I have a maven pom file for an open source project. This pom file has all the info like what other jars it depends on etc. I installed maven. Created a dir samprj and copied the pom file into that dir. Cd into that dir and ran mvn command without any arguments but I got bunch of errors. I am absolutely new to maven so I think I am missing something. I tried also from Eclipse ( Import project -- exisitng maven project) but that also does not work except eclipse creates a project that has just that file pom.xml. I expect something that first it will download the jar for the project and then download all dependent jars and config files but nothing there.
So given a pom file how do I build the project from it?
mvn install should get you going
I have a maven pom file for an open source project. This pom file has all the info like what other jars it depends on etc. I installed maven. Created a dir samprj and copied the pom file into that dir ...
It sounds like you only have the project's POM file. This is not sufficient. You need to checkout the complete source tree for the project. Having done that, change directory to the directory containing the POM file and run mvn install.
Also, don't copy the POM to a different directory. Maven expects to find all of the source files relative to the POM file location.
FOLLOW UP
Thanks for advice. I was not able to use the command mvn install as it gave errors.
Probably because you hadn't checked out the source.
I don't know how to check the source tree of the project ...
Use a subversion client (the svn command for example), or one of the Eclipse subversion plugins.
If this was a properly documented project, there would be clear instructions on what version control and build tools you needed, how to checkout the source code and how to build it.
... as I thought POM itself should have this information to automatically checkout if the source is not check out.
It doesn't necessarily, though in this particular case it does.
Anyway I was able use Eclipse to build the project without errors.
(Other readers can read #icyrock.com's answer for links to the m2eclipse plugin and documentation.)
The only problem is the dependent jars were downloaded but hidden deep paths in .m2 repository folder on my linux box.
But I would like these dependent jars to be relative to dir where POM file is.
Sorry, but that is not the way Maven works.
The ~/.m2/repository directory is a fundamental part of Maven. It is not a problem. It is a feature. (Don't fight it!)
If you want to open this within Eclipse, you need to install m2eclipse:
http://www.eclipse.org/m2e/
and then import the project as a Maven project as described here:
http://books.sonatype.com/m2eclipse-book/reference/creating-sect-importing-projects.html
Try out their getting started guide. It has a lot of good examples:
http://maven.apache.org/guides/getting-started/
Related
My problem is with a project where I use the POI library. It's from apache and allows you to work with excel,word, ... .
I had to add some jar files to my library and it runs perfect.
The problem is when I put my JAR file somewhere else.
It gives me the errors it can't find the librarys.
Is there a way I can put my librarys into the 1 jar?
I already tried to add my lib folder as source package but that didn't help.
there is a Maven plugin for Eclipse called M2Eclipse, which will read a POM and construct a classpath out of jars it finds in the local repository and any remote repositories you've configured. It behaves largely like Maven does in terms of finding the latest version for a given jar (if you've specified a version range in your POM).
You can also have a look on this
http://fredpuls.com/site/softwaredevelopment/java/deploy/five_strategies_for_managing_j.htm
You want to make a 'shaded' or 'uber' jar, which has all of its dependencies included
There is a maven plugin for building a shaded jar.
https://maven.apache.org/plugins/maven-shade-plugin/
For me the fastest/ easiest solution was to just open my project in eclips and export is a runable JAR then it adds the librarys to the JAR.
NetBeans builds your application into the project's dist folder. There is also a readme file in it, that tells you, you should distribute the contents of that folder...
Edit
Remove the lib folder, that is shown on the second image, from your sources.
I created a new Maven project and generated Javadocs through eclipse. It created a lot of html files in the project directory inside a folder called "doc".
Now I want to distribute this project as a dependency to my colleague and he does not have the source of the project I created. He is only adding my project as a dependency. He says he cannot see the javadoc when he hovers on a method that I created in my project.
What am I missing here?
Add the maven-javadoc-plugin to the project (plugins section of your pom.xml), instead of generating the Javadocs through Eclipse. Please have a look at the jar goal. If done correctly, the Maven build will package a javadoc jar beside the normal jar file. The build will result in following jars:
${artifactId}-${version}.jar
${artifactId}-${version}-javadoc.jar
If you want to provide the sources additionally, the maven-source-plugin (goal jar) will do the job for you.
The installation of the jar file, the javadoc file and in case the source file into your colleague's local Maven repository can be done with the maven-install-plugin.
I accidentally converted my project to Maven by going to Configure > Convert to Maven Project. Now I want to undo this. I read that I need to right click Maven > Disable Maven Nature and that worked fine. However I want to totally remove Maven, so I deleted the pom.xml and the target folder. When I try to run my code now, I get the error:
Error: Could not find or load main class
So what am I missing? How do I revert from a Maven project to a non-Maven project?
When you convert a Java project to a Maven project in Eclipse, the Maven Integration for Eclipse (m2eclipse) configures the Java incremental compiler to put the compiled class files in the same location as Maven would put them, i.e. target/classes.
So when you remove the Maven nature and delete the target folder, you now also have deleted the compiled class files and your project can no longer run. AFAIK, the incremental compiler doesn't detect when you remove its output files, so you need to trigger a rebuild by cleaning the project (Project > Clean...)
This will fix the problem that you can not launch your project, but may re-create a target folder. If you also want this to be "fixed", you can switch back to some other folder name for the binaries, e.g. bin, in the project's Java Build Path configuration on the Source tab.
Is it basically a Maven project, i.e., do you have and maintain it through a pom.xml? Then my suggestion is to delete the project in Eclipse but keep the files on the disk (i.e., it removes it from the workspace). Then, run a simple mvn eclipse:clean eclipse:eclipse which creates a simple Java project without the Maven nature based on the POM (so the libraries are linked and the source/output directories are set up correctly - this may solve your ClassNotFoundError).
If it's a simple Java project, I would advise deleting it from the workspace, removing the .classpath and .project files and importing it again with the Create a Java project with existing sources wizard.
Either way, make a backup of your project before you start doing anything :-)
I am using Eclipse Kepler for Java. Normally you can add internal/external .jars to a Java project in the build path located in the properties. Why, when I clone a git repo and import it into my projects, do I lose that ability? I don't understand. I kinda need to do that.
This is probably because the .gitignore has been configured to ignore .jar
Open the .gitignore file and remove the line *.jar, you should be able to add it.
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As an aside - usually, for Java projects .jar files are not committed to repository (as they are large & it can slow down repository cloning), instead maven or gradle is used to configure dependencies. Example - http://www.mkyong.com/maven/how-to-create-a-java-project-with-maven/
Then when you want to work with eclipse just run mvn eclipse:eclipse to generate the necessary files. .gitgnore is usually set up to ignore *.class, *.jar, .project, .settings, .classpath
I found that if you open the run configurations and go to the Classpath tab that you can add internal/external .jars. The run configuration can be accessed by clicking Run > Run configurations. I added my .jar to the user entries. The bootstrap entry caused a null pointer.
When a project relies on libraries/modules, it's best to use a build tool for dependency management. JVM ecosystem is dominated with three build tools: Gradle, Maven and Ant.
How it works:
In a build script we declare dependencies of the project. This tells the build tool where to retrieve libraries/modules our project depends on. Dependencies are resolved at runtime; downloaded from a remote repository, retrieved from a local directory or if required another project to be built in a multi-project setting.
I have a project where I want to add an external JAR file. The desired external JAR file has a nifty Github page with source, but no pre-compiled JAR file.
These are the steps I've completed so far:
1. I have downloaded the source in a zip. (its Twinkle from SwingFx.ch in case you're interested)
2. I have extracted the zip file to my workspace.
3. I have created a new project with the same name as the extracted folder from the zip file. (project loads the source successfully)
4. I select the export option from the File menu and selected the 'JAR file' option and clicked next.
Note: I had to add an external library to the above Twinkle project for it to build successfully (in case that makes a difference to the settings).
On the JAR File Specification page there are multiple check-box options available(see below):
Export generated class file and resources
Export all output folder for checked projects
Export Java source files and resources
Export refactorings for checked projects
Compress the contents of the JAR file
Add directory entries
I am not sure which are supposed to be selected and if it makes a difference in the behaviour of the project I will add the (soon-to-be) exported JAR file to. I tested it by exporting with the default settings. This worked ok.. However, I now do not know if I should have chosen different settings in case of any reasons I am not aware of. I am not sure if there are specific settings I should choose when I intend for the JAR file to, specifically, be added as an external JAR file to another project.
Please enlighten me!
This is a traditional Java library that uses Maven. It should be fairly easy to build using Maven, which should be better and quicker to build this, if you already have Maven and git installed.
Let's consider that you did not download the source file as a zip, but take the github approach, where you'd use git to download the source code.
If you don't have git, download its latest version and install it.
If you don't have Maven, download its latest version and install it.
Once Maven and git are installed, make sure the Maven and git binaries are configured in your environment PATH variable. If not set, you would, on the Windows platform and for Maven binaries, set it this way (using the default installation path):
set PATH=%PATH%;C:\Program Files (x86)\Apache\maven-3.1.1\bin
Create and change directory in a work directory of your choice, that we'll refer to %work_directory% from now on.
Run the following:
cd %work_directory%
git clone https://github.com/spreiter301/Core.git
git clone https://github.com/spreiter301/Twinkle.git
cd Core
mvn clean install
cd ../Twinkle
mvn package
6. Retrieve the twinkle-1.0.0.jar file in the newly created '%work_directory%/Twinkle/target' folder.
In this case, it was necessary to retrieve the Core library because it is a dependency of the Twinkle project. Normally, this is not necessary because dependencies are automatically retrieved from a maven repository. But in that case, that dependency is not available on any Maven repository. Hence we manually retrieved the dependency from github, compiled it and installed it in your local cached repository. Then we could package the Twinkle project into the JAR file.
This should do it. If you want a 5 minutes tutorial on Maven, there is a tutorial for this here. I highly recommend it, you will encounter this often in the Java world. Maven is the standard build tool for Java, just like 'make' is for C, 'rake' for Ruby, 'sbt' for Scala, etc..! Good luck with the rest.