使用slf4j和log4j2动态添加appender

Question

我想动态地创建一个appender并将其添加到记录器中。然而，这似乎不可能使用slf4j。我可以将我的appender添加到log4j记录器中，但是我无法使用slf4j LoggerFactle检索记录器。

我想做的是：创建一个测试类（而不是jUnit测试），并在构造函数中传递一个记录器，供测试类使用。测试类的每个实例都需要自己的记录器和appender来保存日志，以便以后在HTML报告中使用。

我尝试了什么（为了简单起见，我创建了一个jUnit测试）：

  import static org.junit.Assert.assertEquals;

  import java.util.LinkedList;
  import java.util.List;

  import org.apache.logging.log4j.core.LogEvent;
  import org.junit.Test;
  import org.slf4j.helpers.Log4jLoggerFactory;

  import ch.fides.fusion.logging.ListAppender;

  public class ListAppenderTest {

      @Test
      public void test() {

          String testName = "test1";

          // the log messages are to be inserted in this list
          List<LogEvent> testLog = new LinkedList<>();

          // create log4j logger
          org.apache.logging.log4j.core.Logger log4jlogger = (org.apache.logging.log4j.core.Logger) org.apache.logging.log4j.LogManager
                                          .getLogger("Test:" + testName);

          // create appender and add it to the logger
          ListAppender listAppender = new ListAppender("Test:" + testName + ":MemoryAppender", testLog);
          log4jlogger.addAppender(listAppender);

          // get the slf4j logger
          org.slf4j.helpers.Log4jLoggerFactory loggerFactory = new Log4jLoggerFactory();
          org.slf4j.Logger testLogger = loggerFactory.getLogger("Test:" + testName);

          // test it
          final String TEST_MESSAGE = "test message";
          testLogger.info(TEST_MESSAGE);

          assertEquals(1, testLog.size());
          LogEvent logEvent = testLog.get(0);
          assertEquals(TEST_MESSAGE, logEvent.getMessage().getFormattedMessage() );
      }

  }

这是我最基本的附录：

 package ch.fides.fusion.logging;

  import java.util.List;

  import org.apache.logging.log4j.core.LogEvent;
  import org.apache.logging.log4j.core.appender.AbstractAppender;

  public class ListAppender extends AbstractAppender {

      private final List<LogEvent> log;

      public ListAppender(String name, List<LogEvent> testLog) {
          super(name, null, null);
          this.log = testLog;
      }

      @Override
      public void append(LogEvent logEvent) {
          log.add(new TestLogEvent(logEvent));
      }

  }

我能做些什么来使它工作？也许我从错误的角度来处理这个问题，但是我想避免创建我自己的日志记录类。非常感谢任何帮助。

Answer 1

如果其他人对此感到困惑，那么slf4j版本1.7.26需要一个构建器模式，该模式与公认的答案相关。以下实现适用于java 8和scala 2.13（与lqbweb的答案略有不同）：

爪哇：

java prettyprint-override">import org.apache.logging.log4j.LogManager
import org.apache.logging.log4j.Level
import org.apache.logging.log4j.core.LoggerContext

LoggerContext loggerContext = (LoggerContext) LogManager.getContext(false)

Configuration configuration = loggerContext.getConfiguration()
LoggerConfig rootLoggerConfig = configuration.getLoggerConfig("")

PatternLayout.Builder layoutBuilder = PatternLayout.newBuilder()
layoutBuilder.withPattern("%d{HH:mm:ss.SSS} %-5level %logger{36} - %msg%n")

RandomAccessFileAppender.Builder<?> appenderBuilder =
(RandomAccessFileAppender.Builder<?>) RandomAccessFileAppender
      .newBuilder()

appenderBuilder.setLayout(layoutBuilder.build())
appenderBuilder.withBufferedIo(true)
appenderBuilder.setFileName(logFile.getAbsolutePath)
appenderBuilder.setName("OutputDirFileLogger")

RandomAccessFileAppender appender = appenderBuilder.build()

appender.start() // important to make the appender usable instantly 


rootLoggerConfig.addAppender(appender, Level.DEBUG, null)

scala：

    import org.apache.logging.log4j.LogManager
    import org.apache.logging.log4j.Level
    import org.apache.logging.log4j.core.LoggerContext

    val loggerContext = LogManager.getContext(false).asInstanceOf[LoggerContext]

    val configuration: Configuration = loggerContext.getConfiguration
    val rootLoggerConfig: LoggerConfig = configuration.getLoggerConfig("")

    val layoutBuilder: PatternLayout.Builder = PatternLayout.newBuilder()
    layoutBuilder.withPattern("%d{HH:mm:ss.SSS} %-5level %logger{36} - %msg%n")

    val appenderBuilder: RandomAccessFileAppender.Builder[_] = RandomAccessFileAppender
      .newBuilder()
      .asInstanceOf[RandomAccessFileAppender.Builder[_]]

    appenderBuilder.setLayout(layoutBuilder.build())
    appenderBuilder.withBufferedIo(true)
    appenderBuilder.setFileName(logFile.getAbsolutePath)
    appenderBuilder.setName("OutputDirFileLogger")

    val appender: RandomAccessFileAppender = appenderBuilder.build()
    appender.start()

    rootLoggerConfig.addAppender(appender, Level.DEBUG, null) 

Answer 2

通过代码/在运行时通过slf4j访问和操作log4j2：

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.LoggerConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Log4j2OverSlf4jConfigurator {

    final private static Logger LOGGER = LoggerFactory.getLogger(Log4j2OverSlf4jConfigurator.class);

    public static void main(final String[] args) {
        LOGGER.info("Starting");
        LoggerContext loggerContext = (LoggerContext) LogManager.getContext(false);
        Configuration configuration = loggerContext.getConfiguration();

        LOGGER.info("Filepath: {}", configuration.getConfigurationSource().getLocation());
        // Log4j root logger has no name attribute -> name == ""
        LoggerConfig rootLoggerConfig = configuration.getLoggerConfig("");

        rootLoggerConfig.getAppenders().forEach((name, appender) -> {
            LOGGER.info("Appender {}: {}", name, appender.getLayout().toString());
            // rootLoggerConfig.removeAppender(a.getName());
        });

        rootLoggerConfig.getAppenderRefs().forEach(ar -> {
            System.out.println("AppenderReference: " + ar.getRef());
        });

        // adding appenders
        configuration.addAppender(null);
    }
}

参考：https://logging.apache.org/log4j/2.x/manual/customconfig.html

Answer 3

我认为您的情况与我们的类似。生产中的日志更复杂，但在JUnit测试期间更简单，这样我们就可以断言没有错误。

如果您使用的是log4j2，那么就有使用构建器的更清洁的解决方案

@Test
public void testClass() {
    LoggerContext loggerContext = (LoggerContext) LogManager.getContext(false);

    Configuration configuration = loggerContext.getConfiguration();
    LoggerConfig rootLoggerConfig = configuration.getLoggerConfig("");
    ListAppender listAppender = new ListAppender("testAppender");

    rootLoggerConfig.addAppender(listAppender, Level.ALL, null);

    new TestClass();    //this is doing writing an error like org.slf4j.LoggerFactory.getLogger(TestClass.class).error("testing this");

    assertEquals(1, listAppender.getEvents().size());
}

需要注意的是，调用getContext时需要传递“false”，否则它似乎无法获得与slf4j相同的上下文。