Maven - Can't Execute JAR

Question

After building a sample mvn project, I added my org.restlet dependencies & Java code.

Then, I successfully built my JAR via mvn install. Finally, I ran into an error when trying to run the JAR.

vagrant$ java -jar target/my-app-1.0-SNAPSHOT.jar 
Failed to load Main-Class manifest attribute from
target/my-app-1.0-SNAPSHOT.jar

It's above - `Failed to load Main-Class manifest attribute from target/my-app-1.0-SNAPSHOT.jar` — Kevin Meredith, Apr 13 '13 at 16:47
instead of executing "java -jar", can you place your jar in classpath and try to run something like "java MainClass" — Lokesh, Apr 13 '13 at 16:49

score 39 · Accepted Answer · edited May 23 '17 at 11:47

39

You need to set the main class in the manifest using the maven-jar-plugin

    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <configuration>
            <archive>
                <manifest>
                    <mainClass>com.someclass.Main</mainClass>
                </manifest>
            </archive>
        </configuration>
    </plugin>

Taken from here.

EDIT

If you want to package the resulting jar with dependencies you can use this

<plugin>
  <artifactId>maven-assembly-plugin</artifactId>
  <configuration>
    <archive>
      <manifest>
        <mainClass>fully.qualified.MainClass</mainClass>
      </manifest>
    </archive>
    <descriptorRefs>
      <descriptorRef>jar-with-dependencies</descriptorRef>
    </descriptorRefs>
  </configuration>
  <executions>
    <execution>
      <id>make-assembly</id>
      <phase>package</phase>
      <goals>
        <goal>single</goal>
      </goals>
    </execution>
  </executions>
</plugin>

Taken from here.

edited May 23 '17 at 11:47

Community

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1

answered Apr 13 '13 at 16:51

Boris the Spider

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If my package = `com.mycompany.app` and my main class is `com.mycompany.app.MailServerApplication`, `` = latter? – Kevin Meredith Apr 13 '13 at 17:07
Yup, the fully qualified class name of a class that has a `public static void main(String[] args)`. – Boris the Spider Apr 13 '13 at 17:10
Thanks. Looks like I have my next issue to resolve: `vagrant$ java -jar target/my-app-1.0-SNAPSHOT.jar` Exception in thread "main" java.lang.NoClassDefFoundError: org/restlet/Application – Kevin Meredith Apr 13 '13 at 17:14
1

Looks like you need to set a classpath or [package into a single file](http://stackoverflow.com/a/574650/2071828). – Boris the Spider Apr 13 '13 at 17:20

score 4 · Answer 2 · edited Jul 03 '17 at 16:52

4

If you dont have a manifest in your jar invoking java -jar will not work.

Use this command if you dont have a manifest:

java -cp foo.jar full.package.name.ClassName

edited Jul 03 '17 at 16:52

seriousdev

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answered Apr 13 '13 at 16:52

TheEwook

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Hmm: `vagrant$ java -jar target/my-app-1.0-SNAPSHOT.jar com.mycompany.app.MailServerApplication` Failed to load Main-Class manifest attribute from target/my-app-1.0-SNAPSHOT.jar – Kevin Meredith Apr 13 '13 at 17:10
Check your MANIFEST.MF in your jar – TheEwook Apr 13 '13 at 17:11
6

I think you are thinking of `java -cp foo.jar full.package.name.ClassName`. This answer isn't correct. -1 – Boris the Spider Apr 13 '13 at 17:11
@bmorris no no, `java -jar foo.jar full.package.name.ClassName` is the command to execute. Maybe `java -cp` work but I have always used `java -jar` – TheEwook Apr 13 '13 at 17:13
Take a look at the [docs](http://docs.oracle.com/javase/1.5.0/docs/tooldocs/windows/java.html) - "If the -jar option is specified, the first non-option argument is the name of a JAR archive containing class and resource files for the application, with the startup class indicated by the Main-Class manifest header." – Boris the Spider Apr 13 '13 at 17:14

Maven - Can't Execute JAR

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