I Can Do I.T.: June 2016

Wednesday 29 June 2016

[Ubuntu] Setup firewall using UFW

UFW is a default firewall. it is more easier than iptables. But iptables supports more various options and functions for building high-quality service.

1. Set UFW Enable/Disable

#> ufw enable

#> ufw disable

2. Check UFW status

#> ufw status verbose

3. Check default rule

#> ufw show raw

4. Allow/Deny default rule

#> ufw default allow

#> ufw default deny

5. Allow/Deny specific port and protocol

#> ufw allow [port]

#> ufw allow [port]/tcp

#> ufw allow [port]/udp

#> ufw deny[port]

#> ufw deny[port]/tcp

#> ufw deny[port]/udp

[Ubuntu] How to turn off coloring syntax in vi editor

#> vi /etc/vim/vimrc

remove if has("syntax") syntax on end if.

Friday 24 June 2016

[CloudSQL] Getting Started Google Cloud SQL

1. Create new instance

I choose Cloud SQL generation 2. this is more fast and support more disk and more cheaper than generation 1. But, it is beta service yet.

2. Set up resource size

3. Set up options and add network allowed access

4. Set up other options

5. Finished creating instance

6. Set up root password

7. Connect DB using database tool

[Oracle] ORA-00845 : MEMORY TARGET not supported on this system

I used Oracle 11g in CentOS VM image. this image is allocated 16GB memory. But after reducing memory to 8GB, oracle instance was not started.

This error comes up because you tried to use the Automatic Memory Management (AMM) feature of Oracle 11g R2. It seems that your shared memory filesystem (shmfs) is not big enough. In this case, you should increase shmfs.

1. Check shared memory filesystem size

# df -h

2. Remount and increase size

# umount tmpfs
# mount -t tmpfs shmfs -o size=8192m /dev/shm

3. Startup database instance

4. Check parameter related with memory

[Oracle] How to increase line width in SQLPlus

set linesize [SIZE]

Wednesday 22 June 2016

[Windows] How to check Main(Mother) Board model

C:\Users\Administrator>wmic baseboard

Caption

ConfigOptions

CreationClassName

Depth

Description

Height

HostingBoard

HotSwappable

InstallDate

Manufacturer

Model

Name

OtherIdentifyingInfo

PartNumber

PoweredOn

Product

Removable

Replaceable

RequirementsDescription

RequiresDaughterBoard

SerialNumber

SKU

SlotLayout

SpecialRequirements

Status

Tag

Version

Weight

Width

Base Board

Win32_BaseBoard

Base Board

TRUE

FALSE

Dell Inc.

Base Board

TRUE

0D735T

FALSE

TRUE

FALSE

..CN697029CK0163.

Base Board

A00

[Windows] How to check Memory model

C:\Users\Administrator>wmic momorychip

BankLabel

Capacity

Caption

CreationClassName

DataWidth

Description

DeviceLocator

FormFactor

HotSwappable

InstallDate

InterleaveDataDepth

InterleavePosition

Manufacturer

MemoryType

Model

Name

OtherIdentifyingInfo

PartNumber

PositionInRow

PoweredOn

Removable Replaceable SerialNumber

SKU

Speed

Status

Tag

TotalWidth

TypeDetail

Version

BANK0

4294967296

Physical Memory

Win32_PhysicalMemory

Physical Memory

DIMM0

Samsung

Physical Memory

M378B5273CH0-CH9

002D7AA2

1333

Physical Memory 0

128

BANK1

4294967296

Physical Memory

Win32_PhysicalMemory

Physical Memory

DIMM1

Samsung

Physical Memory

M378B5273DH0-CH9

6468CE66

1333

Physical Memory 1

128

BANK2

4294967296

Physical Memory

Win32_PhysicalMemory

Physical Memory

DIMM2

Samsung

Physical Memory

M378B5273DH0-CH9

00421459

1333

Physical Memory 2

128

BANK3

4294967296

Physical Memory

Win32_PhysicalMemory

Physical Memory

DIMM3

Samsung

Physical Memory

M378B5273DH0-CH9

6555173D

1333

Physical Memory 3

128

[Utility] hiltie.me - Make code like Java, Shell, SQL, HTML etc to HTML code

hilite.me converts your code snippets into pretty-printed HTML format, easily embeddable into blog posts, emails and websites.

http://hilite.me/

[Java] What is difference between Class.forName() and Class.forName().newInstance()

In JavaDoc, calling Class.forName( String) returns the Class object associated with the class or interface with the given string name.
On the other hand, calling Class.forName( String).newInstance() creates a new instance of the class represented by this Class object. The class is instantiated as if by a new expression with an empty argument list.
In other words, Class.forName( String CLASS_NAME) is equivalent to new CLASS_NAME()
(Referenced by http://stackoverflow.com/questions/2092659/what-is-the-difference-between-class-forname-and-class-forname-newinstanc)

Class.forName( String) is not create instance, but call static block in class. On the other hand, newInstance() creates instance. The result of below code will make you more understandable.

Class pe.dorbae.test.Driver

package pe.dorbae.test;

/*
 * ************************************************************************************
 *
 * Driver.java
 * 
 * ************************************************************************************
 * 
 * @version 1.0.00 2016-06-21 dorbae Initialize
 * @since 2016-06-21
 * @author dorbae
 * 
 * ************************************************************************************
 */
public class Driver {
 
 static {
  System.out.println( "Static Block");
 }

 public Driver() {
  System.out.println( "Constructure");
  
 }
 
 public void test() {
  System.out.println( "test");
 }
 
}

Calling Class.forName( String) Code and Result

public class Test {
 public static void main(String[] args) throws Exception {
  Class.forName( "pe.dorbae.test.Driver"); // equivalent to Class.forName( "pe.dorbae.test.Driver", true, this.getClass().getClassLoader())
  
 }
}

Calling Class.forName( String, false, ClassLoader) Code and Result

public class Test {
 public static void main(String[] args) throws Exception {
  Class.forName( "pe.dorbae.test.Driver", false, Thread.currentThread().getContextClassLoader());
  
 }
}

Calling Class.forName( String).newInstance()

public class Test {
 public static void main(String[] args) throws Exception {
  Class.forName( "pe.dorbae.test.Driver").newInstance(); // equivalent to Class.forName( "pe.dorbae.test.Driver", true, this.getClass().getClassLoader())
  
 }
}

Calling Class.forName( String, false, ClassLoader).newInstance()

public class Test {
 public static void main(String[] args) throws Exception {
  Class.forName( "pe.dorbae.test.Driver", false, Thread.currentThread().getContextClassLoader()).newInstance();
  
 }
}

When use JDBC driver, we usually call Class.forName( String driverClass). Class.forName( String) is not create JDBC Driver Object instance. If so, how to use driver object?

JDBC Driver generally make driver class that implements java.sql.Driver like this.

public final class <DriverClass> implements java.sql.Driver {

    static {
        try {
            DriverManager.registerDriver(new <DriverClass>());
        } catch (SQLException e) {
            throw new RuntimeException("Could not register driver", e);
        }
    }

    .
    .
    .
    
}

Therefore, if you call Class.forName( String driverClass), static block is called and it register new driver class instance.

However, it is different when JDBC Driver class is loaded in another. DriverManager.getConnection() finds driver object in Thread.current.getContextClassLoader(). DriverManager can't not find driver object, because it is actually loaded in another class loader.

In this case, you should like this.

1 2	java.sql.Driver driver = ( java.sql.Driver)Class.forName( DriverClassName, true, AnotherClassLoader).newInstance(); java.sql.Connection conn = driver.connect( <URL>, <Properties>);

Tuesday 21 June 2016

[Java] Mobile to Desktop URL Transfer using Topic Pub/Sub

When I opened web content and read it in mobile web browser, I sometimes have wanted to read it in desktop web browser.
So I made background program that receive URL from mobile app and open web content in desktop browser.

An architecture of this program is like below.

I have been using iPhone, but I can't develop iOS applications. So I use free app MQTTTest that was developed by Kwang il Cho. (https://appsto.re/kr/CxN--.i)

Mobile

Desktop

Java Code

package pe.dorbae.url.tranfer;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Properties;

import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.Session;

import org.apache.commons.lang3.exception.ExceptionUtils;

/*
 * ************************************************************************************
 *
 * URLTranfer.java
 * 
 * ************************************************************************************
 * 
 * @version 1.0.00 2016-06-21 dorbae Initialize
 * @since 2016-06-21
 * @author dorbae
 * 
 * ************************************************************************************
 */
public class URLTranfer implements Runnable {
 
 private static final org.slf4j.Logger LOG = org.slf4j.LoggerFactory.getLogger( URLTranfer.class);
 
 private static final String OS = System.getProperty( "os.name", "Unknown");
 private static final String[] COMMAND_WINDOW = new String[] { "rundll32", "url.dll,FileProtocolHandler", null};
 private static final String[] COMMAND_MAC = new String[] { "open", null};
 private static final String[] COMMAND_UNIX = new String[] { "xdg-open", null};
 private static String[] command = null;
 static  {
  String osName = OS.toLowerCase();
  if ( osName.indexOf( "win") >= 0)
   command = COMMAND_WINDOW;
  else if ( osName.indexOf( "nux") >= 0)
   command = COMMAND_MAC;
//  else if ( osName.indexOf( "aix") >= 0)
//   osType =  OSType.Aix;
//  else if ( osName.indexOf( "nix") >= 0)
//   osType =  OSType.Unix;
//  else if ( osName.indexOf( "mac") >= 0)
//   osType =  OSType.MacOS;
//  else if ( osName.indexOf( "darwin") >= 0)
//   osType =  OSType.MacOS;
//  else if ( osName.indexOf( "sunos") >= 0)
//   osType =  OSType.Solaris;
  else           // Affiliation with Unix
   command = COMMAND_UNIX;
  
 }
 
 private static String[] envrionmentArray = null;
 static {
  java.util.Map< String, String> env = System.getenv();
  java.util.Iterator< java.util.Map.Entry< String, String>> iterator = env.entrySet().iterator();
  java.util.Map.Entry< String, String> entry = null;
  envrionmentArray = new String[ env.size()];
  int ll = 0;
  while ( iterator.hasNext()) {
   entry = iterator.next();
   envrionmentArray[ ll++] = String.format( "%s=%s", entry.getKey(), entry.getValue());
   
  }
 }
 
 private Thread mThread = null;
 private boolean mIsRunning = false;
 
 private String mBrokerUrl = null;
 private String mTopicName = null;
 private String mClientID = null;
 private String mHostname = null;
 private javax.jms.Connection mConn = null;
 private javax.jms.Session mSession = null;
 private javax.jms.MessageConsumer mSubscriber = null;
 private javax.jms.Topic mTopic = null;

 public URLTranfer(String brokerUrl, String topicName) {
  this.mBrokerUrl = brokerUrl;
  this.mTopicName = topicName;
  try {
   this.mHostname = InetAddress.getLocalHost().getHostName();
  
  } catch ( UnknownHostException e) {
   this.mHostname = "Unknown";
   
  }
  
  this.mClientID = String.format( "iSharkClient.%s.URLTransfer", this.mHostname);
  
 }
 
 @Override
 public void run() {
  LOG.info( "Start URLTranfer.");
  try {
   this.mConn.start();
   this.mSubscriber.setMessageListener( new MessageListener() {
    @Override
    public void onMessage( Message msg) {
     try {
      String url = null;
      
      if ( msg instanceof javax.jms.BytesMessage) {
       javax.jms.BytesMessage byteMessage = ( javax.jms.BytesMessage) msg;
       byte[] payload = new byte[ ( int)byteMessage.getBodyLength()];
       byteMessage.readBytes( payload);
       url = new String( payload, "UTF8");
       
      } else if ( msg instanceof javax.jms.TextMessage) {
       javax.jms.TextMessage textMessage = ( javax.jms.TextMessage)msg;
       url = textMessage.getText();
       
      }
      LOG.info( "url={}", url);
      
      if ( java.awt.Desktop.isDesktopSupported()) {
       LOG.debug( "Deskop Supported");
       java.awt.Desktop.getDesktop().browse( new java.net.URI( url));
      
      } else {
       Runtime runtime = Runtime.getRuntime();
       command[ command.length - 1] = url;
       runtime.exec( command, envrionmentArray, null);
        
      }
      
     } catch ( Exception e) {
      LOG.warn( "Failed to subscribe url and open browser.\n{}", ExceptionUtils.getStackTrace( e));
      
     }
    }
   });

  } catch ( JMSException e) {
   LOG.error( "Error in DataTopicSubWorker.\n{}", ExceptionUtils.getStackTrace( e));
   
  }
 }
 
 public void start() {
  this.connectBroker();
  if ( !this.mIsRunning && this.mThread == null) {
   this.mIsRunning = true;
   this.mThread = new Thread( this);
   this.mThread.setName( "URLTransfer");
   this.mThread.start();
   
  } else {
   LOG.info( "Already running...");
   
  }
  
 }
 
 public void stop() {
  this.disconnectBroker();
  this.mIsRunning = false;
  this.mThread = null;
  
 }
 
 private void disconnectBroker() {
  try {
   if ( this.mSubscriber != null)
    this.mSubscriber.close();
   if ( this.mSession != null)
    this.mSession.close();
   if ( this.mConn != null) {
    this.mConn.stop();
    this.mConn.close();
    
   }
  
  } catch ( Exception ex) {}
 }
 
 
 private boolean connectBroker() {
  try {
   LOG.info( "Initialize URLTranfer.[BrokerURL={}, Topic={}, ClientID={}]", this.mBrokerUrl, this.mTopicName, this.mClientID);
   
   Properties jmsProps = new Properties();
   jmsProps.put( javax.naming.Context.INITIAL_CONTEXT_FACTORY, "org.apache.activemq.jndi.ActiveMQInitialContextFactory");
   jmsProps.put( javax.naming.Context.PROVIDER_URL, this.mBrokerUrl);
   
   javax.naming.InitialContext jndi = new javax.naming.InitialContext( jmsProps);
   javax.jms.ConnectionFactory connectionFactory = ( javax.jms.ConnectionFactory) jndi.lookup( "ConnectionFactory");
   this.mConn = connectionFactory.createConnection();
   this.mConn.setClientID( this.mClientID);
   this.mSession = this.mConn.createSession( false, Session.AUTO_ACKNOWLEDGE); // transacted, acknowolegeMode
   this.mTopic = this.mSession.createTopic( this.mTopicName);
   this.mSubscriber = this.mSession.createConsumer( this.mTopic);
   
   return true;
   
  } catch ( Exception e) {
   LOG.error( "Failed to initialize URLTranfer.\n{}", ExceptionUtils.getStackTrace( e));
   this.disconnectBroker();
   
   return false;
   
  }
  
 }
 
 public static void main( String[] args) {
  org.apache.log4j.PropertyConfigurator.configure( "log4j.properties");
  URLTranfer transfer = new URLTranfer( "nio://192.168.0.85:61616?wireFormat.maxInactivityDuration=0", "Url.Transfer");
  Runtime.getRuntime().addShutdownHook( new Thread( new ShutdownHook( transfer)));
  transfer.start();
  
 }

}

class ShutdownHook implements Runnable {
 private URLTranfer mURLTransfer = null;
 
 public ShutdownHook( URLTranfer urlTransfer) {
  this.mURLTransfer = urlTransfer;
  
 }
 
 @Override
 public void run() {
  this.mURLTransfer.stop();
  
 }
 
}

Friday 17 June 2016

[Java] How to Indent XML Generated by Transformer

● Not Indent

1	<?xml version="1.0" encoding="UTF-8" standalone="no"?><a><b/></a>

● Indent

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<a>
 <b/>
</a>

◎ Java Code

1 2	transformer.setOutputProperty(OutputKeys.INDENT, "yes"); transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2")

Thursday 16 June 2016

[Java] How to get Inherited or same class in ClassLoader (클래스로더에 로드된 클래스 중 특정 클래스나 그 클래스를 상속받는 클래스 찾기)

public class DorbaeClassLoaderUtil {
         public static java.util.List< Class< ?>> findInheritedClasses( ClassLoader classLoader, Class< ?> parentClass) throws SecurityException, NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
  java.util.List< Class< ?>> filteredClasses = new java.util.LinkedList< Class< ?>>();
  
  Field f = ClassLoader.class.getDeclaredField( "classes");
  f.setAccessible( true);

  Vector< Class< ?>> classes = ( Vector< Class< ?>>)f.get( classLoader);
  int size = classes.size();
  Class< ?> cls = null;
  for ( int ll = 0; ll < size; ll++) {
    try {
     cls = classes.get( ll);
                 if ( parentClass.isAssignableFrom( cls)) {
                  filteredClasses.add( cls);
                 }
             
             } catch ( Exception e) {
              continue;

             } catch ( Error e) {
              continue;
              
             }
  }
  
  return filteredClasses;

 }
 
 public static void main( String[] args) throws Exception {
  A a = new A();
  B b = new B();
  C c = new C();
  
  System.out.println( "=================== All Classes ===================");
  java.util.Vector< Class< ?>> clss = DorbaeClassLoaderUtil.getAllLoadedClasses( Thread.currentThread().getContextClassLoader());
  for ( int ll = 0; ll < clss.size(); ll++) {
   System.out.println( clss.get( ll).getName());
   
  }
  
  System.out.println( "=================== Inherited Classes ===================");
  java.util.List< Class< ?>> clsss = DorbaeClassLoaderUtil.findInheritedClasses( Thread.currentThread().getContextClassLoader(), C.class);
  for ( int ll = 0; ll < clsss.size(); ll++) {
   System.out.println( clsss.get( ll).getName());
   
  }
 }

}

class A extends C {
 public A() {}
}

class B {
 public B() {}
 
}

class C {
 public C() {}
}

I Can Do I.T.

Wednesday 29 June 2016

[Ubuntu] Setup firewall using UFW

1. Set UFW Enable/Disable

2. Check UFW status

3. Check default rule

4. Allow/Deny default rule

5. Allow/Deny specific port and protocol

[Ubuntu] How to turn off coloring syntax in vi editor

Friday 24 June 2016

[CloudSQL] Getting Started Google Cloud SQL

1. Create new instance

2. Set up resource size

3. Set up options and add network allowed access

4. Set up other options

5. Finished creating instance

6. Set up root password

7. Connect DB using database tool

[Oracle] ORA-00845 : MEMORY TARGET not supported on this system

1. Check shared memory filesystem size

2. Remount and increase size

3. Startup database instance

4. Check parameter related with memory

[Oracle] How to increase line width in SQLPlus

Wednesday 22 June 2016

[Windows] How to check Main(Mother) Board model

[Windows] How to check Memory model

[Utility] hiltie.me - Make code like Java, Shell, SQL, HTML etc to HTML code

[Java] What is difference between Class.forName() and Class.forName().newInstance()

Tuesday 21 June 2016

[Java] Mobile to Desktop URL Transfer using Topic Pub/Sub

Friday 17 June 2016

[Java] How to Indent XML Generated by Transformer

Thursday 16 June 2016

[Java] How to get Inherited or same class in ClassLoader (클래스로더에 로드된 클래스 중 특정 클래스나 그 클래스를 상속받는 클래스 찾기)

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