How do I log exceptions in Java?

How do I log exceptions in Java?

In Java, you can log exceptions using the java.util.logging package or popular libraries like Log4j or SLF4J.

Can you show me a simple example using Log4j?

Sure! First, add Log4j to your project. Then, you can log an exception like this:

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class Example {
    private static final Logger logger = LogManager.getLogger(Example.class);

    public void riskyMethod() {
        try {
            // code that may throw an exception
        } catch (Exception e) {
            logger.error("An error occurred: ", e);
        }
    }
}

What if I want to log to a file instead of the console?

You can configure Log4j to log to a file by setting up a configuration file (log4j2.xml) with a File Appender. Here's a basic example:

<Configuration>
    <Appenders>
        <File name="FileLogger" fileName="logs/app.log">
            <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1} - %m%n"/>
        </File>
    </Appenders>
    <Loggers>
        <Root level="error">
            <AppenderRef ref="FileLogger"/>
        </Root>
    </Loggers>
</Configuration>