I'd like to know what will Intellij IDEA do with my Maven project when I click "build the project"?
How will Intellij build the project with Maven?
Intellij IDEA will not automatically do a make install when you do a Build Project. In order to do that, proceed as follows:
Under Maven Projects tab (usually on the right hand side), select the goals you want Intellij to run after a Build -> Make Project and then right click and select the trigger (for instance in the above snapshot, the trigger was chosen as 'Execute After Make'. You can choose whatever you wish).
After doing this a Build -> Make Project will run a mvn clean install as well.
IntelliJ's build system refers to the Maven ecosystem for some hints, but at the end of the day it is a separate build system.
In IntellIJ, you have a Project, with many Modules. These are both IntelliJ concepts.
An IntelliJ Module has a responsibility to understand what are its dependencies and libraries. This can be done purely with IntelliJ semantic, or IntelliJ can allow some other build system to declare the dependencies and libraries. That is to say: the IntelliJ Module can be based on a Maven pom.xml or Gradle's build.gradle.
When you click "Make" on an IntelliJ Java Module: IntelliJ will check which libraries your Module asks for, and also resolve the dependencies of your Module to work out which libraries its dependent Modules ask for.
Once the libraries are known: IntelliJ will invoke Javac or the Eclipse Compiler (whichever you've configured as your Java compiler) with all those libraries on the classpath. And it will output a jar, not a Maven artefact.
IntelliJ Make will not run a mvn compile or similar (unless you configure it to explicitly, as per #Ashutosh Jindal's answer.
Why would IntelliJ use its own, separate build system, when you've provided an authoritative definition for how you'd like to build your project? I can imagine various reasons:
Maven generally just outputs an artefact (sources and binary jars, and a pom.xml), whereas IntelliJ needs additional semantic and indexes to provide all its IDE intelligence. It makes sense to perform the indexing process alongside the compile, since: if you do the compile incrementally, you can understand incrementally which indexes are dirtied also.
The IDE benefits from being involved in the compilation process. For example: IntelliJ can do "continue on error" builds using the Eclipse compiler. Additionally, the Eclipse compiler can be used to compile only those files which have changed (IDEs watch you as you code, so they know very well which files are dirtied). I have heard that Maven does incremental compile, but I don't know how its performance compares.
In order to support a variety of build systems (Ant, Maven, Gradle): the easiest engineering choice for IntelliJ is to rely on the minimum possible amount of domain-specific semantic, and use that to inform one IntelliJ-specific build system. This allows them to re-use a large amount of code, and have few domain-specific differences.
Related
I was reading the Kotlin documentation and I came across the statement,
By default, your project will use the Gradle build system with Kotlin DSL.
What does it mean?
I've seen Gradle Kotlin option while making a new project in IntelliJ:
Can somebody explain me these, and which Bundle I should be using as a beginner?
A build system combines and simplifies some of the key tasks involved in building and distributing your program. The main things a build system does include:
Downloading any dependencies your application has
Running tests against your application
Compiling your code
Packaging up your application and its dependencies into a form you can share with others
You could run all of these tasks separately yourself, but build systems make it a lot easier and less prone to mistakes. In practice, all but the smallest projects use some kind of build system. Gradle is one such tool, but you can also use Maven, or the tools built into an IDE like IntelliJ.
Which one should I use?
If this is a personal project, the build system and tools built into an IDE like IntelliJ are more than good enough.
If you're working with other people, you might want to consider a standalone build system instead. That's because standalone build systems like Gradle can be used with multiple IDEs, and can also be used on the command line without an IDE at all. Large projects with many contributors will often run a build server that runs the build system in an automated way against all new changes, to make sure the code builds and runs as expected.
IDEs like IntelliJ have very good integration with the common build systems, including Maven and Gradle, so you won't disadvantage yourself by choosing them over the built-in IDE tools.
Maven, Gradle, or Gradle with Kotlin?
There are plenty of other resources you can find comparing Maven with Gradle. The crucial difference, though, is the way you write the build script that allows you to customise the dependencies, tests, and other parameters of your build.
In Maven, your build script is an XML file. It follows a rigid structure, providing inputs and configuration to existing tasks and plugins.
In Gradle, the build script was historically written in Groovy, a loosely-typed language that gives you a lot of flexibility. As well as configuring tasks and plugins, you can easily add your own tasks and functions.
You can also choose to write Gradle build scripts in Kotlin. This offers the same flexibility and customisation as Groovy, but the addition of a type system means the IDE can give you much more help with writing the script correctly.
I have a multi-module project that uses maven. Is there a way I can point IntelliJ to maven target/ folder so when I start Debug it won't rebuild the project from scratch and re-upload a whole project via JRebel all over again.
Basically, use target/ as a build folder. Changing compile output path didn't work as I expected it to not compile classes that were compiled by mvn already.
The IntelliJ Run/Debug configurations can specify which actions happen before launching the application.
By default for say web applications, this would display
Build
Build x artifact
You may remove both entries if you are happy with building via maven before launching the application.
Regarding the JRebel side of it - it should certainly not be updating the classes on the second compile assuming nothing changed. The classes have their hashes checked before a reload. This is assuming maven and IntelliJ are using the default javac compiler. If either is configured to use ecj compiler, it's best to let JRebel only see classes built with the same compiler.
I've set up a Scala project in IntelliJ idea with several dependency libraries auto-downloaded by the IDE from Maven repositories, using the built-in support for this functionality. The libraries are then automatically downloaded into a local folder and everything works as expected.
My problem is when some of those libraries go missing- either because I've deleted them, or because I'm pulling the project from a clean machine and the library binaries aren't included in version control. I'd like to tell IDEA to automatically re-download all dependency libraries from the Maven repository; I know this is possible because all the necessary information can be found in the .iml file.
If I manually go to every library in the "Project Structure" dialogue and click "Edit," I can repeat the original workflow to redownload from Maven repo without touching any settings. This is inconvenient when there are many libraries, though. Is there any way to tell IDEA to just do this for me for all Maven repo libraries included in the project?
It would be easier to use Apache Maven and maintain a pom file with a list of all dependencies (with the possibility to keep it in source control, etc) which you can simply reimport whenever you need to. IntelliJ and Maven will then manage all your libraries for you, along with their javadocs and sources. There are many, many, other benefits from this approach -- it is highly recommended.
I have been looking into Gradle and looks pretty interesting. I think being able to write your scripts in any other language than XML is pretty cool, and it is not clear to me whether polyglot Maven POM files are still a feasible option.
I am working on a project that uses Maven 2.2.1 as build tool. This project:
is multi-module
uses (also our own) plugins
relies on an Artifactory proxy repository
Are there any experiences out there on migrations from Maven to Gradle? Gotchas, pain points, corner cases? Any sort of experience is very welcome.
The migration from Maven to Gradle isn't as easy as from Ant to Maven (at the least at the moment). You can easily reuse Ant scripts and make them first class citizens in your Gradle build. There's a task on the Gradle roadmap for deep import of Maven builds as well.
So far I migrated two enterprise Maven builds to Gradle. Both of them were multi-module projects using standard Maven plugins. I basically rewrote the builds the Gradle way which requires at least some knowledge about Gradle. Based on my experience you can easily get the same build running in Gradle as well. Gradle doesn't really box you in here and is fairly flexible. Along the way you might find yourself having to write a custom plugin that doesn't exist yet depending on what Maven plugins you are using. However, there's already a wide breath of plugins out there. So far I haven't run into a real roadblock yet. Even though the Gradle documentation is pretty good you might find yourself reading a lot of Gradle forum posts to find the solution to one of your problems. Some of the standard Maven features are not supported out-of-the-box e.g. a provided scope or WAR inplace. However, there're easy ways around it. I haven't used Artifactory repositories. The ones I dealt with were Nexus repositories. As far as I know the Gradle guys have good support for Artifactory though. Edit: JFrog provides a Artifactory Gradle plugin.
A good way to start is to use the migration tool Maven2Gradle which let's you generate a Gradle script from your Maven build. Personally, I didn't use it yet. I developed the Gradle build side-by-side with the Maven build which didn't cause any trouble. Maven put its
output under target, Gradle under build. Make sure you prepare your team for the change. Let them try out the Gradle build and get familiar with the tool.
Once you are fully migrated you'll be very happy about the maintainability and extensibility of your build. It's very easy to add custom build logic and you're going to be grateful that you left XML-land. In terms of performance you are not going to make a step back as well. The incremental build feature does its job very well.
You may also want to read through this write-up of my experience porting a maven project to gradle.
In the directory where you have pom.xml just run the below command:
gradle init --type pom
This should convert your maven pom.xml to build.gradle
You can always change the buildDir to be 'target' under gradle if you want the build output to go under 'target' instead of 'build' like maven:
buildDir = 'target'
maven2Gradle seems to have been replaced with being able to run gradle init from the command line (though it's a rather experimental feature). It seems to work ok for doing some basic Gradle setup from a Maven project.
I am working on a fairly large project (with a number of modules, a bunch of external libraries etc.) and we are now considering switching from Ant to Maven. I understand the differences between the two, but I am not convinced that it is really worth spending time converting the project layout, setting up all the dependencies, teaching developers and configuration managers doing things "the new way" etc.
There are a lot of resources on the web describing how to migrate from Ant to Maven, but I haven't found that many that say why :-)
Before changing your build system, ask yourself (and the group) why you're changing? If you're changing just because Maven is the "new thing", don't. If you actually see a technical reason to migrate, do it.
In general, unless there's a major compelling reason to do so (new capabilities or much simpler management), I'd say stay with what you have for the current project, but consider Maven for future projects.
Have you read chapter 1 of "Maven, the definitive guide"? In particular, 1.7 Comparing Maven with Ant has an interesting discussion.
I agree with the other answers that advise caution. Maven has strong points, but nothing that can't be done by an Ant build process:
dependency management: Ant has the Ivy subproject, which can interact with Maven repositories.
convention over configuration: you can also do that with Ant, it's just a matter of establishing the rules and enforcing them.
build lifecycle: same as above, you can enforce a convention over the tasks exposed by each build.
build logic reuse (Maven plugins): you can also achieve that in Ant with macrodefs and task libraries.
The thing is, with Maven you get these features out-of-the-box, while with Ant you need a rock-solid build, a very strict set of rules and a way to enforce them (for instance, make sure that everyone follows the conventions when they create a new subproject, that they reuse the existing blocks instead of doing everything from scratch, etc.).
Personally, I would see how well the existing process addresses the issues above: how are dependencies managed, is there a central repository? Are the project structures uniform (when I checkout a project I don't know, how long does it take to figure out how to build it)? Is there some form of build logic reuse, or does each project reinvent the wheel? Which of these features are needed?
Then I would try to balance the cost of adding the missing features to the existing Ant script, against the cost of migrating to Maven (if you don't know Maven, that also includes the cost of learning it).
In any case, I suggest you build a small Maven prototype (5 to 10 projects) illustrating the common cases in your build. You can test a lot of Maven's features with dummy projects containing little java logic (use the archetype plugin to generate them).
Before Maven we were checking dependency libraries (typically third-party, open source variety) into source control - so that we could insure our components compiled and got packaged with the precise versions intended.
Now with Maven in place, we're relying on artifact repositories to hold those versions and we let our pom.xml dependency declarations be the official means of defining version dependencies. This has proven to be a simplifying approach that makes project organization in version control repositories (and their Hudson build projects) much easier to devise. Our local artifact repository is under backup policy along with our source control repositories. It's nice to use the Maven tools to go and search and specify a needed library version. We also use parent pom files to specify dependencies that other project poms inherit by default. So if you want all projects to use the same log4j version, then that is specified in one place in the parent pom file. (But any project can at anytime override and specify a specific version instead of just accepting the default from the parent pom.)
Here is the secret to a successful adoption of Maven:
Use Maven project build approach for
your new greenfield projects
Modify existing legacy projects that
use ant build.xml files to incorporate Maven task
for managing depenedencies (a hybrid
approach)
The benefit is that you can then get all of your projects under Maven dependency management, which is of course it's greatest benefit.
The nice thing about the Maven task for ant, where you specify all dependencies in a pom.xml file, is that it involves just modest modification of the existing ant build.xml file to incorporate Maven for this. From the ant file's perspective, Maven is just a means for defining classpath definitions, which are subsequently used by the various ant build task.
The Maven scope classifier of dependencies can be utilized when defining classpaths such that a suitable classpath can be set for compiling, running unit test, packaging, et al. Other definitions in the pom can also be accessed as ant property definitions.
A lot of existing ant build files are rather complex. It can be a formidable undertaking to convert such projects to a full Maven build process. This hybrid approach of having Maven manage all the dependencies and leave the bulk of the ant build.xml file as is, is most pragmatic.
First, like I'm sure a lot of people will mention, Ant and Maven are not exactly intended to solve the same goals. Since you said you understand what each provides, I won't get into the details of that, so suffice it to say that Ant lets you define the details of how to build individual components, while Maven manages the dependencies between components plus Maven lets you define a complete project build cycle from compile through test and deploy in a programmatic way.
I've used Maven on a couple projects in the past, and I just started using it on another one recently. There are plenty of articles on the net that compare Ant and Maven, so you can look at those, but from my experience, its always worthwhile to consider how you can improve a project. Dependency management and build lifecycle are two important aspects of any large project, and Maven helps in both those areas. If you already have a good build system in place using ant, and your dependencies are kept in a easy to access central location, and you don't plan on extending your build process to include any more advanced build management, then maybe you should stay with what you have.
On the other hand, if you want to use a continuous integration server like hudson or an artifact repository like nexus, then moving your project to maven can really help with build efficiency and automation. You probably would like maven in those situations because the full cycle from dependency to build to artifact can be achieved using those types of tools and you'll be able to better control your builds and releases. On my current project we have many modules and dependencies, like you mention. Migrating to maven so we could use hudson and nexus really helped because we could drop all those 3rd party jars into a nexus repository and stop having to check them into version control or email them around. Also, builds were out of hand because the CM people had a build plan as a document that they would sometimes follow, but making that part of your project (i.e., the pom.xml) defines how you are supposed to build and lets you enforce it. Maven is the glue that holds all of those things together.
In the end, its a matter of how long you expect the project to last, how good your process is now, whether you want to clean up your dependencies, whether you want to enforce your build plan, and whether you want to have the option to use continuous integration and artifact management. If you any of those things, Maven is a strong candidate.