JVM Explorer

This project is forked from Naton1/jvm-explorer. Thanks to the original author for the great work.

JVM Explorer is a Java desktop application for browsing loaded class files inside locally running Java Virtual Machines.

Features

• Browse local JVMs
• View all classes inside each JVM
• Search to find specific classes (supports regex)
• View classloader hierarchy
• View decompiled bytecode
• View disassembled bytecode
• Re-assemble bytecode
• Re-compile class file
• Modify method implementations (insert, replace method body with java code)
• Execute code in local JVMs
• Export loaded classes to a JAR file
• Browse the state of all static variables in a class (and their nested fields)
• Modify the state of static variables (and their nested fields)
• Replace class file definitions
• View system properties of running JVMs
• Run JAR files with a patched ProcessBuilder to remove any -XX:+DisableAttachMechanism argument

Demos

Browse Classes And Fields

Notes:

• Ctrl + Click on a class name in the class file viewer to open it
• Search and press enter to open a class with the specified name
• Edit a field value (under Fields tab) through Right Click -> Edit - only works for primitives and Strings

Execute Code In Remote JVM

Notes:

• You can call methods in the remote classes - the loaded classes are used for the compiler classpath

Show Class Loader Hierarchy

Launch Jar With Patched ProcessBuilder

Export Classes In Package

Modify Method

Notes:

• You can insert code to the beginning of a method or replace the entire method body
• The compiler currently uses the loaded classes as the classpath, so if a parameter type or return type isn't loaded, it may fail (you can replace the type with Object to make it compile if you don't need that type)
• To access fields in the class, add a field with the same name and type in the class to compile - the reference will automatically be replaced

Modify Class

Notes:

• Ctrl+S to re-recompile and patch class (or Right-Click -> Save Changes)
• Often, decompiled code is not valid Java code, so it may not compile in some cases - the modify method feature is the workaround for this
• The compiler currently uses the loaded classes as the classpath, so if some required type isn't loaded, it may fail

Modify Bytecode

Notes:

• Ctrl+S to re-assemble and patch class (or Right-Click -> Save Changes)
• The disassembler/assembler isn't perfect - it works most of the time but struggles with some cases (it uses OpenJDK AsmTools)

Getting Started

There are two ways to run the application. Download a provided platform-specific package, or build and run it yourself. This application requires Java 25+ and can attach to JVMs running Java 7+.

Download Package:

1. Download a platform-specific package from the latest release
2. Extract the archive and run the startup script for your platform

Build And Run:

1. Clone with Git

git clone https://github.com/unknowIfGuestInDream/jvm-explorer.git

2. Change into the project directory

cd jvm-explorer

3. Build with Maven (Java 25+, Maven 3.9+)

mvn clean install -DskipTests

4. Run the application

mvn -pl explorer javafx:run

Troubleshooting

Two logs files application.log and agent.log are created at [User Home]/jvm-explorer/logs

• Must run the application with a Java version of at least Java 25
• Must attach to a JVM running a Java version of at least Java 7
• Must attach to a JVM running the same architecture - a 32-bit JVM must attach to a 32-bit JVM
• May have to attach to a JVM that the same user started
• Must attach to a JVM that supports the Java Attach API
• If you run an old version of this application and attach it to a JVM, then update to a newer version and try to re-attach, the agent will be outdated. If there are changes in the client-server protocol, the agent will fail. Restart the target JVM to fix this.

Note: this uses the Java Attach API so any limitations will apply here.

Project Principles

• Maintain a simple and easy-to-use interface
• Take advantage of attaching to running JVMs - this is not a traditional GUI decompiler

Project Structure

Module	Description
protocol	Shared protocol classes for communication
agent	JVM agent injected into target processes
launch-agent	Launch patch agent for JDK compatibility
explorer	JavaFX desktop application (main module)

License

This project is licensed under the MIT License.