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

public class UserService {
    // 獲取Logger實例
    private static final Logger logger = LoggerFactory.getLogger(UserService.class);
    
    public void createUser(User user) {
        logger.info("Creating user: {}", user.getUsername());
        // 業(yè)務(wù)邏輯
    }
}

// 錯誤示例 - 即使日志級別不滿足也會執(zhí)行字符串拼接
logger.debug("Processing order: " + order.getId() + " with amount: " + order.getAmount());

// 正確示例 - 只有在日志級別滿足時才會執(zhí)行參數(shù)替換
logger.debug("Processing order: {} with amount: {}", order.getId(), order.getAmount());

// 檢查日志級別再執(zhí)行耗時操作
if (logger.isDebugEnabled()) {
    logger.debug("Complex calculation result: {}", calculateExpensiveValue());
}

// 跟蹤詳細信息
logger.trace("Entering method with parameters: {}", params);

// 調(diào)試信息
logger.debug("Processing item at index: {}", index);

// 正常業(yè)務(wù)流程信息
logger.info("User {} successfully logged in", username);

// 警告信息
logger.warn("Database connection pool is running low: {} connections left", availableConnections);

// 錯誤信息
logger.error("Failed to process transaction", exception);

import org.slf4j.MDC;

// 在請求處理開始添加上下文
MDC.put("userId", user.getId());
MDC.put("requestId", UUID.randomUUID().toString());

try {
    // 業(yè)務(wù)邏輯處理
    logger.info("Processing user request");
    // 所有日志都會自動包含MDC中的上下文信息
} finally {
    // 請求結(jié)束后清理上下文
    MDC.clear();
}

<pattern>%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} [userId:%X{userId}, requestId:%X{requestId}] - %msg%n</pattern>

try {
    // 業(yè)務(wù)邏輯
} catch (DatabaseException e) {
    // 提供上下文和完整堆棧
    logger.error("Failed to save user data for userId: {}", userId, e);
    
    // 不要這樣做 - 丟失堆棧信息
    // logger.error("Failed to save user data: " + e.getMessage());
}

// 使用Logback的Marker功能
import org.slf4j.Marker;
import org.slf4j.MarkerFactory;

public class SecurityService {
    private static final Logger logger = LoggerFactory.getLogger(SecurityService.class);
    private static final Marker SECURITY_MARKER = MarkerFactory.getMarker("SECURITY");
    
    public void login(String username, boolean success) {
        logger.info(SECURITY_MARKER, "Login attempt: user={}, success={}", username, success);
    }
}

<filter class="ch.qos.logback.core.filter.EvaluatorFilter">
    <evaluator>
        <expression>marker.contains("SECURITY")</expression>
    </evaluator>
    <OnMatch>ACCEPT</OnMatch>
    <OnMismatch>DENY</OnMismatch>
</filter>

<dependency>
    <groupId>net.logstash.logback</groupId>
    <artifactId>logstash-logback-encoder</artifactId>
    <version>7.2</version>
</dependency>

<appender name="JSON" class="ch.qos.logback.core.ConsoleAppender">
    <encoder class="net.logstash.logback.encoder.LogstashEncoder">
        <includeMdcKeyName>userId</includeMdcKeyName>
        <includeMdcKeyName>requestId</includeMdcKeyName>
    </encoder>
</appender>

// 創(chuàng)建自定義日志消息格式化器
public class CustomLogMessageFormatter {
    public static String formatTransaction(String txId, String status, long duration) {
        return String.format("TX[%s] completed with status %s in %dms", txId, status, duration);
    }
}

// 在代碼中使用
logger.info(CustomLogMessageFormatter.formatTransaction("TX12345", "SUCCESS", 134));

<appender name="ASYNC" class="ch.qos.logback.classic.AsyncAppender">
    <appender-ref ref="FILE" />
    <queueSize>512</queueSize>
    <discardingThreshold>0</discardingThreshold>
    <includeCallerData>false</includeCallerData>
</appender>
<root level="INFO">
    <appender-ref ref="ASYNC" />
</root>

// 創(chuàng)建敏感數(shù)據(jù)掩碼工具
public class LogMaskUtil {
    public static String maskCardNumber(String cardNumber) {
        if (cardNumber == null || cardNumber.length() < 8) {
            return "****";
        }
        return "****" + cardNumber.substring(cardNumber.length() - 4);
    }
    
    public static String maskEmail(String email) {
        if (email == null || email.isEmpty() || !email.contains("@")) {
            return "****@****.com";
        }
        String[] parts = email.split("@");
        return parts[0].substring(0, 1) + "***@" + parts[1];
    }
}

// 在日志中使用
logger.info("Processing payment for card: {}", LogMaskUtil.maskCardNumber(card.getNumber()));
logger.info("Sending confirmation to: {}", LogMaskUtil.maskEmail(user.getEmail()));

// 創(chuàng)建業(yè)務(wù)上下文日志工具
public class OrderLogContext {
    private String orderId;
    private String customerId;
    private BigDecimal amount;
    
    public OrderLogContext(String orderId, String customerId, BigDecimal amount) {
        this.orderId = orderId;
        this.customerId = customerId;
        this.amount = amount;
    }
    
    public void setupContext() {
        MDC.put("orderId", orderId);
        MDC.put("customerId", customerId);
        MDC.put("amount", amount.toString());
    }
    
    public void clearContext() {
        MDC.remove("orderId");
        MDC.remove("customerId");
        MDC.remove("amount");
    }
    
    // 使用try-with-resources模式
    public static class LogContextResource implements AutoCloseable {
        private final OrderLogContext context;
        
        public LogContextResource(OrderLogContext context) {
            this.context = context;
            this.context.setupContext();
        }
        
        @Override
        public void close() {
            this.context.clearContext();
        }
    }
}

// 在代碼中使用
try (OrderLogContext.LogContextResource ignored = 
        new OrderLogContext.LogContextResource(new OrderLogContext(order.getId(), 
                                                                 order.getCustomerId(), 
                                                                 order.getAmount()))) {
    logger.info("Processing order");
    orderService.process(order);
    logger.info("Order completed successfully");
}

// 簡易性能日志
public class PerformanceLogger {
    private static final Logger logger = LoggerFactory.getLogger(PerformanceLogger.class);
    
    public static <T> T logExecutionTime(String operationName, Supplier<T> operation) {
        long startTime = System.currentTimeMillis();
        try {
            return operation.get();
        } finally {
            long duration = System.currentTimeMillis() - startTime;
            logger.info("Operation [{}] completed in {}ms", operationName, duration);
        }
    }
    
    // 無返回值版本
    public static void logExecutionTime(String operationName, Runnable operation) {
        long startTime = System.currentTimeMillis();
        try {
            operation.run();
        } finally {
            long duration = System.currentTimeMillis() - startTime;
            logger.info("Operation [{}] completed in {}ms", operationName, duration);
        }
    }
}

// 使用示例
User user = PerformanceLogger.logExecutionTime("fetchUserProfile", 
    () -> userService.getUserById(userId));

// 日志收集器
public class LogCollector {
    private final List<String> messages = new ArrayList<>();
    private final Logger logger;
    private final Level level;
    
    public LogCollector(Logger logger, Level level) {
        this.logger = logger;
        this.level = level;
    }
    
    public void add(String message) {
        messages.add(message);
    }
    
    public void add(String format, Object... args) {
        messages.add(String.format(format, args));
    }
    
    public void flush(String summary) {
        if (messages.isEmpty()) {
            return;
        }
        
        StringBuilder sb = new StringBuilder(summary);
        sb.append(":\n");
        for (int i = 0; i < messages.size(); i++) {
            sb.append("  ").append(i + 1).append(". ")
              .append(messages.get(i)).append("\n");
        }
        
        switch (level.toString()) {
            case "DEBUG":
                logger.debug(sb.toString());
                break;
            case "INFO":
                logger.info(sb.toString());
                break;
            case "WARN":
                logger.warn(sb.toString());
                break;
            case "ERROR":
                logger.error(sb.toString());
                break;
        }
        
        messages.clear();
    }
}

// 使用示例
LogCollector collector = new LogCollector(logger, Level.INFO);
for (Item item : items) {
    try {
        processItem(item);
        collector.add("Item %s processed successfully", item.getId());
    } catch (Exception e) {
        collector.add("Failed to process item %s: %s", item.getId(), e.getMessage());
    }
}
collector.flush("Batch processing results");