This document provides an overview of common tools used for building, logging, and unit testing Java applications: Maven for build automation, Log4J2 and SLF4J for logging, and JUnit for unit testing. It describes the purpose and basic usage of each tool. For Maven, it covers the standard project layout, dependencies, lifecycle, and POM file. For logging, it explains Log4J2 configuration and best practices. And for testing, it introduces the JUnit framework and common assertions.

1. Build, Logging, and Unit Test
Tools
Allan Huang @ Delta DRC

2. Agenda
 Build Tool
◦ Maven
 Logging Tool
◦ Log4J 2 and SLF4J
 Unit Test Tool
◦ JUnit 4

3. Build Tool

4. What is Maven?
 Aspects of building software
◦ How software is built?
◦ What are its dependencies?
 Convention over Configuration
 Maven
◦ Software project management tool
◦ Build-automation tool
 Manage project’s build, dependency
and documentation

5. Maven Overview

6. Standard Directory Layout (1)
 src/main
◦ Contains all of the code and resources needed
for building the artifact.
◦ src/main/java
 Contains the deliverable Java source code for the project.
◦ src/main/resources
 Contains any configuration files, data files, or Java
properties to include in the bundle.
◦ src/main/scripts
 Contains some kinds of application usage scripts, e.g.
windows batch script, Linux shell script.
◦ src/main/webapp
 Contains your Java web application, if your project is a
web application. It is the root directory of the web
application.

7. Standard Directory Layout (2)
 src/test
◦ Contains all of the code and resources for running unit
tests against the compiled artifact.
◦ src/test/java
 Contains the testing Java source code (JUnit or TestNG test cases,
for example) for the project.
◦ src/test/resources
 Contains resources necessary for testing.
 src/assembly
◦ Contains some assembly descriptors for creating
distributions in the target directory.
 target
◦ It is used to house all output of the build.
 pom.xml
◦ The top level files descriptive of the project.

8. Dependency Scope
 Compile
◦ Compile dependencies are available in all class-paths of a
project.
 Provided
◦ Indicates you expect the JDK or a container to provide the
dependency at runtime.
 Runtime
◦ Indicates that the dependency is not required for
compilation, but is for execution.
 Test
◦ Indicates that the dependency is only available for the test
compilation and execution phases.
 System
◦ You have to provide the JAR which contains it explicitly.
The artifact is always available and is not looked up in a
repository.

9. Build Lifecycle
 Clean
◦ Remove all files generated by the
previous build.
 Default
◦ validate → compile → test → package →
integration-test → verify → install →
deploy
 Site
◦ Generates the project's site
documentation.

10. Default Lifecycle (1)
 Validate
◦ validate the project is correct and all necessary
information is available.
 Compile
◦ Compile the source code of the project.
 Test
◦ Test the compiled source code using a suitable
unit testing framework.
◦ These tests should not require the code be
packaged or deployed.
 Package
◦ Take the compiled code and package it in its
distributable format, such as a JAR.

11. Default Lifecycle (2)
 Integration-test
◦ Process and deploy the package if necessary
into an environment where integration tests can
be run.
 Verify
◦ Run any checks to verify the package is valid
and meets quality criteria.
 Install
◦ Install the package into the local repository, for
use as a dependency in other projects locally.
 Deploy
◦ Done in an integration or release environment,
copies the final package to the remote repository
for sharing with other developers and projects.

12. POM
 Project Object Model (POM)
◦ Contains a complete description of how to
build the current project.
◦ pom.xml
 Effective POM
 Parent/Super POM and Sub POM

13. Repository Type
 Local repository
 Remote repository
 Maven Central
repository
◦ http://search.maven.o
rg

14. Build with Maven
 Environment Setup
◦ Set JAVA_HOME
◦ Set M2_HOME
◦ Add M2_HOME/bin to System PATH
◦ Verify with command line
 mvn –version
 Local Repository Setting
◦ M2_HOME/conf/settings.xml
 localRepository & proxies setting
 Build projects with command line
◦ mvn (default goal)
 Target
◦ Classes, Test-classes, Test reports, JAR, WAR, etc.

15. Reference
 Apache Maven
 Maven Tutorial
 Introduction to the Standard Directory
Layout
 Maven Directory Structure
 Introduction to the Dependency
Mechanism
 Introduction to the Build Lifecycle
 Maven in 5 Minutes
 Maven - Environment Setup

16. Logging Tool

17. What is Log4J 2?
 A fast and flexible framework for
logging application debugging
messages.
 Logging behavior can be controlled by
editing a configuration file, without
touching the application binary.
 Log4j 2 is an upgrade to Log4j.

18. What is SLF4J?
 Simple Logging Facade for Java
◦ Serves as a simple facade or abstraction
for various logging frameworks allowing
the end user to plug in the desired logging
framework at deployment time.
 Well-known logging frameworks
◦ Log4j 2, Log4j
◦ Logback
◦ Java Util Logging

19. SLF4J bound to Log4J

20. SLF4J, JDK Logging and
Log4J 2

21. Log Level
 ERROR (be suited for Production environment)
◦ Something terribly wrong had happened, that must be
investigated immediately.
 e.g. Null pointer, Database unavailable, Mission critical.
 WARN (be suited for Production environment)
◦ The process might be continued, but take extra caution.
 e.g. Database connection lost, Socket reaching to its limit.
 INFO (be suited for Test/QA environment)
◦ Important process has finished. Then quickly find out what
the application is doing.
 e.g. Server has been started, Incoming messages, Outgoing
messages.
 DEBUG (be suited for Development environment)
◦ It is used by the developers to debug the systems.
 ALL, FATAL, TRACE, OFF levels are rarely used.

22. SLF4J Common API
 private static final Logger log =
LoggerFactory.getLogger(UserServiceImpl.class);
 void debug(String msg)
 void debug(String format, Object... arguments)
 void debug(String msg, Throwable t)
 void info(String msg)
 void info(String format, Object... arguments)
 void info(String msg, Throwable t)
 void warn(String msg)
 void warn(String format, Object... arguments)
 void warn(String msg, Throwable t)
 void error(String msg)
 void error(String format, Object... arguments)
 void error(String msg, Throwable t)

23. Log4J 2 Configuration (1)
 log4j2.xml
 Appenders
◦ Console Appender
◦ Rolling File Appender
 OnStartup Triggering Policy
 SizeBased Triggering Policy
 TimeBased Triggering Policy
 Loggers
 Root Logger
 Named Logger
 Named Hierarchy

24. Log4J 2 Configuration (2)

25. Logging Tips (1)
 Use the appropriate tools for the job
◦ log.debug("Found {} records matching filter: '{}'", records, filter);
 Don’t forget, logging levels are there
for you
 Do you know what you are logging?
◦ log.debug("Processing request with id: {}", request.getId());
◦ log.debug("Returning users: {}", users);
 Avoid side effects
◦ try {
log.trace("Id=" + request.getUser().getId() + " accesses " +
manager.getPage().getUrl().toString())
} catch(NullPointerException e) {
}

26. Logging Tips (2)
 Be concise and descriptive
◦ log.debug("Message processed");
log.debug(message.getJMSMessageID());
log.debug("Message with id '{}' processed",
message.getJMSMessageID());
 Tune your pattern in log4j2.xml
 Log method arguments and return values
 Watch out for external systems
◦ Communicates with an external system, consider logging every
piece of data that comes out from your application and gets in.

27. Logging Tips (3)
 Log exceptions properly
 Logs easy to read, easy to parse

28. Reference
 Frequently Asked Questions about
SLF4J
 FAQ about Log4j 2
 SLF4J Logger API
 Log4J 2 Appenders
 log4j2 xml configuration example
 10 Tips for Proper Application Logging
 Logging Anti-Patterns
 Logging in Java with slf4j

29. Unit Test Tool

30. What is JUnit 4?
 A simple unit testing framework to
write repeatable tests for Java.
 Test-Driven Development (TDD)
◦ Test-first Development
◦ High Code Coverage
 A static main method vs. Unit test
cases
 JUnit 4 is an upgrade to JUnit 3.

31. JUnit Execution Order

32. Generate a Test Class

33. JUnit 4 Features

34. JUnit 4 Assert method
 assertArrayEquals(message, expecteds, actuals)
◦ Tests whether two arrays are equal to each other.
 assertEquals(message, expected, actual)
◦ Compares two objects for equality, using their equals() method.
 assertTrue(message, condition) & assertFalse(message, condition)
◦ Tests a single variable to see if its value is either true, or false.
 assertNull(message, object) & assertNotNull(message, object)
◦ Tests a single variable to see if it is null or not null.
 assertSame(message, expected, actual) & assertNotSame(message,
unexpected, actual)
◦ Tests if two object references point to the same object or not.
 assertThat(message, actual, matcher)
◦ Compares an object to an org.hamcrest.Matcher to see if the given object matches
whatever the Matcher requires it to match.
 fail(message)
◦ Fails a test with the given message.

35. Reference
 JUnit
 Junit 3 vs Junit 4 Comparison
 Assert Methods
 Assert (JUnit API)

36. Q & A