jdb-debugger

Name: jdb-debugger
Author: brunoborges

62stars5forks

How to install jdb-debugger?

brunoborges/jdb-agentic-debugger/jdb-debugger

$npx -y skills add brunoborges/jdb-agentic-debugger --skill jdb-debugger

Installs into the current project.

Summary

Debug Java applications in real time using JDB (Java Debugger CLI). Attach to running JVMs or launch new ones under JDB, set breakpoints, step through code, inspect variables, analyze threads, and diagnose exceptions. Use when debugging Java programs, investigating runtime behavi

Files · 1

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SKILL.md

1	# Java Debugger (JDB) Skill
2
3	Debug Java applications interactively using the JDK's built-in command-line debugger.
4
5	## Critical Rules for Agents
6
7	1. NEVER create files in the workspace (no `bp.txt`, `cmds.txt`, wrapper scripts, etc.).
8	Use the inline CLI flags (`--bp`, `--cmd`, `--auto-inspect`, `--timeout`) provided by the skill scripts.
9	2. ALWAYS use the skill scripts in `scripts/`. Never write
10	custom JDB wrapper scripts, FIFO-based launchers, or shell scripts to drive JDB.
11	3. Compile first, then debug. Ensure classes are compiled before launching JDB.
12	4. On Windows, invoke scripts via WSL: `wsl bash scripts/<script>.sh`
13
14	## Platform Support
15
16	### Windows (WSL Required)
17
18	The scripts in this skill are Bash scripts. On Windows, invoke them via WSL:
19
20	```bash
21	wsl bash scripts/jdb-launch.sh com.example.MyApp --sourcepath src/main/java
22	```
23
24	If your compiled classes are on the Windows filesystem, WSL accesses them via `/mnt/c/`:
25	```bash
26	wsl bash scripts/jdb-launch.sh com.example.MyApp --classpath /mnt/c/Users/you/project/out
27	```
28
29	Ensure JDK is installed in WSL:
30	```bash
31	# Ubuntu/Debian WSL
32	sudo apt update && sudo apt install -y default-jdk
33
34	# Verify
35	which jdb && jdb -version
36	```
37
38	### Linux / macOS
39
40	Scripts run natively. Ensure JDK is installed and `jdb` is on PATH:
41	```bash
42	export PATH=$JAVA_HOME/bin:$PATH
43	```
44
45	## Decision Tree
46
47	```
48	User wants to debug Java app →
49	├─ App is already running with JDWP agent?
50	│ ├─ Yes → Attach: scripts/jdb-attach.sh --port <port>
51	│ └─ No → Can you restart with JDWP?
52	│ ├─ Yes → Launch with: scripts/jdb-launch.sh <mainclass> [args]
53	│ └─ No → Suggest adding JDWP agent to JVM flags (see below)
54	│
55	├─ What does the user need?
56	│ ├─ Set breakpoints & step through code → Interactive JDB session
57	│ ├─ Collect thread dumps / diagnostics → scripts/jdb-diagnostics.sh
58	│ └─ Catch a specific exception → Use `catch` command in JDB
59	│
60	└─ Done debugging → Detach cleanly with `quit` or Ctrl+C
61	```
62
63	## Quick Start
64
65	### Option 1: Launch a new JVM under JDB
66
67	```bash
68	bash scripts/jdb-launch.sh com.example.MyApp --sourcepath src/main/java
69	```
70
71	### Option 2: Attach to a running JVM
72
73	First, ensure the target JVM was started with the JDWP agent:
74	```bash
75	java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -jar myapp.jar
76	```
77
78	Then attach:
79	```bash
80	bash scripts/jdb-attach.sh --host localhost --port 5005
81	```
82
83	### Option 3: Quick diagnostics (thread dump + deadlock detection)
84
85	```bash
86	bash scripts/jdb-diagnostics.sh --port 5005
87	```
88
89	## Enabling JDWP on a Running Application
90
91	If the target JVM was not started with JDWP, suggest the user restart with:
92
93	```bash
94	# For direct Java launch
95	java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -cp myapp.jar com.example.Main
96
97	# For Maven Spring Boot
98	mvn spring-boot:run -Dspring-boot.run.jvmArguments="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005"
99
100	# For Gradle
101	./gradlew bootRun --jvmArgs="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005"
102
103	# As environment variable
104	export JAVA_TOOL_OPTIONS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005"
105	```
106
107	## Interactive JDB Session Guide
108
109	Once inside a JDB session (launched or attached), use these commands interactively:
110
111	### Setting Breakpoints
112
113	```
114	stop at com.example.MyClass:42 # Break at line 42
115	stop in com.example.MyClass.myMethod # Break at method entry
116	stop in com.example.MyClass.<init> # Break at constructor
117	stop in com.example.MyClass.<clinit> # Break at static initializer
118	```
119
120	For overloaded methods, specify parameter types:
121	```
122	stop in com.example.MyClass.process(int,java.lang.String)
123	```
124
125	### Running and Stepping
126
127	```
128	run # Start the application (if launched, not attached)
129	cont # Continue execution after hitting a breakpoint
130	step # Step into the next line (enters method calls)
131	next # Step over to the next line (skips method internals)
132	step up # Run until the current method returns
133	```
134
135	### Inspecting State
136
137	```
138	locals # Show all local variables in the current frame
139	print myVariable # Print value of a variable or expression
140	print myObj.getX() # Evaluate a method call
141	dump myObject # Show all fields of an object
142	eval 2 + 2 # Evaluate an arbitrary e

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6 picks

Type

jdb-debugger

62stars5forks

View on GitHub

How to install jdb-debugger?

brunoborges/jdb-agentic-debugger/jdb-debugger

$npx -y skills add brunoborges/jdb-agentic-debugger --skill jdb-debugger

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# Java Debugger (JDB) Skill
2
3	Debug Java applications interactively using the JDK's built-in command-line debugger.
4
5	## Critical Rules for Agents
6
7	1. NEVER create files in the workspace (no `bp.txt`, `cmds.txt`, wrapper scripts, etc.).
8	Use the inline CLI flags (`--bp`, `--cmd`, `--auto-inspect`, `--timeout`) provided by the skill scripts.
9	2. ALWAYS use the skill scripts in `scripts/`. Never write
10	custom JDB wrapper scripts, FIFO-based launchers, or shell scripts to drive JDB.
11	3. Compile first, then debug. Ensure classes are compiled before launching JDB.
12	4. On Windows, invoke scripts via WSL: `wsl bash scripts/<script>.sh`
13
14	## Platform Support
15
16	### Windows (WSL Required)
17
18	The scripts in this skill are Bash scripts. On Windows, invoke them via WSL:
19
20	```bash
21	wsl bash scripts/jdb-launch.sh com.example.MyApp --sourcepath src/main/java
22	```
23
24	If your compiled classes are on the Windows filesystem, WSL accesses them via `/mnt/c/`:
25	```bash
26	wsl bash scripts/jdb-launch.sh com.example.MyApp --classpath /mnt/c/Users/you/project/out
27	```
28
29	Ensure JDK is installed in WSL:
30	```bash
31	# Ubuntu/Debian WSL
32	sudo apt update && sudo apt install -y default-jdk
33
34	# Verify
35	which jdb && jdb -version
36	```
37
38	### Linux / macOS
39
40	Scripts run natively. Ensure JDK is installed and `jdb` is on PATH:
41	```bash
42	export PATH=$JAVA_HOME/bin:$PATH
43	```
44
45	## Decision Tree
46
47	```
48	User wants to debug Java app →
49	├─ App is already running with JDWP agent?
50	│ ├─ Yes → Attach: scripts/jdb-attach.sh --port <port>
51	│ └─ No → Can you restart with JDWP?
52	│ ├─ Yes → Launch with: scripts/jdb-launch.sh <mainclass> [args]
53	│ └─ No → Suggest adding JDWP agent to JVM flags (see below)
54	│
55	├─ What does the user need?
56	│ ├─ Set breakpoints & step through code → Interactive JDB session
57	│ ├─ Collect thread dumps / diagnostics → scripts/jdb-diagnostics.sh
58	│ └─ Catch a specific exception → Use `catch` command in JDB
59	│
60	└─ Done debugging → Detach cleanly with `quit` or Ctrl+C
61	```
62
63	## Quick Start
64
65	### Option 1: Launch a new JVM under JDB
66
67	```bash
68	bash scripts/jdb-launch.sh com.example.MyApp --sourcepath src/main/java
69	```
70
71	### Option 2: Attach to a running JVM
72
73	First, ensure the target JVM was started with the JDWP agent:
74	```bash
75	java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -jar myapp.jar
76	```
77
78	Then attach:
79	```bash
80	bash scripts/jdb-attach.sh --host localhost --port 5005
81	```
82
83	### Option 3: Quick diagnostics (thread dump + deadlock detection)
84
85	```bash
86	bash scripts/jdb-diagnostics.sh --port 5005
87	```
88
89	## Enabling JDWP on a Running Application
90
91	If the target JVM was not started with JDWP, suggest the user restart with:
92
93	```bash
94	# For direct Java launch
95	java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -cp myapp.jar com.example.Main
96
97	# For Maven Spring Boot
98	mvn spring-boot:run -Dspring-boot.run.jvmArguments="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005"
99
100	# For Gradle
101	./gradlew bootRun --jvmArgs="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005"
102
103	# As environment variable
104	export JAVA_TOOL_OPTIONS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005"
105	```
106
107	## Interactive JDB Session Guide
108
109	Once inside a JDB session (launched or attached), use these commands interactively:
110
111	### Setting Breakpoints
112
113	```
114	stop at com.example.MyClass:42 # Break at line 42
115	stop in com.example.MyClass.myMethod # Break at method entry
116	stop in com.example.MyClass.<init> # Break at constructor
117	stop in com.example.MyClass.<clinit> # Break at static initializer
118	```
119
120	For overloaded methods, specify parameter types:
121	```
122	stop in com.example.MyClass.process(int,java.lang.String)
123	```
124
125	### Running and Stepping
126
127	```
128	run # Start the application (if launched, not attached)
129	cont # Continue execution after hitting a breakpoint
130	step # Step into the next line (enters method calls)
131	next # Step over to the next line (skips method internals)
132	step up # Run until the current method returns
133	```
134
135	### Inspecting State
136
137	```
138	locals # Show all local variables in the current frame
139	print myVariable # Print value of a variable or expression
140	print myObj.getX() # Evaluate a method call
141	dump myObject # Show all fields of an object
142	eval 2 + 2 # Evaluate an arbitrary e

People who liked this also viewed

6 picks

Type