log4j2: line separator in header's parameter of PatternLayout

Log4j2 provides a new parameter for PatternLayout:

Parameter name: header
Type: String
Description: the optional header string to include at the top of each log file

With the following log4j2.xml configuration:

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<?xml version="1.0" encoding="UTF-8"?> <Configuration status="WARN" monitorInterval="20"> <Appenders> <RollingRandomAccessFile name="file" fileName="logs/app.log" filePattern="logs/app-%d_%i.log.gz"> <PatternLayout> <header> Version: ${env:APP_RELEASE_VERSION} </header> <pattern>%message%n</pattern> </PatternLayout> <Policies> <OnStartupTriggeringPolicy/> </Policies> </RollingRandomAccessFile> </Appenders> <Loggers> <Root level="debug"> <AppenderRef ref="file"/> </Root> </Loggers> </Configuration>

The output will be as follows:

Version: 1.2.0log_message_1
log_message_2
log_message_3

The problem is that the end of the header and the beginning of the log messages are not separated by a new line. But it can be solved by using "line.separator" - a Java system property:

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<?xml version="1.0" encoding="UTF-8"?> <Configuration status="WARN" monitorInterval="20"> <Appenders> <RollingRandomAccessFile name="file" fileName="logs/app.log" filePattern="logs/app-%d_%i.log.gz"> <PatternLayout> <header> ${env:APP_RELEASE_VERSION}${sys:line.separator} </header> <pattern>%message%n</pattern> </PatternLayout> <Policies> <OnStartupTriggeringPolicy/> </Policies> </RollingRandomAccessFile> </Appenders> <Loggers> <Root level="debug"> <AppenderRef ref="file"/> </Root> </Loggers> </Configuration>

The corresponding output:

Version: 1.2.0
log_message_1
log_message_2
log_message_3

To learn more about property substitution go here.