I Can Do I.T.: August 2016

Tuesday, 30 August 2016

[H2] How to check table lock in H2 database

SELECT * FROM INFORMATION_SCHEMA.LOCKS;

SELECT * 
  FROM INFORMATION_SCHEMA.LOCKS
 WHERE TABLE_SCHEMA = '<SCHEMA_NAME>'
   AND TABLE_NAME = '<TABLE_NAME>'
;

Monday, 29 August 2016

[NodeMCU] Lua Crypto Package and interface with Java program using AES-ECB

NodeMCU is an eLua based firmware for the ESP8266 WiFi SOC from Espressif.
NodeMCU support encrypt and decrypt functions which are in crypto packages.

http://nodemcu.readthedocs.io/en/dev/en/modules/crypto/
This is manual for Crypto package.

crypto.encrypt()

Encrypts Lua strings.

Syntax

crypto.encrypt(algo, key, plain [, iv])

Parameters

algo the name of the encryption algorithm to use, one of
- "AES-ECB" for 128-bit AES in ECB mode
- "AES-CBC" for 128-bit AES in CBC mode
key the encryption key as a string; for AES encryption this MUST be 16 bytes long
plain the string to encrypt; it will be automatically zero-padded to a 16-byte boundary if necessary
iv the initilization vector, if using AES-CBC; defaults to all-zero if not given

Returns

The encrypted data as a binary string. For AES this is always a multiple of 16 bytes in length.

Crypto package AES-ECB using no padding. So you should make 16 multiple bytes array from plain text. And NodeMCU use EUCKR encoding in crypto package.

NodeMCU

key = "1234567890abcdef"
cipher = crypto.encrypt("AES-ECB", key, "Hi, I'm secret!")
print(crypto.toBase64(cipher))

cipher = crypto.encrypt("AES-ECB", key, "가나다라마바사")
print(crypto.toBase64(cipher))

Result

LQ95s23+t6PK0mmokJFSYg==
w9kOL6y40iVqhuGdWt6vLw==

Java

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

     String keyValue = "1234567890abcdef";
     String encryptedText1 = "LQ95s23+t6PK0mmokJFSYg==";
     String encryptedText2 = "w9kOL6y40iVqhuGdWt6vLw==";
     java.nio.charset.Charset charset = java.nio.charset.Charset.forName( "euckr");

     java.security.Key key = new javax.crypto.spec.SecretKeySpec( keyValue.getBytes( charset), "AES");
     javax.crypto.Cipher cipher = Cipher.getInstance( "AES/ECB/NoPadding");
     cipher.init( Cipher.DECRYPT_MODE, key);
     
     System.out.println( "DecryptedText1=" + new String( cipher.doFinal( org.apache.commons.codec.binary.Base64.decodeBase64( encryptedText1.getBytes( charset))), charset));
     System.out.println( "DecryptedText2=" + new String( cipher.doFinal( org.apache.commons.codec.binary.Base64.decodeBase64( encryptedText2.getBytes( charset))), charset));
     
}

Result

Wednesday, 24 August 2016

[CentOS] Setup Mail server (메일 서버 구축)

MTA (Mail Transfer Agent)
ex) Sendmail, Qmail, Microsfot Exchange

MUA (Mail user Agent)
ex) Outlook Express

MDA (Mail Delivery Agent)
ex) POP3, IMAP

Send Protocol
SMTP (Simple Mail Transfer Protocol)
: TCP/IP mail transfer protocol. Default port 25.

1. Install Sendmail packages

# yum -y install sendmail*

2. Configure SMTP

# vi /etc/mail/sendmail.mc

Remove 'dnl' command

# m4 /etc/mail/sendmail.mc > /ect/mail/sendmail.cf
# vi /etc/mail/snedmail.cf

Cwlocalhost ->Cw[MAIL_SERVER_DOMAIL]

127.0.0.1 (Internal Mail Server) -> 0.0.0.0

3. Configure Mail Access

# vi /ect/mail/access

# makemap hash /etc/mail/access < /etc/mail/access

# vi /etc/mail/local-host-names

4. SASL security module

# service saslauthd start
# chkconfig saslauthd on
# init 6

5. Disable Firewall

# service iptables stop
# chkconfig --level 345 iptables off
# vi /etc/selinux/config
# getenforce

# service iptables status

6. Install Dovecot packages

# yum -y install dovecot

7. Configure Dovecot

# vi /etc/dovecot/dovecot.conf

# vi /etc/dovecot/conf.d/10-mail.conf

# vi /etc/dovecot/conf.d/10-ssl.conf

# vi /etc/dovecot/conf.d/10-auth.conf

8. Start Dovecot

# service dovecot start
# chkconfig dovecot on

[Java] Convert Hexadeciamal to IP address

public static String convertHex2IP( String hex) throws UnknownHostException {
 java.net.InetAddress address = java.net.InetAddress.getByAddress( javax.xml.bind.DatatypeConverter.parseHexBinary( hex));
 return address.getHostAddress();
  
}
 
public static String convertIP2Hex( String ip) throws UnknownHostException {
 java.net.InetAddress address = java.net.InetAddress.getByName( ip);
 byte[] bytes = address.getAddress();
 StringBuilder sb = new StringBuilder();
 for ( int ll = 0; ll < bytes.length; ll++)
  sb.append( String.format( "%02X", bytes[ ll]));
 
 return sb.toString();
  
}

[Java] How to ping IP address in java (자바에서 Ping 구현)

public static boolean ping( String host, int milisecondTimeout) throws UnknownHostException, IOException {
  java.net.InetAddress address = InetAddress.getByName( host);
  return address.isReachable( milisecondTimeout);
  
}

Friday, 19 August 2016

[RCP] java.lang.ClassCastException: org.eclipse.nebula.widgets.pshelf.PShelf cannot be cast to org.eclise.nebula.widgets.pshelf.PShelf in WindowBuilder when using Nebula PShelf Widget

It seems that the CSS engine sees that it can load the styled widget. Do uninstall pshelf.css feature and plugin.

Wednesday, 17 August 2016

[Windows] How to find domain name from IP address (IP주소를 이용하여 도메인 찾기)

> nslookup [DOMAIN]

Tuesday, 16 August 2016

[RCP] How to remove unnecessary unnecessarypreference pages (불필요 Preference Page 제거)

If you want to remove unnecessary preference pages(Maven and Mylyn),

add commands in postWindowOpen() method which is in ApplicationWorkbenchWindowAdvisor class.

    @Override
    public void postWindowOpen() {
     ...
     
     PreferenceManager pm = PlatformUI.getWorkbench().getPreferenceManager();
     // For checking preference nodes id
//     org.eclipse.jface.preference.IPreferenceNode[] nodes = pm.getRootSubNodes();
//     for ( int ll = 0; ll < nodes.length; ll++) {
//      System.out.println( nodes[ ll].getId());
//     }
     pm.remove( "org.eclipse.m2e.core.preferences.Maven2PreferencePage");
     pm.remove( "org.eclipse.mylyn.preferencePages.Mylyn");
     
     
 }

Friday, 12 August 2016

[Oracle] ORA-28001: the password has expired (Unlock user has expired password)

If you try to log in invalid password continuously, the user is locked. This is a solution that unlock user.

$> sqlplus / as sysdba

ALTER USER [USER_NAME] ACCOUNT UNLOCK;

[Oracle] ORA-00845 : MEMORY TARGET not supported on this system2

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.

1. Create pfile from spfile

cd $ORACLE_HOME/dbs

sqlplus / as sysdba

CREATE pfile='[PFILE_NAME]' from spfile='[SPFILE_NAME]'

2. Edit pfile

$> vi myinit.ora

3. Startup as pfile

$> sqlplus / as sysdba

startup pfile='[PFILE_NAME]';

4. Create sfpile from pfile

create spfile'spfile[INSTANCE_NAME].ora' from pfile'[PFILE_NAME]';

[JSON] How to skip serialize/deserialize variables using jackson annotation

public class JacksonTest {
 
 private String name = null;
 private int age = 0;
 private String[] emails = null;
 private java.util.List< String> favorites = null;
 private String mobile = null;
 private java.util.concurrent.BlockingQueue< String> concurrentQueue = null;
 
 public JacksonTest() {
 }
 
 public JacksonTest( String name, int age, String[] emails, java.util.List< String> favorites, String mobile) {
  this.name = name;
  this.age = age;
  this.emails = emails;
  this.favorites = favorites;
  this.mobile = mobile;
  
 }
 
 public String getName() {
  return name;
 }
 
 public int getAge() {
  return age;
 }
 
 public String[] getEmails() {
  return this.emails;
 }

 public void setEmails(String[] emails) {
  this.emails = emails;
 }
 

 public java.util.List<String> getFavorites() {
  return this.favorites;
 }

 public void setFavorites(java.util.List<String> favorites) {
  this.favorites = favorites;
 }
 

 public String getMobile() {
  return this.mobile;
 }

 public void setMobile(String mobile) {
  this.mobile = mobile;
 }
 

 public void setName(String name) {
  this.name = name;
 }
 

 public void setAge(int age) {
  this.age = age;
 }
 
 public void setConcurrentQueue( java.util.concurrent.BlockingQueue< String> concurrentQueue) {
  this.concurrentQueue = concurrentQueue;
 }
 
 public java.util.concurrent.BlockingQueue< String> getConcurrentQueue() {
  return this.concurrentQueue;
  
 }

 public static void main(String[] args) throws IOException {
  JacksonTest jackson = new JacksonTest( "dorbae", 27, new String[] { "jangsb89@gamil.com", "dorbae@nate.com"}, null, null );
  java.util.List< String> favorites = new java.util.ArrayList< String>();
  favorites.add( "programming");
  favorites.add( "data analytics");
  favorites.add( "data modeling");
  favorites.add( "swimming");
  jackson.setFavorites( favorites);
  
  JacksonTest jackson2 = null;
  
  // Object -> JSON
  com.fasterxml.jackson.databind.ObjectMapper mapper = new com.fasterxml.jackson.databind.ObjectMapper();
  String json = mapper.writeValueAsString( jackson);
  System.out.println( "======== Object -> JSON ========");
  System.out.printf( "%s\n\n", json);
  
  // JSON -> Object
  mapper = new ObjectMapper();
  jackson2 = mapper.readValue( json, JacksonTest.class);
  System.out.println( "======== JSON -> Object ========");
  System.out.printf( "name=%s, age=%d\n", jackson2.getName(), jackson2.getAge());
  
 }

}

    @JsonIgnore
 public void setConcurrentQueue( java.util.concurrent.BlockingQueue< String> concurrentQueue) {
  this.concurrentQueue = concurrentQueue;
 }
 
 @JsonIgnore
 public java.util.concurrent.BlockingQueue< String> getConcurrentQueue() {
  return this.concurrentQueue;
  
 }

[JSON] Convert object to json and convert json to object using Jackson

public class JacksonTest {
 
 private String name = null;
 private int age = 0;
 private String[] emails = null;
 private java.util.List< String> favorites = null;
 private String mobile = null;
 
 public JacksonTest() {
 }
 
 public JacksonTest( String name, int age, String[] emails, java.util.List< String> favorites, String mobile) {
  this.name = name;
  this.age = age;
  this.emails = emails;
  this.favorites = favorites;
  this.mobile = mobile;
  
 }
 
 public String getName() {
  return name;
 }
 
 public int getAge() {
  return age;
 }
 
 public String[] getEmails() {
  return this.emails;
 }

 public void setEmails(String[] emails) {
  this.emails = emails;
 }
 

 public java.util.List<String> getFavorites() {
  return this.favorites;
 }

 public void setFavorites(java.util.List<String> favorites) {
  this.favorites = favorites;
 }
 

 public String getMobile() {
  return this.mobile;
 }

 public void setMobile(String mobile) {
  this.mobile = mobile;
 }
 

 public void setName(String name) {
  this.name = name;
 }
 

 public void setAge(int age) {
  this.age = age;
 }
 

 public static void main(String[] args) throws IOException {
  JacksonTest jackson = new JacksonTest( "dorbae", 27, new String[] { "jangsb89@gamil.com", "dorbae@nate.com"}, null, null );
  java.util.List< String> favorites = new java.util.ArrayList< String>();
  favorites.add( "programming");
  favorites.add( "data analytics");
  favorites.add( "data modeling");
  favorites.add( "swimming");
  jackson.setFavorites( favorites);
  
  JacksonTest jackson2 = null;
  
  // Object -> JSON
  com.fasterxml.jackson.databind.ObjectMapper mapper = new com.fasterxml.jackson.databind.ObjectMapper();
  String json = mapper.writeValueAsString( jackson);
  System.out.println( "======== Object -> JSON ========");
  System.out.printf( "%s\n\n", json);
  
  // JSON -> Object
  mapper = new ObjectMapper();
  jackson2 = mapper.readValue( json, JacksonTest.class);
  System.out.println( "======== JSON -> Object ========");
  System.out.printf( "name=%s, age=%d\n", jackson2.getName(), jackson2.getAge());
  
 }

}

Wednesday, 3 August 2016

[Java] How to make Concurrent Hash Set

Upper Java 1.8

java.util.Set< String> concurrentSet = java.util.concurrent.ConcurrentHashMap.newKeySet();

Lower Java 1.8

java.util.Set< String> concurrentSet = java.util.Collections.newSetFromMap( new java.util.concurrent.ConcurrentHashMap< String, Boolean>());

[DBMS] Table schema meta table (DBMS별 테이블 스키마 테이블)

DBMS	TABLE
H2	INFORMATION>SCHEMA.TABLES
DerbyDB	SYS.SYSTABLES
JavaDB	SYS.SYSTABLES
MySQL	information_schema.TABLES
MariaDB	information_schema.TABLES
Oracle	SYS.ALL_TABLES

H2

COLUMN	DATA_TYPE
TABLE_CATALOG	VARCHAR
TABLE_SCHEMA	VARCHAR
TABLE_NAME	VARCHAR
TABLE_TYPE	VARCHAR
STORAGE_TYPE	VARCHAR
SQL	VARCHAR
REMARKS	VARCHAR
LAST_MODIFICATION	BIGINT
ID	INTEGER
TYPE_NAME	VARCHAR
TABLE_CLASS	VARCHAR

MySQL(MariaDB)

COLUMN	DATA_TYPE
TABLE_CATALOG	VARCHAR(512)
TABLE_SCHEMA	VARCHAR(64)
TABLE_NAME	VARCHAR(64)
TABLE_TYPE	VARCHAR(64)
ENGINE	VARCHAR(64)
VERSION	BIGINT(21) unsigned
ROW_FORMAT	VARCHAR(10)
TABLE_ROWS	BIGINT(21) unsigned
AVG_ROW_LENGTH	BIGINT(21) unsigned
DATA_LENGTH	BIGINT(21) unsigned
MAX_DATA_LENGTH	BIGINT(21) unsigned
INDEX_LENGTH	BIGINT(21) unsigned
DATA_FREE	BIGINT(21) unsigned
AUTO_INCREMENT	BIGINT(21) unsigned
CREATE_TIME	datetime
UPDATE_TIME	datetime
CHECK_TIME	datetime
TABLE_COLLATION	VARCHAR(32)
CHECKSUM	BIGINT(21) unsigned
CREATE_OPTIONS	VARCHAR(255)
TABLE_COMMENT	VARCHAR(2048)