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.
Related
I want to list all maven dependencies (including transitive ones) of my gradle build with their licenses. Is this possible with the IntelliJ gradle plugin? If yes, how? Alternatively a gradle command line instruction would be sufficient, too.
I would recommend the license-gradle-plugin. It can report on licenses from your dependencies via the downloadLicense task.
For anybody who ends up here and discovered the license-gradle-plugin appears to be unmaintained, Gradle-License-Report works for this need as well.
The only plugin that has worked for my Android project is Gradle License Plugin
https://github.com/jaredsburrows/gradle-license-plugin
The setup was quite simple - just one line in the project-level build.gradle and another line in the app-level build.gradle. My project is relatively complex, but doesn't have multiple modules btw.
P.S. I've also tried https://github.com/hierynomus/license-gradle-plugin and https://github.com/jk1/Gradle-License-Report with no success.
You can also try the https://github.com/mikepenz/AboutLibraries
It covers the Kotlin Multiplatform as well.
Actually it covers any gradle type projects.
In general, how well does m2eclipse deal with Maven plugins that modify or amend lifecycle phases?
In particular, I have a project that has a maven-clean-plugin extension to remove an extra generated directory (not in target/) using the configuration filesets tag. This works when running mvn at the command line but not when doing a clean in Eclipse. Is there any way to get m2eclipse to process that plugin?
Another example is flexmojos; there's a lot that can be configured with the flexmojo plugin but those parameters don't seem to get imported by m2eclipse.
Is the integration solely ad-hoc? If m2eclipse embeds Maven, why can't the plugins be executed directly using the underlying pom.xml configuration?
In general, how well does m2eclipse deal with Maven plugins that modify or amend lifecycle phases?
Decently, to my experience. At least for plugin bound to phases from the default lifecycle.
In particular, I have a project that has a maven-clean-plugin extension (...). This works when running mvn at the command line but not when doing a clean in Eclipse. Is there any way to get m2eclipse to process that plugin?
What the clean plugin "extension" is doing and what you're doing (calling mvn clean from Eclipse? calling Project > Clean?) is unclear - at least for me. But maybe have a look at MNGECLIPSE-823 or MNGECLIPSE-156. And don't hesitate to clarify :)
Another example is flexmojos; there's a lot that can be configured with the flexmojo plugin but those parameters don't seem to get imported by m2eclipse.
I don't do flex so the above is too vague for me. But providing a more concrete example might help.
The past week or two I've been studying Maven, and I like it, but there are just a few things that I require Ant tasks for, rather than Maven's complicated and scarcely-documented POM file. However, I believe Maven has a great folder structure going for it, and I like that it natively supports tests, packages the project into a jar by default, and supports a 'resources' folder, from which everything is directly copied into the jar file.
Is there a sample Ant project out there that does the same sort of thing but with an Ant build.xml script? I want the placeholder folders and hello world app and test, just like Maven does when you first create a project from its default archetype:create goal (as demonstrated in the Maven in 5 Minutes page). Or, is there an even better Ant sample project out there that does more or suggests a better folder layout?
If no such thing exists, perhaps someone can help create it in a nice detailed answer? I would be willing to host a permanently-available zip file for anyone who finds this question in the future.
mvn archetype:create
mvn ant:ant
http://maven.apache.org/plugins/maven-ant-plugin/usage.html
... but if there are really "just a few things", you may want to check out the AntRun plugin instead. I'm not trying to sell you on Maven, believe me, but since it's not clear exactly what is stopping you from trying it with your project, I guess I'm suggesting you try to push the issue a little harder.
Refer this: Why you should use the Maven Ant Tasks instead of Maven or Ivy
I also wouldn't recommend Ivy, reasons at the link above.
Quoting the Maven - Frequently Asked Technical Questions and more precisely:
How can I use Maven features in an Ant build?
The Maven Ant Tasks allow many of the
features of Maven, such as dependency
management and repository deployment,
to be used in an Ant build.
Refer to the installation page and the usage page for instructions for installing and using the Maven Ant Tasks respectively. You'll find many links to samples in the usage page and a build.xml showing most of the features in action.
An alternative (direct competitor?) to Maven Ant Tasks would be Apache Ivy.
PS: While it's definitely a good idea to adopt maven standards, even partially, I'd really think about it twice before to drop Maven (but I live in the Maven jungle for a while now - and I like it - so I'm biased).
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.
I was wondering about the best way to manage projects dependencies from ant. What are the pros and cons of the Maven Ant task and of Ivy?
Since what you're wanting to do is add dependency management to an existing Ant project, that's precisely what Ivy's designed to do. Dependency management is a big part of Maven, but far from all of it. Maven is more of a project-oriented tool that does several other things in addition to dependencies. It would be worth considering if you were planning to migrate to Maven and use additional Maven features as well, but it's a bit much if all you'd use it for is to spin off Ant.
Your type of dependencies and your expectations for how they behave will also make a difference. Pulling third-party dependencies is almost trivial in Maven, while Ivy excels in rebuilding your own dependent components. In either case, the tools won't provide decent build, versioning, and repository policies, those are still up to you and needed to get the configuration right.
Ant + Ivy == A campground, where people use the facilities as needed.
Maven == A resort, where you rely on someone else to provide services.
Maven is easier for a team lacking build/integration experience, but when the team needs to diverge from Maven standards they will find themselves reaching for groovy, gradle, and the lack of solid documentation will become frustrating.
Ant + Ivy will take longer to startup a project, but if the team has build/integration experience they can tailor the build system around they way they develop and release code.
In engineering... technology companies I always push for the campsite solution versus the resort.
It is amazing though that both Ant and Maven choose XML as their langauge to express build recipes with. The Java community is stuck on that XML...
I think this blog post covers exactly what the OP is looking for:
Why you should use the Maven Ant Tasks instead of Maven or Ivy
Ivy+Ant is far, far more flexible. Ivy does dependency management, period, and it does that extremely well, better than Maven. And with Ant you can pretty much put together any build system that you want.
Maven tries to control everything - the "lifecycle" (compile, test, package, etc.), where files should live, and so on. Have fun customizing plugins and the like if you don't like the "Maven way".
Maven is the answer to a question no one asked. Writing an Ant script is not hard, and Ivy gives you better dependency management than Maven. I am confused by some of the previous comments stating they couldn't get Ivy working. Ivy is quite a bit simpler than Maven to get up and running.
The Spring Framework uses Ivy in its build process. I think that can be seen as quite a vote of confidence for Ivy.
If your long term goal is to migrate to using Maven to manage the entire build process (which one might intend to do for new greenfield projects), then I heartily recommend using Maven pom.xml files to manage dependencies on behalf of Ant build.xml files. The end result is that both your greenfield projects and your legacy projects are then all using the same mechanism to manage dependencies. And it turns out Maven really does a better job of managing dependencies for Ant build.xml files than does Ivy.
Prior to adopting Maven as our flagship build tool, I had a developer attempt to use Ivy in combination to existing Ant build.xml files. This was most frustrating experience that very soon lead us to reject Ivy. We went ahead with an adoption of Maven. Our greenfield projects began to be built with the stock Maven approach, etc.
However, I went back to the Ant legacy projects and started using the Maven Ant task to define classpath definitions (and occasionally other Ant property definitions pulled in from the pom.xml). This turned out to be a most superlative experience. The existing Ant build.xml files need only be modified slightly to use Maven ant integration to define any classpath that were in use in the build.xml file. All dependencies required by the project became defined in an accompanying pom.xml file that gets processed by Maven via the Ant task incorporated into the build.xml files.
Maven scopes can be used to fine tune classpath definitions such that one suitable for compiling, or running unit test, or for packaging, et al, can be established. Also, pretty much any element of something defined in the pom.xml file can be referenced as an Ant property within the build.xml file.
Really with the Ant task for Maven there is no viable reason for Ivy to even exist.
Comparing Maven with ivy/ant is to compare a smartphone to telegraphy.
If you want to leverage a real enduring effect in your build infrastructure, it's better to use Maven because it anticipates and abstracts all processes and tasks every software project or other software-like project is faced with. I took part in many projects and if your projects get more complex and more diverse and more heterogeneous, you will praise even more the simplicity of a Maven project configuration. Indeed, it will become complex but not complicated compared to ivy/ant-driven projects.
The main advantage of Maven is "convention over configuration" (http://en.wikipedia.org/wiki/Convention_over_configuration) a very important paradigm. In short, this means that you don't need to know/configure things that are obvious/trivial/commonplace. Although Maven and all its plugins ship with many default-settings, you always have the option to configure your projects for your special needs. With Maven, on the one hand you can setup a project very easy and quickly; on the other hand, you can customize a growing project up to your needs with minimum effort. If you have understood the key concepts behind Maven you will leverage every project and also projects that are not typical software development projects as well.
In the past, I wrote many ant scripts and with upcoming Maven I began to hate ant. One disadvantage is that you always copy scripts and repeat yourself, develop ant tasks that don't repeat tasks that don't repeat tasks that don't repeat... And the main disadvantage is that growing ant scripts tend to get unmaintainable, especially if a dozen ant geeks want to pimp up each others ant scripts.
Many ant-enthusiasts suffer from getting overall control over trivial things like copying of artifacts and printing buildmessages. But because Maven's key concept is to hide these trivial things the legend will forever keep alive that Maven restricts customization needs. But don't worry, that’s a legend! And so you finally understand my initial statement: don't bother with trivial things that are already solved.
Maybe ivy/ant is an option for simple projects but for complex growing projects you need simplicity and conventions. Otherwise you will be overwhelmed with more and more maintaining problems. Especially if you have many dependent projects, technologies and heterogeneous product parts in a global project you don't have time and money for developing and testing ant scripts or solving dependency problems.
Another advice should be mentioned: Ant offers the integration of Maven. This integration is often used to test and play with maven in projects that are grown up with ant. Avoid this stupid approach because it generates more problems. Instead stay with ant and its pain or migrate fully to maven.
If you are in doubt about the migration costs I suggest you to use the contrary way of integrating that different worlds by the Maven-Ant-Plugin. With this standard plugin you can run every ant-script without any effort. Sure it’s a legacy solution for a while, but it gives you as much time you need to understand mega-lines of monstrous distorted uncommented ant scripts of your predecessor.
And now you will praise the next advantage of maven: You need very less documentation of your configuration, because documentation is part of every maven-plugin you want to use.
So I confess I was a Maven-Antagonist.
I know that one advantage of Ivy is that it can use different kinds of repositories. Maven is typically very rigid in the format of the repository it will use. That's all I know.
I've just spent 2 days reading through the Ivy documentation and I have to say, USE MAVEN if you have any kind of choice. Ivy is complete and utter garbage as far as I can tell. I just wasted 2 days trying to incorporate it into my build and am cutting my losses now. Why?
Ivy is a half-assed attempt at dependency management
Ivy documentation is a total joke
Ivy examples and tutorial are useless
As soon as I introduced 'configurations' (read as maven profiles), Ivy started going bezerk downloading all sorts of junk I don't need then failing. The documentation for Ivy is an utter joke. Maven documentation in comparison reads like a dream. If you want an example of how impenetrable and badly written the Ivy documentation is, take a look at the reference page for configurations. These are an essential part of any build, but in Ivy they seem to be a badly designed after thought.