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Error in programmatically creating FileAppender using log4j2

I wanted to try and test the FileAppender on my local machine after reading the documentation online. When i create the object by calling the build method i get errors.
I will be upgrading the log4j version in an application and was learning about file appenders when i failed to create and test one locally.I tried looking on the internet and found some code on how to create it. When i try the same i get errors show below in the stack trace. I am using a windows machine and running the code on netbeans.
package logtest;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.appender.FileAppender;
class Test
{
public void appendLogs(String logEvent)
{
LoggerContext ctx = (LoggerContext)LogManager.getContext(false);
Configuration conf = ctx.getConfiguration();
FileAppender.Builder b = FileAppender.newBuilder();
b.withFileName("TestFile");
b.withAppend(true);
b.build();
FileAppender fa = b.build();
System.out.println(fa.toString());
fa.start();
fa.error("Error message");
}
}
public class LogTest {
private static final Logger LOG = LogManager.getLogger(LogTest.class);
public static void main(String[] args) {
Test t = new Test();
t.appendLogs("Test log");
System.out.println(t.toString());
t.appendLogs("This is an error in a file");
LOG.debug("This Will Be Printed On Debug");
LOG.info("This Will Be Printed On Info");
LOG.warn("This Will Be Printed On Warn");
LOG.error("This Will Be Printed On Error");
LOG.fatal("This Will Be Printed On Fatal");
LOG.info("Appending string: {}.", "Hello, World");
}
}
I get the error during the call to build() method.
Exception in thread "main" java.lang.NullPointerException: name
at java.util.Objects.requireNonNull(Objects.java:228)
at org.apache.logging.log4j.core.appender.AbstractAppender.<init>(AbstractAppender.java:205)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.<init>(AbstractOutputStreamAppender.java:120)
at org.apache.logging.log4j.core.appender.FileAppender.<init>(FileAppender.java:259)
at org.apache.logging.log4j.core.appender.FileAppender.<init>(FileAppender.java:42)
at org.apache.logging.log4j.core.appender.FileAppender$Builder.build(FileAppender.java:104)
at logtest.Test.appendLogs(LogTest.java:17)
at logtest.LogTest.main(LogTest.java:31)
Java Result: 1
I dont understand why i get the null exception.

You need to set a name for the appender.
FileAppender.Builder b = FileAppender.newBuilder();
b.withFileName("TestFile");
b.withAppend(true);
b.setName("my-appender");
b.build();
FileAppender fa = b.build();

How to load a http .txt file as a Java FileSystem

I am studying for the Java 1.8 OCP exam and I ran across something in the Oracle study guide p.459 where it says you can load a remote URL as a FileSystem object. I tried this and can't get it to work. What is the simplest hello-world style answer to get this working?
import java.net.*;
import java.nio.file.*;
public class FileTest {
public static void main(String[] args) throws URISyntaxException, MalformedURLException {
FileSystem remoteFS = FileSystems.getFileSystem(
new URI("http://www.gutenberg.org/files/55007")
);
Path remotePath = remoteFS.getPath("55007-0.txt");
System.out.println(remotePath.isAbsolute());
}
}
It throws the error:
Exception in thread "main" java.nio.file.ProviderNotFoundException:
Provider "http" not found
at java.nio.file.FileSystems.getFileSystem(FileSystems.java:224)
at qa.test.FileTest.main(FileTest.java:7)
Addendum:
FileSystemProvider.installedProviders() returns
[sun.nio.fs.MacOSXFileSystemProvider#4554617c, com.sun.nio.zipfs.ZipFileSystemProvider#74a14482]

Creating a Web App with Bootstrap and Tomcat Embedded and Java SE 8 not running

I am following this Oracle tutorial
http://www.oracle.com/webfolder/technetwork/tutorials/obe/java/basic_app_embedded_tomcat/basic_app-tomcat-embedded.html
I have downloaded the zip containing the maven project and run it following the instructions here
http://www.oracle.com/webfolder/technetwork/tutorials/obe/java/basic_app_embedded_tomcat/basic_app-tomcat-embedded.html
But when I execute the final command
java -jar employees-app-1.0-SNAPSHOT-jar-with-dependencies.jar
I get this error message:
Error: Could not find or load main class com.example.employees.Main
I have set the JAVA_HOME to point to the Oracle jdk1.8.0_102.
Any idea on how to solve this?

Did you create the Main class in step 1?
package com.example.employees;
import java.util.Optional;
import org.apache.catalina.startup.Tomcat;
public class Main {
public static final Optional<String> port = Optional.ofNullable(System.getenv("PORT"));
public static void main(String[] args) throws Exception {
String contextPath = "/";
String appBase = ".";
Tomcat tomcat = new Tomcat();
tomcat.setPort(Integer.valueOf(port.orElse("8080") ));
tomcat.getHost().setAppBase(appBase);
tomcat.addWebapp(contextPath, appBase);
tomcat.start();
tomcat.getServer().await();
}
}

Apache Spark eventLog configuration on Windows Giving error

I am using Spark 1.5 on Windows. I haven't installed any separate binaries of Hadoop.
I running a Master and a single worker.
It's a simple HelloWorld Program as below :
package com.java.spark;
import java.io.Serializable;
import java.util.Arrays;
import java.util.List;
import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.VoidFunction;
public class HelloWorld implements Serializable{
/**
*
*/
private static final long serialVersionUID = -7926281781224763077L;
public static void main(String[] args) {
// Local mode
//SparkConf sparkConf = new SparkConf().setAppName("HelloWorld").setMaster("local");
SparkConf sparkConf = new SparkConf().setAppName("HelloWorld").setMaster("spark://192.168.1.106:7077")
.set("spark.eventLog.enabled", "true")
.set("spark.eventLog.dir", "file:///D:/SparkEventLogsHistory");
//.set("spark.eventLog.dir", "/work/");
//tried many combinations above but all gives error.
JavaSparkContext ctx = new JavaSparkContext(sparkConf);
String[] arr = new String[] { "John", "Paul", "Gavin", "Rahul", "Angel" };
List<String> inputList = Arrays.asList(arr);
JavaRDD<String> inputRDD = ctx.parallelize(inputList);
inputRDD.foreach(new VoidFunction<String>() {
public void call(String input) throws Exception {
System.out.println(input);
}
});
}
}
The exception I am getting is :
Exception in thread "main" java.io.IOException: Cannot run program "cygpath": CreateProcess error=2, The system cannot find the file specified
at java.lang.ProcessBuilder.start(Unknown Source)
at org.apache.hadoop.util.Shell.runCommand(Shell.java:206)
at org.apache.hadoop.util.Shell.run(Shell.java:188)
at org.apache.hadoop.fs.FileUtil$CygPathCommand.<init>(FileUtil.java:412)
at org.apache.hadoop.fs.FileUtil.makeShellPath(FileUtil.java:438)
at org.apache.hadoop.fs.FileUtil.makeShellPath(FileUtil.java:465)
at org.apache.hadoop.fs.RawLocalFileSystem.execCommand(RawLocalFileSystem.java:592)
at org.apache.hadoop.fs.RawLocalFileSystem.setPermission(RawLocalFileSystem.java:584)
at org.apache.hadoop.fs.FilterFileSystem.setPermission(FilterFileSystem.java:420)
at org.apache.spark.scheduler.EventLoggingListener.start(EventLoggingListener.scala:130)
at org.apache.spark.SparkContext.<init>(SparkContext.scala:541)
at org.apache.spark.api.java.JavaSparkContext.<init>(JavaSparkContext.scala:61)
at com.java.spark.HelloWorld.main(HelloWorld.java:28)
Caused by: java.io.IOException: CreateProcess error=2, The system cannot find the file specified
at java.lang.ProcessImpl.create(Native Method)
at java.lang.ProcessImpl.<init>(Unknown Source)
at java.lang.ProcessImpl.start(Unknown Source)
... 13 more
16/04/01 20:13:24 INFO ShutdownHookManager: Shutdown hook called
Does anyone has any idea how to resolve this exception, so that Spark can pick the eventLogs from local directory.
If I dont give configure eventLog.dir then exception changes to :
Exception in thread "main" java.io.FileNotFoundException: File file:/H:/tmp/spark-events does not exist
at org.apache.hadoop.fs.RawLocalFileSystem.getFileStatus(RawLocalFileSystem.java:468)
at org.apache.hadoop.fs.FilterFileSystem.getFileStatus(FilterFileSystem.java:373)
at org.apache.spark.scheduler.EventLoggingListener.start(EventLoggingListener.scala:100)
at org.apache.spark.SparkContext.<init>(SparkContext.scala:541)
at org.apache.spark.api.java.JavaSparkContext.<init>(JavaSparkContext.scala:61)
at com.java.spark.HelloWorld.main(HelloWorld.java:28)

Asterisk-java for AMI not working correctly

I am an absolute newbee in asterisk. I am trying to use asterisk-java for event listening through AMI. I am currently using the version 11.2.1 asterisk. When I tries to compiles the code as
javac -cp asterisk-java-0.3.jar HelloEvents.java
it complets successfully. But when I try to execute the file, I give the following error.
Exception in thread "main" java.lang.NoClassDefFoundError: HelloEvents
Caused by: java.lang.ClassNotFoundException: HelloEvents
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: HelloEvents. Program will exit.
the code is
import java.io.IOException;
import org.asteriskjava.manager.AuthenticationFailedException;
import org.asteriskjava.manager.ManagerConnection;
import org.asteriskjava.manager.ManagerConnectionFactory;
import org.asteriskjava.manager.ManagerEventListener;
import org.asteriskjava.manager.TimeoutException;
import org.asteriskjava.manager.action.StatusAction;
import org.asteriskjava.manager.event.ManagerEvent;
public class HelloEvents implements ManagerEventListener
{
private ManagerConnection managerConnection;
public HelloEvents() throws IOException
{
ManagerConnectionFactory factory = new ManagerConnectionFactory(
"localhost", "manager", "password");
this.managerConnection = factory.createManagerConnection();
}
public void run() throws IOException, AuthenticationFailedException,
TimeoutException, InterruptedException
{
// register for events
managerConnection.addEventListener(this);
// connect to Asterisk and log in
managerConnection.login();
// request channel state
managerConnection.sendAction(new StatusAction());
// wait 10 seconds for events to come in
Thread.sleep(10000);
// and finally log off and disconnectaaaa
managerConnection.logoff();
}
public void onManagerEvent(ManagerEvent event)
{
// just print received events
System.out.println(event);
}
public static void main(String[] args) throws Exception
{
HelloEvents helloEvents;
helloEvents = new HelloEvents();
helloEvents.run();
}
}

java -cp ".;asterisk-java.jar" HelloEvents
works fine.
And the class path separator is OS dependent. If you are using linux / mac, use : (colon) instead of ; (semicolon)

We can avoid adding class path every time while compiling or executing code. Now go to the location where jar file is located. Then run,
For linux :- export CLASSPATH=$CLASSPATH:asterisk-java-2.0.3.jar:.
For windows:- set CLASSPATH=$CLASSPATH:asterisk-java-2.0.3.jar:.
Now compile code by
javac HelloEvents.java
Execute it by java HelloEvents