Question

我对Log4j2很新，所以可能它不是一个bug，只是我不知道如何正确使用它。

我想通过log4j.configurationFile系统属性指定的配置文件配置Log4j2。在我之前的实验中，我能够使用正确放置的log4j2.xml配置log4j2，并且工作正常。 现在，如果系统属性存在，我得到NullPointerException：

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 T E S T S
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Running newpackage.Log4jSyspropProblemTest
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
Caused by: java.lang.NullPointerException
    at java.io.Writer.write(Writer.java:157)
    at java.io.BufferedWriter.newLine(BufferedWriter.java:243)
    at java.io.PrintStream.newLine(PrintStream.java:544)
    at java.io.PrintStream.println(PrintStream.java:824)
    at java.lang.Throwable$WrappedPrintStream.println(Throwable.java:748)
    at java.lang.Throwable.printStackTrace(Throwable.java:655)
    at java.lang.Throwable.printStackTrace(Throwable.java:643)
    at org.apache.logging.log4j.simple.SimpleLogger.logMessage(SimpleLogger.java:165)
    at org.apache.logging.log4j.status.StatusLogger.logMessage(StatusLogger.java:220)
    at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:1336)
    at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1325)
    at org.apache.logging.log4j.spi.AbstractLogger.error(AbstractLogger.java:551)
    at org.apache.logging.log4j.core.pattern.PatternParser.createConverter(PatternParser.java:528)
    at org.apache.logging.log4j.core.pattern.PatternParser.finalizeConverter(PatternParser.java:569)
    at org.apache.logging.log4j.core.pattern.PatternParser.parse(PatternParser.java:364)
    at org.apache.logging.log4j.core.pattern.PatternParser.parse(PatternParser.java:163)
    at org.apache.logging.log4j.core.layout.PatternLayout.<init>(PatternLayout.java:124)
    at org.apache.logging.log4j.core.layout.PatternLayout.<init>(PatternLayout.java:54)
    at org.apache.logging.log4j.core.layout.PatternLayout$Builder.build(PatternLayout.java:368)
    at org.apache.logging.log4j.core.config.DefaultConfiguration.<init>(DefaultConfiguration.java:56)
    at org.apache.logging.log4j.core.LoggerContext.<init>(LoggerContext.java:72)
    at org.apache.logging.log4j.core.selector.ClassLoaderContextSelector.locateContext(ClassLoaderContextSelector.java:218)
    at org.apache.logging.log4j.core.selector.ClassLoaderContextSelector.getContext(ClassLoaderContextSelector.java:144)
    at org.apache.logging.log4j.core.selector.ClassLoaderContextSelector.getContext(ClassLoaderContextSelector.java:80)
    at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:72)
    at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:37)
    at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:468)
    at newpackage.Log4jSyspropProblemTest.testLoggerSuccesfullyLoaded(Log4jSyspropProblemTest.java:44)
    ... 30 more

我不知道。对我来说似乎一切都很好。这是我的属性文件“src / main / resources / AppProperties.properties”：

log4j.configurationFile=src/main/resources/log4j2_custom.xml

src / main / resources / log4j2_custom.xml的相关部分：

<configuration status="info" monitorIntervall="30" strict="true">
    <properties>
        <Property name="filename">logs/myLog.log</Property>
    </properties>
    <appenders> 
        <appender type="File" name="fileAppender" filename="${filename}">
            <layout type="PatternLayout">
                <pattern>%d %p %C{1.} [%t] %m%n</pattern>
            </layout>
        </appender>
    </appenders>
    <loggers>
        <logger name="fileLogger">
            <appenderRef ref="fileAppender"/>
        </logger>
    </loggers>
</configuration>

测试：

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class Log4jSyspropProblemTest {
    private Logger fileLogger;
    private static final String PROPERTIES_FILE = "src/main/resources/AppProperties.properties";
    private static final String LOG4J_CONFIGURATION_PROPERTY_NAME = "log4j.configurationFile";
    @Test
    public void testPropertyIsValid(){
        final String configFile = System.getProperty(LOG4J_CONFIGURATION_PROPERTY_NAME);
        Assert.assertNotNull(configFile);
        Assert.assertTrue(new File(configFile).exists());
    }

    @Test
    public void testLoggerSuccesfullyLoaded(){
        fileLogger = LogManager.getLogger("fileLogger");
        Assert.assertNotNull(fileLogger);
    }

}

最后这里是pom.xml的依赖项：

<dependencies>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.0.1</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.0.1</version>
    </dependency>
</dependencies>

如果你发现了什么，请告诉我。非常感谢任何想法。

Answer 1

我终于意识到这个问题与Log4j2完全无关。当我打算将属性添加到系统属性时，我意外地清除了除log4j.configurationFile之外的每个系统属性。这是源自JDK的所有奇怪异常的根本原因。

当log4j.configurationFile系统属性存在时，Log4j会因NullPointerException而崩溃

1 个答案: