How to use logging to track Java exceptions?

Logging is a valuable tool for tracking Java exceptions. To use logging, you need to configure a logging framework (such as Logback or SLF4J). Exceptions can be logged using the Logger class and using the log(Level, Throwable) method in the catch block. A practical case is to log NullPointerException exceptions. By setting the log level to DEBUG, a stack trace log can also be generated.

How to use logging to track Java exceptions

Logging is valuable for tracking application behavior, finding errors, and diagnosing problems tool. Java provides a powerful logging framework that helps you log exceptions easily and efficiently.

Configuring the logging framework

First, you need to configure the logging framework to log exceptions. You can use widely used logging libraries such as Logback or SLF4J. Here's how to configure logging using Logback:

<configuration>

    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>

    <root level="INFO">
        <appender-ref ref="STDOUT" />
    </root>

</configuration>

Logging exceptions

Exceptions can be logged using the Logger class. The Logger class provides a set of methods, such as info(), error(), and debug(), for different Level logging messages. To record exceptions, you can use log(Level, Throwable) method:

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

public class Main {

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

    public static void main(String[] args) {
        try {
            // 代码块可能会抛出异常
        } catch (Exception e) {
            // 使用 logger 记录异常
            logger.error("异常已发生", e);
        }
    }
}

Practical case

The following is the use of logging to track NullPointerException Practical example of exception:

public class NullPointerExceptionExample {

    public static void main(String[] args) {
        try {
            // 尝试访问未初始化的对象
            String s = null;
            System.out.println(s.length());
        } catch (NullPointerException e) {
            // 使用日志记录器记录异常
            Logger logger = LoggerFactory.getLogger(NullPointerExceptionExample.class);
            logger.error("空指针异常已发生", e);
        }
    }
}

Running this code will generate the following log output:

16:10:35.567 [main] ERROR c.example.NullPointerExceptionExample - 空指针异常已发生
java.lang.NullPointerException
        at c.example.NullPointerExceptionExample.main(NullPointerExceptionExample.java:12)

By setting the log level to DEBUG, a stack trace log can also be generated to provide details of the exception occurrence .

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