Getting NoClassDefFoundError -> com/sun/jna/platform/win32/Psapi with Eclipse

Question

My program relies on the following code to get available system memory:

import oshi.SystemInfo;
import oshi.hardware.HardwareAbstractionLayer;


SystemInfo si = new SystemInfo();
HardwareAbstractionLayer hal = si.getHardware();

// Next line throws exception: NoClassDefFoundError -> com/sun/jna/platform/win32/Psapi
long availableBytes = hal.getMemory().getAvailable();
double availableMegabytes = ((double) availableBytes) / 1048576;
double availableGigabytes = ((double) availableMegabytes)/1024;

Update: After deleting every occurrence of oshi-core from every project in Workspace (to remove possibility of transient conflict dependency - only 4.2.1 is left). Now the error I get is -> java.lang.NoClassDefFoundError: com/sun/jna/platform/win32/VersionHelpers

In pom.xml I've added oshi-core dependency - I've tried almost every version starting from version 3.4.0 to latest version 4.2.1 and they all result in the same error.

I realize oshi-core relies on jna and jna-platform. In Dependency Hierarchy I see both have resolved (compiled) to version 5.5.0.

What is causing this error and how can it be solved?

Thanks!

P.S

I've seen some other threads with similar error but could not find any thread with this exact problem (missing com/sun/jna/platform/win32/Psapi)

Answer 1

Seems oshi-core relies on internal undocumented features of the Sun / Oracle JVM, and you're running on a different and/or newer JVM that doesn't have that undocumented feature anymore. That's the risk of using undocumented features.

Get a newer/other version of oshi-core that supports the version of the JVM you're using, or switch to use a JVM that oshi-core supports.

Answer 2

While you've pointed out in your comments that you think the latest version of JNA is being resolved, the errors indicate that your project does not have the most recent version of jna-platform (or possibly it has multiple versions linked on the classpath). This is nearly always the case for NoClassDefFoundError and while you're troubleshooting in the right direction, evidence indicates there's an old jna-platform version in your project somewhere.

The com.sun.jna.platform.win32.VersionHelpers class is in jna-platform version 5.3.0 and newer. The GetPerformanceInfo() method required for the method call giving you the error is in the com.sun.jna.platform.win32.Psapi class is in jna-platform version 4.3.0 and newer. If your classloader can't find these classes, then you don't have the correct jars linked to your project -- or you have incorrect jars linked alongside the correct ones.

Maven resolves dependencies by level... first it does all the dependencies you list in your POM (in order), then the transitive dependencies of those projects (in order) and so on. Ensuring the most recent version of JNA is used can be enforced by either (or both) of:

• Specify oshi-core dependency earlier in your list of dependencies in your POM, specifically, before any project that depends on an earlier version of JNA.
• Explicitly specify the jna and jna-platform versions (5.5.0) in your top-level POM.

Also, in Eclipse, be sure to go through the menus to Update Maven Project to ensure your dependencies are in sync after changes in the POM.

It's possible that your local repository is not downloading the updated jar, in which case you can purge it (or just delete any JNA artifacts, or everything, from C:\Users\<username>\.m2\repository and let it rebuild.)

Also check the classpath in Eclipse. If you have manually added dependencies (e.g., to JNA) before setting up your POM to get them from Maven, you could be using those.

If the above hints do not resolve your problem, please post the contents of the dependencies section your pom.xml file so we can provide additional advice.