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.
Related
I want to convert a Java/Dynamic web project to a Maven project. I use Eclipse IDE to develop Java applications.
One of the straight forward options available to me is to use 'Convert to Maven project' in Eclipse. But there are situations where I cannot use that option since the Maven plugin doesn't work in some networks like my Work environment.
So I want to know a Maven command (on Command Line) that would help me convert my Eclipse-built Java Web App to a Maven project.
Thank you in advance, Happy learning.
The Eclipse feature "Convert to Maven Project" works on projects that already have an appropriate POM. A project that was initially created by Eclipse doesn't have that POM.
So what you must do, is simply create a POM with packaging type WAR, then put it into the root of the project.
You also have to take care of the source directories. The Maven standard way is to have all sources under these four directories:
src/main/java
src/main/resources
src/test/java
src/test/resources
Eclipse simply stores everything under src. So you either change your file and directory structure, or you change the appropriate <build> parameters in the POM. I suggest the former.
The "Convert to Maven Project" feature does more than adding the Maven nature to the Eclipse build settings. It also creates and configures the Eclipse project meta files (the files .project and .classpath and the folder .settings). Therefore I suggest to delete them first in your project directory, so Eclipse can start on a clean project.
Afterwards you simply can convert your project with the above mentioned feature. It should create the meta files, and - as it is a web project (packaging type WAR) - it also should add the appropriate natures that let Eclipse show the project as a web project.
I have a Java project that depends on a 3-rd party component. This component is available both as a jar and as a Maven/Ant project. One option for me is to simply add the jar as a library. However, I prefer to add the source code into my project since I may need to slightly modify their source code to better suit my needs.
What's the right way to do it in Eclipse?
My main project has a simple structure: src/ and lib/. The external component also has a standard structure: src/, test/, build/, target/, pom.xml, build.xml. So do I need to copy piece by piece (like contents of one src/ into the other src/), in which case what goes where? Or do I somehow copy it all at once? Or smth else?
The best way would be if you use maven on your projet for dependency management. This way, if you have the other projects open in eclipse, your project will resolve them as local projects, but if you don't, maven will try to fetch the jars from the configured nexus repository.
This way, you avoid having to manually configure your Eclipse projects. Maven will be able to configure your project anywhere you want to build it, not having to manually configure dependency resolution.
Import both the projects into eclipse. Add the reference of 3pp jar project to your project as a reference by clicking on Add on build path option. While delivering it as output there will be a dependency to the 3pp jar project. So either deliver it as separate jar and add it to classpath while executing your project else you have to copy the entire source files into your project and deliver it test complete jar.
Making a jar will be handled by eclipse itself.
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 currently using eclipse for working with Java. Additionaly I use git to synchronize my project between my laptop and my desktop PC.
The problem is now the following: I added external JARs to the project (Slick-Util, LWJGL).
But the path to each library is another on each device. So everytime I start working on the other device, I have to change the path to the jar files and the javadocs.
The libraries are all stored in my eclipse workspace. So the libraries and the projects are all in the same folder. And this folder is also commited with git.
Is there a way to change the eclipse settings (or do something else) so I do not have to change the path to the libraries and javadocs everytime?
I already googled and searched for it, but I could not find something about it.
Just don't add the libraries' jars to git. There are multiple build tools for java, which manage dependencies for you - you just state the libraries you're going to use, and the build tool downloads it for you at build time.
I would recommend Gradle, but Maven is also a very popular choice.
In gradle, you would create a file build.gradle, and define your dependencies in it:
apply plugin: 'eclipse'
apply plugin: 'java'
repositories {
mavenCentral()
}
dependencies {
compile 'org.lwjgl.lwjgl:lwjgl:2.9.0'
compile 'org.lwjgl.lwjgl:lwjgl_util:2.9.0'
}
Then you would run gradle eclipse from the command line - that would add the libraries you use to the classpath in eclipse. And when you want to compile and package your project you would run gradle build from the command line. You should read about it if you're going to use it, what I describe may not be exactly what you need.
Also, there are instructions for using LWJGL with maven.
add jar files to a lib folder inside your project like this : D:\Workspace\myproject\lib\your-jar-file.jar
then go to your projects build path select libraries tab and click on add jars and NOT add external jars this way your jar files path will be relative to your project
EDIT :
I highly recommend to use a build tool as Kiril Raychev described.
it will look a bit confusing to start with but after a while and after a normal growth in your application that will lead to using different frameworks, controlling and managing dependencies and their conflicts without a build tool will literally kill you.
You can simply use -f flag on add command.
git add -f test.jar
And, then commit and push to your repo.
Up until now i usually use svn so i'm not entirely sure how it works out in git, but have you tried to store the JARs in the lib folder of the project they are used in? (Eclipse displays the lib folder so you can easiely add them to the buildpath with a right click on the library in the package explorer.)
That way the relative location/path of the libraries to the project should stay the same. Furthermore if you plan to pack the project into a JAR later you ship the libraries inside that JAR without having to worry whether the user of that file even has them on his computer.
PS: Looks like i'm a minute too late. Dave basically said the same thing.
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/