java - 正确使用log4j和异常

Question

我对 log4j 与异常的使用有疑问。我想将消息记录到我的日志文件中，但我不知道如何处理异常。我必须仅使用异常(因为已经在我的日志文件中打印)或以下内容:

try {
        Configurations.getInstance().getProperty("DynamoDBProfileCredentials");
        credentials = new ProfileCredentialsProvider( Configurations.getInstance().getProperty("DynamoDBProfileCredentials")).getCredentials();

    } catch (Exception e) {
        log.error(new AmazonClientException("Cannot load the credentials from the credential profiles file. " +
                "Please make sure that your credentials file is at the correct " +
                "location (C:\\Users\\your username\\credentials), and is in valid format.",e));

或者这个

try {
        Configurations.getInstance().getProperty("DynamoDBProfileCredentials");
        credentials = new ProfileCredentialsProvider( Configurations.getInstance().getProperty("DynamoDBProfileCredentials")).getCredentials();

    } catch (Exception e) {
        log.error("Cannot load the credentials from the credential profiles file. " +
                "Please make sure that your credentials file is at the correct " +
                "location (C:\\Users\\your username\\credentials), and is in valid format.",e);
        throw new AmazonClientException(
                "Cannot load the credentials from the credential profiles file. " +
                        "Please make sure that your credentials file is at the correct " +
                        "location (C:\\Users\\your username\\credentials), and is in valid format.",
                        e);

提前致谢。

Answer 1

异常只是信号/事件；在您的应用程序范围内发生的情况。记录这些是另一个主题。

我了解您需要在应用程序中记录有用的消息。在您的情况下，您可以在您的方法的使用者上触发日志事件，或者直接按照您的操作触发日志事件。

最简单的情况可能是:

try {
  Configurations.getInstance().getProperty("DynamoDBProfileCredentials");
  credentials = new ProfileCredentialsProvider( Configurations.getInstance().getProperty("DynamoDBProfileCredentials")).getCredentials(); 
} catch (Exception e) {
  AmazonClientException ace = AmazonClientException(
      "Cannot load the credentials from the credential profiles file. " +
      "Please make sure that your credentials file is at the correct " +
      "location (C:\\Users\\your username\\credentials), and is in valid format.", e);

  log.error(ace.getMessage(), ace);
  throw ace;
}

或

try {
  Configurations.getInstance().getProperty("DynamoDBProfileCredentials");
  credentials = new ProfileCredentialsProvider( Configurations.getInstance().getProperty("DynamoDBProfileCredentials")).getCredentials(); 
} catch (Exception e) {
  log.error("Cannot load the credentials from the credential profiles file. " +
      "Please make sure that your credentials file is at the correct " +
      "location (C:\\Users\\your username\\credentials), and is in valid format.",e);
  throw new AmazonClientException(e);
}

上面的例子只是一个实现，并不是对你原来问题的答案。要回答最初的问题，您必须清楚地了解您的 API 以及 API 设计中产生的职责。您想要登录 API 还是只想向调用者发出发生异常的信号？或者两者兼而有之(就像上面的例子一样？)。

在使用异常或任何其他方式传播意外状态之前，请回答以下问题:应如何处理这种情况？异常后应该发生什么？日志记录也不异常(exception)；这只是记录。找到答案后，您可以寻找适当的方式来传达意外状态。