linux terminal commands for beginner level

NAVIGATION
  • ls - list directory contents
  • pwd - print name of current/working directory
  • cd - change working directory
  • pushd/popd - put working directory on a stack
  • file - determine file type
  • locate - find files by name
  • updatedb - update database for locate
  • which - locate a command
  • history - display bash command history

GETTING HELP
  • whatis - display the on-line manual descriptions
  • apropos - search the manual page names and descriptions
  • man - an interface to the on-line reference manuals

WORKING WITH FILES
  • mkdir - create a directory/make directories
  • touch - change file timestamps/create empty files
  • cp - copy files and directories
  • mv - move (rename) files
  • rm - remove files or directories
  • rmdir - remove empty directories

TEXT FILES
  • cat - concatenate files and print on the standard output
  • more/less - page view
  • nano - command line text editor

USERS
  • sudo - execute a command as superuser
  • su - change user ID or become another user
  • users - print the user names of users currently logged in
  • id - print real and effective user and group IDs

CHANGING FILE PERMISSIONS
  • chmod - change permissions of a file

KILLING PROGRAMS AND LOGGING OUT
  • Ctrl+C - kill a running command
  • killall - kill processes by name
  • exit - log out of bash

Maven use local jar without installing

You can install a local jar by using  mvn install:install-file command/goal as I discussed in my earlier blog post. This ensures the re-usability of jar file across your projects but as a drawback, this requires every team member and build server to run the same command/goal to build their project.

To avoid to the manual hassle, you can add the .jar in pom.xml file without running the mvn install:install-file goal. The idea is to refer a .jar from your project base directory using the <systemPath> element.

In example below, I put my jar files to /myjars directory and point to the jar file as
        <systemPath>${project.basedir}/myjars/[Jar file name]</systemPath>

Directory Structure

..
/src/..
pom.xml
/myjars/my-lib-core.jar
/myjars/third-party.jar

Pom.xml

<dependencies>
    <dependency>
        <groupId>com.my.library</groupId>
        <artifactId>mylib-core</artifactId>
        <version>1.VERSION</version>
        <scope>system</scope>
        <systemPath>${project.basedir}/myjars/my-lib-core.jar</systemPath>
    </dependency>
    <dependency>
        <groupId>com.third-party.library</groupId>
        <artifactId>thirdparty</artifactId>
        <version>1.VERSION</version>
        <scope>system</scope>
        <systemPath>${project.basedir}/myjars/third-party.jar</systemPath>
    </dependency>

For web project (war files )

If you are working on a web project, the above configuration won't add the jars to war file by default. You need to do following.

Here we are asking maven-war-plugin to add all jar ( **/*.jar) from  ${project.basedir}/myjars  to WEB-INF/lib folder when creating the war file.

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <configuration>
                <warSourceDirectory>src/main/webapp/</warSourceDirectory>
                <webResources>
                    <resource>
                        <directory>${project.basedir}/myjars</directory>
                        <targetPath>WEB-INF/lib</targetPath>
                        <includes>
                            <include>**/*.jar</include>
                        </includes>
                    </resource>
                </webResources>
            </configuration>
        </plugin>
    </plugins>
</build>

Acoustic Alchemy - The Beautiful Game - Instrumental JAZZ

Acoustic Alchemy - The Beautiful Game - Instrumental JAZZ



Isn't it awesome ?



Catalina Kiss - Acoustic Alchemy - Instrumental JAZZ

Catalina Kiss - Acoustic Alchemy - Instrumental JAZZ

Here's another ...





Enjoy !

Spring MVC download content of String as text file

To download a text file out of a String :

JSP View :
 <a href="download">Download String </a> 

Controller Method :

 @RequestMapping(value = "/download", method = RequestMethod.GET)
 public @ResponseBody
 void downloadFile(HttpServletResponse resp) {
  String downloadFileName= "download.txt";
  String downloadStringContent= getStringToWrite(); // implement this
  try {
   OutputStream out = resp.getOutputStream();
   resp.setContentType("text/plain; charset=utf-8");
   resp.addHeader("Content-Disposition","attachment; filename=\"" + downloadFileName + "\"");
   out.write(downloadStringContent.getBytes(Charset.forName("UTF-8")));
   out.flush();
   out.close();

  } catch (IOException e) {
  }
 }

Check this as well : spring mvc download a file from server

Spring MVC file download from server example code

To download a file - from request parameter

JSP View :
 <a href="downloadFile?fileName=log.txt">Download String </a> 

Controller Method :


@RequestMapping(value = "/downLoadFile", method = RequestMethod.GET)
public void downLoadFile( HttpServletRequest request, HttpServletResponse response ) {
try {
 String fileName = request.getParameter( "fileName" );
 File file = getFileToDownload(fileName) // implement this to return a valid file object
 InputStream in = new BufferedInputStream( new FileInputStream( file ) );

 response.setContentType( "text/plain" ); // define your type
 response.setHeader( "Content-Disposition", "attachment; filename=" + fileName  );

 ServletOutputStream out = response.getOutputStream( );
 IOUtils.copy( in, out ); //import org.apache.commons.io.IOUtils;
 response.flushBuffer( );
} catch ( Exception e ) {
 e.printStackTrace( );
}
}

 

Java - Convert HTML to PDF File - Using iText

Here's how you can convert HTML to PDF using iText and Flying Saucer PDF libraries in Java. The steps are described within the code below.

You can easily add some methods below to read HTML content from a file and convert the HTML file to PDF ( instead of HTML string to PDF).

package g.t.test;

import org.xhtmlrenderer.pdf.ITextRenderer;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
public class HtmlToPDFConverter {

    public static void convert(String htmlContent, File pdfFile) throws Exception {
        ByteArrayOutputStream os = new ByteArrayOutputStream();

        //step1: render html to memory         
        ITextRenderer renderer = new ITextRenderer();
        renderer.setDocumentFromString(htmlContent);
        renderer.layout();
        renderer.createPDF(os);

        //step2: conver to byte array stream         
        byte[] pdfAsBytes = os.toByteArray();
        os.close();

        //step3: write byte array stream to file         
        FileOutputStream fos = new FileOutputStream(pdfFile);
        fos.write(pdfAsBytes);
        fos.flush();
        fos.close();
    }

    // let's test !! 
    public static void main(String[] args) throws Exception{
        convert("<html> <body> " +
            "<h1>Hello Crazy World !!</h1> <br/> " +
            "<h2> I hope you are doing great.</h2> " +
            "</body> </html>", new File("test.pdf"));
    }
}

Used Maven Dependencies:

<dependency>
    <groupId>com.lowagie</groupId>
    <artifactId>itext</artifactId>
    <version>2.1.7</version>
</dependency>
<dependency>
    <groupId>org.xhtmlrenderer</groupId>
    <artifactId>flying-saucer-pdf</artifactId>
    <version>9.0.9</version>
</dependency>


jQuery effects - jQuery basic tutorial 10

10. jQuery Effects

jQuery provides a trivially simple interface for doing various kind of amazing effects. jQuery methods allow us to quickly apply commonly used effects with a minimum configuration.
This tutorial covers all the important jQuery methods to create visual effects.

Showing and Hiding elements:

The commands for showing and hiding elements are pretty much what we would expect: show() to show the elements in a wrapped set and hide() to hide them.

Syntax:

Here is the simple syntax for show() method:
[selector].show( speed, [callback] );
Here is the description of all the parameters:
  • speed: A string representing one of the three predefined speeds ("slow", "normal", or "fast") or the number of milliseconds to run the animation (e.g. 1000).
  • callback: This optional parameter represents a function to be executed whenever the animation completes; executes once for each element animated against.
Following is the simple syntax for hide() method:
[selector].hide( speed, [callback] );
Here is the description of all the parameters:
  • speed: A string representing one of the three predefined speeds ("slow", "normal", or "fast") or the number of milliseconds to run the animation (e.g. 1000).
  • callback: This optional parameter represents a function to be executed whenever the animation completes; executes once for each element animated against.

Example:

Consider the following HTML file with a small JQuery coding:
<html>
<head>
<title>the title</title>
   <script type="text/javascript" 
   src="/jquery/jquery-1.3.2.min.js"></script>
   <script type="text/javascript" language="javascript">
   
   $(document).ready(function() {

     $("#show").click(function () {
        $(".mydiv").show( 1000 );
     });

     $("#hide").click(function () {
        $(".mydiv").hide( 1000 );
     });

   });

   </script>
   <style>
   .mydiv{ margin:10px;padding:12px;
      border:2px solid #666;
      width:100px;
      height:100px;
    }
  </style>
</head>
<body>
   <div class="mydiv">
      This is  SQUAR
   </div>

   <input id="hide" type="button" value="Hide" />   
   <input id="show" type="button" value="Show" />   

</body>
</html>

Toggling the elements:

jQuery provides methods to toggle the display state of elements between revealed or hidden. If the element is initially displayed, it will be hidden; if hidden, it will be shown.

Syntax:

Here is the simple syntax for one of the toggle() methods:
[selector]..toggle([speed][, callback]);
Here is the description of all the parameters:
  • speed: A string representing one of the three predefined speeds ("slow", "normal", or "fast") or the number of milliseconds to run the animation (e.g. 1000).
  • callback: This optional parameter represents a function to be executed whenever the animation completes; executes once for each element animated against.

Example:

We can animate any element, such as a simple <div> containing an image:
<html>
<head>
<title>the title</title>
   <script type="text/javascript" 
   src="/jquery/jquery-1.3.2.min.js"></script>
   <script type="text/javascript" language="javascript">

   $(document).ready(function() {
      $(".clickme").click(function(event){
          $(".target").toggle('slow', function(){
             $(".log").text('Transition Complete');
          });
      });

   });
   </script>
   <style>
   .clickme{ margin:10px;padding:12px;
      border:2px solid #666;
      width:100px;
      height:50px;
    }
   </style>
</head>
<body>
   <div class="content">
      <div class="clickme">Click Me</div>
      <div class="target">
         <img src="/images/jquery.jpg" alt="jQuery" />
      </div>
      <div class="log"></div>
</body>
</html>

JQuery Effect Methods:

You have seen basic concept of jQuery Effects. Following table lists down all the important methods to create different kind of effects:

Methods and Description
animate( params, [duration, easing, callback] )
A function for making custom animations.
fadeIn( speed, [callback] )
Fade in all matched elements by adjusting their opacity and firing an optional callback after completion.
fadeOut( speed, [callback] )
Fade out all matched elements by adjusting their opacity to 0, then setting display to "none" and firing an optional callback after completion.
fadeTo( speed, opacity, callback )
Fade the opacity of all matched elements to a specified opacity and firing an optional callback after completion.
hide( )
Hides each of the set of matched elements if they are shown.
hide( speed, [callback] )
Hide all matched elements using a graceful animation and firing an optional callback after completion.
show( )
Displays each of the set of matched elements if they are hidden.
show( speed, [callback] )
Show all matched elements using a graceful animation and firing an optional callback after completion.
slideDown( speed, [callback] )
Reveal all matched elements by adjusting their height and firing an optional callback after completion.
slideToggle( speed, [callback] )
Toggle the visibility of all matched elements by adjusting their height and firing an optional callback after completion.
slideUp( speed, [callback] )
Hide all matched elements by adjusting their height and firing an optional callback after completion.
stop( [clearQueue, gotoEnd ])
Stops all the currently running animations on all the specified elements.
toggle( )
Toggle displaying each of the set of matched elements.
toggle( speed, [callback] )
Toggle displaying each of the set of matched elements using a graceful animation and firing an optional callback after completion.
toggle( switch )
Toggle displaying each of the set of matched elements based upon the switch (true shows all elements, false hides all elements).
jQuery.fx.off
Globally disable all animations.

jQuery and Ajax - jQuery basic tutorial 9

9. jQuery Ajax

AJAX is an acronym standing for Asynchronous JavaScript and XML and this technology help us to load data from the server without a browser page refresh.
If you are new with AJAX, I would recommend you go through our Ajax Tutorial before proceeding further.
JQuery is a great tool which provides a rich set of AJAX methods to develope next generation web application.

Loading simple data:

This is very easy to load any static or dynamic data using JQuery AJAX. JQuery provides load() method to do the job:

Syntax:

Here is the simple syntax for load() method:
[selector].load( URL, [data], [callback] );
Here is the description of all the parameters:
  • URL: The URL of the server-side resource to which the request is sent. It could be a CGI, ASP, JSP, or PHP script which generates data dynamically or out of a database.
  • data: This optional parameter represents an object whose properties are serialized into properly encoded parameters to be passed to the request. If specified, the request is made using the POST method. If omitted, the GET method is used.
  • callback: A callback function invoked after the response data has been loaded into the elements of the matched set. The first parameter passed to this function is the response text recieved from the server and second parameter is the status code.

    Example:

    Consider the following HTML file with a small JQuery coding:
    <html>
    <head>
    <title>the title</title>
       <script type="text/javascript" 
       src="/jquery/jquery-1.3.2.min.js"></script>
       <script type="text/javascript" language="javascript">
       $(document).ready(function() {
          $("#driver").click(function(event){
              $('#stage').load('/jquery/result.html');
          });
       });
       </script>
    </head>
    <body>
       <p>Click on the button to load result.html file:</p>
       <div id="stage" style="background-color:blue;">
              STAGE
       </div>
       <input type="button" id="driver" value="Load Data" />
    </body>
    </html>
    
    Here load() initiates an Ajax request to the specified URL /jquery/result.html file. After loading this file, all the content would be populated inside <div> tagged with ID stage. Assuming, our /jquery/result.html file has just one HTML line:
    <h1>THIS IS RESULT...</h1>
    
    When you click the given button, then result.html file gets loaded. To understand it in better way you can Try it yourself.

    Getting JSON data:

    There would be a situation when server would return JSON string against your request. JQuery utility function getJSON() parses the returned JSON string and makes the resulting string available to the callback function as first parameter to take further action.

    Syntax:

    Here is the simple syntax for getJSON() method:
    [selector].getJSON( URL, [data], [callback] ); Here is the description of all the parameters:
  • URL: The URL of the server-side resource contacted via the GET method.
  • data: An object whose properties serve as the name/value pairs used to construct a query string to be appended to the URL, or a preformatted and encoded query string.
  • callback: A function invoked when the request completes. The data value resulting from digesting the response body as a JSON string is passed as the first parameter to this callback, and the status as the second.

Example:

Consider the following HTML file with a small JQuery coding:
<html>
<head>
<title>the title</title>
   <script type="text/javascript" 
   src="/jquery/jquery-1.3.2.min.js"></script>
   <script type="text/javascript" language="javascript">
   $(document).ready(function() {
      $("#driver").click(function(event){
          $.getJSON('/jquery/result.json', function(jd) {
             $('#stage').html('<p> Name: ' + jd.name + '</p>');
             $('#stage').append('<p>Age : ' + jd.age+ '</p>');
             $('#stage').append('<p> Sex: ' + jd.sex+ '</p>');
          });
      });
   });
   </script>
</head>
<body>
   <p>Click on the button to load result.html file:</p>
   <div id="stage" style="background-color:blue;">
          STAGE
   </div>
   <input type="button" id="driver" value="Load Data" />
</body>
</html>
Here JQuery utility method getJSON() initiates an Ajax request to the specified URL /jquery/result.json file. After loading this file, all the content would be passed to the callback function which finally would be populated inside <div> tagged with ID stage. Assuming, our /jquery/result.json file has following json formatted content:
{
"name": "Zara Ali",
"age" : "67",
"sex": "female"
}
When you click the given button, then result.json file gets loaded. To understand it in better way you can Try it yourself.

Passing data to the Server:

Many times you collect input from the user and you pass that input to the server for further processing. JQuery AJAX made it easy enough to pass collected data to the server using data parameter of any available Ajax method.

Example:

This example demonstrate how can pass user input to a web server script which would send the same result back and we would print it:
<html>
<head>
<title>the title</title>
   <script type="text/javascript" 
   src="/jquery/jquery-1.3.2.min.js"></script>
   <script type="text/javascript" language="javascript">
   $(document).ready(function() {
      $("#driver").click(function(event){
          var name = $("#name").val();
          $("#stage").load('/jquery/result.php', {"name":name} );
      });
   });
   </script>
</head>
<body>
   <p>Enter your name and click on the button:</p>
   <input type="input" id="name" size="40" /><br />
   <div id="stage" style="background-color:blue;">
          STAGE
   </div>
   <input type="button" id="driver" value="Show Result" />
</body>
</html>
Here is the code written in result.php script:

<?php
if( $_REQUEST["name"] )
{
   $name = $_REQUEST['name'];
   echo "Welcome ". $name;
}
?> 

jQuery Event handlers - jQuery basic tutorial 8

8. jQuery Event handlers

We have the ability to create dynamic web pages by using events. Events are actions that can be detected by your Web Application.
Following are the examples events:
  • A mouse click
  • A web page loading
  • Taking mouse over an element
  • Submitting an HTML form
  • A keystroke on your keyboard
  • etc.
When these events are triggered you can then use a custom function to do pretty much whatever you want with the event. These custom functions call Event Handlers.

Binding event handlers:

Using the jQuery Event Model, we can establish event handlers on DOM elements with the bind() method as follows:
$('div').bind('click', function( event ){
   alert('Hi there!');
});
selector.bind( eventType[, eventData], handler)
Following is the description of the parameters:
  • eventType: A string containing a JavaScript event type, such as click or submit. Refer to the next section for a complete list of event types.
  • eventData: This is optional parameter is a map of data that will be passed to the event handler.
  • handler: A function to execute each time the event is triggered.

Removing event handlers:

Typically, once an event handler is established, it remains in effect for the remainder of the life of the page. There may be a need when you would like to remove event handler.
jQuery provides the unbind() command to remove an exiting event handler. The syntax of unbind() is as follows:
selector.unbind(eventType, handler)

or 

selector.unbind(eventType)
Following is the description of the parameters:
  • eventType: A string containing a JavaScript event type, such as click or submit. Refer to the next section for a complete list of event types.
  • handler: If provided, identifies the specific listener that.s to be removed.

Event Types:

The following are cross platform and recommended event types which you can bind using JQuery:
Event Type Description
blur Occurs when the element loses focus
change Occurs when the element changes
click Occurs when a mouse click
dblclick Occurs when a mouse double-click
error Occurs when there is an error in loading or unloading etc.
focus Occurs when the element gets focus
keydown Occurs when key is pressed
keypress Occurs when key is pressed and released
keyup Occurs when key is released
load Occurs when document is loaded
mousedown Occurs when mouse button is pressed
mouseenter Occurs when mouse enters in an element region
mouseleave Occurs when mouse leaves an element region
mousemove Occurs when mouse pointer moves
mouseout Occurs when mouse pointer moves out of an element
mouseover Occurs when mouse pointer moves over an element
mouseup Occurs when mouse button is released
resize Occurs when window is resized
scroll Occurs when window is scrolled
select Occurs when a text is selected
submit Occurs when form is submitted
unload Occurs when documents is unloaded

The Event Object:

The callback function takes a single parameter; when the handler is called the JavaScript event object will be passed through it.
The event object is often unneccessary and the parameter is omitted, as sufficient context is usually available when the handler is bound to know exactly what needs to be done when the handler is triggered, however there are certail attributes which you would need to be accessed.

The Event Attributes:

The following event properties/attributes are available and safe to access in a platform independent manner:
Property Description
altKey Set to true if the Alt key was pressed when the event was triggered, false if not. The Alt key is labeled Option on most Mac keyboards.
ctrlKey Set to true if the Ctrl key was pressed when the event was triggered, false if not.
data The value, if any, passed as the second parameter to the bind() command when the handler was established.
keyCode For keyup and keydown events, this returns the key that was pressed.
metaKey Set to true if the Meta key was pressed when the event was triggered, false if not. The Meta key is the Ctrl key on PCs and the Command key on Macs.
pageX For mouse events, specifies the horizontal coordinate of the event relative from the page origin.
pageY For mouse events, specifies the vertical coordinate of the event relative from the page origin.
relatedTarget For some mouse events, identifies the element that the cursor left or entered when the event was triggered.
screenX For mouse events, specifies the horizontal coordinate of the event relative from the screen origin.
screenY For mouse events, specifies the vertical coordinate of the event relative from the screen origin.
shiftKey Set to true if the Shift key was pressed when the event was triggered, false if not.
target Identifies the element for which the event was triggered.
timeStamp The timestamp (in milliseconds) when the event was created.
type For all events, specifies the type of event that was triggered (for example, click).
which For keyboard events, specifies the numeric code for the key that caused the event, and for mouse events, specifies which button was pressed (1 for left, 2 for middle, 3 for right)

The Event Methods:

There is a list of methods which can be called on an Event Object:

Method Description
preventDefault() Prevents the browser from executing the default action.
isDefaultPrevented() Returns whether event.preventDefault() was ever called on this event object.
stopPropagation() Stops the bubbling of an event to parent elements, preventing any parent handlers from being notified of the event.
isPropagationStopped() Returns whether event.stopPropagation() was ever called on this event object.
stopImmediatePropagation() Stops the rest of the handlers from being executed.
isImmediatePropagationStopped() Returns whether event.stopImmediatePropagation() was ever called on this event object.