I have added to my pom.xml a section that specifies the mainClass and allows it to essentially create an executable jar. I have included a bunch of dependencies that maven manages as well. It executes fine, but fails to run when it gets to a section of code that needs to know the location of a jar package that was made inhouse by somebody (i.e., not from Maven). In the project in eclipse I had put the jar in src/lib and my code is in src/main/java. I had to select properties and Java Build Path and specify there the src/lib location for the jar to get it to even compile. However, trying to run java -jar name.jar has it fail and complain because it fails to import the classes from the src/lib jar. Since it is not a maven thing, how to I make sure this is a dependency for this project and that it is seen on the project's classpath?
The thing with maven is that maven has to control all of the dependencies and that includes this jar you want to reference. That doesn't mean that you have to build that other jar using maven, you could mvn install it in your local repository or use a tool like Artifactory to put it in a private remote repository. I know that installing regular jars via Artifactory creates a pom file for the jar and from then on you can treat the jar like any other maven dependency.
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my Java Project uses a "/libs" folder containing ~100 .jar files. Almost all of them are not in an official maven repository.
1.) In the moment I manually added to whole folder to the classpath with my Eclipse IDE. That enables to compile and run the App using the Eclipse IDE. But if I want to maven to compile and create jar-with-dependencies, maven of course does not know about the "/libs" folder.
2.) I know that I can add a jar file to my local maven repo with mvn install:install-file but this would take a very long time because I would also have to open every jar and find the whole package name to insert as '-DgroupId' and the Name of the Main Class to add as '-DartifactId'
3.) My Questions:
3.1) Is there an easy way to let maven just include all jars in a folder like I did with my Eclipse IDE? I know that would break the principle of maven that every jar is identified with group and artifact id, but it would be a quick solution.
3.2) If it is not possible to add a folder with jars as a dependency in maven, is there a faster way to add a jar file into a local repo. It would be easier if there is a maven command where groupId and artifactId are automatically discovered by the jar that I do not have to open every jar file and find the Main Class and its classpath
Quick answer: No.
In the past, I have written a script for that because there is not support in Maven for this.
I am working with a proprietary maven plugin that generates connection code for artifacts created in a third party application. The proprietary plugin requires different settings in the POM file depending on the artifact it is generating the code for. I am attempting to make it so my Java application doesn't require a code change in the POM between deploying to TEST and deploying to PROD that way I can use the same jar for my application in the TEST and the PROD deployment. The issue is the connection artifacts and thus the POM code for the plugin will be different between TEST and PROD.
The solution I have in the works is to run the code generating plugin for TEST and for PROD separately then jar the generated code and use a script to include the correct generated code jar in the classpath depending on which environment the Java application jar is being deployed to.
I was able to jar the generated libraries and include the jar in the classpath which makes Eclipse happy with the dependencies, but when I attempt to run a "mvn compile" and generate the Jar for my Java application Maven isn't recognizing the generated code jar I added to the classpath which prevents the spring-boot-maven-plugin from creating my application jar.
All the solutions I have seen so far for getting maven to recognize a jar seem to involve specifying the name of the jar in the POM which I wanted to avoid since the names of the TEST and PROD generated code jars will be different (ex. generated_TEST.jar, generated_PROD.jar) and the whole point of this is to not modify any code between the TEST and PROD deployments so I can use the same Java application jar in both TEST and PROD.
Is there a way to get maven to include any jars on the classpath without having to specify the jar by name in the POM?
EDIT:
This might end up being easier than I thought. I used Eclipse to export the generated code to a jar, then I ended up renaming the jar from Generated.jar to Generated-TEST.jar. I added Generated-TEST.jar to the classpath in Eclipse and tried to run "mvn compile" but the jar was not recognized. When I tried changing the name of the jar back to Generated.jar and added it to the classpath I was able to run "mvn compile" successfully. I am not sure why changing the name of the jar made a difference as I put the appropriate name in the classpath both times.
I have maven project required dependencies in my local, I need to create an executable jar without dependency and need to use those dependencies in my local during the runtime, instead of packing it along with the project.
how to create a maven project jar without dependency in eclipse and how to execute that jar feeding the local location where the dependencies exist?
You can use mvn dependency:build-classpath to generate the necessary classpath to run your jar
https://maven.apache.org/plugins/maven-dependency-plugin/build-classpath-mojo.html
and then run your jar with java and adding the generated classpath as -cp argument.
I have a Java program in IntelliJ which has a pom.xml and uses Maven. The packages were downloaded and currently they are found by IntelliJ.
I'm a little confused though because the Maven repository is not part of the CLASSPATH as far as I can tell. So does IntelliJ just do a bit of magic where it looks into its Maven repository to find the packages? (I think that IntelliJ has its own Maven repo. I separately have Maven 3 installed, but I think it isn't using it.)
But more generally: If you build a JAR using Maven then I guess it will put the dependencies in the JAR where the Java program can find them, so there won't be a problem. But if you just run a Java program directly, do you need to add the Maven repository to your classpath or does something else happen?
Thanks for any information you can provide to lessen my confusion :)
When you start the program from IntelliJ using a runtime configuration for your main() method IntelliJ constructs the classpath from all the project dependencies. You can see this in the Run window, the first log line is the java command used to start the main(). It's a long line but it usually looks similar to:
java -javaagent:/opt/idea/idea-IC-173.3727.127/lib/idea_rt.jar=40165:/opt/infra/idea/idea-IC-173.3727.127/bin -Dfile.encoding=UTF-8 -classpath /home/ [...]
IntelliJ constructs the -classpath argument adding both the module target directory and the Maven dependencies referenced from the local Maven repository.
When you package the project using Maven mvn clean package usually it becomes a standalone JAR with just your code (unless you changed the defaults). Now you have a few choices how to provide dependencies needed to start your main():
Provide them using -classpath parameter just like IntelliJ.
Add maven-shade-plugin and use shade goal to the build a runnable Uber JAR. This creates a fat JAR which doesn't require -classpath.
Use some other Maven plugin to perform point 2 e.g. Spring Boot spring-boot:repackage goal.
All the required dependencies, defined in the pom.xml file(s), are downloaded from Maven Central (or others if configured) to the local Maven repository. That repository is located at <user home>/.m2/repository.
Maven generates/calculates a dependency tree to know all the required dependencies for the project. (you can also dump that tree with the command mvn dependency:tree. I always pipe the result to a file, because the tree can be large mvn dependency:tree > deptree.txt). Maven put them all on the classpath when executing a maven command like mvn compile
IntelliJ also use/calculate the dependency tree and add all the jar files to the projects classpath (point to the files in the <user home>/.m2/repository folder). You can see them all in the list with External Libraries, and they will be used / on the classpath for compilation and running the application.
When building a JAR file the dependencies are NOT added to the JAR. Only the bytecode (java classes) and resources from your own project are packaged into the JAR file. (Source files can also be packaged if you configure that)
By adding a Maven plugin (maven-shade-plugin) you can configure your project to also pack dependencies into the JAR. SpringBoot projects also will do that.
I'm building a Java project using the Maven Project package in Eclipse Java EE IDE. I'm using different dependencies, some of them will be provided by the system where the java program will be run on, others will not. I added the provided scope tag into the pom file to the one I know are provided by the system and I now I would like to export a runnable .jar. Eclipse exports the .jar package with all the dependencies (provided and not) but there's a way to have the runnable .jar file with just the not provided dependencies packaged?
If you exporting a jar with eclipse, eclipse Jar-Packager will be used and the runnable jar will contain all dependencies. Eclipse jar-builder don't know about pom.xml.
In your case you should use mvn build, for example:
mvn clean package