AspectJ Example with log4j2

Develop an web application using AspectJ and log4j2.

1.       First we have to add required jars in WEB-INF/lib folder. The following jars are need to develop AspectJ with web application.

2.       Secondly we will create META-INF folder under src folder.

3.       Next we will add aop.xml file under META-INF folder like below structure.

4.       My requirement is I want to log each and every public method entrance and exit inside my project.

5.       For this we need to create one aspect class and one configuration file (aop.xml).

6.       AspectJ provides some annotations like @Before, @After, @AfterReturning, @AfterThrowing ,@Around, @Pointcut

7.       Now we are using @Before and @After. Here @Before defines before each and every public method calling and @After defines each and every public method after calling.

8.       Create a class for aspect  .Here I am creating LogAspect.java

LogAspect.java

@Aspect

public class LogAspect {

       private static Logger logger = LogManager.getLogger(LogAspect.class);

       @Pointcut("execution(public * *.*(..))")

       public void defineEntryPoint() {

       }

       @Before("defineEntryPoint()")

       public void beforeMethod(JoinPoint joinPoint) {

//            System.out.println("Before" + joinPoint.getSignature());

              logger.info("Before : " + joinPoint.getSignature());

       }

       @After("defineEntryPoint()")

       public void afterMethod(JoinPoint joinPoint) {

//            System.out.println("After" + joinPoint.getSignature());

       logger.info("After :" + joinPoint.getSignature());

       }

}

9.       Now add aop.xml file. In this file we configure LogAspect class and what are all the packages weave the AspectJ agent.

           aop.xml

<!DOCTYPE aspectj PUBLIC "-//AspectJ//DTD//EN" "http://www.eclipse.org/aspectj/dtd/aspectj.dtd">

<aspectj>

       <weaver>

              <!-- only weave classes in our application-specific packages -->

              <include within="com.msr..*" />

       </weaver>

       <aspects>

              <!-- weave in just this aspect -->

              <aspect name="com.msr.aspects.LogAspect" />

       </aspects>

</aspectj>

10.   For testing purpose I am creating one servlet class.

Test.java

@WebServlet("/Test")

public class Test extends HttpServlet {

       private static final long serialVersionUID = 1L;

       public Test() {

              super();

              // TODO Auto-generated constructor stub

       }

       protected void doGet(HttpServletRequest request,

                     HttpServletResponse response) throws ServletException, IOException {

              PrintWriter out = null;

              try {

                     out = response.getWriter();

                    Sample.mySample();

                     out.write("hello from MyServlet");

              } catch (IOException e) {

                     e.printStackTrace();

              } finally {

                     if (out != null)

                           out.close();

              }

       }

}

Sample.java

public class Sample {

 public static void mySample(){

        System.out.println("this is my sample method");

 }

}

11.  For logs where we have store which pattern we have to store logs we have to configure in log4j2.xml file

               Log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>

<Configuration status="warn" complete="true">

       <Appenders>

       <Console name="Console" target="SYSTEM_OUT">

              <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36}  -%l                                                                                                                                                        %msg%n -%X{userName}%n" />

              </Console>

       </Appenders>

       <Loggers>

              <Root level="all" additivity="false">

                     <AppenderRef ref="Console" />

              </Root>

       </Loggers>

</Configuration>

12.   Its important point now we have to configure aspetjweaver agent. Aspectj given agent for this i.e apectjweaver-1.8.5.jar in your class path and vm argument .

13.   If you are using eclipse for your application development follow below steps.

Right click on your project -> Run as -> Run configurations ->Arguments tab -> vm arguments  inside this pass path your aspectjweaver-1.8.5.jar.

e.g : -javaagent:D:\log4jproject\aspectjweaver-1.8.5.jar.

final structure like below.

14.   Run the web application and test using below url .

http://localhost:1111/AspectjOnTomcatExample/Test

The output comes like below.

16:53:02.378 [http-bio-1111-exec-3] INFO  com.msr.aspects.LogAspect-com.msr.aspects.LogAspect.beforeMethod(LogAspect.java:25) – Before : void com.msr.aspects.Sample.mySample()

-

this is my sample method

16:53:02.381 [http-bio-1111-exec-3] INFO  com.msr.aspects.LogAspect-com.msr.aspects.LogAspect.afterMethod(LogAspect.java:31) – After : void com.msr.aspects.Sample.mySample()

 -

Slf4j with log4j2 Example.

What is slf4j :- The Simple Logging Facade for Java (SLF4J) serves as a simple facade or abstraction for various logging frameworks (e.g. java.util.logging, logback, log4j) allowing the end user to plug in the desired logging framework at deployment time.Here we are using log4j2 logging framework at deployment time for this we need to add below jars.

Now create java class with slf4j logger object.

Test.java

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

public class Test {

private static final Logger logger = LoggerFactory.getLogger(Test.class);

public static void main(String[] args) {

               logger.debug("this is debug msg");

               logger.info("this is info mesg");

      

}

}

Now where we have to store logs and which pattern we have to print logs these are all configure in log4j2.xml

log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>

<Configuration>

  <Appenders>

    <Console name="STDOUT" target="SYSTEM_OUT">

        <PatternLayout pattern="current date-%d LEVEL-%-5p  Thread-[%t]  Method-%M()   Class name-%C   Message-%m%n"/>

    </Console>

  </Appenders>

   <loggers>

  <Logger name="org.apache.log4j.xml" level="all"/>

    <root level="all">

      <appender-ref ref="STDOUT"/>

    </root>

  </loggers>

</Configuration>

Note: the configuration file log4j2.xml put in class path means under src folder.

How to Create a Custom Appender in log4j2?

In log4j2, you would create a plugin for create custom appender in log4j2.

When you annotate your custom Appender class with @Plugin(name=”MyCustomAppender”, category=”core” elementType=”appender” ,printObject=true) the plugin name becomes the configuration element name, so a configuration with your custom appender would then look like this:

Log4j2.xml

<?xml version="1.0" encoding="UTF-8"?>

<Configuration status="warn" packages="com.madhu.appender">

    <Appenders>

        <MyCustomAppender name="myapp" >

       <PatternLayout pattern="serial no: %sn |  Date: %d |  level:%level | class name:%logger | method name:%M() |  line number:%L |  Location: %l | message:%m%n" />

        </MyCustomAppender>

    </Appenders>

       <Loggers>

              <Root level="all" additivity="false">

                     <AppenderRef ref="myapp" />

              </Root>

       </Loggers>

</Configuration>

In log4j2.xml file don’t forgot packages attribute here configure your custom appender package.

Now we are create plugin for appender.

MyCustomImpl.java

@Plugin(name="MyCustomAppender", category="Core", elementType="appender", printObject=true)

public class MyCustomImpl extends AbstractAppender {

    private final ReadWriteLock rwLock = new ReentrantReadWriteLock();

    private final Lock readLock = rwLock.readLock();

    protected MyCustomImpl(String name, Filter filter,

            Layout<? extends Serializable> layout, final boolean ignoreExceptions) {

        super(name, filter, layout, ignoreExceptions);

    }

    @PluginFactory

    public static MyCustomImpl createAppender(

            @PluginAttribute("name") String name,

            @PluginElement("Layout") Layout<? extends Serializable> layout,

            @PluginElement("Filter") final Filter filter,

            @PluginAttribute("otherAttribute") String otherAttribute) {

        if (name == null) {

            LOGGER.error("No name provided for MyCustomAppenderImp");

            return null;

        }

        if (layout == null) {

            layout = PatternLayout.createDefaultLayout();

        }

        return new MyCustomImpl(name, filter, layout, true);

}

       @Override

       public void append(LogEvent event) {

                readLock.lock();

               try {    

                   final byte[] bytes = getLayout().toByteArray(event);

// here I am printing logs into console

                   System.out.println("LOG: " +new String(bytes, "UTF-8"));

               } catch (Exception ex) {

                   if (!ignoreExceptions()) {

                       throw new AppenderLoggingException(ex);

                   }

               } finally {

                   readLock.unlock();

               }

       }

}

Now we can test our custom appender. For this we can write one test class.

Note: Here custom appender plugin name and configuration appender name is same otherwise its won’t work.

Test.java

public class Test {

       public static final Logger LOGGER=LogManager.getLogger(Test.class);

public static void main(String[] args) throws IOException {

       LOGGER.info("this is info message");

       LOGGER.warn("this is warning message");

      

}

}

The output comes like below.

LOG: serial no: 1 |  Date: 2015-06-23 15:32:56,069 |  level:INFO | class name:com.madhu.appender.Test | method name:main() |  line number:15 |  Location: com.madhu.appender.Test.main(Test.java:15) | message:this is info message

LOG: serial no: 2 |  Date: 2015-06-23 15:32:56,072 |  level:WARN | class name:com.madhu.appender.Test | method name:main() |  line number:16 |  Location: com.madhu.appender.Test.main(Test.java:16) | message:this is warning message