Develop Reference

Using third-party libraries in Eclipse RCP Tycho app

I've created a boiler-plate project following vogella's extensive Tycho tutorial.
Facts:
There's no feature, and there's no plugin. The only plugin is the RCP app, which is also the entry-point.
Problem:
I have no idea in which pom.xml do I include the 3rd party dependencies.
I cannot include them in the RCP project, because the packaging of that pom is eclipse-plugin, and not jar. From what I've noticed, if I change the packaging to jar, then the "Maven Dependencies" library is added automatically. If I change back to eclipse-plugin, they get removed.
Questions:
Where do I add the dependencies? There's no pom with jar packaging in my project.
Should I create a separate project with the necessary JARs? How do I include that dependency to my entire project?
Is it really that much of a good practice to create a separate plugin and a feature for this RCP app?
Related solutions:
"Update projects" doesn't work, and neither do the n other solutions in the other SO questions.
There's also this question and that question, but I don't fully get the answers

I think that you have a fundamental misunderstanding.
Maven: Maven determines all of the project dependencies via the pom.xml and resolves transitive dependencies automatically (assuming that all of the pom files and artifacts exist in repositories that you've configured and correctly declare their dependencies).
Tycho: The problem is that Eclipse already has its own project model based on product files, feature.xml files, and plug-in MANIFEST.MF files. Tycho leverages the Maven machinery for Eclipse, but the idea is that the pom.xml files just configure the Maven plug-ins and declare the packaging type. That provides an entry point for Maven, but then Tycho takes over. While Maven would normally build the dependency chain from information in the pom.xml files, Tycho is building the dependency change from information in the product, feature, and MANIFEST.MF files. You don't put any dependencies in the pom.xml files. Tycho also uses Eclipse p2 repositories (instead of normal Maven repositories) for finding dependent plug-ins that are not found in the local modules or target platform.
That's actually a benefit for many Eclipse developers since they've already set up everything properly in their Eclipse plug-ins, features, and products. They do not want to have to repeat all of the dependencies in the pom.xml.
Using Libraries in Eclipse plug-ins: In Eclipse, if you want to use a library that is not already packaged as an Eclipse plug-in, you have a few options. Your plug-in can include a set of JARs in a libs folder and then include that libs folder in the plug-in and runtime classpath (see the build.properties file). Another option is to create your own "library plug-in" that repackages a JAR library as an Eclipse plug-in. See also https://wiki.eclipse.org/FAQ_What_is_the_classpath_of_a_plug-in%3F. That's the answer that you're getting above.
The problem is that if you're trying to include a complex library with multiple JARs that is normally distributed and included in a standard Java project via Maven. We hit this problem with the Jersey JAX-RS implementation in my project. There's no p2 repository that includes all of the pieces of the libraries as plug-ins with correct dependency information.
Easy Solution: If you need a common library, check the Orbit project first to see whether the libraries have already been packaged as Eclipse plug-ins, http://www.eclipse.org/orbit/. In that case, you can download them and include them in your target platform, or you can pull them in dynamically at (Tycho) build time from their p2 repository. Your plug-ins would just include those plug-ins as dependencies (in the their MANIFEST.MF files).
Workaround / Solution: In our case, Jersey JAX-RS was not available as an Eclipse plug-in, and it had a bunch of transitive dependencies. The workaround was to create an Eclipse "library plug-in" like I mentioned above with two pom files. We initially created a skeleton plug-in with an empty libs folder. One pom file is just a standard Maven pom file with <packaging>jar</packaging> that declares the top-level dependencies required to pull in the Jersey JAX-RS implementation and all of its dependencies. The dependencies are declared with <scope>compile</scope>. We use the maven-dependency-plugin to copy all of those dependencies into the project's libs folder.
<plugin>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>copy-dependencies</id>
<phase>compile</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>libs</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>
We actually ended up running Maven with that pom by hand from time to time to update the libs, and then we just checked the plug-in with all of its dependent JARs into source control. Checking the build later, I see that we actually populate the libs folder on-the-fly with Maven with a separate build task just before we start the Maven/Tycho part of the build. Of course, plug-in's MANIFEST-MF file's Bundle-ClassPath and Export-Package entries are coming straight from source control. We have to check those from time to time to ensure that they match the libraries and packages that we're getting from Maven. (That doesn't tend to change much unless we bump major library versions or add a new dependency at the Maven level.) The plug-in's build.properties has the libs/ folder as part of bin.includes.
In the development environment, after we first check out the code, we just run mvn (with an External Tools launch config that's also checked in with the project) on the project's "copy dependencies" pom file. That populates the libs folder with all of the JAX-RS libraries and dependencies. We only have to run it again when we update something about the dependencies or when we're jumping between branches that have different versions of the JAX-RS dependencies. We set .gitignore to ensure that we don't commit the libs to Git.
The other pom for this project is set up like a normal Tycho pom file with <packaging>eclipse-plugin</packaging>. During our automated build, we run one step early in the build process (just after check out) that calls mvn with the jar pom to populate the libs. Then we proceed with the main Maven/Tycho build using the eclipse-plugin pom. The eclipse-plugin pom has no dependency information (as I said above). It's just providing Tycho a way to recognize the Eclipse plug-in and build it based on its MANIFEST.MF and build.properties files. But the built plug-in includes and exposes all of those libs that were populated by the mvn call to the jar pom step.
So, it's a bit of a mess, but that's the best solution we found a couple of years ago when we hit this problem. I'm not sure whether Tycho is doing any work to permit some sort of hybrid Maven/Tycho build that could do this automatically as part of the build. I guess I should ask the developers. :)
Your questions:
Where do I add the dependencies? There's no pom with jar packaging in my project. Answer: The workaround above lets you do it with one project. You just have two pom files, like pom_deps.xml and pom.xml. You just have to invoke the pom_deps.xml separately to populate the libs folder (in the dev environment and with your automated builds).
Should I create a separate project with the necessary JARs? How do I include that dependency to my entire project? Answer: the workaround that I described above lets you do it with a single project. Another way to do it is to create a separate JAR project, but I don't think that your Eclipse RCP app can really include a <packaging>jar</packaging> module in a useful way. The only way I've found to do it is to use a similar workaround. You build the JAR module first, install it into the maven repository, and then have one of your plug-in projects bundle the JAR in its libs folder. (If you really want to do it that way, ask. We have a case where we have to do that, too, and I can provide the steps we do in development and the build to make it work. I think the single project workaround that I provided above makes more sense for your case.)
Is it really that much of a good practice to create a separate plugin and a feature for this RCP app? Answer: that's really a separate question. If you have a feature with multiple plug-ins, you have the same problem. Tycho can handle the product/feature/plug-ins, but it cannot jump across into Maven-based dependency resolution. You'll end up having to use the same workarounds
Summary: The fundamental issue is that Eclipse plug-ins can't "see" a bare JAR library. The plug-in needs to have the library included in its local libs folder (with a matching Bundle-ClassPath entry in MANIFEST.MF), or it needs to depend on some other plug-in that exports the appropriate packages. Tycho just resolves dependencies via Eclipse plug-ins, and it cannot leverage normal Maven dependency resolution directly to pull in a bunch of JARs. If all of your dependencies are already plug-ins, you're fine. If not, you may have to use the workaround above to package a set of libraries for your plug-ins to use.

Just adding the plugin to pom dependencies and including the entry <pomDependencies>consider</pomDependencies> in the configuration of target-platform-configuration makes it work.
<plugins>
<plugin>
<groupId>org.eclipse.tycho</groupId>
<artifactId>target-platform-configuration</artifactId>
<version>${tycho.version}</version>
<configuration>
<!-- The configuration to make tycho consider the maven dependencies -->
<pomDependencies>consider</pomDependencies>
<!-- other configurations -->
</configuartion>
</plugin>
<!-- other plugins-->
</plugins>
<dependencies>
<!-- An example third-party bundle (plugin) present in maven repository-->
<dependency>
<groupId>org.apache.felix</groupId>
<artifactId>org.apache.felix.gogo.shell</artifactId>
<version>1.1.0</version>
</dependency>
</dependencies>
Reference link here.

Can't see how to tell Maven to install jars on lib folder

Sorry if this is too trivial, but I've recently jumped into Wep Applications from standard console java projects, and since in java projects I successfully used maven to download jars and include them into the classpath... in the web app I don't know how to accomplish the same stuff and downloading to the lib folder on WEB-INF instead of just adding the jars to my classpath.
I have searched stack overflow and the google for an answer, but since I haven't found any single answer, I'm afraid I should be completely wrong with my approach for this.
I have just created my webapp on eclipse, then converted it to maven project, and then added this dependencies in pom.xml, as I used to do in a normal java project:
<dependencies>
<dependency>
<groupId>joda-time</groupId>
<artifactId>joda-time</artifactId>
<version>2.9.1</version>
</dependency>
</dependencies>
Everything seems to be ok, and no error is shown, but the jars are not downloaded into the WEB-INF/lib folder.
Thanks in advance for any help you can provide.

If your project is correctly configured as "Maven project" there should be a folder called "Maven Dependencies" in your package view.
A good hint if your project is configured as Maven project is a little "M" on the top level folder.
Eclipse will download in a so called "Repository". This is mostly located in $HOME/.m2
Generally you don't have to care about jars directly. Maven will download them and create a classpath transparently for you.
The eclipse maven integration is called m2e.
The concept of Repositories is central to maven. They are the place where your dependencies and external dependencies are stored. Two repositories you can always assume to exist are the already mentioned local one and the other so called "Maven-Central" see here. Beside that you can setup , for example, company wide Repositories with tools like Nexus or Artifactory.
To upload a dependency in your local Repo use the mvn install command.
What maven within mvn install is executing the install lifecycle.
and then uploads the resulting artifact (generally a jar or war, but not necessarily) and some metadata (your pom mainly) to the repository.
You can then develop against these dependencies via the dependency mecahnism.
Dependencies in you installed in your local Repository are always of type "SNAPSHOT". There is more to know about the difference between SNAPSHOT and Release (only version number) and how to deploy/release them, but these questions are already awnsered several times.

Adding this plugin to pom.xml will help to get jars in lib folder.
<plugin>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<phase>install</phase>
<goals>
<goal>copy-dependencies</goal>
</goals>
<configuration>
<outputDirectory>WebContent/WEB-INF/lib</outputDirectory>
</configuration>
</execution>
</executions>
</plugin>

Run app in tomcat using maven with IntelliJ

Without using maven, to run the app on tomcat from the Intellij IDE, all you have to do is create an artifact and a "tomcat" run configuration pointing to that artifact, this way you can see tomcat output, restart the server, and other stuff right in the IDE.
Now using maven, there's no need to create an artifact, because maven already does the compiling, packaging, etc.
I know i can deploy it using the command mvn tomcat7:redeploy but this way i can't see standart output/errors and debug.
So what is the standard way to run the app from IntelliJ without having to create an artifact?

In pom.xml add
<build>
<plugin>
<groupId>org.apache.tomcat.maven</groupId>
<artifactId>tomcat7-maven-plugin</artifactId>
<version>2.2</version>
<configuration>
<uriEncoding>UTF-8</uriEncoding>
<path>/your-path</path>
<update>true</update>
</configuration>
</plugin>
</build>
In IntelliJ, open Menu > View > Tool Windows > Maven Projects
Plugins > tomcat7 > tomcat7:run

If you have set
<packaging>war</packaging>
in your pom, IDEA should automatically identify the artifact (your WAR file) to deploy. No need to manually create an artifact.

When you setup this: n IntelliJ, open Menu > View > Tool Windows > Maven Projects, you will see this menu:
When you click on this picture you can enter the goal of Maven, for example tomcat7:run

Moving Eclipse M2E Web App Dependencies Into Project File System

I am currently working on a web app in Eclipse that I plan to push to Heroku. I am using the maven Eclipse plugin (m2e) for downloading dependencies for my app. Maven works great except for one thing.
Maven is downloading all my dependencies into ~/.m2 which is fine except for one thing. When I push my app up to Heroku those dependencies won't go up with it, so I need the dependencies within the project file system. So my problem is finding the best way (or any way in fact) to get the dependencies into my project.
I'm still a noob so any help is appreciated!

If you have a maven plugin in your eclipse, you can configure this directory on:
Window - Preferences -> Maven -> User Settings
But this is not you problem, because this maven file system is just to archive your repositories and the maven don need download it everytime.
Maybe you need to configure a war plugin in yout pom.xml.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-war-plugin</artifactId>
<version>2.1</version>
<configuration>
<failOnMissingWebXml>false</failOnMissingWebXml>
</configuration>
</plugin>

Multi Module Maven2 Project with WTP

I'm having a hard time to make my Maven2 multi module project, with a deep project structure, appear as a single ear (with its dependencies - which includes 1 war, 2 ejbs and 1 jar) to be deployed in my JBOSS 5 server inside my Eclipse Ganymede (tab Servers).
I've been trying to use Maven Eclipse Plugin to turn my projects into a WTP project without success. Therefore they appear to be deployed in the server they appear as separated projets.
My project has 1 war, 2 ejbs and 1 jar that must be packaged inside an ear, each of the "subprojects" is a separate module.
Project's pom.xml (type pom):
...
<modules>
<module>ejb1</module>
<module>ejb2</module>
<module>war</module>
<module>jar</module>
<module>ear</module>
</modules>
...
The ear module is only responsable to pack the other modules together.
Is there a way to tell eclipse (ganymede) that all those projects (ejbs, war and jar) are inside the ear module so I can deploy the ear in the server?

What you want to do is have maven create the eclipse projects via mvn eclipse:eclipse This might be helpful.

try m2eclipse (google it) and install the WTP integration tool, create a project using the maven wizard, change the type to pom in the pom xml editor, create a sub modules from the pom and that adds it as child, if its a web project it get the WTP behavior i.e it can be deployed to a j2ee container ( jboss / tomcat ), add a dep to the web module for ejb module in the web pom etc, deploy the web app to the container

Installing the m2eclipse with the optional WTP configuration worked for me. I also added the following to my parent pom to ensure the right natures and builders in the eclipse files
This yields eclipse .project files that are ready for m2eclipse. then I can Update the project files using m2eclipse allowing hot deploy the webapp and its dependencies
<build>
...
<plugin>
<artifactId>maven-eclipse-plugin</artifactId>
<version>2.5.1</version>
<!--
Eclipse project natures: http: //vikashazrati.wordpress.com/2007/12/22/adding-project-nature-to-your-maven-pomxml/
Maven-eclipse-plugin: http: //maven.apache.org/plugins/maven-eclipse-plugin/
-->
<configuration>
<additionalProjectnatures>
<projectnature>org.springframework.ide.eclipse.core.springnature</projectnature>
<projectnature>org.eclipse.jem.workbench.JavaEMFNature</projectnature>
<projectnature>org.eclipse.wst.common.modulecore.ModuleCoreNature</projectnature>
<projectnature>org.eclipse.wst.common.project.facet.core.nature</projectnature>
<projectnature>org.eclipse.jdt.core.javanature</projectnature>
<projectnature>org.eclipse.wst.jsdt.core.jsNature</projectnature>
<projectnature>org.maven.ide.eclipse.maven2Nature</projectnature>
</additionalProjectnatures>
<buildcommands>
<buildcommand>org.eclipse.wst.jsdt.core.javascriptValidator</buildcommand>
<buildcommand>org.eclipse.jdt.core.javabuilder</buildcommand>
<buildcommand>org.eclipse.wst.common.project.facet.core.builder</buildcommand>
<buildcommand>org.eclipse.wst.validation.validationbuilder</buildcommand>
<buildcommand>org.springframework.ide.eclipse.core.springbuilder</buildcommand>
<buildcommand>org.maven.ide.eclipse.maven2Builder</buildcommand>
</buildcommands>
</configuration>
</plugin>

use -Dwtpversion=2.0 parameter of maven or on command line mvn -Dwtpversion=2.0 in super pom project. i use m2eclipse plugin but has got some issues for multi module project. I use m2eclipse plugin for dependency management. If i want to clean, install etc. all project with super pom, i do it on command line. Also project properties must check in eclipse. Project Facets, Java EE Module dependencies must check. You can also export to ear project, but be carefull to check maven modules is compiled after changing.