Posts Tagged ‘m2eclipse’
  • Migrating from m2eclipse to m2e

    Since Indigo, the Maven Ecliple plugin formerly known as m2eclipse became part of Eclipse release (at least in the pure Java release). The name of the plugin also changed from m2eclipse to m2e. This was not the sole change, however:

    • The number of tabs on the POM has shrinked drastically, and the features as well. This will probably be the subject of a later post since I feel quite cheated by the upgrade.
    • The POM configuration has been more integrated with Eclipse build (which can cause unwanted side-effects as I described in my last article).

    More importantly, projects that began with m2eclipse can be built in Indigo but no contextual Maven menu is accessible on the project itself (though a contextual menu is available on the POM).

    In order to migrate flawlessly and have our contextual menu back, some actions are necessary. They are gruesome because it involves updating by hand Eclipse configuration file.

    Warning: at this point, you have the choice to stop reading. If you decide to continue and use the process described below, it’s at your own risk!

    The Maven plugin recognizes a project as a Maven one based the .project Eclipse proprietary configuration file. To display it, go to the Project Explorer view, click on the scrolling menu at the top right and choose Customize View. You have to uncheck *.resources: along the .project file , you should see a .classpath file as well as a .settings folder.

    1. In the .project:
      • Replace org.maven.ide.eclipse.maven2Builder by org.eclipse.m2e.core.maven2Builder in the buildSpec section
      • Replace org.maven.ide.eclipse.maven2Nature by org.eclipse.m2e.core.maven2Nature in the natures section
    2. In the .classpath, replace org.maven.ide.eclipse.MAVEN2_CLASSPATH_CONTAINER by org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER
    3. Finally, in the .settings folder, rename the org.maven.ide.eclipse.prefs file to org.eclipse.m2e.core.prefs. Contents should be left unchanged.

    Now, the contextual menu should appear and work accordingly.

    Remember, this is a big hack you should only use with the right parachute (at least a source control management system) since it will hurt you plenty if it fails. For me, it has always worked… yet.

    Categories: Java Tags: eclipsem2eclipsemaven
  • Better Maven integration leads to unforeseen consequences (bugs)

    This week, I was faced with what seemed an near-insuperable problem. I was called by one of my dev: as soon as he upgraded his Eclipse (or more precisely, our own already-configured Eclipse), he couldn’t deploy to Tomcat through WTP. Here are the steps I took to resolve the problem and more general thoughts about upgrading and tooling.

    The log displayed a ClassNotFoundException, one involving Spring. So, the first step is to look under the hood. Provided you used the default configuration - to use workspace metadata - it should be located under <WORKSPACE>/.metadata/.plugins/org.eclipse.wst.server.core/tmp<i>/wtpwebapps where WORKSPACE is your workspace location and i is an incremental number beginning with 0 assigned by Eclipse to each virtual application server in WTP. There you should see the applications deployed in Eclipse. When I checked, I realized the application was deployed alright, but found no WEB-INF/lib folder.

    I had already experienced such deployment problems: I solved them by first forcing publish (right-click on the server and choose Publish) and if not successful, cleaning (it removes all deployment and starts again from scratch). Well, this didn’t work.

    Also, sometimes classes are not deployed because there aren’t there in the first place: compilation doesn’t occur (because of bad code or Eclipse may be playful) and this prevents generating .class files. This didn’t seem like the problem but hell, this was a lead like any other. In order to force compilation, clean the project and check recompile afterwards (or check auto build is on). This didn’t work too…

    It happened before that closing the project and reopening it resolved some code-unrelated compilation problems. Closing and restarting Eclipse may yield the same results. I did both to no avail. At this point, I was disappointed because all previous steps should have resolved the problem… yet they hadn’t.

    Since the project used Maven (and we had m2eclipse installed), I also checked the Maven Dependencies library was correctly referenced: it was. Just to be sure, I disabled and re-enabled dependencies management. Guess what? Nothing changed.

    Desperate, I hopelessly browsed through the POM and the following caught my attention:


    This configuration creates skinny WARs so that libraries are not packaged in the WAR but are in the EAR, provided they are referenced, of course (for the right way to create such WARs, see my post from last week). With a faint gleam of hope, I removed the configuration part and it worked, the libraries were finally deployed.

    Yes, dear readers, it seems newer versions of the m2eclipse plugin are able to parse some portions of the POM that were not parsed before and act accordingly. Although this is a good news in general, it means we have to carefully check about potential side-effects of upgrading to those newer versions. Of course, this was stupid to upgrade in the first place but think that sometimes it’s mandatory for a newer project.

    However, the problem is much more widespread than m2eclipse. It’s very similar to issues adressed in Andrew Spencer’s post, only more so since if we don’t upgrade, we may have to keep an Eclipse instance for each project, that has to be shared between all team members. Right now, I don’t have any solutions for this problem, apart from changing the code to keep in synch with the tool.

    PS : since we still wanted to have skinny WARs, I just moved the configuration part in a profile… which was what was configured in the archetype provided by the support team :-)

    Categories: JavaEE Tags: m2eclipsemaven
  • Top Eclipse plugins I wouldn't go without

    Using an IDE to develop today is necessary but any IDE worth his salt can be enhanced with additional features. NetBeans, IntelliJ IDEA and Eclipse have this kind of mechanism. In this article, I will mention the plugins I couldn’t develop without in Eclipse and for each one advocate for it.


    Maven is my build tool of choice since about 2 years. It adds some very nice features comparing to Ant, mainly the dependencies management, inheritance and variable filtering. Configuring the POM is kind of hard once you’ve reached a fairly high number of lines. The Sonatype m2eclipse plugin (formerly hosted by Codehaus) gives you a tabs-oriented view of every aspect of the POM:

    • An Overview tab neatly grouped into : Artifact, Parent, Properties, Modules, Project, Organization, SCM, Issue Management and Continuous Integration,

      m2eclipse Overview tab

    • A Dependencies tab for managing (guess what) dependencies and dependencies management. For each of the former, you can even exclude dependent artifacts. This tab is mostly initialized at the start of the project, since its informations shouldn’t change during the lifecycle,
    • A Repositories tab to deal with repositories, plugin repositories, distribution, site and relocation (an often underused feature that enable you to change an artifact location without breaking builds a.k.a a level of indirection),
    • A Build tab for customizing Maven default folders (a usually very bad idea),
    • A Plugins tab to configure and/or execute Maven plugins. This is one of the most important tab since it’s here you will configure maven-compiler-plugin to use Java 6, or such,
    • A Report tab to manage the ` part,
    • A Profiles tab to cope with profiles,
    • A Team tab to fill out team-oriented data such as developers and contributors information,
    • The most useful and important tab (according to me) graphically displays the dependency tree. Even better, each scope is represented in a different way and you can filter out unwanted scope.

      m2eclipse Dependencies tab

    • Last but not least, the last tab enables you to directly edit the underlying XML.

    Moreover, m2eclipse adds a new Maven build Run configuration that is equivalent for the command line:

    m2eclipse Run Configuration

    With this, you can easily configure the -X option (Debug Output) or the -Dmaven.test.skip option (Skip Tests).

    More importantly, you can set up the plugin to resolve dependencies from within the workspace during Eclipse builds; that is, instead of using your repository classpath, Eclipse will use the project’s classpath (provided it is in the desired version). It prevents the need to build an artifact each time it is modified because another won’t compile after the change. It merely duplicates the legacy Eclipse dependency management.

    I advise not to use the Resolve Workspace artifacts in the previous Run configuration because it will use this default behaviour. In Maven build, I want to distance myself from the IDE, using only the tool’s features.

    TestNG plugin

    For those not knowing TestNG, it is very similar to JUnit4. It was the first to bring Java 5 annotations (even before JUnit) so I adopted the tool. Now as to why I keep it even though JUnit4 uses annotations: it has one important feature JUnit has not. You can make a test method dependent on another, so as to develop test scenarios. I know this is not pure unit testing anymore; still I like using some scenarios in my testing packages in order to test build breaks as early as possible.

    FYI, Maven knows about TestNG and runs TestNG tests as readily as JUnit ones.

    The TestNG plugin for Eclipse does as the integrated JUnit plugin does, whether regarding configuration or run or even test results.

    TestNG Plugin Run configuration


    When developing, and if one uses tests, one should know about one’s test coverage over code. I used to use Cobertura Maven plugin: I configured in the POM and, every once in a while, I ran a simple mvn cobertura:cobertura. Unfortunately, it is not very convenient to do so. I searched for an Eclipse plugin to have the same feature; alas, there’s none.  However, I found the EclEmma Eclipse plugin that brings the same functionality. It uses Emma (an OpenSource code coverage tool) under the hood and, though I searched thoroughly, Emma has no Maven 2 plugin. Since I value equally IDE code coverage during development and Maven code coverage during nightly builds (on a Continuous Integration infrastrcuture), so you’re basically stuck with 2 different products. So?

    EclEmma line highlighting

    ElcEmma provides a 4th run button (in addition to Run, Debug and External Tools) that launches the desired run configuration (JUnit, TestNG or what have you) in enhanced mode, the latter providing the code coverage feature. In the above screenshot, you can see line 20 was not run during the test.

    Even better, the plugin provides a aggregation view for code coverage percentage. This view can be decomposed on the project, source path, package and class levels.

    EclEmma statistics

    Spring IDE

    Spring does not need to be introduced. Whether it will be outed by JEE 5 dependency injection annotations remains to be seen. Plenty of projects still use Spring and that’s a fact. Still, XML configuration is very ankward in Spring in a number of cases:

    • referencing a qualified class name. It is not neither easy nor productive to type it; the same is true for properties
    • understanding complex or big configurations files
    • referencing a Spring bean in a hundred or more lines of file
    • refactoring a class name or a property name without breaking the configurations files
    • being informed of whether a class is a Spring bean in a project and if so, where it is used

    Luckily, Spring IDE provides features that make such tasks easy as a breeze:

    • auto-completion on XML configuration files
    • graphic view of such files

      Spring IDE Graph View

    • an internal index so that refactoring is takes into account the XML files (though I suspect there is some bugs hidden somewhere for I regularly have errors)
    • a enhanced Project Explorer view to display where a bean is used

      Spring Project Explorer View

    This entire package guarantees a much better productivity when using XML configuration in Spring than plain old XML editor. Of course, you can still use Annotation configuration, though I’m reluctant to do so (more in a latter post).

    I conclusion, these 4 integration plugins mean I feel really more comfortable using their underlying tools. If I were in an environment where I couldn’t update my Eclipse however I choose, I would definitely think about using these tools at all (except Maven), or use Annotations configuration for Spring. You can have exceptional products or frameworks, they have to integrate seamlessly into your IDE(s) to really add value: think about the fate of EJB v2!