如何在使用Eclipse创建的可运行jar中指定外部log4j2配置文件

Question

Log is created when running project in Eclipse, however when a runnable jar is created (Library handling option: Extract required libraries into generated JAR) the configuration file cannot be found and no log is produced.

When running the jar through the command line (cd into the directory containing the runnable jar) the following is output:

ERROR StatusLogger Unrecognized format specifier [d]
ERROR StatusLogger Unrecognized conversion specifier [d] starting at position 16 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [thread]
ERROR StatusLogger Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [level]
ERROR StatusLogger Unrecognized conversion specifier [level] starting at position 35 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [logger]
ERROR StatusLogger Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [msg]
ERROR StatusLogger Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern.
ERROR StatusLogger Unrecognized format specifier [n]
ERROR StatusLogger Unrecognized conversion specifier [n] starting at position 56 in conversion pattern.
ERROR StatusLogger No log4j2 configuration file found. Using default configuration: logging only errors to the console.

The last bit of the message tells me that the config file cannot be found, although it's reading a configuration PatternLayout from somewhere. When the option -Dlog4j.configurationFile option is added to the command, the following exception occurs (in addition to the previous error messages):

Exception in thread "main" java.lang.ExceptionInInitializerError
Caused by: java.lang.NullPointerException: No Configuration was provided
        at java.util.Objects.requireNonNull(Unknown Source)
        at org.apache.logging.log4j.core.LoggerContext.setConfiguration(LoggerContext.java
:477)
        at org.apache.logging.log4j.core.LoggerContext.reconfigure(LoggerContext.java:561)
        at org.apache.logging.log4j.core.LoggerContext.reconfigure(LoggerContext.java:577)
        at org.apache.logging.log4j.core.LoggerContext.start(LoggerContext.java:212)
        at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextF
actory.java:242)
        at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextF
actory.java:45)
        at org.apache.logging.log4j.LogManager.getContext(LogManager.java:174)
        at org.apache.logging.log4j.LogManager.getLogger(LogManager.java:618)
        at test.SmokeTest.<clinit>(SmokeTest.java:41)

I have tried specifying the -Dlog4j.configurationFile value as "c:/path/to/config/log4j2.xml" and "file://c:/path/to/config/log4j2.xml" and get the same error. That last line in the exception message is the initialization of the logger. In the code I have tried to initialize the logger with the following options:

 - private static final Logger logger =
   LogManager.getLogger("c:/path/to/config/log4j2.xml");
 - private static final Logger logger = LogManager.getLogger("logger name specified in config file");

Before writing to the file, I set the log4j.configurationFile system property. Tried the following options:

- System.setProperty("log4j.configurationFile", "C:\\path\\to\\config\\log4j2.xml")
- System.setProperty("log4j.configurationFile", "file://c:/path/to/config/log4j2.xml")

I have also tried using the BasicConfigurator.configure() and PropertyConfigurator.configure() methods from importing import org.apache.log4j.BasicConfigurator and PropertyConfigurator from original log4j (log4j-1.2.17.jar).

Thinking that maybe log4j2 was unable to get its configuration from an external file, I put a copy of the log4j2.xml file in the src folder of the project. Then tried initializing the logger with:

- private static final Logger logger = LogManager.getLogger(MyClass.class.getName());
- private static final Logger logger = LogManager.getLogger(SmokeTest.class);

Both gave me the same errors, but perhaps that's why it works when running from Eclipse?

Also, if I double click the program icon or run from command line without -Dlog4j.configurationFile option, the application launches but does not produce log.

Please help me to troubleshoot this problem and let me know if you need me to provide any further information. I know similar questions have been asked before, but I am unable to find a solution that works for my issue; runnable jar, Eclipse, external log4j2 configuration file. Not using Ant or Maven.

Answer 1

My problem was that I was calling the log before initializing it.
Everything was packaged correctly and the main class had the proper code for log4j. The culprit was a class level object that was initialized before main executed. That object's constructor logged its creation. This did not cause any error when debugging in Eclipse, but stopped the executable from running.
Thanks @Andreas for giving me the ideal of starting over from a new project.

Answer 2

Don't know what you're doing wrong, but here is an MCVE .

Test.java

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

public class Test {
    private static transient Logger log = LogManager.getLogger(Test.class);
    public static void main(String[] args) {
        log.info("Hello World");
    }
}

log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Root level="info">
      <AppenderRef ref="Console"/>
    </Root>
  </Loggers>
</Configuration>

Add Apache Log4j 2 to Eclipse build path: log4j-api-2.7.jar and log4j-core-2.7.jar .

Create jar file using Eclipse File > Export... > Runnable JAR file > Extract required libraries into generated JAR with name Test.jar .

Run with:

java -Dlog4j.configurationFile=C:\path\to\log4j2.xml -jar Test.jar

Output

14:06:23.728 [main] INFO  Test - Hello World