Breaking change in logback 1.5.13 breaks `%property{key}` patterns

[jordanjennings]

Describe the bug
When upgrading logback-classic to 1.5.13 or newer (which is transitively part of Spring Boot 3.3.8+ and 3.4.2+) you can no longer use %property{key} patterns due to a breaking internal change in logback.

See discussion here: qos-ch/logback#931

To Reproduce
Steps to reproduce the behavior:

1. Use this build.gradle (or equivalent maven configuration)

plugins {
  id 'java'
}

repositories {
  mavenCentral()
}

dependencies {
  implementation 'net.logstash.logback:logstash-logback-encoder:8.0'
  implementation 'ch.qos.logback:logback-classic:1.5.13'
}

2. Use this logback.xml configuration

<?xml version="1.0" encoding="UTF-8"?>
<configuration>

  <appender name="JSON" class="ch.qos.logback.core.ConsoleAppender">
    <encoder class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder">
      <providers>
        <timestamp />
        <logLevel />
        <pattern>
          <pattern>
            {
              "java.runtime.version": "%property{java.runtime.version}"
            }
          </pattern>
        </pattern>
        <message />
      </providers>
    </encoder>
  </appender>

  <root level="info">
    <appender-ref ref="JSON"/>
  </root>

</configuration>

2. Start the app, sample Main.java for reference:

package com.example;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Main {

  private static final Logger log = LoggerFactory.getLogger(Main.class);

  public static void main(String[] args) {
    log.info("Hello World!");
  }
}

3. See error on startup:

09:48:37,738 |-ERROR in net.logstash.logback.composite.loggingevent.LoggingEventPatternJsonProvider@57d7f8ca - Invalid [pattern]: Invalid JSON property '//process.runtime.version' (was '%property{java.runtime.version}'): class java.lang.String cannot be cast to class java.util.function.Supplier (java.lang.String and java.util.function.Supplier are in module java.base of loader 'bootstrap') net.logstash.logback.pattern.AbstractJsonPatternParser$JsonPatternException: Invalid JSON property '//process.runtime.version' (was '%property{java.runtime.version}'): class java.lang.String cannot be cast to class java.util.function.Supplier (java.lang.String and java.util.function.Supplier are in module java.base of loader 'bootstrap')
	at net.logstash.logback.pattern.AbstractJsonPatternParser$JsonPatternException: Invalid JSON property '//process.runtime.version' (was '%property{java.runtime.version}'): class java.lang.String cannot be cast to class java.util.function.Supplier (java.lang.String and java.util.function.Supplier are in module java.base of loader 'bootstrap')
	at 	at net.logstash.logback.pattern.AbstractJsonPatternParser.parseNode(AbstractJsonPatternParser.java:328)
	at 	at net.logstash.logback.pattern.AbstractJsonPatternParser.parseObject(AbstractJsonPatternParser.java:378)
	at 	at net.logstash.logback.pattern.AbstractJsonPatternParser.parse(AbstractJsonPatternParser.java:307)
	at 	at net.logstash.logback.composite.AbstractPatternJsonProvider.initializeNodeWriter(AbstractPatternJsonProvider.java:104)
	at 	at net.logstash.logback.composite.AbstractPatternJsonProvider.start(AbstractPatternJsonProvider.java:85)
	at 	at net.logstash.logback.composite.JsonProviders.start(JsonProviders.java:48)
	at 	at net.logstash.logback.composite.AbstractCompositeJsonFormatter.start(AbstractCompositeJsonFormatter.java:120)
	at 	at net.logstash.logback.encoder.CompositeJsonEncoder.start(CompositeJsonEncoder.java:129)
	at 	at ch.qos.logback.core.model.processor.ImplicitModelHandler.postHandleComplex(ImplicitModelHandler.java:207)
	at 	at ch.qos.logback.core.model.processor.ImplicitModelHandler.postHandle(ImplicitModelHandler.java:186)
	at 	at ch.qos.logback.core.model.processor.DefaultProcessor.secondPhaseTraverse(DefaultProcessor.java:257)
	at 	at ch.qos.logback.core.model.processor.DefaultProcessor.secondPhaseTraverse(DefaultProcessor.java:253)
	at 	at ch.qos.logback.core.model.processor.DefaultProcessor.secondPhaseTraverse(DefaultProcessor.java:253)
	at 	at ch.qos.logback.core.model.processor.DefaultProcessor.traversalLoop(DefaultProcessor.java:90)
	at 	at ch.qos.logback.core.model.processor.DefaultProcessor.process(DefaultProcessor.java:106)
	at 	at ch.qos.logback.core.joran.GenericXMLConfigurator.processModel(GenericXMLConfigurator.java:222)
	at 	at ch.qos.logback.core.joran.GenericXMLConfigurator.doConfigure(GenericXMLConfigurator.java:178)
	at 	at ch.qos.logback.core.joran.GenericXMLConfigurator.doConfigure(GenericXMLConfigurator.java:123)
	at 	at ch.qos.logback.core.joran.GenericXMLConfigurator.doConfigure(GenericXMLConfigurator.java:66)
	at 	at ch.qos.logback.classic.util.DefaultJoranConfigurator.configureByResource(DefaultJoranConfigurator.java:68)
	at 	at ch.qos.logback.classic.util.DefaultJoranConfigurator.configure(DefaultJoranConfigurator.java:35)
	at 	at ch.qos.logback.classic.util.ContextInitializer.invokeConfigure(ContextInitializer.java:128)
	at 	at ch.qos.logback.classic.util.ContextInitializer.autoConfig(ContextInitializer.java:103)
	at 	at ch.qos.logback.classic.util.ContextInitializer.autoConfig(ContextInitializer.java:66)
	at 	at ch.qos.logback.classic.spi.LogbackServiceProvider.initializeLoggerContext(LogbackServiceProvider.java:52)
	at 	at ch.qos.logback.classic.spi.LogbackServiceProvider.initialize(LogbackServiceProvider.java:41)
	at 	at org.slf4j.LoggerFactory.bind(LoggerFactory.java:199)
	at 	at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:186)
	at 	at org.slf4j.LoggerFactory.getProvider(LoggerFactory.java:486)
	at 	at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:472)
	at 	at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:421)
	at 	at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:447)
	at 	at com.example.Main.<clinit>(Main.java:8)
Caused by: java.lang.ClassCastException: class java.lang.String cannot be cast to class java.util.function.Supplier (java.lang.String and java.util.function.Supplier are in module java.base of loader 'bootstrap')
	at 	at ch.qos.logback.core.pattern.parser.Compiler.createConverter(Compiler.java:100)
	at 	at ch.qos.logback.core.pattern.parser.Compiler.compile(Compiler.java:64)
	at 	at ch.qos.logback.core.pattern.parser.Parser.compile(Parser.java:85)
	at 	at ch.qos.logback.core.pattern.PatternLayoutBase.start(PatternLayoutBase.java:132)
	at 	at net.logstash.logback.pattern.PatternLayoutAdapter.start(PatternLayoutAdapter.java:100)
	at 	at net.logstash.logback.pattern.AbstractJsonPatternParser.buildLayout(AbstractJsonPatternParser.java:231)
	at 	at net.logstash.logback.pattern.AbstractJsonPatternParser.makeLayoutValueGetter(AbstractJsonPatternParser.java:204)
	at 	at net.logstash.logback.pattern.AbstractJsonPatternParser.makeComputableValueGetter(AbstractJsonPatternParser.java:190)
	at 	at net.logstash.logback.pattern.AbstractJsonPatternParser.parseNode(AbstractJsonPatternParser.java:324)
	at 	... 32 common frames omitted

4. Observe log output is incorrect (it is missing the %property):

{"@timestamp":"2025-04-03T09:48:37.74953-04:00","level":"INFO","message":"Hello World!"}

Expected behavior

%property patterns work as expected

Additional context
In reported issue to logback they indicated no appetite to fix their breaking change since the fix is easy on the logstash-logback-encoder side. The fix is detailed in the linked ticket.

• logstash-logback-encoder version = 8.0
• logback version = 1.5.13
• jackson version = default
• java version = reproduced on 17 and 21

[jordanjennings]

The fix for this is included in the 8.1 release: https://github.com/logfellow/logstash-logback-encoder/releases/tag/logstash-logback-encoder-8.1