I have several projects that need the same core database and utility classes so I have decided to make a "core" module to put these in. Is there any way to use this module in multiple projects or am I using modules for the wrong purpose?
Yeah! While I obviously can't provide a thorough critique of how you're using modules given what you've told us, the fact that you've encapsulated reusable functionality in this one is certainly a good sign!
Given that such is the purpose of modules, surely intelliJ would want to make it easy to share them across projects - and they did: In the File menu, there's an option to "Import Module". Click that and walk through the wizard, selecting the directory where your module is stored, and it'll appear in your Projects menu as normal.
Related
I am a C# developer and I am messing around with Java. In C# I would normally have my front end project and then when I need to add another layer to the project (i.e service layer etc) I would add a class library in the solution and add a reference to it.
What is the convention in Java? Do you add another Java project to the workspace and then reference the project? Or do you add a package to the project which contains your front end?
UPDATE
Sorry, I am using eclipse...hence the reference to 'workspace'
There's no real convention. When you say "workspace" you're not referring to Java, but rather a development environment (sounds like Eclipse). There are a number of ways to do it; you could do it the way you're suggesting, you could include the dependency via Maven, you could combine them all together in one project, etc.
Which to choose depends on your needs, who else will be consuming either the individual libraries or the completed project, and so on.
How to divide your source code depends a lot on the structure of your project. It is important to pay attention to a good code organization. You should keep classes for a common task or for a distinct application layer in own packages. You should watch for inter-package dependencies.
Using different "projects" (be it Maven or Eclipse projects) helps ensuring that you (your developers) do not violate structural boundaries because the compiler checks the dependencies (one project references the other project, like in C#/VS). Maven generates a build artifact (e.g. a JAR file) for every project.
To summarize, I think it is a good idea to create new individual projects for each program module in order to be able to manage the dependencies between the projects explicitly.
You are assuming everyone works with eclipse, it seems (your references to "workspace").
You can do anything you want, but keep in mind others might not be able to include 'separate' projects for various components of the application.
You can easily address that issue by using some build tool (ant, maven) to build appropriate jars for the various app components, like data-model, persistence, API, etc.
If you front-end is an RIA, might make more sense to develop it as a separate project, although not necessary. If your app is some sort of Java driven UI, you can still do whatever you want, in both cases make sure the UI components have their own package hierarchy.
Yes, I guess I would create a separate package. So your UI code might be in com.mycompany.app.ui, your service code in com.mycompany.app.service, etc. However you want to organize your classes is up to you. Java itself doesn't care what packages the classes are in. The packages just help to make the code more manageable for the developers.
Unlike most things in Java, there's no real convention defined for how to split up project.
In my experience, it makes sense to include code that serves a particular business purpose in a single project, and to separate out code that you intend to share between multiple projects, or code that is not specific to a particular business purpose (e.g. database access, JMS libraries, etc.), into a separate project.
If the UI and the server layer are being developed in a single project, which means packaged and deployed in the same WAR file, I'd create a new package for the service and add classes and interfaces as needed.
If the service layer is deployed separately, I'd add dependencies as a JAR to the web project. All I should need are clients for the service.
If you're working in Eclipse follow these steps:
1) Right-click the project and choose "Build Path"-"Configure Build Path..."
2) Switch to Libraries tab and click Add External JARs (or just Add JARs if they're already in the workspace).
3) Now you can either manually add import of the corresponding class, or just hit Ctrl+Shift+O (Source-Organize Imports) and Eclipse will do the job for you.
I suggest you can use netbeans then you can create a java class library,when you deploy your project,netbeans will generate jar files for you,and place them at the right location.I'm also a ms developer,hope it helps
I have a medium size project split into 3 modules: Core, plugins (in short its an interpretation layer), and implementation. There are a few global dependencies, and module specific dependencies. There is a custom ant target for generating javadoc excluding the implementation (for obvious reasons). This is stored in an public online SVN repository and therefor needs to be independent of any machine sans the JRE
Right now I'm using the built in NetBeans project management, and it sucks, probably mainly do the fact that the project management system was not designed for modules. Lack of a global library set (you can import a library specific to your nb installation, but then it doesn't get updated), lack of auto resolving of library dependencies (dependency on a project means the project and its dependencies), lack of an independent multi-project formatting style (either tied to profile specific "Global options" or individually setup and synced module-specific options), and other things make managing my project a pain.
When I was experimenting with IDEA, one of the things I loved was its project management. It was close to what I wanted, but like most things in IDEA could of been simpler. However the IDE itself was bad (not up for debate), so I switched back to NetBeans. And Maven looks bad, both from having to traverse its file structure manually and general opinion.
Are their better options out there that can be stored in a standard SVN repository with limited tools to use, are pretty easy to use for 1-3 developers, and for 2-5 modules? It must be able to handle java, and (in the perfect world) integration with NetBeans.
Honestly maven is your best bet. I wouldn't knock it you haven't actually tried it yet. It tends to be a very divisive technology, but those who love it love it for a damn good reason. If you are someone who prefers to keep your hands off the build script/files after you initially set it up, and it looks like you are given you were using Netbeans' built in projects which generate an ant build.xml behind the scenes, then you should just try maven and see what happens.
I'm not sure why you think you need to "traverse the directory structure" with maven if you are in netbeans. See this screenshot for an example of what it looks like. You don't ever see src/main/java or target/ or anything on the file system (unless you need to).
(source: netbeans.org)
If you use a maven multi-module project, you'll get the modularity you are looking for within Netbeans as well. If you want a sample, go checkout an open source project that has tons of modules and load it in Netbeans and play around with it: http://camel.apache.org/source.html
As I understand, using modules allows us to control some dependencies.
I mean that we can allow one module to interact with another one but not vise versa. We also can make some reusable things and we can make deploying easier, if, for example, put all tests stuff into a separate module and won't deploy it to production.
I haven't ever use modules but if described things are really possible I'd like to know how to make them.
How to set dependencies?
How to do this without IDE and any tools?
How to do it in IntelliJ IDEA?
Managing the dependencies yourself can quickly get complicated for non-trivial applications. For dependency management in Java, I suggest looking at Maven. Using the "test" scope you can bundle the project without all of the testing code. IntelliJ, like other populate IDEs, has built-in support for Maven.
Maven - Introduction to the Dependency Mechanism
Hope it helps!
in IntelliJ,you can select the module and right click it,and set the properties(include dependencies) for the selected module.
I have recently joined a project that is using multiple different projects. A lot of these projects are depending on each other, using JAR files of the other project included in a library, so anytime you change one project, you have to then know which other projest use it and update them too. I would like to make this much easier, and was thinking about merging all this java code into one project in seperate packages. Is it possible to do this and then deploy only some of the packages in a jar. I would like to not deploy only part of it but have been sassked if this is possible.
Is there a better way to handle this?
Approach 1: Using Hudson
If you use a continuous integration server like Hudson, then you can configure upstream/downstream projects (see Terminology).
A project can have one or several downstream projcets. The downstream projects are added to the build queue if the current project is built successfully. It is possible to setup that it should add the downstream project to the call queue even if the current project is unstable (default is off).
What this means is, if someone checks in some code into one project, at least you would get early warning if it broke other builds.
Approach 2: Using Maven
If the projects are not too complex, then perhaps you could create a main project, and make these sub-projects child modules of this project. However, mangling a project into a form that Maven likes can be quite tricky.
If you use Eclipse (or any decent IDE) you can just make one project depend on another, and supply that configuration aspect in your SVN, and assume checkouts in your build scripts.
Note that if one project depends on a certain version of another project, the Jar file is a far simpler way to manage this. A major refactoring could immediately means lots of work in all the other projects to fix things, whereas you could just drop the new jar in to each project as required and do the migration work then.
I guess it probably all depends on the specific project, but I think I would keep all the projects separate. This help keep the whole system loosely coupled. You can use a tool such as maven to help manage all the dependencies between the projects. Managing dependencies like this is one of maven's main strengths.
Using Ant as your build tool, you can package your project any way that you want. However, leaving parts of your code out of the distribution seems like it would be error prone; you might accidentally leave out necessary classes (presumably, all of your classes are necessary).
In relation to keeping your code in different projects, I have a loose guideline. Keep the code that changes together in the same project and package it in its own jar file. This works best when some of your code can be broken out into utility libraries that change less frequently than your main application.
For example, you might have an application where you've generated web service client classes from a web service WSDL (using something like the Axis library). The web service interface will likely change infrequently, so you don't want to have the regeneration step reoccurring all the time in your main application build. Create a separate project for this piece so that you only have to recreate the web service client classes when the WSDL changes. Create a separate jar and use it in your main application. This style also allows other projects to reuse these utility modules.
When following this style, you should place a version number in the jar manifest so that you can keep track of which applications are using which versions of your module. Depending on how far you want to take this, you could also keep a text file in the jar that details the changes that have occurred for each revision (much like an open source library).
It's all possible (we had the same situation some years ago). How hard or easy it'll be depends on your IDE (refactoring, merging, organizing new project) and you build tool (deploying). We used IDEA as IDE and Ant as build tool and it wasn't too hard. One sunday (nobody working+committing), 2 people on one computer.
I'm not sure what you mean by
"deploy only some of the packages in a jar"
I think you will need all of them at runtime, won't you? As I understood they depend on each other.
I'm currently working on a project that contains many different Eclipse projects referencing each other to make up one large project. Is there a point where a developer should ask themselves if they should rethink the way their development project is structured?
NOTE: My project currently contains 25+ different Eclipse projects.
My general rule of thumb is I would create a new project for every reusable component. So for example if I have some isolated functionality that can be packaged say as a jar, I would create a new project so I can build,package and distribute the component independently.
Also, if there are certain projects that you do not need to make frequent changes to, you can build them only when required and keep them "closed" in eclipse to save time on indexing, etc. Even if you think that a certain component is not reusable, as long as it is separated from the rest of the code base in terms of logic/concerns you may be well served by just separating it out. Sometimes seemingly specific code might be reusable in another project or in a future version of the same project.
When compiled, a project would typically result in a jar. So if your application consists of potentially reusable components, it is ok to use a project for each.
I'm a big fan of using a lot of projects, I feel that this "breaks down" large things beyond what I can do with packages, and helps me orient and navigate.
Of course, if you're developing Eclipse plug-ins, everything would be a project anyway.
The only thing I would watch out for has to do with your source-control and it's ability to handle moves of files between projects. Subclipse had been giving me trouble with it, or maybe it's my SVN server that did.
If your project has that many sub-projects, or modules, needed to actually compose your final artifact then it is time to look at having something like Maven and setting up a multi-module project. It will a) allow you to work on each module independently without ide worries and allow easy setup in your ide (and others' IDEs) through the mvn eclipse:eclipse goal. In addition, when building your entire top level project, maven will be able to derive from list of dependencies you have described what modules need to be built in what order.
Here's a quick link via google and a link to the book Maven: The Definitive Guide, which will explain things in much better detail in chapter 6 (once you have the basics).
This will also force your project to not be explicitly tied to Eclipse. Being able to build independent from an ide means that any Joe Schmoe can come along and easily work with your code base using whatever tools he/she needs.
Create jars for the projects you don't work in often. That should greatly reduce the clutter. If you work on all the projects often, then you can add targets to your build that will jar up the respective projects for you, which condenses everything down to one file that you can then include on the class path.
An additional method is to create many different workspaces. The benefit of separate workspaces is that you can remove some of the visual clutter/ performance overhead of having lots of projects. You can use targets to jar up all of you projects and put them in a repository so you can reference them in each workspace.
At a former job the entire application was more then +170 projects. While it was rarely necessary to have all projects checked out locally, even the 30-40 projects constantly in our scope made reindexing, etc. very slow.
Yeesh. One Project for each Project. If you are using reusable projects, make them into a library for heavens sake. Break the none re-usable projects into packages, that's what they are there for.
That's a hard question and answers span from having one eclipse project at all to having one eclipse project for every single class.
My bottomline:
You can have too few projects,
and never too many (of course use
automation e.g. mvn eclipse:eclipse)
Use
-Declipse.useProjectReferences=true/false
when using maven to switch workspace
mode btw jar and project
dependencies
Use mvn release plugin to generate
consecutive releases (automatic
version increase)
Multiple projects gives you
independent versioning which is
extremely important. E.g. one dev may work on a new version of a
module while you still depends on
the previous one and you at some
point decide to upgrade to the newer
version(possibly by increasing its version in pom.xml dependency section). Or in other scenario if one
project contains a bug you downgrade
to its previous version.
Multiple projects makes you think
about the architecture more than if
you have just packages.
Multiple projects generally make
architectural problems evident more
than if you have just one project.
Anyone would like to comment on
this?
You never know if you project
evolves into OSGI/SOA/EDA where you
need separation.
Even if you're 100% sure that you
projects will be deployed as one jar
in an old way in a single jvm, it
still does not hurt(mvn assembly
plugin) to have multiple eclipse
projects for logically independent
pieces of code
BTW, the project I work on is divided into 24 eclipse projects.
Hell, we have more than 100. Projects don't cost anything.