Java: Proper organization of external libraries?

Question

So I took a Coursera course that had me work with external libraries. Two .jar files which most of the weekly projects depended upon.

I'm not entirely sure how eclipse compiles and runs the files, and how it links to these external libraries -- what is the proper way of organizing this? Do I put a copy of each .jar file in each project directory?

Is there another, cleaner way that I should be organizing this?

Thanks --

Answer 1

As a beginner programmer it is OK to put it in each project. But consider that this is ongoing work and at some time in future you want to upgrade to a new version of these external libraries. Then you would have to copy it everywhere.

Instead another option is to store them in one place and add it in classpath in each project. Now you have only one copy of it, which is always better.

Now, if and when you do get a new version then the file names might change, so you will still have to change the classpath of each project.

But I advise you to worry about these and other such problems later. For now, focus on programming related problems rather than configuration.

Answer 2

If you want to maintain your libraries professionally in a formal manor then you're better of using a build tool like Gradle of Maven.

I'd suggest you to use Gradle to maintain the project since it has a whole lot of useful build tools available to you to use. Eclipse has a Gradle plugin available which allows you to use Gradle projects with it. See link below.

To give you a idea of how Gradle is used professionally. Android uses it by default to maintain their projects now. So Android java projects uses the Gradle build tool to maintain its library sources, compilation processes and such.

The difference between a Gradle project and a normal java project is that a Gradle project has a list of pre-defined scripts available to you which fetches the libraries, compiles them and prepares them before exporting the final bundle (jar). So really all Gradle does in before hand is fetch the libraries and prepares the specified tools before compilation so you won't need to mess with them your self. It prepares your project directory and remotely maintains your libraries so if they're available from a repository then it'll make sure to prepare them appropriately in before hand and setup your projects directories.

So really the difference you'd physically notice is that instead of using the default Eclipse export button to create your bundle (jar) you'd instead use a button from the side menu which the Gradle plugin adds and also you'd cleanly list the libraries in a structured order in a file that gets added to your project root.

If you want to get a basic understanding of how it works and really want to start to proffesionally or formally structure your project then try to create a very basic android app in Android Studio. see link below

If this isn't what you want at all and don't want to take it to this advanced level yet then adding the library bundles into some kind of lib folder that's located in your project root is properly best practice.

If you wonder why? Well basically different projects might use different versions of the library which may add or remove support to them. So to keep the versions consistent and make sure to have the right version available to you, you have the direct source near the project it self.

Here's some useful link:

• http://www.vogella.com/tutorials/EclipseGradle/article.html
• http://developer.android.com/sdk/index.html