How to Use Log4j in Selenium WebDriver

This article will show how to use Log4j in your Selenium WebDriver tests. Log4j makes it possible to add logging in your Selenium tests.

Let’s dive in

• What is Log4j?
• How to get started
• The properties file
• Creating a Maven project
• Adding dependencies
• Properties file creation
• Base class creation
• Your first test
• TestNG run configuration
• Exporting logs to a file
• Properties file in detail

What is Log4j?

How to get started

There are four ways to configure Log4j.

1. Using a configuration file written in XML, JSON, YAML, or properties format
2. By creating a ConfigurationFactory and Configuration implementation. (programmatically)
3. By calling the APIs exposed in the Configuration interface to add components to the default configuration. (programmatically)
4. By calling methods on the internal Logger class. (programmatically)

In this article, we will be using option one with a properties configuration file.

The properties file

The properties file may contain various components, including a logger, filter, and appender. Furthermore,

• Each component must have a type attribute specified that identifies the component’s Plugin type.
• The logger element must have a name attribute specified, will usually have a level attribute set, and may also have an additivity attribute specified.
• To configure the level, you can use TRACE, DEBUG, INFO, WARN, ERROR, ALL, or OFF. If no level is specified, it will default to ERROR.
• You may assign a true or false value to the additivity attribute. The default value of true will be used if you omit the attribute.
• Every configuration must have a root logger, with LoggerConfig being the default. LoggerConfig has a level of ERROR and a Console appender attached. The main differences between the root logger and other loggers are:
  • The root logger does not have a name attribute.
  • The root logger does not support the additivity attribute since it has no parent.

Don’t worry if any or all of this doesn’t make sense now. It will all start making more and more sense the more you work with Log4j.

Creating a Maven project

If you are using IntelliJ IDEA, go to File > New > Project > Select Maven > Click Next > Give project a name > Click Finish.

Adding dependencies

Let’s begin by adding the Selenium and TestNG dependencies.

Click here for the latest dependency versions and add them to your pom.xml file.

Next, we need to add the Log4j dependencies.

Log4j consists of an API and an implementation (Core). You will need to add both dependencies to your pom.xml file. Ensure that you select Apache Log4j Core and Apache Log4j API dependencies and not the Apache Log4j dependency (this is the old Log4j 1.x version).

By now, your pom.xml file should look something like this:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>Log4j2Example</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.seleniumhq.selenium</groupId>
            <artifactId>selenium-java</artifactId>
            <version>3.141.59</version>
        </dependency>

        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>7.1.0</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>7.1.0</version>
            <scope>compile</scope>
        </dependency>

        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.13.3</version>
        </dependency>

        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.13.3</version>
        </dependency>
    </dependencies>
</project>

Properties file creation

Add the following properties to log messages to the console.

# configuration syntax
status=error
dest=err
name=PropertiesConfig

# publish console logs
appender.console.type=Console
appender.console.name=STDOUT
appender.console.layout.type=PatternLayout
appender.console.layout.pattern=[%-5level] %d{DEFAULT} %c:%L - %m%n

# capture logs
logger.app.name=base
logger.app.level=debug
logger.app.additivity=false
logger.app.appenderRef.console.ref=STDOUT

# root logger
rootLogger.level=info
rootLogger.appenderRef.stdout.ref=STDOUT

Base class creation

Lastly, add a setUp and tearDown method to the BaseClass with some logging statements.

package base;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.openqa.selenium.WebDriver;
import org.testng.annotations.AfterSuite;
import org.testng.annotations.BeforeSuite;

public class BaseClass {
    public static WebDriver driver;
    public static Logger log = LogManager.getLogger();

    @BeforeSuite
    public void setUp() {
        if (driver == null) {
            log.info("Hello World!");
        }
    }

    @AfterSuite
    public void tearDown() {
        log.info("Goodbye!");
        if (driver != null) {
            driver.quit();
        }
    }
}

Your first test

Create a test called test testHelloWorld and add several logging statements as follows.

package com.automation.testcases;

import base.BaseClass;
import org.testng.annotations.Test;

public class HelloWorld extends BaseClass {

    @Test
    public void testHelloWorld() {
        log.debug("Sample DEBUG message");
        log.error("Sample ERROR message");
        log.info("Sample INFO message");
        log.warn("Sample WARN message");
    }
}

Run TestNG Test

Click the green arrow next to the test name and select Run to execute the test.

As a result, the console output should look something like this:

Congratulations! You have successfully configured Log4j with your Selenium project.

Exporting logs to a file

That was great, but what if you want to export the logs to a file?

To log messages to a file, add a new appender to the properties file of type File with a corresponding logger (logger.app.appenderRef.file.ref). The updated log4j2.properties file should be as follows.

# configuration syntax
status=error
dest=err
name=PropertiesConfig

# publish console logs
appender.console.type=Console
appender.console.name=STDOUT
appender.console.layout.type=PatternLayout
appender.console.layout.pattern=[%-5level] %d{DEFAULT} %c:%L - %m%n

# publish file logs
appender.file.type=File
appender.file.name=LOGFILE
appender.file.fileName=logs/myLog.log
appender.file.layout.type=PatternLayout
appender.file.layout.pattern=[%-5level] %d{DEFAULT} %c:%L - %m%n
appender.file.append=false

# capture logs
logger.app.name=base
logger.app.level=debug
logger.app.additivity=false
logger.app.appenderRef.console.ref=STDOUT
logger.app.appenderRef.file.ref=LOGFILE

# root logger
rootLogger.level=info
rootLogger.appenderRef.stdout.ref=STDOUT

Re-run the test. As a result, this creates a new folder called logs. This folder will contain a file called myLog.log. This log file will have the same log statements as in the console.

Now you know how to use Log4j in your Selenium WebDriver tests.

If you feel that you haven’t had enough yet, read on! Next, we’ll dive deeper into the contents of the properties file by looking at one line at a time.

Properties file in detail

status – The level of internal Log4j events that should be logged to the console. Valid values for this attribute are “trace”, “debug”, “info”, “warn”, “error” and “fatal”. Log4j will log details about initialization, rollover and other internal actions to the status logger. Setting status=”trace” is one of the first tools available to you if you need to troubleshoot log4j.

dest – Accepts either “err” for stderr, “out” for stdout, a file path, or a URL.

name – The name of the configuration.

appender.console.type=Console – The appender which publishes logs to the console.

appender.console.name=STDOUT – The name of the console appender, can be any name you choose.

appender.console.layout.type=PatternLayout – An Appender uses a Layout to format a LogEvent into a form that meets the needs of whatever will be consuming the log event. Click here to learn more about PatterLayout.

appender.console.layout.pattern=[%-5level] %d{DEFAULT} %c:%L – %m%n – Let’s break this down

• %-5level = by default, the amount of space allocated for the log level will be five characters; the “-“ means it will be left-aligned
• %d{DEFAULT} = default date format (example: 2020-01-01 15:00:00,123)
• %c = Outputs the name of the logger that published the logging event
• %L = Outputs the line number from where the logging request was issued
• %m = Outputs the application supplied message associated with the logging event
• %n = Outputs the platform dependent line separator character or characters

appender.file.append – Whether or not you wish to keep adding to the same file or create a new one each time the test runs.

logger.app.name=base – Refers to the package’s name where the Logger is.

logger.app.level=debug – Sets the Logger’s LogLevel to DEBUG.

logger.app.additivity=false – Disables additivity
Click here to learn more.

logger.app.appenderRef.console.ref=STDOUT – The name of the Console appender as entered in appender.console.name (the names must match).

logger.app.appenderRef.file.ref=LOGFILE – The name of the File appender as entered in appender.file.name (the names must match).

rootLogger.level=info – Sets the rootLogger’s LogLevel to INFO

rootLogger.appenderRef.stdout.ref=STDOUT – Specified the rootLogger’s appender as entered in appender.console.name or appender.file.name (the names must match).

References

Log4j documentation