Logging

SLF4J Facade

We added logging support via Simple Logging Facade for Java (SLF4J). Doing so everybody is able to configure own logging framework according to wishes and requirements.

Important: From now on it's required to set up some kind of logging in your test project. Otherwise, you will see the following message in the console durign execution of the tests:

SLF4J(W): No SLF4J providers were found.
SLF4J(W): Defaulting to no-operation (NOP) logger implementation
SLF4J(W): See https://www.slf4j.org/codes.html#noProviders for further details.
[ERROR] SLF4J(W): No SLF4J providers were found.
[ERROR] SLF4J(W): Defaulting to no-operation (NOP) logger implementation
[ERROR] SLF4J(W): See https://www.slf4j.org/codes.html#noProviders for further details.

Setup logging with Log4j

If you are not sure, what framework to take for logging, we recommend Apache Log4j 2.

To use it, simply add the dependency to your pom.xml:

    <dependency>
      <groupId>org.apache.logging.log4j</groupId>
      <artifactId>log4j-slf4j2-impl</artifactId>
      <version>2.23.1</version>
      <scope>test</scope>
    </dependency>

Now you should be able to instantiate a logger and find messages of level warning and above within the console. Additionally, every logging event of severity error or above will be appended to [PROJECT_PATH]\target\log\neodymium-error.log.

Unfortunately, Log4j doesn't provide a non-programmatic way of extending an existing configuration. Hence, the easiest way to change our configuration is to overwrite ours with your own.

The following listing shows the Log4j configuration provided by Neodymium. This is a good starting point to write your own. Please check out the official Log4j documentation for more details.

  status = warn
  name = NeodymiumConfiguration

  property.filename = target/log/neodymium-error.log

  appender.console.type = Console
  appender.console.name = STDOUT
  appender.console.layout.type = PatternLayout
  appender.console.layout.pattern = %d{HH:mm:ss} %p - %c{1.}: %m%n
  appender.console.filter.threshold.type = ThresholdFilter
  appender.console.filter.threshold.level = trace

  appender.file.type = File
  appender.file.name = FILE
  appender.file.append = true
  appender.file.fileName = ${filename}
  appender.file.layout.type = PatternLayout
  appender.file.layout.pattern = %d %p - %c{1.} [%t]: %m%n
  appender.file.filter.threshold.type = ThresholdFilter
  appender.file.filter.threshold.level = error

  rootLogger.level = warn
  rootLogger.appenderRef.file.ref = FILE
  rootLogger.appenderRef.console.ref = STDOUT

Usage

Before you can log a message you'll need a proper logger instance. The easiest and recommended way to retrieve a Logger instance is to use LoggerFactory.getLogger() as follows:

  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;

  ...

  Logger logger = LoggerFactory.getLogger("NAME_OF_LOGGER"));
  logger.trace("trace");
  logger.debug("debug");
  logger.info("info");
  logger.warn("warn");
  logger.error("error");