A to my local repo and adding this as dependency to my pom. This works but is cumbersome because I always have to install a new version of project A when something changed.
Shouldn't the plugin handle such a situation for me?

Providing that you have both maven projects open in your workbench then make sure you have the "Enable Workspace Resolution" option enabled in the Maven context menu.

Yes Eclipse handle this situations.
You can add both the Projects A and B in the same work-space.
I could help you creating a simple work-space from the scratch.
I am assuming that you have already installed the MAVEN plugin M2Eclipse for Eclipse.
Start a new Eclipse in a blank Work-space
Right click on Project Explorer --> Go to Import dialog and add a Maven Module.
Locate the POM directory and add that directory.
It will list all the projects in all the sub folders.
Add as many as Maven Based modules in a single work-space.
By doing this you dont need to install the dependencies. Any change will be reflected on the derived module.
Hope that will help you.

The way you did it is correct, because it assumes that project B will be using the dependency of project A that will be in the artifactory, so you can develop both independently.
And anyway, for the project A, if you are using maven, don't you use maven clean install for compiling and deploying? That way you are sure you always have the latest version
The other option is, in case both of the are more dependent of each other, you should consider make one of them as a module of the other, or maybe make a project C that contains both modules, but that would mean both of them are part of the same project (like an ear containing two jars), depends on the situation

In IDEA, after adding a dependency in maven, my artifact always show's the library needs to be 'fixed'

So every time I add a dependency to a library using maven in my pom.xml, it doesn't get deployed until I go to module settings and then click on 'fix'.
This happened when I added freemarker.
Why doesn't IDEA do this for me? Am I missing a step?

Not sure about previous versions but with IntelliJ 9, IntelliJ shows me a Import Changes link when I modify a pom.xml and also offers to Enable Auto-Import:
alt text http://www.imagebanana.com/img/emcut3ku/screenshot_008.png
The auto-import option is also available from the Maven Integration dialog: File > Settings > Maven > Importing > Import Maven projects automatically.

IDEA stores all of your module's dependencies in either a .iml or .classpath file (based on your preference).
When you change the pom.xml file, it needs to resolve the new set of dependencies (Re-import) and update the file accordingly. I can only imagine that they don't do this automatically for you because they can never really know when you are done working with the file, and causing resolution of dependencies to start while you're still typing would make working with pom.xml from within idea very irritating.
AFAIK, you're doing it right. In my version of IDEA, I see a "re-import" button that appears in the pom file editor (which saves a couple of clicks)... or you can go to the "Maven Projects" window and click the "Re-Import Maven Projects" button, but these should do the same thing as your "Fix" button in the project settings.

The original question referred to a library that wasn't deployed -
IntelliJ uses artifacts to deploy build output and required libraries to application/web servers, and currently those can include a constant list of dependencies. Clicking the "fix" simply adds module dependencies to the artifact, if they weren't already there.
Since in most use-cases this is 1:1, i.e. artifacts contain all module dependencies, I have opened an feature issue for it:
http://youtrack.jetbrains.com/issue/IDEA-99458

Adding referenced Eclipse projects to Maven dependencies

Right now, I have two Eclipse projects - they both use Maven 2 for all their jar-dependency goodness.
Inside Eclipse, I have project Foo included in project Bar's build path, so that I can use Foo's classes from project Bar. This works really well in Eclipse land, but when I try:
mvn compile
inside Bar's directory, it fails because Maven doesn't know about the project-to-project relationship in Eclipse's build path.
If I were using Ant, I would just use it to do something silly like copy foo.jar into project Bar's classpath, but as far as I can tell, things are done a lot less hackishly in Maven-land.
I'm wondering if there's a standard workaround for this type of problem - it seems like it would be fairly common, and I'm just missing something basic about how Maven works.

Maybe you are referencing the other project via Eclipse configure-> build path only. This works as long as you use Eclipse to build your project.
Try running first mvn install in project Bar (in order to put Bar in your Maven repository), and then add the dependency to Foo's pom.xml.
That should work!.

Check out the m2eclipse plugin. It will automatically and dynamically update the project build path when you change the pom. There is no need for running mvn eclipse:eclipse.
The plugin will also detect if any dependency is in the same workspace and add that project to the build path.
Ideally, if you use m2eclipse, you would never change the project build path manually. You would always edit pom.xml instead, which is the proper way to do it.
As has been previously stated, Maven will not know about the Eclipse project build path. You do need to add all dependencies to the pom, and you need to make sure all dependencies are built and installed first by running mvn install.
If you want to build both projects with a single command then you might find project aggregation interesting.

I just needed to do this and I needed it to build with the external mvn clean install command. Here is the proper way to configure this in Eclipse. (With project B as a dependency of A)
Open the pom.xml for project A in Eclipse.
Go to the Dependencies tab.
Click the Add... button in the middle of the page (for the left side Dependencies box)
In the popup, there should be a box under a line with text above it saying Enter groupId, artifactId or sha1 prefix or pattern (*):. Enter the artifact ID for project B into this box.
Double click the jar you want to add as a dependency to this project
You may need to update the project after.
Right click project A in you Package explorer
Maven -> Update Project...
Then hit OK in the popup.

You might want to try an alternative approach, where you have a parent maven project and two children project. let's say:
Parent (pom.xml has references to both children projects/modules)
--> A (depends on B)
--> B
then when you run mvn eclipse:eclipse from the root of Parent, maven will generate eclipse projects for A and B, and it will have B as a required project in the classpath of A.
You can run mvn install from the root of Parent to get both projects to compile.
To complete your setup, you'll have to import both A and B into Eclipse, making sure you don't check "Copy projects into workspace".

I think the best way to handle it is to make Bar a Maven project just like Foo, and then mvn install it so it is available in your local Maven repository. The drawback is that you have to install that project every time you want Maven to see the changes you make to Bar.

Not a complete answer:
Bar's pom needs to include Foo in order to use maven to compile it.
I'm interested in this question too, but from the perspective of how to get eclipse to recognise a maven-added dependency is actually another project in the same workspace. I currently alter the build path after performing mvn eclipse:eclipse

If you reference a local project, but its version has been updated (usually increased), it could maybe only be found in your local repo and you have to update the (likely fixed) version of it in your POM(s).
We have a "common project" (used everywhere) which does not necessarily need to be versioned since we tag it via source control. so either
keeping it at a fixed version or
referencing it with the special LATEST version
are good workarounds to always be on the safe side.