Pervius

Modern Java / Kotlin decompiler, source recompiler, and bytecode editor.

Vineflower decompilation · ClassForge bytecode rewriting · Native Rust UI

Features · Requirements · Build · Shortcuts · 中文

Features

Decompilation

Powered by Vineflower, with both batch JAR decompilation and on-demand single-class decompilation. Small JARs are fully decompiled upfront; large JARs decompile class-by-class on demand. Vineflower progress is parsed in real time and tracked per class. Results are cached by the JAR's SHA-256, so reopening never triggers a rebuild. Kotlin classes can be emitted either as .kt (Vineflower/Kotlin output) or as .java (Java output mode), with original line-number mapping preserved.

Bytecode Editing

Structured .class editor: the left pane navigates class info, fields, and methods; the right pane provides the matching editor. Access flags, inheritance, annotations, and descriptors are all editable, along with method instructions. On save, ClassForge (built on ASM 9.7.1) handles constant-pool rebuilding, StackMapTable recomputation, and max_stack / max_locals. Untouched methods are byte-copied; only modified methods trigger frame recomputation.

Source Recompilation

Decompiled Java / Kotlin sources can be unlocked from the code view context menu (Right Click → Allow Editing). Ctrl+S or Recompile Now compiles the edited source asynchronously and replaces the generated .class entries in the in-memory JAR. Java recompilation uses the JDK javax.tools.JavaCompiler; Kotlin recompilation uses kotlin-compiler-embeddable on a dedicated -cp launch path so the normal ClassForge modes do not load the Kotlin compiler. Compiler diagnostics are returned to the editor and shown as gutter markers without blocking further edits.

Source editing is mutually exclusive with the structured bytecode editor: save or discard one path before switching to the other.

Tri-View

Every .class can be toggled between three views with Tab:

• Decompiled view — syntax-highlighted Java / Kotlin source, read-only by default and unlockable for source recompilation
• Bytecode view — structured editor
• Hex view — interactive hex inspector

Non-.class text files (XML, YAML, JSON, etc.) are editable directly with syntax highlighting; binary files open in the hex view.

Code Navigation

Ctrl+Click (macOS Cmd+Click) jumps to class, method, or field definitions. Supports import resolution, same-package inference, wildcard matching, and Kotlin/JVM special names such as backtick-quoted or $ methods. Ctrl+Click on a method declaration triggers Find Usages, searching all references automatically.

Global Search

Double Shift opens the search panel across every decompiled source, with regex and case-sensitivity support. Results stream back grouped by class with line-level highlighted previews; double-click to jump. The index is built in the background after decompilation completes and never blocks the UI.

Archive Browsing

The left-hand resource tree lists JAR contents and supports jar, zip, war, and ear. Type to filter (Speed Search) with filtering computed on a background thread. Modified and decompilation states are reflected in real time. Dropping a file onto the window opens the first dropped archive or standalone file. The Classpath panel is shown directly inside the explorer, accepts archive/directory additions through its + action, and its height can be resized by dragging the top edge. Recent files are also tracked.

Export

• Save / overwrite source JAR (Ctrl+S) — writes in-memory modified entries back to the currently opened archive when no editable source tab is pending
• Export JAR (Ctrl+Shift+S) — writes modifications back and produces a new archive
• Export decompiled sources (Ctrl+Shift+E) — exports .java / .kt to a directory, preserving the package layout

Requirements

• A working Java runtime is required for decompilation / ClassForge execution; Pervius can use the Java path configured in Settings, JAVA_HOME, or java from PATH
• A JDK (not just a JRE) is required for Java and Kotlin source recompilation, because ClassForge calls the system javac
• Vineflower and Kotlin compiler dependencies are downloaded automatically from the Huawei Cloud Maven mirror into the Environment tools directory (by default under the decompile cache root)

ClassForge is bundled and extracted to the data directory on first launch. Vineflower is resolved from the configured Environment directory and downloaded on demand; a matching vineflower-{version}.jar next to the executable still takes priority for local/offline override. Kotlin dependencies (kotlin-stdlib and kotlin-compiler-embeddable) are intentionally not bundled to keep the default distribution small and are downloaded only when Kotlin source recompilation is used. Download progress is surfaced in the status bar, and non-JAR Maven artifacts declared only as POM metadata are skipped automatically during dependency resolution.

Build

cargo build --release

ClassForge is embedded via include_bytes!; Vineflower and Kotlin dependencies are resolved by the Environment settings and downloaded on demand, with progress shown in the status bar.

Build ClassForge (only required after modifying ClassForge sources):

cd classforge
./gradlew jar    # Windows: .\gradlew.bat jar

ClassForge declares Kotlin dependencies as compileOnly: Gradle / javac can type-check KotlincCompiler, but Kotlin stdlib/compiler are not packed into classforge-*.jar. Copy the resulting classforge-1.1.jar into crates/pervius-java-bridge/libs/, replacing the bundled JAR if ClassForge sources change, then rebuild Rust. Keep the default Kotlin version in classforge/build.gradle and crates/pervius-java-bridge/src/environment.rs in sync; runtime Kotlin recompilation downloads the configured Kotlin dependencies automatically.

cargo run --release

Shortcuts

Shortcut	Action
Ctrl+O	Open archive or single file
Ctrl+S	Save source edit / overwrite current JAR
Ctrl+F	Find
Double Shift	Global search
Ctrl+Click	Go to definition / Find Usages
Tab	Switch view
Alt+1	Toggle resource tree
Ctrl+Shift+S	Export JAR
Ctrl+Shift+E	Export decompiled sources
Ctrl+,	Settings

All shortcuts can be customized in Settings.

Credits

• Vineflower — Java decompilation engine
• ASM — Java bytecode manipulation framework
• egui — Rust immediate mode GUI
• tree-sitter — syntax highlighting

License

MIT