Kruders.com

How to change Java Version in Linux?

admin — Fri, 22 Mar 2013 03:21:24 +0000

In this article, you will see how to change default java version to latest version.

Check the current version used on your system.

[root@localhost /]# java -version

Example Output

java version “1.4.2″
gij (GNU libgc) version 4.1.2 2008704 (Red Hat 1.4.2-48)

If there are multiple versions of java, you can change the default version by executing following command. It will also display which is default version used by your machine (indicated by *).

[root@localhost /]#update-alternatives –config java

Example Output

[root@localhost /]#update-alternatives –config java

There are 2 programs which provide ‘java’.

Selection Command

——————————————————————-
*+ 1 /usr/java/jdk1.4.2/jre/bin/java
2 /usr/lib/jvm/jre-1.7.0.-openjdk.x86_64/bin/java

Enter to keep the current selection[+], or type selection number : 2

Now again check the current version used on your system.

[root@localhost /]# java -version

Example Output

java version “1.7.0_09-icedtea”

Installing MySql Workbench in Fedora

admin — Thu, 21 Mar 2013 09:25:19 +0000

In this article, you will see how to install and launch Mysql Workbench in Fedora 18

1. Change root user

su –
OR
sudo -i

2. Install Remi repository

** Remi Dependency on Fedora 18 **
rpm -Uvh http”//download1.rpmfusion.org/free/fedora/rpmfusion-free-release-stable.noarch.rpm

** Fedora 18 **
rpm -Uvh http://rpms.famillecollet.com/remi-release-18.rpm

3. Install MySql Workbench

yum –enablerop=remi install mysql-workbench

4. Launching MySql Workbench

Once MySQL Workbench has been installed it can be launched by selecting Applications – > Programming – > MySQL Workbench from the main menu.

MySQL Workbench can also be launched from command line on Linux.

shell> /usr/bin/mysql-workbench

Logback Logging Example

admin — Thu, 31 Jan 2013 06:53:51 +0000

In this article, you will see very basic logging using Logback.

First create a new Java Project and configure it as Maven Project. For Reference, Click Here

Add the following dependencies in pom.xml

  
     
         ch.qos.logback
         logback-classic
         1.0.7
     
     
         ch.qos.logback
         logback-core
         1.0.7

1. Logback Configuration

The following configuration generates simple logs on console.

logback.xml



    
        
            %d{HH:mm:ss.SSS} [%thread] %-5level  %logger{35} - %msg%n

2. Logback in Java Program

The following Java class is a very simple example that initializes, and then uses, the Logback logging library for Java applications.

package com.kruders;
 
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
 
public class HelloWorld {
static final Logger logger = LoggerFactory.getLogger(HelloWorld.class);
     
    public static void main(String[] args) {
        logger.info("Hello World!!!");
    }
}

When you run the above example you’ll get an output like:

12:26:48.079 [main] INFO com.kruders.HelloWorld – Hello World!!!

Limit WordPress Search To Post Titles

admin — Wed, 16 Jan 2013 06:34:24 +0000

In this article, you will see how to limit your wordpress search to post titles only.

WordPress version

WordPress 3.5

Source Code

$search .= “{$searchand}(($wpdb -> posts.post_title LIKE ‘{$n}{$term}{$n}’) OR ($wpdb -> posts.post_content LIKE ‘{$n}{$term}{$n}’))”;

Remove the OR part (in bold) to make it specific to post title.

$search .= “{$searchand}(($wpdb->posts.post_title LIKE ‘{$n}{$term}{$n}’))”;

Source File

Source code is located in wp-includes/query.php.

JDBC Introduction

admin — Wed, 16 Jan 2013 06:07:09 +0000

The Java Database Connectivity (JDBC) API is the industry standard for database-independent connectivity between the Java programming language and a wide range of databases SQL databases and other tabular data sources, such as spreadsheets or flat files. The JDBC API provides a call-level API for SQL-based database access. JDBC technology also provides a common base on which tools and alternate interfaces can be built.

JDBC Architecture

Two-tier and Three-tier Processing Models

The JDBC API supports both two-tier and three-tier processing models for database access.

In the two-tier model, a Java applet or application talks directly to the data source. This requires a JDBC driver that can communicate with the particular data source being accessed. A user’s commands are delivered to the database or other data source, and the results of those statements are sent back to the user. The data source may be located on another machine to which the user is connected via a network. This is referred to as a client/server configuration, with the user’s machine as the client, and the machine housing the data source as the server. The network can be an intranet, which, for example, connects employees within a corporation, or it can be the Internet.

In the three-tier model, commands are sent to a “middle tier” of services, which then sends the commands to the data source. The data source processes the commands and sends the results back to the middle tier, which then sends them to the user. MIS directors find the three-tier model very attractive because the middle tier makes it possible to maintain control over access and the kinds of updates that can be made to corporate data. Another advantage is that it simplifies the deployment of applications. Finally, in many cases, the three-tier architecture can provide performance advantages.

JDBC API

The JDBC API is comprised of two packages:

The JDBC API provides the following interfaces and classes:

Reference

http://docs.oracle.com/javase/tutorial/jdbc/overview/index.html

Spring + Log4j + Maven Example

admin — Tue, 15 Jan 2013 10:02:12 +0000

In this tutorial, I will show you how to integrate Spring 3 with Log4j.

Tools and technologies used :

Spring
Log4j
Maven
Eclipse

Following example demonstrates a simple Hello World web application using Spring MVC that will show logging message on Console.

First create a new Dynamic Web Project and configure it as Maven Project. For Reference, Click Here

Add the following dependencies in pom.xml

  
		3.0.5.RELEASE
  

  

		
		
			org.springframework
			spring-core
			${spring.version}
		

		
			org.springframework
			spring-web
			${spring.version}
		

		
			org.springframework
			spring-webmvc
			${spring.version}
		
		
		    log4j
		    log4j
		    1.2.17

1. Controller

To provide a basic infrastructure, all of Spring’s various Controller inherit from AbstractController. When using the AbstractController as the baseclass for your controllers you only have to override the handleRequestInternal(HttpServletRequest, HttpServletResponse) method, implement your logic, and return a ModelAndView object.

HelloWorldController.java

package com.kruders.controller;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.AbstractController;

public class HelloWorldController extends AbstractController{
	
	@Override
	protected ModelAndView handleRequestInternal(HttpServletRequest arg0,
			HttpServletResponse arg1) throws Exception {
		ModelAndView model = new ModelAndView("helloworld");
		model.addObject("message", "Hello World!!!");
		return model;
	}
}

2. Create View

Create jsp folder in WEB-INF and create helloworld.jsp file in jsp folder

Now write the following code in helloworld.jsp file

${message}

3. Configuration

Create Spring Bean Configuration in WEB-INF folder and name it dispatcher-servlet.xml and add the following code.


 

    
        /WEB-INF/jsp/
    
     
    
        .jsp

4. Integrate Spring in Web App

To integrate Spring in Web Application, write the following code in web.xml


    dispatcher
    org.springframework.web.servlet.DispatcherServlet
    1

 

    dispatcher
    /

 

    contextConfigLocation
    /WEB-INF/dispatcher-servlet.xml

 

    org.springframework.web.context.ContextLoaderListener

5. Properties file

Create log4j.properties file that defines standard rules required for Log4J to handle logging messages.

log4j.properties

log4j.rootLogger=DEBUG, CA

log4j.appender.CA=org.apache.log4j.ConsoleAppender

log4j.appender.CA.layout=org.apache.log4j.PatternLayout
log4j.appender.CA.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n

6. Integrate Log4j in Spring MVC

Create a Class variable for Logger as shown below:

package com.kruders.controller;

import org.apache.log4j.Logger;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
@RequestMapping("/helloworld.html")
public class HelloWorldController {
	static final Logger logger = Logger.getLogger(HelloWorldController.class);
	@RequestMapping(method = RequestMethod.GET)
	public String printWelcome(ModelMap model) {
		logger.info("Hello World!!!");
		model.addAttribute("message", "Hello World!!!");
		return "helloworld";

	}
}

When you run the above example you’ll get an output (on console) like:

1531 [http-8181-2] INFO com.kruders.controller.HelloWorldController – Hello World!!!

Spring + Hibernate + MySql + Maven Example

admin — Tue, 15 Jan 2013 05:08:46 +0000

In this tutorial, I will show you how to integrate Hibernate with Spring 3.

Tools and technologies used :

Hibernate
Spring
MySql
Maven
Eclipse

First create a new Dynamic Web Project and configure it as Maven Project. For Reference, Click Here

Add the following dependencies in pom.xml


	3.1.0.RELEASE
  

  

	
	
		org.springframework
		spring-core
		${spring.version}
	

	
		org.springframework
		spring-web
		${spring.version}
	

	
		org.springframework
		spring-webmvc
		${spring.version}
	
	
        mysql
        mysql-connector-java
        5.1.15
    
    
        org.hibernate
        hibernate-core
        3.6.3.Final
    
    
        javassist
        javassist
        3.12.1.GA
    
    
        org.slf4j
        slf4j-log4j12
        1.6.6

1. Sql Script

Use the following Sql Script for creating table.

create table User(
    ID int(10) primary key NOT NULL AUTO_INCREMENT,
    username varchar(50),
    password varchar(50));

2. Pojo

Now create User class that maps java class to User table.

User.java

package com.kruders.model.bean;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "User")
public class User{
    @Id
    @GeneratedValue(strategy= GenerationType.AUTO)
    private Integer Id;
    @Column(name="username")
    private String username;
    @Column(name="password")
    private String password;
	public Integer getId() {
		return Id;
	}
	public void setId(Integer id) {
		Id = id;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	} 
  
}

3. Hibernate Configuration File

Now create the hibernate configuration file and add all the mapping files.

hibernate.cfg.xml





	com.mysql.jdbc.Driver
	jdbc:mysql://localhost:3306/test
	root
	password
	1
	org.hibernate.dialect.MySQLDialect
	true

4. Hibernate Utility Class

Now create HibernateUtil class. The HibernateUtil class helps in creating the SessionFactory from the Hibernate configuration file. A org.hibernate.SessionFactory is used to obtain org.hibernate.Session instances. A org.hibernate.Session represents a single-threaded unit of work. The org.hibernate.SessionFactory is a thread-safe global object that is instantiated once.

package com.kruders.util;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
  
public class HibernateUtil {
  
    private static final SessionFactory sessionFactory = buildSessionFactory();
  
    private static SessionFactory buildSessionFactory() {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            return new AnnotationConfiguration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
  
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

5. Model

Following is the Login class.

package com.kruders.domain;
 
public class Login {
    String email;
    String password;
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
}

6. Controller

In order to handle spring forms, you need your controller to extend SimpleFormController. Following class shows you how to extend SimpleFormController

LoginController.java

package com.kruders.controller;
 
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.SimpleFormController;
 
import com.kruders.domain.Login;
 
public class LoginController extends SimpleFormController{
    public LoginController(){
        setCommandClass(Login.class);
        setCommandName("loginForm");
    }
    @Override
    protected ModelAndView onSubmit(Object command) throws Exception {
        Login login = (Login) command;
        return new ModelAndView("loginSuccess","login",login);
    }
}

Extending SimpleFormController makes the controller to handle form requests. Here in LoginController contructor, controller will bind values to/from Spring’s form tags.

public LoginController(){
    setCommandClass(Login.class);  //Spring form values gets stored into Login object
    setCommandName("loginForm");    //if loginForm is submitted, Spring will forward request to this Controller
}

When loginForm is submitted, onsubmit() method will be executed to handle form’s request and return ModelAndView on success. All the forms field values will be submitted as Strings to the form controller.

7. Form Validation

To validate the form fields we have a seperate LoginValidator class that implements the Validator interface, override the validate() method perform all the validations.

Following in the LoginValidator class.

package com.kruders.validator;

import java.util.List;

import org.springframework.validation.Errors;
import org.springframework.validation.ValidationUtils;
import org.springframework.validation.Validator;
import com.kruders.domain.Login;
import com.kruders.model.bean.User;
import com.kruders.util.HibernateUtil;

import org.hibernate.Session;

public class LoginValidator implements Validator{
	@Override
	public boolean supports(Class clazz) {
		return Login.class.isAssignableFrom(clazz);
	}

	@Override
	public void validate(Object target, Errors errors) {
		Login loginuser = (Login) target;
		ValidationUtils.rejectIfEmptyOrWhitespace(errors, "email", "email.required");
		ValidationUtils.rejectIfEmptyOrWhitespace(errors, "password", "password.required");
		Session session = HibernateUtil.getSessionFactory().openSession();
        List userList = session.createQuery("from User where username ='" + loginuser.getEmail() + "' and password ='" + loginuser.getPassword() + "'").list();
        if(userList.size() == 0) {
        	errors.reject("wrongcredential","Wrong Username or Password!!!");	
        }
        
	}
}

8. Properties File

A properties file to store all the error messages. Here we have the error messages in a seperate properties file so we add the error code, you can even add the error messages directly.

messages.properties

email.required = User Name is required
password.required = Password is required

9. View

Following is the form login form that contains Spring’s Form Tags and display error message if any.

form:errors tag to display errors in jsp files.

loginForm.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
	pageEncoding="ISO-8859-1"%>
<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form"%>




Login Page



	
		
			
			
			
		
		
			Email :
			
			
		
		
			Password :

On successful submission of loginform, loginSuccess.jsp page will be displayed.

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>




Login Successful


${login.email} successfully logged in

10. Spring Bean Configuration

We now declare the controller and validator for the loginform Spring Bean Configuration file.

Also add the properties file.

You can download the source code of this example here.

Next and Previous Links for same Category in WordPress

admin — Thu, 10 Jan 2013 05:32:03 +0000

I created a category and call it “WordPress”. Then I created some posts and assign “WordPress” as category for the posts. Now I want the next/previous to be shown for the same category only.

WordPress version

WordPress 3.5

Arguments

function previous_post_link($format=’« %link’, $link=’%title’, $in_same_cat = false, $excluded_categories = ”)

You can change the in_same_cat to true to display the previous post in same cateogry.

Similarly you can show next post in the same category.

Source File

previous_posts_link() is located in wp-includes/link-template.php.
next_post_link() is located in wp-includes/link-template.php.

Get URL Parameter Using Javascript

admin — Thu, 10 Jan 2013 04:26:36 +0000

It is sometimes required to get the query parameters of an URL in JavaScript. So following example demonstrates how to get parameter value from a URL.

Source Code

Hibernate – @MappedSuperclass How to override column identifier

admin — Wed, 09 Jan 2013 10:01:09 +0000

In this tutorial I will show how to override an attribute from mapped super class.

1. Sql Script

Use the following Sql Script for creating table.

create table User(
    ID int(10) primary key NOT NULL AUTO_INCREMENT,
    Name varchar(50));

2. Pojo

Now create GenericId and User Class as following.

GenericId.java : an abstract class, annotated with @MappedSuperclass that have id column

package com.kruders.model.bean;

import javax.persistence.MappedSuperclass;

@MappedSuperclass
public abstract class GenericID {
	private Integer id;

	public Integer getId() {
		return id;
	}

	public void setId(Integer id) {
		this.id = id;
	}
}

User.java : an @Entity class that extends the super class and overriding the getters of the id.

package com.kruders.model.bean;

import javax.persistence.AttributeOverride;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "User")
@AttributeOverride(name = "id", column = @Column(name = "ID"))
public class User extends GenericID{
	
	
	@Id
    @GeneratedValue
    private Integer Id;
    @Column(name="Name")
    private String name;
    @Column(name="content")
    
    @Override
    public Integer getId() {
		return Id;
	}
	public void setId(Integer id) {
		Id = id;
	}
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

3. Hibernate Configuration File

Now create the hibernate configuration file and add all the mapping files.

hibernate.cfg.xml





	com.mysql.jdbc.Driver
	jdbc:mysql://localhost:3306/test
	root
	
	1
	org.hibernate.dialect.MySQLDialect
	true

package com.kruders.util;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
  
public class HibernateUtil {
  
    private static final SessionFactory sessionFactory = buildSessionFactory();
  
    private static SessionFactory buildSessionFactory() {
        try {
            // Create the SessionFactory from hibernate.cfg.xml
            return new AnnotationConfiguration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }
  
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

5. Run Program

Create Main.java class that adds a record and run it as Java Application

package com.kruders.core;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.kruders.model.bean.User;
import com.kruders.util.HibernateUtil;
public class Main {
    public static void main(String args[]) {
        Session session = HibernateUtil.getSessionFactory().openSession();
        Transaction transaction = null;
        try {
            transaction = session.beginTransaction();
            User user = new User();
            user.setName("Puneet");
            session.save(user);
            transaction.commit();
        }catch (HibernateException e) {
            transaction.rollback();
            e.printStackTrace();
        } finally {
            session.close();
        }
    }
}

You can download the source code of this example here.