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Implementing a Logging Utility Class in HarmonyOS Next

Implementing a Logging Utility Class in HarmonyOS Next

1. LogUtil Implementation

A wrapper around the native hilog module for simplified logging:

import hilog from '@ohos.hilog';

const LOGGER_DOMAIN: number = 0x0000;
const LOGGER_TAG: string = 'AppLogger';

export class LogUtil {
  private static domain: number = LOGGER_DOMAIN;
  private static tag: string = LOGGER_TAG;
  private static format: string = '%{public}s';
  private static showLog: boolean = true;

  /**
   * Enable/disable logging globally
   * @param showLog - Enable logging (default: true)
   */
  static setShowLog(showLog: boolean = true) {
    LogUtil.showLog = showLog;
  }

  /**
   * DEBUG level logging
   * @param args - Log messages
   */
  static debug(...args: string[]): void {
    if (LogUtil.showLog) {
      hilog.debug(LogUtil.domain, LogUtil.tag, 
                 LogUtil.format.repeat(args.length), args);
    }
  }

  /**
   * INFO level logging
   * @param args - Log messages
   */
  static info(...args: string[]): void {
    if (LogUtil.showLog) {
      hilog.info(LogUtil.domain, LogUtil.tag, 
                LogUtil.format.repeat(args.length), args);
    }
  }

  /**
   * WARN level logging
   * @param args - Log messages
   */
  static warn(...args: string[]): void {
    if (LogUtil.showLog) {
      hilog.warn(LogUtil.domain, LogUtil.tag, 
                LogUtil.format.repeat(args.length), args);
    }
  }

  /**
   * ERROR level logging
   * @param args - Log messages
   */
  static error(...args: string[]): void {
    if (LogUtil.showLog) {
      hilog.error(LogUtil.domain, LogUtil.tag, 
                 LogUtil.format.repeat(args.length), args);
    }
  }

  /**
   * FATAL level logging
   * @param args - Log messages
   */
  static fatal(...args: string[]): void {
    if (LogUtil.showLog) {
      hilog.fatal(LogUtil.domain, LogUtil.tag, 
                 LogUtil.format.repeat(args.length), args);
    }
  }
}
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Key Features:

  1. Log Level Support: DEBUG, INFO, WARN, ERROR, FATAL
  2. Global Toggle: Enable/disable all logging with setShowLog()
  3. Domain Management: Isolate logs using domains
  4. Public Formatting: Ensures log content visibility
  5. Variadic Parameters: Accepts multiple log arguments

2. Usage Examples 

// Basic logging
LogUtil.info("Application started successfully");

// Multiple parameters
LogUtil.debug("User login", `ID: ${userId}`, `Session: ${sessionToken}`);

// Error handling
try {
  riskyOperation();
} catch (err) {
  LogUtil.error("Operation failed", err.message);
}

// Conditional logging (e.g., in production)
if (__DEV__) {
  LogUtil.setShowLog(true);
} else {
  LogUtil.setShowLog(false);
}
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Best Practices:

  1. Use Appropriate Levels:
    • DEBUG: Development diagnostics
    • INFO: Normal operations
    • WARN: Potential issues
    • ERROR: Recoverable failures
    • FATAL: Critical failures
  2. Tag Organization: 
// Module-specific logger
class PaymentService {
  private static loggerTag = 'PaymentService';

  processPayment() {
    LogUtil.info(this.loggerTag, "Processing payment");
  }
}
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  1. Performance Considerations: 
// Avoid expensive operations in logs
// Bad:
LogUtil.debug(`User data: ${JSON.stringify(largeObject)}`);

// Good:
if (LogUtil.showLog) {
  LogUtil.debug(`User data: ${JSON.stringify(largeObject)}`);
}
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  1. Log Filtering: 
# View logs in terminal
hdc shell hilog | grep AppLogger
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This utility class simplifies logging while maintaining the power of HarmonyOS' native logging system, making it easier to implement consistent logging practices across your application.

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