In log4j, multiple Logger objects can be configured to write multiple logs.

To begin, open the log4j configuration file (usually log4j.properties or log4j.xml), and add configurations for multiple loggers. For example, you can add two logger objects, one for writing to the console and another for writing to a file.

Set the root logger level to INFO and output logs to the console and file.

Console output logs

log4j’s console appender is set to use the org.apache.log4j.ConsoleAppender class, targeting the System.out stream. It uses the org.apache.log4j.PatternLayout for its formatting, with the conversion pattern for the layout set as %d{yyyy-MM-dd HH:mm:ss} %5p %c{1}:%L – %m%n.

Output logs from files

The logging configuration specifies a RollingFileAppender that writes to a log file at a specific path. The log file is limited to 5MB in size and retains up to 10 backup files. The log messages are formatted by a PatternLayout that includes the timestamp, log level, source class, line number, and message.

Then, in Java code, different Logger objects can be obtained using the Logger.getLogger method and different log levels can be used to write logs. For example, the following code can be used to write logs to both the console and a file accordingly:

Bring in the Logger class from the org.apache.log4j package.

Log4jExample class with two Logger instances: consoleLogger and fileLogger.

public static void main(String[] args) {
    consoleLogger.info("This is a console log message");
    fileLogger.error("This is a file log message");
}

Could you please explain the situation in more detail for better understanding?

By utilizing the above configuration and code, it is possible to log simultaneously to both the console and a file. It is important to note that separate Appenders for the console and file need to be configured in the configuration file, each with their own specified Logger name. In the Java code, simply call the Logger.getLogger method to retrieve the respective Logger object, and use different methods to log information.