https://github.com/quackster/simplelogger4j
A very simple logger for Java that supports console, file appending, colours and formatting.
https://github.com/quackster/simplelogger4j
Last synced: 29 days ago
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A very simple logger for Java that supports console, file appending, colours and formatting.
- Host: GitHub
- URL: https://github.com/quackster/simplelogger4j
- Owner: Quackster
- License: apache-2.0
- Created: 2026-01-14T02:06:10.000Z (6 months ago)
- Default Branch: main
- Last Pushed: 2025-09-25T23:38:18.000Z (10 months ago)
- Last Synced: 2026-04-27T03:06:27.891Z (3 months ago)
- Size: 55.7 KB
- Stars: 0
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# SimpleLogger4j
A lightweight, dependency-free Java logger that gives you:
- A simple API (`logger.info()`, `logger.error()`, etc.)
- A pattern engine for shaping log output
- ANSI colour support for easy visual scanning
- String utilities for alignment, clipping, and formatting
- Clean exception handling
**Built and tested against Java 1.8**
[](https://opensource.org/licenses/Apache-2.0)
## Installation
### Gradle
Add the [JitPack](https://jitpack.io/#lovepigeons/SimpleLogger4j) repository:
```groovy
repositories {
maven { url 'https://jitpack.io' }
}
```
Then add the dependency:
```groovy
dependencies {
implementation 'com.github.lovepigeons:SimpleLogger4j:v1.0.4'
}
```
### Maven
Add the [JitPack](https://jitpack.io/#lovepigeons/SimpleLogger4j) repository:
```xml
jitpack.io
https://jitpack.io
```
Then add the dependency:
```xml
com.github.lovepigeons
SimpleLogger4j
v1.0.4
```
## API Summary
```java
SimpleLog logger = SimpleLog.of(T.class);
logger.info("Test arguments: {} {} {}", 123, 123.456, "testing");
logger.debug("debug msg");
logger.info("info msg");
logger.success("success msg");
logger.warn("warn msg");
logger.error("error msg");
logger.critical("critical msg");
logger.error("error with stack", throwable);
logger.critical("critical with stack", throwable);
```
**Levels:** DEBUG, INFO, SUCCESS, WARN, ERROR, CRITICAL
## Configuration
### Creating a Logger
```java
// Uses default config (simplelogger4j.xml if exists, else internal defaults)
SimpleLog logger = SimpleLog.of(MyClass.class);
// Or specify a custom XML config file
SimpleLog logger = SimpleLog.of(MyClass.class, "mylog.xml");
```
### XML Configuration
Create a `simplelogger4j.xml` file in your classpath (or specify a custom filename):
```xml
DEBUG
[%{timestamp:BRIGHT_BLACK}] [%{level:LEVEL|padRight(8)}] (%{package:CYAN}) #%{sequence:BRIGHT_BLACK} %{message}
true
```
**Configuration options:**
- `minLevel` - Minimum log level to output (DEBUG, INFO, SUCCESS, WARN, ERROR, CRITICAL)
- `pattern` - Output format pattern using tokens and specs
- `consoleColour` - Enable/disable ANSI colours for console output
- `appenders/console` - Console output settings
- `appenders/file` - File output settings with path, buffer size, and append mode
- `levelPalette` - Colour mapping for each log level (empty string = no colour)
**Configuration priority:**
1. Custom XML file (if specified in `SimpleLog.of()`)
2. `simplelogger4j.xml` (if found in classpath)
3. Internal defaults
### Output
```
2025-09-11T10:11:12 INFO This is logged at info level
2025-09-11T10:11:12 WARN This is logged at warn level
2025-09-11T10:11:12 SUCCESS This is logged at success level
2025-09-11T10:11:12 DEBUG This is logged at debug level
2025-09-11T10:11:12 ERROR This is logged at error level
2025-09-11T10:11:12 CRITICAL This is logged at critical level
2025-09-11T10:11:12 ERROR error
java.lang.RuntimeException: Forced error!
at ...
2025-09-11T10:11:12 CRITICAL error
java.lang.RuntimeException: Forced critical error!
at ...
```
## Advanced Formatting with PatternEngine
The PatternEngine is where you take full control of how logs look.
Instead of being locked into a rigid format, you describe the output with a **pattern string**.
### 1. Tokens
Tokens are placeholders written as `%{...}`. They pull data from the log event:
- `timestamp` → when the event happened
- `level` → log level (INFO, ERROR, etc.)
- `message` → your log text
- `thread` → thread name
- `class` → simple class name
- `package` → package name
- `sequence` → monotonic counter
**Example:**
```
%{timestamp} %{level} %{message}
```
Might render as:
```
2025-09-11T10:20:45 INFO Hello, World!
```
### 2. Specs (Format Modifiers)
Specs are added after a `:`. You can chain multiple with `|`.
- `datetime(pattern[, locale])` → custom date/time
- `padRight(width[, char])` → pad to a fixed width
- `substring(start[, end])` → clip text
**Example:**
```
%{timestamp:datetime('yyyy-MM-dd HH:mm:ss')|padRight(20)} %{level:padRight(5)} %{message:substring(0,30)}
```
**Output:**
```
2025-09-11 10:20:45 INFO Hello, World ttttttttttttttttt
```
### 3. Colouring
Add ANSI colours by name:
- **Fixed colours**: Use any of the available colour names directly in your pattern
- **Palette colouring**: Use `LEVEL` to apply colours based on log level (configured once)
**Available Colours:**
*Regular Colours:*
`BLACK`, `RED`, `GREEN`, `YELLOW`, `BLUE`, `MAGENTA`, `CYAN`, `WHITE`
*Bright Colours:*
`BRIGHT_BLACK`, `BRIGHT_RED`, `BRIGHT_GREEN`, `BRIGHT_YELLOW`, `BRIGHT_BLUE`, `BRIGHT_MAGENTA`, `BRIGHT_CYAN`, `BRIGHT_WHITE`
*Background Colours:*
`BG_BLACK`, `BG_RED`, `BG_GREEN`, `BG_YELLOW`, `BG_BLUE`, `BG_MAGENTA`, `BG_CYAN`, `BG_WHITE`
*Bright Background Colours:*
`BG_BRIGHT_BLACK`, `BG_BRIGHT_RED`, `BG_BRIGHT_GREEN`, `BG_BRIGHT_YELLOW`, `BG_BRIGHT_BLUE`, `BG_BRIGHT_MAGENTA`, `BG_BRIGHT_CYAN`, `BG_BRIGHT_WHITE`
*All possible colours*
**Pattern using palette:**
```
%{timestamp:datetime('HH:mm:ss')} %{level:LEVEL} %{message}
```
**Pattern using fixed colours:**
```
%{timestamp:CYAN} %{level:BRIGHT_RED} %{message:GREEN}
```
### 4. Walkthrough Examples
#### Example A: Simple plain text
```
"%{timestamp} %{level} %{message}"
```
**Output:**
```
2025-09-11T10:21:05 INFO Hello, World!
```
#### Example B: Neat columns with padding
```
"%{timestamp:datetime('HH:mm:ss')|padRight(12)} %{level:padRight(7)} %{message}"
```
**Output:**
```
10:21:05 INFO Hello, World!
10:21:06 ERROR Something broke
```
#### Example C: Multilingual date + clipped messages
```
"%{timestamp:datetime('EEEE d MMM yyyy HH:mm', 'fr-FR')|padRight(28)} %{level:padRight(5)} %{message:substring(0,30)|padRight(30,' ')}"
```
**Output:**
```
jeudi 11 sept. 2025 10:21 INFO Bonjour le monde
```
#### Example D: Colourized layout
```
"%{timestamp:datetime('HH:mm:ss')|padRight(12)} [%{thread:BRIGHT_BLUE}] %{level:LEVEL|padRight(5)} %{message}"
```
**Output:**
```
10:21:07 [main] INFO Hello, World!
```
Here, `main` is bright blue, `INFO` is green (from palette).
#### Example E: Columnar, with package/class dimmed
```
"%{timestamp:datetime('yyyy-MM-dd')|padRight(12)} %{timestamp:datetime('HH:mm:ss')|padRight(10)} %{level:LEVEL|padRight(5)} %{package:DIM_WHITE}.%{class:BRIGHT_WHITE} - %{message:substring(0,60)|padRight(60,' ')} #%{sequence}"
```
**Output:**
```
2025-09-11 10:21:08 INFO com.example.Demo - Hello, World! tttt... #42
```
Happy logging! 🧩