Develop Reference

Including dependencies in Java project on Intellij/Maven?

This sounds dumb but is there anyway for me to specify dependencies for my Java project like how I would in a package.json file so that someone else who was to download the project code from my GitHub repo, would be able to run it without any errors or missing libraries?
I have never tried using external Java libraries before, such as apache commons. The most I ever used was JavaFX but on a personal project level. My main concern is that if I were to push my code up to the repo and have someone else clone it. It might not run properly as the imported libraries are not downloaded.
Is there something similar to package.json dependencies where the person who runs the code would automatically download all dependency libraries and have it run on their system?

You can use Maven or Gradle for this purpose. Maven has pom.xml where you can specify all your dependencies. Similarly gradle has build.gradle which does the same job.

Why does external dependencies added in Project Structure doesn't appear in compile time (Intellij)?

So I've created a library which is not released as not tested, so I'm importing it manually using the Project structure to test it out, just like explained in here.
Here's a snapshot as well:
And it even seems that it is imported in the intellij as it is shown in the editor, as well as I can navigate to its definition.
But unfortunately the build fails see this:
And i tried changing the scoped of the dependency, but nothing worked.
How could I solve this, any help would be appreciated 😊.

Finally i got it working by removing external dependencies I had added manually from Intellij IDEA's Project structure.
And add the external dependencies by using the gradle:
compile files('path/to/the/jar/my-plugin.main.jar')
This file() uses project's folder as root, then we can navigate through that.
Issue may have been occured because of using both gradle and intellij project management at the same time.
Hopefully if somebody having same issue, he/she may fix it using gradle.

Intellij Idea not finding jar

I have a single java file to compile. It uses javax.servlet-api-3.1.0.jar. I added it to maven with mvn-install and it says it built successfully. However, in Intellij it still throws errors during compilation saying:
package javax.servlet does not exist.
This was after restarting it.
Am I missing anything with adding this jar to my program?
Thanks!

You need a pom.xml file in order to build a maven based project. In short, a pom.xml file is used to tell maven how exactly to build your project, and what dependencies it requires. I'd strongly recommend reading the quickstart guide for maven here

How to specify dependency on tomcat libraries with gradle

A bit of background about my knowledge level: I'm currently trying to learn how to build a project with gradle. So far I don't have much experience with build tools (almost none). I do understand the general idea and have seen ant and maven files before but never written them myself. Until now I just used other peoples build scripts or configured my builds using Eclipse. So I might be on a completely wrong track here, if so please point me in the correct direction.
Also, I sadly don't have much experience building jars by hand.
I have an Eclipse project which I want to compile into a jar. Required library jars are on my local file system. I managed to make gradle use these via
dependencies {
compile fileTree(dir:'lib', include:'*.jar')
}
in addition I have my source files in src/main/java and just use apply plugin: 'java' in the build.gradle file. Trying to build the project with gradle build seems to do the right thing, as far as I can tell.
However, the library is supposed to be used in a web project running on a tomcat and makes use of some libraries that are supplied by tomcat, as far as I understand. E.g. I'm using javax.servlet.http.HttpServletRequest.
The project works fine in Eclipse, but there I have the tomcat library added to my Eclipse build path. When I check in Eclipse I can see that javax.servlet.http.HttpServletRequest is part of the servlet-api.jar which is part of the Tomcat library.
Now, when I build the project I get build errors because the java compiler cannot find the class because I didn't specify the servlet-api.jar in the dependencies. I guess I could download it somehow (or learn how to specify it as an external dependency to make gradle download it from some repository) but I am not sure whether that would be correct.
Is there a way to tell gradle to use the same library that Eclipse uses? Or some other general way to tell it about all the tomcat jars, the same way I can simply add the complete Tomcat library in Eclipse?
Or do I actually need another copy of these jars somehow and have to specify each one individually?
Also, do I need to add these library jars to my build-result library jar? As far as I know I need to add any jar I depend on to the resulting jar as well. But then again, I have read somewhere that some libraries are supplied by tomcat itself so they would have to be part of any war deployed on it.
I'm afraid, I'm confused by the combination of how to build a jar-file to be used in a war-file to be deployed on a tomcat using gradle and I don't know from which of these parts my problems originate. I hope someone reading this can help me untangle my thoughts and point me in the right direction or at least tell me how to add the jars included in the Tomcat library to my gradle dependencies.

With Gradle, whenever you add files or directories as dependencies, they are not treated as full-fledged artifacts (with group, name and version), but rather as simple files containing classes. It means that Gradle will not perform any conflicts resolutions on them, or pull transitive dependencies.
For you, just to get started, I recommend just to add tomcat dependency. Make sure it is the same version as the one in Eclipse.
apply plugin: 'war'
repositories {
mavenCentral()
}
dependencies {
providedCompile 'org.apache.tomcat:tomcat-catalina:7.0.47'
}
Also, look into Eclipse Integration Gradle project as a long-term solution.

Created Simpl JAR file, imported to Maven project but Maven install is complainining "package does not exist"

I guess I haven't really had to do this much before because I am running into a strange issue. I am trying to generate a JAR from an existing Java project and then and putting it into a Spring Maven project. I'm sure I'm including it correctly, I have done this many times before with 3rd party JARs that I get (even though its a Maven project I have included some obscure JARs in it and put on buildpath, etc), with my JAR within Eclipse it is showing up fine as if its included, I have a test class that is importing a class from the JAR, instantiating it, etc and its not showing any errors (imports are fine in the IDE, etc), however when I go to do a Maven install I get:
[ERROR] /media/src/main/java/org/jadefalcon/automation/DataSetup/test.java:[11,15] package org.test does not exist
[ERROR] /media/src/main/java/org/jadefalcon/automation/DataSetup/test.java:[21,2] cannot find symbol
I have tried doing a Maven clean but still the same problem, the JAR class I am testing with is this: (was trying a more complex one but then tried this to troubleshoot the issue)
package org.test;
public class something {
public String main () {
return "it is definitely working fine";
}
}
Here is the JAR I generated (with sources visible):
https://docs.google.com/leaf?id=0BzB_xvrbRpbYODQyMjEzOWEtOTdjNS00YjM3LTlkZGUtNjY5NmIwN2RiNTRj&hl=en
I would appreciate any advice as I am rather perplexed and frustrated by this. Thanks

You can include a 'regular' jar in your maven project -just as you described- though it's not a best practice mainly because then you not even lose the functionality of Maven for that jar, but also the whole point of Maven dependency management: you will have to include that jar with your source to make it build.
You can of course also create a Maven artifact for that jar, build it with Maven, install it with Maven and use it as a normal Maven dependency.
You also can create a parent .pom and have your dependency project as a module in it and also your real application (or also your real app can be your parent). See further here.

Since this caused me quite a bit of grief, I figure I should post the solution I found. Apparently you aren't supposed to just include a regular lib JAR in a maven project (although I swear I have done it before and it worked), I found this way to include a local JAR that isn't form a repository from this post:
Can I add jars to maven 2 build classpath without installing them?
I did this and its doing the maven install properly (where version and artifactID are just made up value)
<dependency>
<groupId>org.test</groupId>
<artifactId>test</artifactId>
<version>1.0</version>
<scope>system</scope>
<systemPath>${basedir}/lib/testjar.jar</systemPath>
</dependency>