来自 XML 字节流的 Log4J2 编程配置

Question

我对 Log4J2 的束缚已经走到了尽头，希望有人能提供帮助。启动后不久，我有以下代码来初始化 Log4J2：

try (InputStream configStream = new ByteArrayInputStream(writer.toString().getBytes("UTF-8"))) {            
    ConfigurationSource configurationSource = new ConfigurationSource(configStream);
    Configurator.initialize(null, configurationSource);
}

其中 writer 是 StringWriter 并且 toString() 产生以下配置（我已通过其他方式验证它是正确的）：

<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
    <Appenders>
        <Console name="C" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS z} %-5p %m%n"/>
        </Console>
        <RollingFile name="R" fileName="C:\temp\logfile.log" filePattern="C:\temp\logfile.log.%d{yyyy-MM-dd}">
            <PatternLayout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS z} %-5p [%t] %m%n"/>
            <Policies>
                <TimeBasedTriggeringPolicy interval="1" modulate="true"/>
            </Policies>
        </RollingFile>
    </Appenders>
    <Loggers>
        <Logger name="somename" level="debug">
            <appender-ref ref="R"/>
        </Logger>
        <Root level="debug" additivity="false">
            <appender-ref ref="C" level="info"/>
        </Root>
    </Loggers>
</Configuration>

正如您可能已经猜到的那样，这不起作用，除了预期之外，我没有收到任何错误消息：

ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console.

之所以这么说是意料之中的，是因为我正在手动配置 Log4J2 并且还没有抑制此消息。

很遗憾，由于遗留原因，我无法从文件中读取配置。

更新 1：

在听取 Remko 的建议后，我在调用初始化方法之前添加了以下代码块：

System.setProperty("log4j2.disable.jmx", "true");
StatusLogger status = StatusLogger.getLogger();
status.clear(); // remove old listeners that may prevent status output
status.setLevel(Level.TRACE);
status.reset(); // I could not see any trace info until I called this
status.trace("Status -- TRACE"); // I added this to prove that trace level logging was working

这给了我以下输出：

ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console.
TRACE StatusLogger Status -- TRACE
DEBUG StatusLogger Stopping LoggerContext[name=sun.misc.Launcher$AppClassLoader@647e05, org.apache.logging.log4j.core.LoggerContext@a3defe]
DEBUG StatusLogger Stopping LoggerContext[name=sun.misc.Launcher$AppClassLoader@647e05, org.apache.logging.log4j.core.LoggerContext@a3defe]...
DEBUG StatusLogger Unregistering MBean org.apache.logging.log4j2:type=sun.misc.Launcher$AppClassLoader@647e05
DEBUG StatusLogger Unregistering MBean org.apache.logging.log4j2:type=sun.misc.Launcher$AppClassLoader@647e05,component=StatusLogger
DEBUG StatusLogger Unregistering MBean org.apache.logging.log4j2:type=sun.misc.Launcher$AppClassLoader@647e05,component=ContextSelector
DEBUG StatusLogger Unregistering MBean org.apache.logging.log4j2:type=sun.misc.Launcher$AppClassLoader@647e05,component=Appenders,name=Console
TRACE StatusLogger Stopping org.apache.logging.log4j.core.config.DefaultConfiguration@1a1440e...
TRACE StatusLogger AbstractConfiguration stopped 0 AsyncLoggerConfigs.
TRACE StatusLogger AbstractConfiguration stopped 0 AsyncAppenders.
DEBUG StatusLogger Shutting down OutputStreamManager SYSTEM_OUT
TRACE StatusLogger AbstractConfiguration stopped 1 Appenders.
TRACE StatusLogger AbstractConfiguration stopped 0 Loggers.
DEBUG StatusLogger Stopped org.apache.logging.log4j.core.config.DefaultConfiguration@9a6398 OK
DEBUG StatusLogger Stopped LoggerContext[name=sun.misc.Launcher$AppClassLoader@647e05, org.apache.logging.log4j.core.LoggerContext@9a6398]...

更新 2：

我决定找出一种方法来处理文件而不是 ByteArrayInputStream 并让它工作。 FWIW，我认为 Log4J2 代码中存在错误，当尝试使用 InputStream 进行初始化时，我的理论：

在Log4jContextFactory中如下方法：

public LoggerContext getContext(final String fqcn, final ClassLoader loader, final Object externalContext,
                                final boolean currentContext, final ConfigurationSource source)

有以下if语句，总是返回false，表示总是返回默认配置...

if (ctx.getState() == LifeCycle.State.INITIALIZED) {
    if (source != null) {
        ContextAnchor.THREAD_CONTEXT.set(ctx);
        final Configuration config = ConfigurationFactory.getInstance().getConfiguration(source);
        LOGGER.debug("Starting LoggerContext[name={}] from configuration {}", ctx.getName(), source);
        ctx.start(config);
        ContextAnchor.THREAD_CONTEXT.remove();
    } else {
        ctx.start();
    }
}

Answer 1

乍一看，我不明白为什么您的配置不起作用。 （您可以尝试在路径中使用正斜杠以确保绝对确定，但很可能斜杠不是问题。）

您可以尝试以下操作以生成更多 log4j2 调试输出，以查看配置出错的地方吗？请在您的问题中发布结果。

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.status.StatusLogger;

// In an XML configuration you can just use <Configuration status="TRACE"...
// Here we use less elegant code to switch on status logging 
// since we're not sure where things break down.
System.setProperty("log4j2.disable.jmx", "true");
StatusLogger status = StatusLogger.getLogger();
status.clear(); // remove old listeners that may prevent status output
status.setLevel(Level.TRACE);

// now configure log4j2...
// This should generate trace-level debug output to the console.
try (InputStream configStream = new ByteArrayInputStream(writer.toString().getBytes())) {            
    ConfigurationSource configurationSource = new ConfigurationSource(configStream);
    Configurator.initialize(null, configurationSource);
}