Java debugger

Debugger for client .java code compiled by engine-java. The IDE bridges the browser UI to the JDT.LS-managed Debug Adapter Protocol (DAP) server, which in turn attaches to the JVM over JDWP.

Protocol and ports

Browser (debug.js) <-WebSocket-> JavaDebugWebSocketHandler
                                  -> JavaDebugManager
                                  -> JavaDebugBridge (per workspace)
                                  -> DAP TCP socket
                                  -> JDT.LS (vscode.java.startDebugSession)
                                  -> JDWP TCP (port 8000 by default)
                                  -> Target JVM

• JDWP default port: 8000. Override with DIRIGIBLE_JAVA_DEBUG_JDWP_PORT.
• Host: always localhost. Not configurable from the UI.

The DAP port is allocated dynamically by JDT.LS at attach time; the view fetches it from GET /services/ide/java-debug/config and falls back to 8000 for the JDWP target if the config endpoint is unreachable.

UI

Compact toolbar on top:

• Attach - connect to the JDWP target and start a DAP session.
• Disconnect - tear down the DAP session without terminating the JVM (the bridge sends a disconnect with terminateDebuggee:false).
• Step controls - continue, step over, step into, step out, pause, terminate.

A status strip below the toolbar reports the current state (disconnected, connecting, connected, paused, error). Three collapsible panels below that:

• Call stack - stack frames at the current pause; click a frame to switch context.
• Variables - locals and fields for the selected frame. Expand objects to navigate.
• Breakpoints - every breakpoint across all files; toggle, remove, or jump to the source line.

Workspace scope

The bridge is keyed by (username, workspace) - one DAP session per user per workspace. The active workspace is read from localStorage[${prefix}.workspace.selected] and kept in sync via the platform.workspace.changed hub topic; switching workspace in the Projects view drops the current session.

Breakpoints

• Set or remove a breakpoint by clicking the Monaco gutter (glyph margin) next to a line.
• Breakpoints persist in localStorage['dirigible.java.debug.breakpoints'] as { virtualPath: int[] }. They survive page reloads.
• The debug view broadcasts the current set on the java.debug.breakpoints topic; the Monaco editor restores the red-circle glyph for its file.
• When paused, the editor highlights the current line via the java.debug.highlight topic (yellow triangle in the glyph margin, faint yellow line background).

See also

• JavaScript debugger
• Monaco editor