I've run into a big issue, and it's stalling my project that is due this weekend. Here are the details.
IDE: Eclipse/Maven
API: JAXB, an xml reader/writer API
Issue: Maven is hanging when building the dependency in pom.xml.
More Information: I copy and pasted the jar into a project folder "lib". Then moved the project over to the resource folder. After that, I used maven from eclipse (I think that's the embedded Maven), to add the dependency to the pom.xml. It's been over 4 hours now. I also stopped eclipse through Windows Task Manager. When eclipse started after that, it is continuing with the Maven dependency build, and will not finish.
It is step 5, in this stackoverflow thread. How do I add a Maven dependency in Eclipse?
Any help would be greatly appreciated. This has sucked a whole day out of actual coding; and turned into a configuration issue.
Thanks!
I'm posting this as an answer, not that I think it will give you a complete answer, but as a way to try to get more useful information about your situation.
It would help if you provided more details about exactly what you're doing, and what exactly is happening.
Maven does not "build" dependencies, it downloads dependency artifacts from an artifact repository.
When you say that something is "hanging", that means that an operation starts and doesn't complete, as opposed to failing with an error message. If what you're doing is truly "hanging", then it's important to be exactly clear on exactly what operation and point in the process it is hanging.
You then say that you copied the jar into a folder named "lib" and then "moved the project over to the resource folder".
By "the jar", do you mean the Maven artifact that you're trying to download, which you said was "hanging"? What is the significance of this "lib" folder? Is your build somehow referencing jars in that folder as additional dependencies, subverting the typical maven dependency process? If so, how exactly are you doing this?
Next, what do you mean by "moved the project over to the resource folder"?
Consider all of this from an external perspective. You have to give us enough information to understand exactly what problem you're having, and what you've done that isn't working. So far, you haven't done that.
Related
I just checked out maven based java project from svn to local box in eclipse where maven 3.0.2 is available. However while reviewing class path configuration many of dependencies are broken such as org.restlet-2.0.15.jar. Strange part is C:/Users/daeyoung/.m2/repository has that broken jar file but .lastUpdated is appended. After reading many posts from WWW, the way I understood to fix the problem is delete *.lastUpdated file then re-download it from central repo.
But when I reviewed pom.xml file there is no mention of repository (strange...) and as soon as I delete *.lastUpdated file, it comes back (e.g. org.restlet-2.0.15.jar.lastUpdated).
I am new to Maven.
I'd appreciate if someone can guide me to a right direction to fix this problem.
[update]
I created following user settings.xml file under /Users/daeyoung/.m2/ directory. I thought at least that would take care of downloading org.restlet package.
However when I ran mvn command (literally mvn) inside of project folder, system was saying..
I don't want to modify pom.xml file but rather via user settings.xml I thought I could connect to maven restlet repo and download specified target package but I am not sure what I am missing in here. I think contents of settings.xml is not correct.
I just want to say thanks to all who have given me advice. First I was not well equipped to understand the advice but more I looked at the problem/read about maven articles. It was clear what needs to be done to fix the problem.
Bottom line is I manually downloaded dependencies to ${user_name}/.m2/repository for missing jars. I configured ${MAVEN_HOME}/conf/settings.xml to point to local repository then I ran mvn validate/clean/package sequentially from eclipse via m2e plugin (or I could have done same thing from command line).
I'm a newbie to J2ee though not a complete newbie. I'm unable to find a good resource (book or video) that could help me understand what exactly happens when we build, deploy and publish. I have a fair idea though. So my questions are -
Is there a good resource out there that can help me understand these concepts? I've read some books on struts and servlets/jsp but they don't delve into eclipse and how/what it does. The eclipse documentation has been helpful but only slightly.
When we build an application the the java files are converted into the class files and stored in the java build path. What else happens during build? Many people use the term 'library dependencies', what does this mean? Also, when people refer to dependencies do they refer to files like xml and tld?
At what stage (build or run on server) does the container check to see if the dependencies are alright? Say for instance, if the servlet class/name in the web.xml file.
Is it appropriate to say that build is basically compilation while deploying the project and running it is the same as executing it?
Familiarity with the servlet specification would help you (perhaps some older version would be quicker to read like 2.4), but general understanding of what you build and how you do it in Eclipse is what you are after.
The way I see it is that during the build Eclipse creates almost complete version of WAR (or some other archive, if you use EJBs for instance) and by publishing you deploy it to some server (this is practically the same thing although Eclipse might just configure the server to use exploded WAR that it just prepared instead of copying it to some "deploy" dir that you are supposed to do if you work without an IDE).
If you configure your project well, the build can only mean compilation, but if you have more ceremony in it, then some source generation and moving files around might happen too.
To address your second question, library dependencies can be files that reside in WEB-INF/lib for instance. Read the spec to know what should be there and what should not. Eclipse tries to copy there all defined dependencies of your project.
I have started reading and trying maven since yesterday. But its making me go crazy.
I am java developer but never came across ant or maven before.
I want to know what exactly happens with the dependency tag in POM.xml file?
Lets say, I am using camel framework and want to use camel core jars.
If one of my class file contains following line:
CamelContext context = new DefaultCamelContext();
so what exactly I need to do after that?
Do I need to include the jars myself in the class path or dependency tag will download the jar files over internet for me?
If the case is former, what dependency tag will do? & where should I place my jar files? I mean is there any specific location on my hard drive? and
if the case is lateral then during compile time I get error "cannot be resolved to a type"
And the imports are to be specified or not?
I know the question might sound silly but I am not able to find its answer.
I have tried googling alot, it didn't help me still.
Any help would be greatful, even help on maven topics which I might come across in near future would be appreciated.
Thanks in advance.
Solved. Please check https://stackoverflow.com/a/20094312/1121208 for help
dependency tag will download the jar specified in the dependency tag for you if available. Otherwise will raise a pom.xml error - could not found dependency..
Imports have nothing to do with maven. They will appear when you will you another class in your class/java file. So if you import in build path the jar by yourserf or if you put it there with maven, you will have the import.
Are you using eclipse or any other ide ?
First of all, Maven is a build tool. It doesn't run your app. It builds it. So, at runtime, the classpath needs to be set like for any oter application yo would have built with something else.
When you build an app, you depend on external libraries. The dependencies mechanism of Maven simply lets you declare wwhich libraries your ap needs. When you build your app, Maven downloads these libraries from a central repository (or sevaral ones), and stores them in a local repository on your hard drive. These jars are automatically added to the build classpath by Maven. At runtime though, depending on the kind of ap you're building, you'll have to copy or embed those jars in order to create a runnable application.
The rules of Java don't change just you build them with Maven. Meven uses the stadard Java compiler (javac). And of course, if you want to use a class by its simple name, you'll have to add an import statement for this class.
I think that, before using Maven, you should try to compile and run a simple application depending on an external library without using any IDE. You would then understand better all the steps that are required to build and run an app, the concept of build and runtime classpath, etc.
Finally got what I needed to know
Sharing it for others who may stuck up in same situation
Does dependency tag download the jar specified?
maven dependency tag actually downloads the jar files you specify in the dependency tag. It downloads and save it under .m2/repositories(local repository) folder on your hard drive (along with some information like last updated, etc)
Local repository is shared among all your projects
from where it downloads?
It downloads the jar from the central repositories. There central repositories contain almost all the open source jar files one needs in a project. It downloads based on information you provide in groupid, artifactid, etc.
http://repo1.maven.org/maven/
http://mvnrepository.com/
can be checked for correct groupid, etc
Once these jar files are downloaded, they are automatically added to the classpath and are available in your project for use.
If the jar files you are searching for, are not available in the central repository, maven may throw error, in that case you can download it manually and let maven know about it.
Without maven you need to put jars into lib folder.
With maven you specify as declaration inside <dependencies>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
and when you do mvn package, maven will download required jars on your PC.
With Eclipse and m2e (maven eclipse integration) you can do that all not leaving Eclipse,
and even get sources for used libraries automatically.
Read http://maven.apache.org/ It worth it.
I'm evaluating Maven 3 at work. For several example projects I have to deploy them to a server (no repository), but that's not the problem.
In my current example-project I'm trying to upload only the "jar-with-dependencies".
and exactly that's my problem.
It all works fine, except that the main-artifact AND the jar-with-dependencies (created by the assembly-plugin) are uploaded.
How do I prevent Maven or rather the deploy-phase from uploading the main-jar and only upload a given or specified file (in this case, the assembly-file "jar-with-dependencies")?
Referring to the question Only create executable jar-with-dependencies in Maven, I can't just alter the packaging-setting to pom, because it will also prevent the assembly-plugin from adding my classes to the JAR file. It only creates a JAR file with the files of the dependencies.
I hope I'm clear about my problem, and you can help me ;)
if you just looking how to add a file to be deployed you can take a look here:
http://mojo.codehaus.org/build-helper-maven-plugin/attach-artifact-mojo.html
May be this helps. If not express your needs more in detail.
There seems to be no way to configure the deploy plugin to filter out some of the artifacts from a project and selectively deploy the others. Faced with a similar problem, we solved this with the ease-maven-plugin. It fit well into our release process but might not be the right choice for everyone as it mandates a two-step approach. During the build you would make a list of all artifacts and filter out those that you want deployed. In a second step, you then run mvn deploy on a separate project (or separate profile) in which the list of artifacts is attached to the project as the only artifacts which then get deployed. See the examples in the source code of the ease maven plugin to better understand how it works.
The original version is not able to filter out specific artifacts of a project. I have forked the project and added patches that add this.
Occasionally I see eclipse lose the reference to the third party jars contained in the a projects. (you get the the build path error stating the jar cannot be found)
Its easy enough to fix as you can remove the jar, save the properties of the project and then go in and re-add the jar that it could not find, eclipse can then see the path to the jar and you can then compile again.
the problem is that if you have a lot of projects in your build you would have to do this task a lot.
Is there anything you can do to force eclipse to recognise that it actually has the jar on its classpath?
I have also faced the similar situation many times with my projects in eclipse. The jar file path is correct in the .classpath file and the jar is present still eclipse do that. To fix it you open the .classpath file and resave it and refresh the probject in eclipse and it builds fine.
That's a weird behaviour...
If that's ok you can use Maven 2 for your projects. This means that you have to follow Maven's project structure, which is quite ok, but it can be a pain if you decide to migrate old projects.
Then you can run mvn eclipse:eclipse whenever you want and that will fix your problem in a few seconds.