Maven (Eclipse plugin and mvn) not including main class with pom.xml setup

Question

I've been trying to work this out for the last few hours and I've got nowhere. I've just installed the Maven for Eclipse plugin (M2E, I think) and also the maven too, mvn. I've created a very simple Hello World project and am trying to get the built jar to run on using: java -jar pimidi-0.0.1-SNAPSHOT.jar

Regardless of what I try, I always get the same error: no main manifest attribute, in target/pimidi-0.0.1-SNAPSHOT.jar

Here is my pom.xml:

<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>

    <groupId>com.dan</groupId>
    <artifactId>pimidi</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>pimidi</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>
<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-eclipse-plugin</artifactId>
            <configuration>
                <wtpversion>1.5</wtpversion>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <source>1.6</source>
                <target>1.6</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <version>2.4</version>
            <configuration>
                <archive>
                    <manifest>
                        <mainClass>com.dan.pimidi.App</mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>
    </plugins>
</build>

I've tried countless different options within the manifest nodes of the POM (classpath, manifest location), different plugins (assembly, compile, etc) to no avail. On looking at the effective POM in Eclipse, I can see that maven-jar-plugin is already included from a higher-level POM an any changes to the project POM are omitted.

Does anyone have any ideas about how to get this working? Apologies if this question lacks detail - I have expired my mental power for this evening. Any assistance would be greatly appreciated!

Answer 1

After following numerous pieces of advice, I decided to delete my project (which was only a mvn archetype), uninstall eclipse (to remove the m2e plugin) along with my ~/.m2 folder. I then did everything from the command line:

mvn archetype:generate -DgroupId=com.dan.pimidi -DartifactId=pimidi -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

Added this to my pom.xml:

<build>
        <plugins>
                <plugin>
                        <groupId>org.apache.maven.plugins</groupId>
                        <artifactId>maven-jar-plugin</artifactId>
                        <configuration>
                                <archive>
                                        <manifest>
                                                <mainClass>com.dan.pimidi.App</mainClass>
                                        </manifest>
                                </archive>
                        </configuration>
                </plugin>
        </plugins>
</build>

Then a quick:

mvn clean package

And a:

java -jar target/nameofjar.jar

Solved my problem!

Answer 2

Have you tried running:

mvn clean install exec:java

In the same folder as your pom.xml (from the root of your project)?