I am in the processing of integrating Maven into my my projects. While maven has plenty of pros i'm finding it difficult to figure out how to maintain my current development process, which is as follows:
For creating SDKs I will create a sample app, which will depend on and directly reference the SDK source code, all from within the same code project. This means that I can make easily change/debug the SDK code with one click run/debugging.
I fear this won't really be possible with Maven. Can I create some type of Hybrid approach, where I continue my normal development approach and then push builds to Maven when it is appropriate.
Update - For Clarity
My problem is that when everything is done through maven, the dependencies are built and published to Maven. Then, the dependent project pulls down compiled references and uses them. My issues is that I don't want to go through this whole process every time I make a small change to a dependency.Thanks.
You should try creating parent level pom.xml with two modules - your library and simple app to test it. In simple app's pom.xml provide a dependency on library module.
Then open in your IDE parent pom as maven project. This should be sufficient for normal debug.
Other possible approach - install you library artifact into maven repo with sources. In this case you will be able to debug it, but test app still have to load use jars from repo.
Related
I have a set of applications, all use Maven and the local repository. The applications form a dependency tree using <dependency> in their pom.xml. All of these projects have -SNAPSHOT in their version.
Is it possible for Maven (or some compatible dependency manager) to build an application together with all of its local dependencies whose source changed?
I do not want to create a multi-module project, because:
the projects are exactly libraries, not modules;
I do not want an additional complexity just to have a form of build which is already precisely defined;
I want the process to be dynamic: if a library is mature enough to be put into a remote repository, it would be no more rebuilt with the main project and that's ok.
For now, there is a lot of refactoring, moving code from one library to another etc. and it happens often that substantial parts of the dependency tree need to be rebuilt. I thus need to manually write mvn install in several projects in order to assure that there is no stale code.
No, it doesn't work. Even with a multi-module project, maven does not detect which modules have changed sources in it and which do not.
There was a (flaky) implementation in Maven 2, but it was not continued in 3.x, see How to get maven 3.0 to only build modules with local scm changes
I hoped they would include it again in maven 4, but I didn't see it yet: https://maarten.mulders.it/2020/11/whats-new-in-maven-4/
I once did a similar setup, but had to use shell scripts with some git magic to get it working.
You can also decide to put your libraries in separate repo's from the start, and use the repo tool that google uses for android development: https://github.com/GerritCodeReview/git-repo/blob/main/README.md
Once you run mvn install on the particular Maven project, it will be accessible for all other Maven projects, which are on the same workstation, during dependency collection (before the compile phase).
Official Maven Build Lifecycle description:
install - install the package into the local repository, for use as a dependency in other projects locally
It's not necessary to keep libraries as part of the same project(or have it as a multi-module project). But once you want to share those libraries with your teammates, you would need either to force them installing libraries locally (as you did), or store those libraries at some external repo, like Artifactory or Nexus
I am currently starting my adventure with Maven, and I actually don't understand the idea behind using it to automate compilation of my source code. For the time being I am working on small projects with up to 15-20 classes, and 1 main method in the "app" class. Could someone please give me the explanation with examples, when it's necesarry (or recommended) to use build automatation tool to compile the source code and how could I benefit from using it regarding source code compilation?
Thank you very much in advance!
I was looking for different answers and I have a lot of work to do but since I've seen this question, as a Maven fanboy, I couldn't resist anymore and this below is my answer.
First of all, I agree with JF Meier which answered before me, but I think the answer can be improved.
IMO you have to consider Maven not just as a build tool, but as a multi-purpose tool which can help you to do very different things. The best 3, for me are:
Compiler. Obviously. Maven allows you to easily compile giant projects with a lot of submodules, even if some of these modules are interdependent one with each other.
Dependency and repository manager. Maven allows you to automatically download third party software and bind this downlaod to the build. This is immediately understandable if you think to framework or api dependencies from big corps (Apache found., Spark, Spring, Hibernate and so on ...) but it's really powerful in every enterprise context.
Example: you have a Maven project (let's say project A) which manages requests coming from a webservice and provides responses. This Maven project relys on another Maven project (let's say project B) which actually generates webservice jar and uploads it to a company repository. Well, when you have to add a field or a method to the webservice you just have to implements new software in project B, upload it the repo and change the version in Maven poms in both project A and B. Voilà: now EVERY developer of the company just have to "mvn clean install" project A to have the new version.
Sources and code automatic generator. Since Maven 2.x are available a lot of plugins (from Apache found. and others) which allow you to generate code and sources (tipically xml files) starting from little to none implementations.
Example 1: CXF plugin is commonly used to generate java classes from xml or xsd files.
Example 2: JAXWS plugin is commonly used to generate wsdl from SOAP webservice implementations or implementation starting from wsdl file.
Do you feel the power now?
-Andrea
The question is not very specific, but I will try to answer.
Usually, you want your source code to end up in a jar or war, so that you can use it as a library or run it somewhere (e.g. on an application server).
Maven not only compiles the classes you have and creates the final artifact (jar, war), but also handles your dependencies, e.g. the libraries your project depends upon.
I am a total beginner at maven, I have read about it online but I am still confused how it can be used. I have eclipse Oxygen version installed and when I open projects I can see maven project option is already there. I was even able to create a maven project using YouTube tutorial. But now then I saw popular plugin called m2eclipse but I am not able to comprehend why is it actually used; when my application ran without it.
I am learning maven to get started with spring boot but I am finding it really overwhelming where to begin with, and many of the tutorial sites state to download maven (But maven already comes along with eclipse?)
Please explain.
Apache Maven is a build tool - a tool for compiling the source code of a project into a program that you can run (for example a jar file, or a war file that can be deployed on a Java EE application server). Besides automating all the tasks for building a project, it also gives you a standard way to organize your project and to keep track of dependencies (libraries that your project needs).
Why do you need such a tool?
When you write a small program that consists of one, or maybe a few source files, it's easy enough to compile it by hand on the command line, by directly using the Java compiler javac that comes with the JDK.
But when your project becomes more complex, and you have hundreds or even thousands of source files in multiple modules, it becomes really hard to keep track of everything and cumbersome to compile the files using javac. If your program needs libraries, it becomes even more complex, because you have to make sure that all the libraries are on the classpath, and some libraries need other libraries, which also have to be on the classpath.
A tool such as Maven helps you to compile all the source files in the right order and to keep track of all the libraries. Maven can automatically download libraries from the web and add them to your project, and downloading everything and building the whole project can be done with one simple command such as mvn clean package.
Spring Boot is part of the Spring Framework, which is a huge framework with tons of useful functionality for developing projects in Java. A Spring Boot project typically needs dozens of libraries, and it would be very hard to use if you'd have to keep track of all those libraries by hand - so that's why it uses Maven to manage all of this for you.
A Maven project is configured using a file named pom.xml - in that file, you describe your project and you put a list of libraries that your project needs. When you build your project, Maven will read the pom.xml file and figure out automatically what source files need to be compiled, and what libraries need to be downloaded.
m2eclipse comes preinstalled in Eclipse (at least when selecting "Eclipse for Java developers" or "Eclipse for Java EE developer"), thats why you were able to use Maven by default.
Still you probably want a command line Maven, because that's most likely how it will eventually run on the CI server, sometimes Eclipse Maven installation can produce different result than the command line install.
I have a top-level maven project with submodules. The first submodule is a Java project which generates some JavaScript library code from the compiler's annotation processor. I want to include those generated JS files into the second submodule, a webpack NPM managed project, for the build and then publish the webpack BACK into the first submodule before packaging into a fat-jar. Does anyone know of a way to accomplish this?
What you describe is a circular dependency. You have to break this circular dependency. (You probably do similar things in your code all the time.)
I have solved the same problem by breaking up the Java project. Once you do that you will recognize that, in fact, your first project was serving two separate roles that then become separated:
From:
Java project with code and assembly
JavaScript project
To:
Java project with code
JavaScript project
JAR-packaged project with assembly
I've often seen this happen in multi-module projects that build into a WAR file, and I've adopted the rule of thumb that the WAR project should not have any Java (production) code, acknowledging its role as the aggregator/assembler.
Some folks will think this third project is frivolous, some always argue that you're easily getting too many Maven modules. I think that often stems from tooling or build pipeline limitations, once you break through those, you can just embrace a growing number of Maven modules, given that the boundaries are chosen well, and I see no problems here.
One hesitation, though: why is the JavaScript project separate to begin with? If it is not deployed separately (evidently it isn't since you're assembling the "fat-jar"), the JavaScript code is following the delivery lifecycle of the "fat-jar", which would benefit from being in the same source repository, so why even make it a separate Maven module? (If they were in separate source repositories, there's a cost in version management between the modules that I'm unsure you have reasons for.) There's no shame in having a monolith (if done well -- it happens, microservices make you believe otherwise, but in that world you'd probably deploy the JavaScript code separately anyway).
I have a project, which is written using the Play Framework, say myproject-web. It is mostly a thin HTTP layer over another project, which forms the core of the entire business logic, called myproject-engine. In my build setup, myproject-web is a sbt project, whereas myproject-engine is a Gradle one.
What I want to achieve is that Play recognize myproject-engine as a dependency, and invoke gradle to build it whenever I try to build the play application (either on run, or automatically, as it happens in the dev mode) or when I do play dist. Is it possible? What is most important for me is that it automatically loads any dependencies that myproject-engine has.
Eventually, the state I want it to reach is that I host my Maven repo for these projects and then SBT can simply pull this package from over there and will get all its dependencies. Is this rather easy to setup? Even if it is, is it relatively easy to maintain?
As #Peter-Niederwieser pointed out in his comment, I think the only viable solution is to have a maven/ivy/gradle repository where the myproject-engine Gradle project is published to. With the correct resolvers the project becomes yet another project dependency, regardless of the build tool it uses.
See Resolvers in the official documentation of sbt.