log4j2 RollingFileAppender.setlayout

`RollingFileAppender` is a class in the Log4j2 logging framework that writes log messages to a file and rolls over to a new file when a certain size or time threshold is reached.

The `setLayout()` method of `RollingFileAppender` is used to set the layout that will be used to format the log messages before they are written to the file. The layout defines the format of the log messages and can include information such as timestamp, log level, thread name, logger name, and the actual log message.

Here's an example of how you can use `setLayout()` to set a `PatternLayout` for a `RollingFileAppender`:

RollingFileAppender appender = RollingFileAppender.newBuilder()
        .withFileName("logs/app.log")
        .withFilePattern("logs/app-%d{yyyy-MM-dd}.log")
        .withLayout(PatternLayout.newBuilder().withPattern("%d{yyyy-MM-dd HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n").build())
        .withPolicy(SizeBasedTriggeringPolicy.createPolicy("10MB"))
        .withStrategy(DefaultRolloverStrategy.newBuilder().withMax("10").build())
        .build();

In this example, we're creating a `RollingFileAppender` that writes log messages to a file named `app.log` and rolls over to a new file every day. We're also setting a `PatternLayout` that includes the timestamp, thread name, log level, logger name, and log message. The `SizeBasedTriggeringPolicy` is set to roll over to a new file when the log file reaches 10MB, and the `DefaultRolloverStrategy` is set to keep a maximum of 10 rolled-over files.