Java日志：灵活记录自定义消息与异常处理实践

import java.io.FileHandler;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.logging.SimpleFormatter;

public class Example {
    private static final Logger logger = Logger.getLogger("MyLog"); // 获取名为"MyLog"的Logger实例

    public static void init() {
        FileHandler fh;
        try {
            // 创建一个FileHandler，将日志写入指定文件
            // 第二个参数为true表示追加模式，否则会覆盖文件
            fh = new FileHandler("/Users/hp/Desktop/example1.log", true); 

            logger.addHandler(fh); // 将处理器添加到Logger
            SimpleFormatter formatter = new SimpleFormatter(); // 使用简洁的格式化器
            fh.setFormatter(formatter); // 设置处理器的格式化器

            logger.info("Logger Initialized successfully."); // 记录一条初始化成功的消息
        } catch (Exception e) {
            // 如果初始化失败，记录一个警告级别的异常日志
            logger.log(Level.WARNING, "Error initializing logger file handler: ", e);
        }
    }

    public static void main(String[] args) {
        init(); // 初始化日志系统

        try {
            int a = 10 / 0; // 模拟一个算术异常
        } catch (Exception e) {
            // 默认的异常日志记录，消息比较固定
            logger.log(Level.WARNING, "An unexpected error occurred: ", e); 
        }
        logger.info("Program execution finished."); // 记录程序结束消息
    }
}

import java.io.FileHandler;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.logging.SimpleFormatter;

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

    public static void init() {
        FileHandler fh;
        try {
            fh = new FileHandler("/Users/hp/Desktop/example1.log", true);
            logger.addHandler(fh);
            SimpleFormatter formatter = new SimpleFormatter();
            fh.setFormatter(formatter);
            logger.info("Logger Initialized successfully.");
        } catch (Exception e) {
            logger.log(Level.SEVERE, "Fatal error: Could not initialize logger file handler.", e);
        }
    }

    public static void main(String[] args) {
        init();

        // 示例1：记录一个普通的自定义信息
        String userName = "Alice";
        logger.info("User '" + userName + "' attempted to log in.");

        try {
            // 模拟一个文件操作
            String filePath = "/path/to/nonexistent/file.txt";
            if (filePath.contains("nonexistent")) {
                throw new java.io.FileNotFoundException("File not found at: " + filePath);
            }
            // ... 实际文件操作 ...
        } catch (java.io.FileNotFoundException e) {
            // 示例2：记录带有自定义消息和异常堆栈的日志
            logger.log(Level.WARNING, "Failed to process file. Please check the path.", e);
        } catch (Exception e) {
            // 示例3：更通用的异常处理，提供更多上下文信息
            logger.log(Level.SEVERE, "An unexpected critical error occurred during file operation.", e);
        }

        try {
            int a = 10 / 0; // 模拟另一个算术异常
        } catch (ArithmeticException e) {
            // 示例4：针对特定异常类型记录更精确的自定义消息
            logger.log(Level.SEVERE, "Arithmetic error: Division by zero detected.", e);
        } catch (Exception e) {
            // 示例5：捕获其他未预期的异常
            logger.log(Level.SEVERE, "An unknown exception occurred in the calculation block.", e);
        }

        logger.info("Program execution finished.");
    }
}