Logback-Extra

Custom classes for use with Logback

Set up

Add through the JitPack repo to your project:

Gradle build.gradle (Gradle 6.2+)

repositories {
    exclusiveContent {
        forRepository { maven { url "https://jitpack.io"} }
        filter { includeGroup "com.github.apatchydev" }
    }
}

dependencies {
    implementation "com.github.apatchydev:logback-extra:1.0.0"
}

• Java 11 or higher
  • Java 8 compatible if build.gradle is modified to sourceCompatibility = 8 and use logback 1.3.+

Features

Custom pattern layout converters

Define custom conversion rules in logback.xml as follows:

<configuration>
    <conversionRule conversionWord="specifier-without-percent" converterClass="fully.qualified.class.name"/>
</configuration>

Code for examples below are available in the sample program

• Execute example program with ./gradlew example

JsonKeyValueConverter

A converter for PatternLayout to group all key-value pairs into a JSON object in order of addition,
falling back to Map::toString if JSON-stringify fails.

Accepts 1 argument pretty to enable pretty-printing of JSON object.

Example (Override %kvp to use JsonKeyValueConverter)

pattern = "[%msg | %kvp]%n";
data1 = {"text": "abc",  "object": null};
data2 = {"text" : "def", "object" : [ 1, 2, 3 ]};
        
log.atInfo()
    .addKeyValue("data1", data1)
    .addKeyValue("data2", data2)
    .log("This log writes key-value pairs as JSON");

    log.atInfo()
    .log("This log has no key-value entries");

// ...
    
pattern = "[%msg | %kvp{pretty}]%n";

log.atInfo()
    .addKeyValue("data1", data1)
    .addKeyValue("data2", data2)
    .log("This log writes key-value pairs as JSON with pretty print");

log.atInfo()
    .log("This log has no key-value entries");

Result

[This log writes key-value pairs as JSON | {"data1":{"text":"abc","object":null},"data2":{"text":"def","object":[1,2,3]}}]
[This log has no key-value entries | ]
// ...
[This log writes key-value pairs as JSON with pretty print | {
  "data1" : {
    "text" : "abc",
    "object" : null
  },
  "data2" : {
    "text" : "def",
    "object" : [ 1, 2, 3 ]
  }
}]
[This log has no key-value entries | ]

WrapIfEmptyCompositeConverter

A composite converter for PatternLayout that adds a prefix/suffix when input is not empty, otherwise put a placeholder.

Arguments are ordered: {prefix,suffix,placeholder} with each defaulting to ch.qos.logback.core.CoreConstants.EMPTY_STRING

Example (Set %if to use WrapIfEmptyCompositeConverter)

pattern = "[%if(%marker){<,'> '}%msg]%n";

log.atInfo()
    .addMarker(MarkerFactory.getMarker("someMarker"))
    .log("This log prepends the log message with '<marker> ' only if present");

log.atInfo()
    .log("This log has no markers");

Result

[<someMarker> This log prepends the log message with '<marker> ' only if present]
[This log has no markers]