Java 日志记录：slf4j over jul 和 log4j2

Question

应用程序无法覆盖 jul 和 log4j2 日志框架，但可以覆盖：log4j、jcl 和 log4j

应用程序使用slf4j 网桥和logback 作为日志框架。 该应用程序还依赖并调用使用不同日志框架的模块：

1. 七月，
2. log4j (v1),
3. jcl 与 log4j
4. log4j2.

每个模块都有自己的日志配置文件，具体取决于日志框架。配置文件在每个模块的resorces 中定义。

我尝试强制所有模块，不使用自己的日志框架和配置，而只使用slf4j 与logback 桥接。

这里是java代码：

new Slf4jLoggingExample().doLog();
new JulLoggingExample().doLog();
new Log4jLoggingExample().doLog();
new Log4jV2LoggingExample().doLog();
new JclLog4jLoggingExample().doLog();

这里是 maven 配置 WITHOUT 多个桥接库，例如 log4j-over-slf4j、jul-to-slf4j、jcl-over-slf4j。请注意，工件 ID 只是自定义组件：jul、log4j、log4j-v2、jcl-log4j 以突出显示该组件中使用的日志记录框架：

  <dependencies>
    <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.30</version>
    </dependency>
    <dependency>
      <groupId>ch.qos.logback</groupId>
      <artifactId>logback-classic</artifactId>
      <version>1.2.3</version>
    </dependency>
    <dependency>
      <groupId>com.savdev.example.logging</groupId>
      <artifactId>jul</artifactId>
      <version>1.0.0</version>
    </dependency>
    <dependency>
      <groupId>com.savdev.example.logging</groupId>
      <artifactId>log4j</artifactId>
      <version>1.0.0</version>
    </dependency>
    <dependency>
      <groupId>com.savdev.example.logging</groupId>
      <artifactId>log4j-v2</artifactId>
      <version>1.0.0</version>
    </dependency>
    <dependency>
      <groupId>com.savdev.example.logging</groupId>
      <artifactId>jcl-log4j</artifactId>
      <version>1.0.0</version>
    </dependency>
  </dependencies>

这是输出，根据选择和配置的日志框架，每组日志语句具有不同的格式：

12:18:08.316 [main] INFO  c.s.e.logging.Slf4jLoggingExample - This is an info message, (originally, slf4j with logback)
12:18:08.318 [main] ERROR c.s.e.logging.Slf4jLoggingExample - This is an error message, (originally, slf4j with logback)
12:18:08.318 [main] WARN  c.s.e.logging.Slf4jLoggingExample - This is a warning message, (originally, slf4j with logback)
12:18:08.318 [main] DEBUG c.s.e.logging.Slf4jLoggingExample - Here is a debug message, (originally, slf4j with logback)
Feb 24, 2021 12:18:08 PM com.savdev.example.logging.jul.JulLoggingExample doLog
INFO: This is an info message (originally, JUL)
Feb 24, 2021 12:18:08 PM com.savdev.example.logging.jul.JulLoggingExample doLog
SEVERE: This is an error message (originally, JUL)
Feb 24, 2021 12:18:08 PM com.savdev.example.logging.jul.JulLoggingExample doLog
WARNING: This is a warning message (originally, JUL)
Feb 24, 2021 12:18:08 PM com.savdev.example.logging.jul.JulLoggingExample doLog
FINE: Here is a debug message (originally, JUL)
[main] INFO  com.savdev.example.logging.log4j.Log4jLoggingExample  - This is an info message, (originally, log4j)
[main] ERROR com.savdev.example.logging.log4j.Log4jLoggingExample  - This is an error message, (originally, log4j)
[main] WARN  com.savdev.example.logging.log4j.Log4jLoggingExample  - This is a warning message, (originally, log4j)
[main] DEBUG com.savdev.example.logging.log4j.Log4jLoggingExample  - Here is a debug message, (originally, log4j)
[INFO ] 2021-02-24 12:18:08.722 [main] Log4jV2LoggingExample - This is an info message, (originally, log4j2)
[ERROR] 2021-02-24 12:18:08.724 [main] Log4jV2LoggingExample - This is an error message, (originally, log4j2)
[WARN ] 2021-02-24 12:18:08.724 [main] Log4jV2LoggingExample - This is a warning message, (originally, log4j2)
[DEBUG] 2021-02-24 12:18:08.724 [main] Log4jV2LoggingExample - Here is a debug message, (originally, log4j2)
[main] INFO  com.savdev.example.logging.jcl.logback.JclLog4jLoggingExample  - This is an info message (originally, jcl with log4j)
[main] ERROR com.savdev.example.logging.jcl.logback.JclLog4jLoggingExample  - This is an error message (originally, jcl with log4j)
[main] WARN  com.savdev.example.logging.jcl.logback.JclLog4jLoggingExample  - This is a warning message (originally, jcl with log4j)
[main] DEBUG com.savdev.example.logging.jcl.logback.JclLog4jLoggingExample  - Here is a debug message (originally, jcl with log4j)

5 组不同格式的消息。我正在添加多个桥接库：

<!-- https://mvnrepository.com/artifact/org.slf4j/jul-to-slf4j -->
<dependency>
  <groupId>org.slf4j</groupId>
  <artifactId>jul-to-slf4j</artifactId>
  <version>1.7.30</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.slf4j/log4j-over-slf4j -->
<dependency>
  <groupId>org.slf4j</groupId>
    <artifactId>log4j-over-slf4j</artifactId>
  <version>1.7.30</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.slf4j/jcl-over-slf4j -->
<dependency>
  <groupId>org.slf4j</groupId>
  <artifactId>jcl-over-slf4j</artifactId>
  <version>1.7.30</version>
</dependency>

这是新的输出：

12:44:40.385 [main] INFO  c.s.e.logging.Slf4jLoggingExample - This is an info message, (originally, slf4j with logback)
12:44:40.387 [main] ERROR c.s.e.logging.Slf4jLoggingExample - This is an error message, (originally, slf4j with logback)
12:44:40.387 [main] WARN  c.s.e.logging.Slf4jLoggingExample - This is a warning message, (originally, slf4j with logback)
12:44:40.387 [main] DEBUG c.s.e.logging.Slf4jLoggingExample - Here is a debug message, (originally, slf4j with logback)
12:44:40.399 [main] INFO  c.s.e.l.log4j.Log4jLoggingExample - This is an info message, (originally, log4j)
12:44:40.400 [main] ERROR c.s.e.l.log4j.Log4jLoggingExample - This is an error message, (originally, log4j)
12:44:40.400 [main] WARN  c.s.e.l.log4j.Log4jLoggingExample - This is a warning message, (originally, log4j)
12:44:40.400 [main] DEBUG c.s.e.l.log4j.Log4jLoggingExample - Here is a debug message, (originally, log4j)
Feb 24, 2021 12:44:40 PM com.savdev.example.logging.jul.JulLoggingExample doLog
INFO: This is an info message (originally, JUL)
Feb 24, 2021 12:44:40 PM com.savdev.example.logging.jul.JulLoggingExample doLog
SEVERE: This is an error message (originally, JUL)
Feb 24, 2021 12:44:40 PM com.savdev.example.logging.jul.JulLoggingExample doLog
WARNING: This is a warning message (originally, JUL)
Feb 24, 2021 12:44:40 PM com.savdev.example.logging.jul.JulLoggingExample doLog
FINE: Here is a debug message (originally, JUL)
[INFO ] 2021-02-24 12:44:40.793 [main] Log4jV2LoggingExample - This is an info message, (originally, log4j2)
[ERROR] 2021-02-24 12:44:40.795 [main] Log4jV2LoggingExample - This is an error message, (originally, log4j2)
[WARN ] 2021-02-24 12:44:40.795 [main] Log4jV2LoggingExample - This is a warning message, (originally, log4j2)
[DEBUG] 2021-02-24 12:44:40.796 [main] Log4jV2LoggingExample - Here is a debug message, (originally, log4j2)
12:44:40.798 [main] INFO  c.s.e.l.j.l.JclLog4jLoggingExample - This is an info message (originally, jcl with log4j)
12:44:40.798 [main] ERROR c.s.e.l.j.l.JclLog4jLoggingExample - This is an error message (originally, jcl with log4j)
12:44:40.798 [main] WARN  c.s.e.l.j.l.JclLog4jLoggingExample - This is a warning message (originally, jcl with log4j)
12:44:40.798 [main] DEBUG c.s.e.l.j.l.JclLog4jLoggingExample - Here is a debug message (originally, jcl with log4j)

我可以看到，只有带有 log4j 的组件和带有 log4j 的 jcl 更改了它们的日志格式，现在按预期使用主应用程序的日志格式。

但 log4j2 和 jul - 仍然使用自己的日志记录格式，不受此设置的影响。

我已阅读，但 JUL to SLF4J Bridge 没有帮助。以下是所有模块的完整代码：logging github repo

我错过了什么，请你帮忙。

Answer 1

Log4j 2 仍然使用自己的配置的原因是因为您只使用 SLF4J 的 log4j-over-slf4j 用于 Log4j 1（尽管没有明确记录）。对于 Log4j 2 到 SLF4J，您还必须添加 Log4j 2 to SLF4J Adapter (dependency information)。

对于jul-to-slf4j，您必须按照SLF4JBridgeHandler documentation 中描述的步骤进行操作：

• 要么在 JRE 的 logging.properties 文件中指定它。但是，如果您无法控制应用程序运行的环境，那么这可能不是一个选择。
• 或以编程方式安装它：

  static {
    // Verify that it is not installed yet; other dependency might have already
    // installed it which would cause duplicate handler
    // Unfortunately SLF4J provides no built-in method for this procedure, so
    // race condition between different classes could happen
    if (!SLF4JBridgeHandler.isInstalled()) {
      // Remove default handler logging to System.err
      SLF4JBridgeHandler.removeHandlersForRootLogger();
      // Install the SLF4J handler
      SLF4JBridgeHandler.install();
    }
  }
  

此外，您应该为 Logback 配置 LevelChangePropagator。否则，由于 SLF4J 类只是一个处理程序，因此降低 SLF4J 日志级别（例如用于调试）对java.util.logging 没有影响。

但是请注意，重定向java.util.logging 通常会很痛苦，尤其是在您的项目有多个入口点的情况下。您必须在每个入口点中执行 SLF4J 桥初始化检查。

附带说明：java.util.logging 到 Log4j 2 桥 (Log4j JDK Logging Adapter) 的情况也好不到哪里去。该库改为实现LogManager，因此更紧密地集成到java.util.logging，但缺点是必须使用系统属性（或logging.properties文件）指定它并且必须指定在加载 java.util.logging.LogManager 之前（可能不在您的控制范围内），之后无法再指定自定义的 LogManager 实现。
还有一个名为 Log4jBridgeHandler 的 JUL Handler 类，但它只存在于尚未发布的 3.0.0 分支上，尚未向后移植，请参阅 backport pull request。