IntelliJ Remote Debugging Setup Guide | Generated by AI

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Short answer: yes—if you keep the build and the running JVM in sync, IntelliJ remote debug will attach cleanly. Here’s a solid, low-drama way to do it across Liberty locally and Cloud Foundry.

1) Prevent “class mismatch” before you attach

2) Auto-rebuild only when it matters (30-minute rule)

If you want to rebuild only when compiled classes are older than 30 minutes, wrap Maven in a tiny check.

Bash (macOS/Linux)

#!/usr/bin/env bash
set -euo pipefail

CLASSES_DIR="target/classes"
THRESHOLD_MIN=30

needs_build() {
  # no classes yet?
  [[ ! -d "$CLASSES_DIR" ]] && return 0
  # latest class mtime older than threshold?
  last_mod_epoch=$(find "$CLASSES_DIR" -type f -name '*.class' -printf '%T@\n' 2>/dev/null | sort -n | tail -1)
  [[ -z "${last_mod_epoch:-}" ]] && return 0
  now_epoch=$(date +%s)
  diff_min=$(( ( now_epoch - ${last_mod_epoch%.*} ) / 60 ))
  (( diff_min >= THRESHOLD_MIN ))
}

if needs_build; then
  echo "Classes are old (>= ${THRESHOLD_MIN}m) or missing — building…"
  mvn clean package -DskipTests
else
  echo "Classes are fresh (< ${THRESHOLD_MIN}m) — skipping build."
fi

PowerShell (Windows)

$classes = "target\classes"
$thresholdMin = 30

function Needs-Build {
  if (-not (Test-Path $classes)) { return $true }
  $last = Get-ChildItem $classes -Recurse -Filter *.class |
          Sort-Object LastWriteTime -Descending |
          Select-Object -First 1
  if (-not $last) { return $true }
  $age = (New-TimeSpan -Start $last.LastWriteTime -End (Get-Date)).TotalMinutes
  return ($age -ge $thresholdMin)
}

if (Needs-Build) {
  Write-Host "Classes are old (>= $thresholdMin m) or missing — building…"
  mvn clean package -DskipTests
} else {
  Write-Host "Classes are fresh (< $thresholdMin m) — skipping build."
}

3) Liberty (local) — start in debug and attach from IntelliJ

You have two easy options:

A. One-shot debug start

server debug myServer   # default JDWP at port 7777

B. Permanent config

-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:7777

WLP_DEBUG_ADDRESS=7777
WLP_DEBUG_SUSPEND=false

IntelliJ attach

Tip: after a rebuild, Liberty picks up updated classes for most features via hot swap. If a method signature or class shape changed, you’ll need a server restart for those changes to load.

4) Cloud Foundry (PCF) — what’s realistic

CF runs apps behind its routing layer; you typically cannot expose a JDWP port directly. You have two workable patterns:

Option 1: Buildpack debug + SSH tunnel (for dev/staging only)

  1. Enable JVM debug in the Java buildpack:

    • Set env before push (names vary slightly by buildpack version):
    cf set-env <APP> JBP_CONFIG_DEBUG '{enabled: true, port: 7777}'

  2. Restage:

    cf restage <APP>

  3. Open an SSH tunnel:

    cf ssh -N -L 7777:localhost:7777 <APP>

  4. In IntelliJ, attach to localhost:7777.

Option 2: Use CF SSH JMX/Diagnostics instead of JDWP

Reality check: many CF orgs disable debug ports in prod. Treat remote JDWP on CF as a debug-only path for non-prod spaces. If your platform team blocks it, fall back to logs + SSH diagnostics.

5) Common “couldn’t bind breakpoints” causes (and fixes)

If you wire it up like above—either always mvn clean package or the “30-minute freshness” wrapper—IntelliJ remote debug will attach reliably to Liberty, and it can work on CF via an SSH tunnel in non-prod.

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