Udun's Labs

Mavenize an Eclipse Project

I had a simple eclipse java SE project and I wanted to start using maven (in 5 Minutes) for dependency management. What I did was (eclipse Luna, JEE pack - comes with m2e plugin [1.5.0.20140524-0005]):

  • RClick on the project > Configure > Convert to Maven project

  • Maven Pom dialogue: I had to choose group id, artifact id etc. Had a look at Guide to naming conventions on groupId, artifactId and version, Maven artifact and groupId naming, Maven artifact and group naming conventions. Ok - pick a groupId (should be unique), an artifact Id (will be the name of your jar minus the version) and a version (have to decide on a scheme for this - must read: Understanding Maven Version Numbers. Have also a look at How do I tell Maven to use the latest version of a dependency?). Enter a name and description for your project.

  • Maven dependencies dialogue: Identify existing project references as Maven dependencies:

    images

    well at a loss here… Glad it found Junit. I left the “Delete original references from project” unticked. It went on to create the POM. Now I cheated a bit here.

    • I had already tried once and saw the Unidentified dependencies pictured above. Well - hamcrest was resolved but jgrapht not - resulting in build errors. What I had to do was google “maven jgrapht 0.9.0” and at long last end up here. Copied:

      <dependency>
    <groupId>org.jgrapht</groupId>
    <artifactId>jgrapht-core</artifactId>
    <version>0.9.0</version>
</dependency>

      in the pom and was good to go.

    • Now the second time I followed the same procedure (after --hard reseting the branch) apparently m2e kept the jgrapht jar in its cache. So despite the fact the jars showed as unidentified the second time round I had no built errors. Actually I don’t know what the reason was but the diff from the first time up to the second was:

       $ git diff 1stTry 2ndTry
 diff --git a/.classpath b/.classpath
 index a92a607..c5171d8 100644
 --- a/.classpath
 +++ b/.classpath
 @@ -11,6 +11,8 @@
            <attribute name="maven.pomderived" value="true"/>
        </attributes>
    </classpathentry>
 +  <classpathentry kind="con" path="org.eclipse.jdt.USER_LIBRARY/jgraph"/>
 +  <classpathentry kind="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/4"/>
    <classpathentry kind="con" path="org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER">
        <attributes>
            <attribute name="maven.pomderived" value="true"/>
 diff --git a/.settings/CCM_RUN.launch b/.settings/CCM_RUN.launch
 index 3cc26b2..632106d 100644
 --- a/.settings/CCM_RUN.launch
 +++ b/.settings/CCM_RUN.launch
 @@ -6,8 +6,6 @@
 <listAttribute key="org.eclipse.debug.core.MAPPED_RESOURCE_TYPES">
 <listEntry value="1"/>
 </listAttribute>
 -<stringAttribute key="org.eclipse.jdt.launching.CLASSPATH_PROVIDER" value="org.eclipse.m2e.launchconfig.classpathProvider"/>
 <stringAttribute key="org.eclipse.jdt.launching.MAIN_TYPE" value="gr.uoa.di.mde515.Main"/>
 <stringAttribute key="org.eclipse.jdt.launching.PROJECT_ATTR" value="project"/>
 -<stringAttribute key="org.eclipse.jdt.launching.SOURCE_PATH_PROVIDER" value="org.eclipse.m2e.launchconfig.sourcepathProvider"/>
 </launchConfiguration>
 diff --git a/pom.xml b/pom.xml
 index 0f9e725..dffb4a5 100644
 --- a/pom.xml
 +++ b/pom.xml
 @@ -1,20 +1,17 @@
 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    #### UNIMPORTANT ###
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
        </dependency>
 -      <dependency>
 -          <groupId>org.jgrapht</groupId>
 -          <artifactId>jgrapht-core</artifactId>
 -          <version>0.9.0</version>
 -      </dependency>
    </dependencies>
    <build>
        <sourceDirectory>src</sourceDirectory>

      It seems the second time it kept jgrapht as an eclipse lib. Dunno. Runs fine.

  • I added the jgrapht as a maven dependency - as well as logging:

      +       <dependency>
  +           <groupId>ch.qos.logback</groupId>
  +           <artifactId>logback-classic</artifactId>
  +           <version>1.1.2</version>
  +       </dependency>
  +       <dependency>
  +           <groupId>org.jgrapht</groupId>
  +           <artifactId>jgrapht-core</artifactId>
  +           <version>0.9.0</version>
  +       </dependency>

    yep - that’s all (see Dependency management for SLF4J and Logback). Wow !

  • But now I wanted to add the logging configuration (must read: How to setup SLF4J and LOGBack in a web app - fast). In this article (from where I downloaded the logback[-test].xml) it is said that these files belong in the src/[main|test]/resources folder. Great. I went ahead and manually moved the src to src/main/java, deleted src in Build path > source folders and added src/main/java. Classpath:

      -   <classpathentry kind="src" output="target/classes" path="src">
  -       <attributes>
  -           <attribute name="optional" value="true"/>
  -           <attribute name="maven.pomderived" value="true"/>
  -       </attributes>
  -   </classpathentry>
  +   <classpathentry kind="src" path="src/main/java"/>

    Then tried to Alt+F5 (RClick > Maven > Update Project…) but I had the “nesting errors”:

MESSAGE Cannot nest ‘project/src/main/java’ inside ‘project/src’. To enable the nesting exclude ‘main/’ from ‘project/src’

Gibberish. Solved in Eclipse Build Path Nesting Errors. Basically there was a line in the pom that caused the problem - hitting then Alt+F5 modified the classpath:

---------------------------------- .classpath ----------------------------------
index 37a3013..982ad3d 100644
@@ -1,6 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <classpath>
-   <classpathentry kind="src" path="src/main/java"/>
+   <classpathentry kind="src" output="target/classes" path="src/main/java">
+       <attributes>
+           <attribute name="optional" value="true"/>
+           <attribute name="maven.pomderived" value="true"/>
+       </attributes>
+   </classpathentry>
    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.7">
        <attributes>
            <attribute name="maven.pomderived" value="true"/>
@@ -12,5 +17,11 @@
            <attribute name="maven.pomderived" value="true"/>
        </attributes>
    </classpathentry>
+   <classpathentry kind="src" output="target/test-classes" path="src/test/java">
+       <attributes>
+           <attribute name="optional" value="true"/>
+           <attribute name="maven.pomderived" value="true"/>
+       </attributes>
+   </classpathentry>
    <classpathentry kind="output" path="target/classes"/>
 </classpath>

----------------------------------- pom.xml -----------------------------------
index 6b5f4af..8f37398 100644
@@ -24,7 +24,6 @@
        </dependency>
    </dependencies>
    <build>
-       <sourceDirectory>src</sourceDirectory>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>

So m2e actually automatically added a test folder (which was not created resulting in an error in the build path - but not on the markers view - you need to open the build path to see it). So what about the resources folders ? Well just create two new folders (NOT source folders) and hit Alt+F5. Boom:

6/12/14, 12:57:19 AM GMT+1: [INFO] Update started
6/12/14, 12:57:19 AM GMT+1: [INFO] Using org.eclipse.m2e.jdt.JarLifecycleMapping lifecycle mapping for MavenProject: gr.uoa.di.mde515.ccm:ccm:0.0.1-SNAPSHOT @ C:\Dropbox\eclipse_workspaces\javaSE\hw2_db\pom.xml.
6/12/14, 12:57:19 AM GMT+1: [INFO] Adding source folder /hw2_db/src/main/java
6/12/14, 12:57:19 AM GMT+1: [INFO] Adding resource folder /hw2_db/src/main/resources
6/12/14, 12:57:19 AM GMT+1: [INFO] Adding source folder /hw2_db/src/test/java
6/12/14, 12:57:19 AM GMT+1: [INFO] Adding resource folder /hw2_db/src/test/resources
6/12/14, 12:57:19 AM GMT+1: [ERROR] The resource tree is locked for modifications.
6/12/14, 12:57:19 AM GMT+1: [INFO] Using org.eclipse.m2e.jdt.JarLifecycleMapping lifecycle mapping for MavenProject: gr.uoa.di.mde515.ccm:ccm:0.0.1-SNAPSHOT @ C:\Dropbox\eclipse_workspaces\javaSE\hw2_db\pom.xml.
6/12/14, 12:57:19 AM GMT+1: [INFO] Update completed: 0 sec
6/12/14, 12:57:20 AM GMT+1: [WARN] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent!
6/12/14, 12:57:20 AM GMT+1: [INFO] Copying 0 resource
6/12/14, 12:57:20 AM GMT+1: [WARN] Using platform encoding (Cp1252 actually) to copy filtered resources, i.e. build is platform dependent!
6/12/14, 12:57:20 AM GMT+1: [INFO] Copying 0 resource

Dunno if I should worry about [ERROR] The resource tree is locked for modifications. Alt+F5 produces:

---------------------------------- .classpath ----------------------------------
index 982ad3d..8e85ec6 100644
@@ -23,5 +23,15 @@
            <attribute name="maven.pomderived" value="true"/>
        </attributes>
    </classpathentry>
+   <classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
+       <attributes>
+           <attribute name="maven.pomderived" value="true"/>
+       </attributes>
+   </classpathentry>
+   <classpathentry excluding="**" kind="src" output="target/test-classes" path="src/test/resources">
+       <attributes>
+           <attribute name="maven.pomderived" value="true"/>
+       </attributes>
+   </classpathentry>
    <classpathentry kind="output" path="target/classes"/>
 </classpath>

Great. Now that I seem to get the hang of it I will turn to WTP project mavenizing.

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