JNet: .NET suite for Java™/JVM™

JNet is a comprehensive suite of libraries and tools to use Java™/JVM™ APIs (Java, Scala, Kotlin, ...) and .NET side-by-side.

Key Features

• ✅ Java 8+ Support - Works with legacy Java 8 systems through modern Java 25
• ✅ Zero Migration Required - Integrate existing Java 8 code with .NET applications
• ✅ Direct API Access - Call any Java API directly from C#/VB.NET
• ✅ Bidirectional - Java can call .NET and vice versa (see JCOReflector)
• ✅ Production Ready - Trusted in enterprise environments

💡 Legacy Integration: Still running Java 8 in production? JNet enables integration with modern .NET applications without requiring Java upgrades—saving months of migration work and significant costs.

Libraries and Tools

JNet	JNet.Templates	JNetCLICore	JNetPSCore	JNetCLI	JNetReflector	JNetPS

Pipelines

Project disclaimer

JNet is a suite, curated by MASES Group, can be supported by the open-source community.

Its primary scope is to support other, public or internal, MASES Group projects: open-source community and commercial entities can use it for their needs and support this project, moreover there are dedicated community and commercial subscription plans.

The repository code and releases may contain bugs, the release cycle depends from critical discovered issues and/or enhancement requested from this or other projects.

Looking for the help of experts? MASES Group can help you design, build, deploy, and manage applications mixing .NET and JVM™ enabled languages.

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Scope of the project

This project aims to create a set of libraries and tools to direct access, from .NET, all the features available in the Java™ Platform, this is the counterpart of JCOReflector.

There are many client libraries written to manage communication with Java™. Conversely, this project use directly the Java™ packages giving more than one benefit:

• all implemented features are availables at no extra implementation costs, see JNet usage;
• avoids any third party communication protocol implementation;
• access all features made available from Java™ platform.

So, for example, do you want an ArrayList? Just write in C# a line of code like this:

Java.Util.ArrayList<string> alist = new Java.Util.ArrayList<string>();

See JNet usage for a comprehensive example.

Community and Contribution

Do you like the project?

• Request your free community subscription.

Do you want to help us?

• put a :star: on this project
• open issues to request features or report bugs :bug:
• improves the project with Pull Requests

This project adheres to the Contributor Covenant code of conduct. By participating, you are expected to uphold this code. Please report unacceptable behavior to coc_reporting@masesgroup.com.

Summary

• Roadmap
• Current state
• JNet usage
• JNet performance tips
• JNet APIs extensibility
• JNet JVM™ callbacks
• JNet CLI usage
• JNet Docker usage
• JNet Reflector usage
• JNet PowerShell usage
• JNet Command-line switches

News

• V1.4.8+: From version 1.4.8 there is a new project, named JNetReflector (still in development phase), able to build C# gateway classes from JARs containing the JVM™ classes, exactly the same JCOReflector does for .NET in JVM™.
• V1.4.9+: From version 1.4.9 there are two new projects:
  • JNetPSCore: the core library for PowerShell development, it can be extended in other projects based on JNet;
  • JNetPS: a PowerShell module to use JNet within a PowerShell shell.
• V1.5.2+: strong improvement of JNetReflector; it is used to generate almost all Java™ 11 classes available in the corresponding JNet version
• V1.5.3+: JNetReflector manages generics and almost all classes of Java™ SE 11 are covered: see JNet Reflector usage
• V2.0.0+: the most notable changes in this version are in:
  • JNet: complete review of all classes based on automatic generation done using JNetReflector
  • JNetReflector: improvements in many areas from generation of .NET interfaces to generics and where clauses, full story in https://github.com/masesgroup/JNet/issues/178
• V2.3.0+: the most notable changes in this version are in:
  • JNet: review of classes based on latest updates of JNetReflector
  • JNetReflector: use Java.Lang.String, by default, instead of string (System.String) (see https://github.com/masesgroup/JNet/issues/363)
• V2.4.0+: the most notable changes in this version are in:
  • JNet: review of classes based on latest updates of JNetReflector
  • JNetReflector: use native types only when JVM™ counter-part is a native type (see https://github.com/masesgroup/JNet/issues/371)
  • JNetReflector: can use signature to invoke JVM™ methods (see https://github.com/masesgroup/JNet/issues/374) or fallback to current behavior
• V2.5.0+: the most notable changes in this version are in:
  • Tools and Docker images update to .NET 8
  • JNetReflector: create side-by-side class on each listener used in case of pure JVM™ interface (see https://github.com/masesgroup/JNet/issues/393)
  • JNet:
    • review of classes based on latest updates of JNetReflector
    • enhanced ByteBuffer management
    • speed-up array/list conversion
• V2.5.11: updates to JCOBridge 2.5.21 and adds management of CET on recent Intel CPU due to latest change on .NET 9: usage explanation on this
• V2.5.13: adds JNetCLICore to help CLI operations across projects based on JNet
• V2.6.x: aligns to JCOBridge 2.6.* series
  • V2.6.6: adds support for JavaSE 8

Frequently Asked Questions

Does JNet support Java 8?

Yes! JNet fully supports Java 8 (JRE 1.8.0_161 or later) through Java 25. This is critical for enterprises with legacy Java 8 systems in production.

Do I need to upgrade my Java 8 code to use JNet?

No! JNet works with your existing Java 8 bytecode without any modifications. You can integrate legacy Java 8 systems with modern .NET applications immediately.

What about Java 8 End of Life?

Oracle provides Extended Support for Java 8 until December 2030. Many vendors (Amazon Corretto, Azul, Red Hat) provide free long-term support. JNet gives you flexibility: integrate now with Java 8, migrate Java when your timeline permits.

Can I mix different Java versions in my application?

Yes! Java is backward compatible. A newer JVM can execute bytecode compiled with older Java versions.

Example: Using Java 17 JVM, you can call:

• Java 8 libraries ✅
• Java 11 libraries ✅
• Java 17 libraries ✅

All in the same .NET process, with zero migration needed for older code!

Simple rule: Use the highest Java version required by any of your dependencies. That JVM will run all older bytecode versions.

Do I need to upgrade my Java 8 code to use newer Java libraries?

No! Just upgrade the JVM to Java 17 (or whatever version the new library requires). Your Java 8 bytecode will continue working without any code changes.

This is Java's backward compatibility guarantee in action.

What if I try to use Java 17 bytecode with Java 8 JVM?

You'll get an UnsupportedClassVersionError. Java doesn't support forward compatibility - older JVMs cannot run newer bytecode.

Solution: Upgrade to Java 17 JVM. Your Java 8 code will still work!

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Runtime engine

JNet uses JCOBridge, and its features, to obtain many benefits:

• Cyber-security:
  • JVM™ and CLR, or CoreCLR, runs in the same process, but are insulated from each other;
  • JCOBridge does not make any code injection into JVM™;
  • JCOBridge does not use any other communication mechanism than JNI;
  • .NET (CLR) inherently inherits the cyber-security levels of running JVM™;
• Direct access to the JVM™ from any .NET application:
  • Any Java/Scala/Kotlin/... class can be directly managed;
  • No need to learn new APIs: we try to expose the same APIs in C# style;
  • No extra validation cycle on protocol and functionality: bug fix, improvements, new features are immediately available;
  • Documentation is shared;
• Dynamic code: it helps to write a Java/Scala/Kotlin/etc seamless language code directly inside a standard .NET application written in C#/VB.NET: look at this simple example and JNet APIs extensibility.

JCOBridge 2.6.* can be used for free without any obligations; you need to purchase a commercial license, or uninstall the software, if you have direct or indirect incomes from the product usage.

Supported Versions

Java:

• ✅ Java 8 (JRE 1.8.0_161 or later)
• ✅ Java 11 (LTS)
• ✅ Java 17 (LTS)
• ✅ Java 21 (LTS)
• ✅ Java 25 (LTS)

Note: Works with Oracle JDK, OpenJDK, Amazon Corretto, Azul Zulu, and other compatible distributions.

.NET:

• .NET Framework 4.6.2+
• .NET 6, 8, 9, 10

Java 8 Extended Support runs until December 2030. JNet provides a migration path: integrate Java 8 systems with modern .NET now, migrate Java when ready.

JCOBridge resources

Have a look at the following JCOBridge resources:

JCOBridge	2.5.* series	2.6.* series
JNet	> 1.5.* series	> 2.6.* series
Release notes	Link	Link
Community Edition	Conditions	Conditions
Commercial Edition	Information	Information

Latest release: