Compiling and Running Java program by using another Java program.

package com.ranga;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

/**
  Program: Compiling and Running Java program by using another Java program.
  java.lang.Runtime.exec()
*/

public class Main {
  public static void main(String[] args) {
    System.out.println("I am in Main class begin.");
    Process process = null;
    try {
      process = Runtime.getRuntime().exec("javac Test.java");
      System.out.println("Test class successfully compiled.");
    } catch (IOException ex) {
      ex.printStackTrace();
    } catch (Exception ex) {
      ex.printStackTrace();
    }

    try {
      process = Runtime.getRuntime().exec("java Test");
      printMessage(" stdout:", process.getInputStream());
      System.out.println("Test class successfully runned.");
    } catch (IOException ex) {
      ex.printStackTrace();
    }
    catch (Exception ex) {
      ex.printStackTrace();
    }
    System.out.println("I am in Main class end.");
  } // end main()

  private static void printMessage(String name, InputStream ins) throws Exception {
    String line = null;
    BufferedReader in = new BufferedReader(new InputStreamReader(ins));
    while ((line = in.readLine()) != null) {
      System.out.println(name + " " + line);
    }
  } // end printMessage()
} // end Main class

class Test {
  public static void main(String a[]) {
     System.out.println("I am in Test class");
  }
}

Read More

Different ways to get the Connection object using Hibernate

Getting the java.sql.Connection object using Session:

---------------------------------------------------------------------------

org.hibernate.Session is nothing but get the one physical connection from the database. 

By using Session we can get the Connection object several ways.

1) session.connection() - this method is deprecated. it is not available on Hibernate4.

2) session.doWork() - this method doesn't return Connection object, but inside what ever operation we want to do using connection object we can do. 

3) session.doReturningWork() - this method returns dynamic type value. In the below example i am return Connection object. 

4) SessionImpl.connection() - Down casting the Session object to SessionImpl. By using SessionImpl we will get the Connection object.

5) ConnectionProvider.getConnection() - Using ConnectionProvider getConnection() method.

Full Example:

package com.varasofttech.client;

import java.sql.Connection;
import java.sql.SQLException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.engine.jdbc.connections.spi.ConnectionProvider;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.internal.SessionImpl;
import org.hibernate.jdbc.ReturningWork;
import org.hibernate.jdbc.Work;

import com.varasofttech.util.HibernateUtil;

public class Application {
    
    public static void main(String[] args) {
        
        // Different ways to get the Connection object using Session
        
        SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
        Session session = sessionFactory.openSession();
        
        // Way1 - using doWork method
        session.doWork(new Work() {
            @Override
            public void execute(Connection connection) throws SQLException {
                // do your work using connection
            }
            
        });
        
        // Way2 - using doReturningWork method
        Connection connection = session.doReturningWork(new ReturningWork<Connection>() {
            @Override
            public Connection execute(Connection conn) throws SQLException {
                return conn;
            }
        });
        
        // Way3 - using Session Impl
        SessionImpl sessionImpl = (SessionImpl) session;
        connection = sessionImpl.connection();
        // do your work using connection
        
        // Way4 - using connection provider
        SessionFactoryImplementor sessionFactoryImplementation = (SessionFactoryImplementor) session.getSessionFactory();
        ConnectionProvider connectionProvider = sessionFactoryImplementation.getConnectionProvider();
        try {
            connection = connectionProvider.getConnection();
            // do your work using connection
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Read More

How to Create Custom Dialect class in Hibernate?

Creating a Custom Dialect in Hibernate:

In order to create any new Dialect class we need to extends org.hibernate.dialect.Dialect class. Dialect class is a abstract class.

If you look at the Dialect class,

public abstract class Dialect implements ConversionContext {

protected Dialect() {

// here we are registering the functions, ColumnType, HibernateTypes

// for registering function's we can use registerFunction() method.

// for registering columntype's we can use registerColumnType() method.

// for registering hibernatetype's we can use registerHibernateType() method.

}

// some others methods

}

For connecting MySQL database, Hibernate people created a dialect class called 'org.hibernate.dialect.MySQLDialect'.

public class MySQLDialect extends MySQLDialect {

      public MySQLDialect() {

  // here they resisted mysql functions, column types

}

// some other methods

}

In the same way, in order to connect with Oracle database, hibernate people developed a 5 dialect classes based on Oracle Version.

org.hibernate.dialect.OracleDialect

org.hibernate.dialect.Oracle8iDialect

org.hibernate.dialect.Oracle9Dialect

org.hibernate.dialect.Oracle9iDialect

org.hibernate.dialect.Oracle10gDialect

if you see the OracleDialect class signature

public class OracleDialect extends Oracle9Dialect {

public OracleDialect() {

// here they resisted oracle functions, column types

}

}

Now we can see how to create Custom Dialect classes.

My requirement is, based on current time, i want to display greeting message say for example if time is 10:01:59 AM then i need to display "Morning" other time is 14:12:15 PM then i need to display "Afternoon". So for this one there is no function exists in any database. 

so for this one what i did is, i created one function in mysql database i.e say_gretting and i am using that function. In order to use that function i need to one new class and extends MySQLDialect class. Finally i need to register say_greeting function in Custom dialect class.

package com.varasofttech.dialect;

import org.hibernate.dialect.MySQL5Dialect;
import org.hibernate.dialect.function.StandardSQLFunction;

public class VaraSoftTechMySQLDialect extends MySQL5Dialect {
    public VaraSoftTechMySQLDialect() {
        super();
         // here i am registring custom function to display greeting message.
        registerFunction("say_greeting", new StandardSQLFunction("say_greeting"));
    }
}

Finally this dialect class, we need to register in hiberante.cfg.xml file.

<!-- Dialect class -->
<property name="hibernate.dialect">com.varasofttech.dialect.VaraSoftTechMySQLDialect</property>

Now lets see how to create 'say_greeting' function in mysql.

DROP FUNCTION IF EXISTS say_greeting;
DELIMITER $$
CREATE FUNCTION say_greeting(name TEXT)
  RETURNS TEXT
BEGIN
  DECLARE greetingMessage CHAR(10);
  SET greetingMessage = (SELECT IF((SELECT TIME_FORMAT(now(),'%H') from DUAL) < 12,'Morning', IF((SELECT TIME_FORMAT(now(),'%H') from DUAL) < 15,'Afternoon','Evening')));
  RETURN CONCAT('Hello ', name, ', Good ', greetingMessage, '!');
END;
$$
DELIMITER ;

SELECT say_greeting('ranga') from DUAL;

Now write client application in order to use say_greeting function. Here i am using NativeSQLQuery.

        Configuration configuration = new Configuration();
        configuration.configure("hibernate.cfg.xml");
        
        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
                        .applySettings(configuration.getProperties())
                        .build();
        
        SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry); 
        Session session = sessionFactory.openSession();
        

        SQLQuery query  = session.createSQLQuery("SELECT say_greeting('ranga') from DUAL");
        String greetingMessage = (String) query.list().get(0);
        System.out.println(greetingMessage);
        
        session.close();
        
        sessionFactory.close();

Output:

Dec 29, 2014 6:45:09 AM org.hibernate.dialect.Dialect <init>

INFO: HHH000400: Using dialect: com.varasofttech.dialect.VaraSoftTechMySQLDialect

Hibernate: 
    SELECT
        say_greeting('ranga') 
    from

        DUAL

Hello ranga, Good Evening!

Reference:
http://myjourneyonjava.blogspot.in/2014/12/displaying-greeting-message-based-on.html

Happy Coding!!!!

Read More

Displaying the Greeting Message based on Time in MySQL

Hi, My requirement is based on Current time i want to display Greeting message.

For example, if time is less than 12PM then i need to display "Morning" and if time is less than 5PM then i need to display "Afternoon" and if time is above 5 PM i need to display "Evening".

Step1: Selecting the Current time.

SELECT now() from DUAL;

Output:

 '2014-12-28 17:35:46'

Step2: In the Current time getting the hours.

SELECT TIME_FORMAT(now(),'%H') from DUAL;

Output: 

17

Step3: Now based on hours we need to display greeting message. So we need to use if condition.

SELECT IF((SELECT TIME_FORMAT(now(),'%H') from DUAL) < 12,'Morning', IF((SELECT TIME_FORMAT(now(), 
'%H') from DUAL) < 17,'Afternoon','Evening'));

Output:

'Evening'

Happy coding!

Read More

How to get all table names using Hibernate.

This post demonstrates the how to get the all table names using Hibernate.

Configuration configuration = new Configuration();
configuration.configure("hibernate.cfg.xml");
SessionFactory sessionFactory = configuration.buildSessionFactory();

// Way1 - get the all Class Mapping Information using Configuration
Iterator<PersistentClass> classMappings = configuration.getClassMappings();
while(classMappings.hasNext()) {
    PersistentClass persistentClass = classMappings.next();
    Table table = persistentClass.getTable();
    String tableName = table.getName();
    System.out.println(tableName);
}

// Way2 - get the all Class Metadata Information using SessionFactory
Map<String, ClassMetadata> classMetaDataMap = sessionFactory.getAllClassMetadata();
for(Map.Entry<String, ClassMetadata> metaDataMap : classMetaDataMap.entrySet()) {
    ClassMetadata classMetadata = metaDataMap.getValue();
    AbstractEntityPersister abstractEntityPersister = (AbstractEntityPersister) classMetadata;
    String tableName = abstractEntityPersister.getTableName();
    System.out.println(tableName);
}

// Way3 - using Session 
SessionImpl sessionImpl = (SessionImpl) sessionFactory.openSession();
try {
    Connection connection = sessionImpl.connection();
    DatabaseMetaData databaseMetaData = connection.getMetaData();
    ResultSet resultSet = databaseMetaData.getTables(null, null, null, new String[] {"TABLE"});
    while(resultSet.next()) {
        String tableName = resultSet.getString(3);
        System.out.println(tableName);
    }
} catch (Exception e) {
    e.printStackTrace();
}

References:

• https://stackoverflow.com/questions/4813122/get-all-table-names-set-up-in-sessionfactory
• http://www.herongyang.com/JDBC/sqljdbc-jar-Table-List.html
• http://tutorials.jenkov.com/jdbc/databasemetadata.html

Read More