Using a XML File (log4j2.xml) to configure

问题:

I want to use the new Log4J 2 - Java Logging Framework. Everything work fine, but I tried since a hour to load a custom configuration file to configure the logging (like log level).

This is my log4j2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<configuration status="OFF">
  <appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </appenders>
  <loggers>
    <root level="error">
      <appender-ref ref="Console"/>
    </root>
  </loggers>
</configuration>

I tried the following, but nothing works:

• Move the log4j2.xml file so it's located in the default package.
• Move the log4j2.xml file anywhere in the project
• Name the log4j2.xml file as "log4j.xml"
• Create a folder in your project, place your log4j2.xml file there and add that folder to your runtime classpath

Since the official website can't help me, I hope you can help me get Log4j 2 working with my configuration file.

回答1:

Important: make sure the name of the configuration file is log4j2.xml (note the 2 before the period) as opposed to log4j.xml

My guess is nothing's happening because nothing is logged using the error level. You may want to try adding another logger like so:

<logger name="com.foo.Bar" level="trace">
  <appender-ref ref="Console"/>
</logger>

Looks like the Configuration section might be a good resource.

To elaborate further, you're specifying a logger with the level set to "error":

<root level="error">
  <appender-ref ref="Console"/>
</root>

This means that only the messages logged using Level.ERROR will show up in the log. Adding a logger with a less restrictive level will allow for more messages to appear in the log. I recommend taking a look at the Architecture section of the manual (if you scroll down the page you'll see the table that explains logging levels). Alternatively, you could just change the level of the root logger to trace (instead of adding a new logger)

Given the configuration you specified, executing the code below yields something like 13:27:50.244 [main] ERROR com.example.Log4j2Tester - testing ERROR level

package com.example;

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

public class Log4j2Tester {
    private static final Logger LOG = LogManager.getLogger(Log4j2Tester.class);

    public static void main(String[] args) {
        LOG.error("testing ERROR level");

//if you change the level of root logger to 'trace'
//then you'll also see something like
//    13:27:50.244 [main] TRACE com.example.Log4j2Tester - exiting application
        LOG.trace("exiting application");
    }
}

回答2:

TIP : To use custom log4j files. (Rather default "log4j2.xml" thingie). It might be useful to have multiple configurations in some instances.

Just in case if any one using maven and wish to configure log4j2, Here is what you need in your pom.xml :

                <systemProperties>
                    <property>
                        <name>/log4j.configuration</name>
                        <value>.../../Foo-log4j.xml</value>
                    </property>
                </systemProperties>

By default, "log4j2.xml" is the file name expected. But however, we can override that by setting log4j.configuration system property. In the above example, I have used custom configuration file as "Foo-log4j.xml".

You can do the same via CLI :

-Dlog4j.configuration="Foo-log4j.xml"

回答3:

My 2 cents:

Software system: log4j 2, NetBeans and TestNG.

I had the same problem, but with the testing environment.

In default, (that is, in log4j2.xml file located in src/) the logging level is set to error. But when running the tests, I want the logging to be trace. And, of course logged to some more or less hardcoded file.

That is, originally I did something like:

public class someTestClass {
       static final Logger log=LogManager.getLogger("test.someTestClass");
......
@Test
public void SomeMethod(){

System.setProperty("log4j.configurationFile", "resources/log4j2_conf.xml");

log.trace("This will not show because the default logging level is ERROR
and the resources/log4j2_conf.xml is not loaded");

}

The problem is that by the time the System.setProperty instruction will be executed, the log4j will be already be set (That is, the static final Logger log =... will be executed first.)

What I did, is use the @BeforeClass like this:

 public class someTestClass {
    Logger log;      
    @BeforeClass
    public void setLogger(){
        SetEnv.SetEnvironment();
        log = LogManager.getLogger("TestRealClientRealServer");
    }
......
    @Test
    public void SomeMethod(){

        log.trace("This will show, because in log4j2_conf.xml
 the root level is set to TRACE");

    }
}

BTW, resources/ can be placed in test packages so you don't ship the "test" log4j setup.

Hope it helps

回答4:

Besides to use the default configuration file, log4j2.xml (or log4j2-test.xml) in the class path root folder, you can use this system property to specify the configuration file path (use the -D in the java command line)

log4j.configurationFile='xxxx/xxx/xxx'  

回答5:

A tip for eclipse users:

Right click on the project and click "refresh". Make sure you could see the log4j2.xml file in eclipse.

Full answer here: log4j 2 - configuration issue

回答6:

Put the LOG4J2.XML in the project´s root folder src/main.