[maven-2] Setting Java heap space under Maven 2 on Windows

I get this message during build of my project

java.lang.OutOfMemoryError: Java heap space

How do I increase heap space, I've got 8Gb or RAM its impossible that maven consumed that much, I found this http://vikashazrati.wordpress.com/2007/07/26/quicktip-how-to-increase-the-java-heap-memory-for-maven-2-on-linux/ how to do it on linux, but I'm on windows 7. How can I change java heap space under windows ?

If you are running out of heap space during the surefire (or failsafe) JUnit testing run, changing MAVEN_OPTS may not help you. I kept trying different configurations in MAVEN_OPTS with no luck until I found this post that fixed the problem.

Basically the JUnits fork off into their own environment and ignore the settings in MAVEN_OPTS. You need to configure surefire in your pom to add more memory for the JUnits.

Hopefully this can save someone else some time!

Edit: Copying solution from Keith Chapman's blog just in case the link breaks some day:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <configuration>
    <forkMode>pertest</forkMode> 
    <argLine>-Xms256m -Xmx512m</argLine>
    <testFailureIgnore>false</testFailureIgnore> 
    <skip>false</skip> 
    <includes> 
      <include>**/*IntegrationTestSuite.java</include>
    </includes>
  </configuration>
</plugin>

Update (5/31/2017): Thanks to @johnstosh for pointing this out - surefire has evolved a bit since I put this answer out there. Here is a link to their documentation and an updated code sample (arg line is still the important part for this question):

  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <version>2.20</version>
    <configuration>
        <forkCount>3</forkCount>
        <reuseForks>true</reuseForks>
        <argLine>-Xmx1024m -XX:MaxPermSize=256m</argLine>
        <systemPropertyVariables>
            <databaseSchema>MY_TEST_SCHEMA_${surefire.forkNumber}</databaseSchema>
        </systemPropertyVariables>
        <workingDirectory>FORK_DIRECTORY_${surefire.forkNumber}</workingDirectory>
    </configuration>
  </plugin>

You are looking for 2 options to java:

• -Xmx maximum heap size
• -Xms starting heap size

Put them in your command line invocation of the java executable, like this:

java -Xms512M -Xmx1024M my.package.MainClass

Keep in mind that you may want the starting and max heap sizes to be the same, depending on the application, as it avoids resizing the heap during runtime (which can take up time in applications that need to be responsive). Resizing the heap can entail moving a lot of objects around and redoing bookkeeping.

For every-day projects, make them whatever you think is good enough. Profile for help.

It worked - To change in Eclipse, go to Window -> Preferences -> Java -> Installed JREs. Select the checked JRE/JDK and click edit.

Default VM Arguments = -Xms128m -Xmx1024m

On the Mac: Instead of JAVA_OPTS and MAVEN_OPTS, use _JAVA_OPTIONS instead. This works!

After trying to use the MAVEN_OPTS variable with no luck, I came across this site which worked for me. So all I had to do was add -Xms128m -Xmx1024m to the default VM options and it worked.

To change those in Eclipse, go to Window -> Preferences -> Java -> Installed JREs. Select the checked JRE/JDK and click edit.

It should be the same command, except SET instead of EXPORT

• set MAVEN_OPTS=-Xmx512m would give it 512Mb of heap
• set MAVEN_OPTS=-Xmx2048m would give it 2Gb of heap

On windows:

Add an environmental variable (in both system and user's variables, I have some weird problem, that it gets the var from various places, so I add them in both of them).

Name it MAVEN_OPTS.

Value will be: -Xms1024m -Xmx3000m -XX:MaxPermSize=1024m -XX:+CMSClassUnloadingEnabled

The numbers can be different, make them relative to your mem size.

I had that problem and this fixed it, nothing else!