Question

我正在尝试获取log4j日志文件的文件名。我尝试了以下答案中给出的解决方案。

https://stackoverflow.com/a/4401387/1015678

Enumeration e = Logger.getRootLogger().getAllAppenders();
while ( e.hasMoreElements() ){
  Appender app = (Appender)e.nextElement();
  if ( app instanceof FileAppender ){
    System.out.println("File: " + ((FileAppender)app).getFile());
  }
}

但是，Logger.getRootLogger().getAllAppenders()返回空枚举。（我注意使用答案中提到的rootLogger

以下是我的log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="DEBUG">
    <Properties>
        <!-- This will be used if LOG_FILE_NAME env variable is not set  -->
        <Property name="LOG_FILE_NAME">my_app_log</Property>
    </Properties>
    <Appenders>
        <RollingFile name="RollingFile-${web:contextPath}"
                     fileName="${sys:catalina.base}/logs/${env:LOG_FILE_NAME}.log" immediateFlush="true"
                     filePattern="${sys:catalina.base}/logs/${env:LOG_FILE_NAME}.log.%d{yyyy_MM_dd.HH_mm_ss}">
            <PatternLayout pattern="%d{yyyyMMdd-HHmmss.SSS}|%-5p|%t| %-100m (%c{1})%n"/>
            <Policies>
                <OnStartupTriggeringPolicy/>
            </Policies>
        </RollingFile>
    </Appenders>
    <Loggers>
        <Root level="DEBUG" includeLocation="false">
            <AppenderRef ref="RollingFile-${web:contextPath}"/>
        </Root>
    </Loggers>
</Configuration>

知道为什么吗？

Answer 1

我刚刚对grep apache-log4j-2.3-src的所有来源getAllAppenders进行了@SuppressWarnings("rawtypes") public Enumeration getAllAppenders() { return NullEnumeration.getInstance(); }，我发现它只在一个地方实现了。

在Category.java中

/**
 * Add an appender and see if it can be retrieved.
 *  Skipping this test as the Appender interface isn't compatible with legacy Log4j.
public void testAppender1() {
    logger = Logger.getLogger("test");
    a1 = new ListAppender("testAppender1");
    logger.addAppender(a1);

    Enumeration enumeration = logger.getAllAppenders();
    Appender aHat = (Appender) enumeration.nextElement();
    assertEquals(a1, aHat);
} */

/**
 * Add an appender X, Y, remove X and check if Y is the only
 * remaining appender.
 * Skipping this test as the Appender interface isn't compatible with legacy Log4j.
public void testAppender2() {
    a1 = new FileAppender();
    a1.setName("testAppender2.1");
    a2 = new FileAppender();
    a2.setName("testAppender2.2");

    logger = Logger.getLogger("test");
    logger.addAppender(a1);
    logger.addAppender(a2);
    logger.removeAppender("testAppender2.1");
    Enumeration enumeration = logger.getAllAppenders();
    Appender aHat = (Appender) enumeration.nextElement();
    assertEquals(a2, aHat);
    assertTrue(!enumeration.hasMoreElements());
}  */

上述方法返回其中没有元素的Enumeration。

另一个是在LoggerTest.java中，来执行测试用例。

Logger logger = LogManager.getLogger();
Map<String, Appender> appenderMap = 
        ((org.apache.logging.log4j.core.Logger) logger).getAppenders();

看到上面的评论，看起来它已被弃用，甚至测试用例都被注释掉了。但我不确定，我试图找出他们是否曾在任何地方宣布，但无法找到。

所以我认为这会有所帮助，除非现在浪费时间进行调试。

正如本answer中所述，使用getAppenders api

var request = FBSDKGraphRequest(graphPath:"/me/taggable_friends", parameters: nil);

Answer 2

您正在将Log4j 1构造与Log4j 2混合使用。您无法使用Log4j 1 API查询Log4j 2配置。

打印出FileAppender的文件名：

final LoggerContext ctx = (LoggerContext) LogManager.getContext(false);
final Configuration config = ctx.getConfiguration();
for (Map.Entry<String, Appender> entry : config.getAppenders().entrySet()) {
    if (entry.getValue() instanceof FileAppender) {
        System.out.println("File: " + ((FileAppender)entry.getValue()).getFileName());
    }
}

Log4j getAllAppenders（）返回null枚举

2 个答案: