Friday, October 28, 2011

Configuring your eclipse JEE6 project to use JPA (Step by Step guide)

Driver definition
The driver is vendor specific and it will allow the application to connect to the database.
To create a new driver definition for your app that follow this steps in eclipse:
         1- Select Window > Preferences from the main menu bar.
        2- Expand Data Management > Connectivity and select Driver Definitions.
        3- Click Add.                 
       4-In the Name/Type tab, indicate the version of Derby on which you want to create the driver definition.

    1. Select Derby Client JDBC Driver for the non embedded version
    2. Select Derby Embedded JDBC Driver for the embedded version
    3.  (Optional) Modify the Driver Name if a driver definition with this name already exists.  
      Location of the driver in windows systems is often: C:\jeeAplicationServer\glassfishv3/javadb/lib/derbyclient.jar
      5-In the JAR List tab, highlight the default derby.jar file and click Edit JAR/Zip to indicate the fully qualified  path of the Derby JAR file.

    1. Browse to the location of the ZIP file.
    2. Click Open.
6- (Optional) In the Properties tab, modify the default properties for the driver definition template.
Options in the Properties tab vary based on database server type. You can edit or enter a property in the Value box.

7- Click Ok

NOTE: THE driver.jar is for emdebed database while driverclient.jar is for normal database(driverclient should be used)

Start the derby database from the console
To be able to work with the derby database, you need first to start it. To do so, follow this steps:
1-Open the command line and place yourself at the glassfish server bin folder
2-And then enter the command: asadmin start-database

Create a new Connection Profile

Lets say that the connection profile is the configuration that will allow you interact with the database.

1-In the Data Source Explorer tab. Right click on Database Connections and select New…
2- Select the Derby profile
3- In the name field type the name of the database(Type the same as you typed in the Properties tab when you reated the driver definition)
5- Click next
6- In the Connection Details page, pick the driver you configured before and type the correct database. Select the save password option
7- Click on Test Connection to see all is correct. (You will receive a Ping Succeeded! message if all is ok)
8-Click Finish

Create a Connection Pool
In a nutshell, a connection pool allows the database recycle the already used connections. So here is explained how to create a connection pool for the previously created connection profile.

1- Once the glassfish server is started, go to http://localhost:4848
2- At the admin panel select connection Pools and click on New…
3- In general settings; give a name to the pool, The resource type is javax.sql.DataSource and the Database Vendor is Derby and click next
4-In the step 2 of 2. Let all by default, but just edit the setting below to look like this:

5- Click on finish

Adding JPA facelet and Referencing the JDBC resource from the application
At this point GlassFish knows about a database, but we still don’t reference it from the application. Let’s do that now. So here what we do is tell our application to use all the configurations that we configured before.

1- Enable JPA in the application by including the JPA facet:
Right click on Project->Properties->And search for project facets and select JPA
2- In the persistence.xml file you should add the name of the database(datasource) as says in the image:

Create entities
Now lets see how it works all we configured. Try creating an entity with a couple of fields and annotate it with the JPA annotations.

Remember that every entity must have an @Id attribute, if it doesn’t exist you should see something like this:
Create tables from entities
How to transform our entities into tables(Object Relational Mapping) follow this steps:

1- Right click on the project and select  Generate Tables from Entities
2- If this message appears in the screen click in Add a connection to JPA project…

3- The last missing piece is to add the connection name so all JPA features can work

4- Back at the schema selection dialog, you can now choose the schema that will be used for storing the tables.
By default USER schema will be used, so click cancel.
5-If a red error that says that the schema ‘USER’ cannot be found appears, just restart(build) the application.

Saturday, August 13, 2011

JXL, great java API for parsing excel documents

Most of the times i use Apache POI for my ms document parsing, but the other day i found an interesting tool, very easy to use, that allows you to parse excel. It is called JXL.
Here a very simple program that will parse the contents of an excel sheet and display the values in the console:

 import jxl.Cell;  
 import jxl.CellType;  
 import jxl.Sheet;  
 import jxl.Workbook;  
 public class Convertor {  
      private String inputFile;  
      private FileWriter fosStream;  
      private PrintWriter out = null;  
      private String outputFilePath = "";  
      public void setInputFile(String inputFile) {  
           this.inputFile = inputFile;  
      public void read() throws IOException {  
           File inputWorkbook = new File(inputFile);  
           Workbook w;  
           try {  
                w = Workbook.getWorkbook(inputWorkbook);  
                // Get the first sheet  
                Sheet sheet = w.getSheet(0);  
                fosStream = new FileWriter(outputFilePath + "output.xml");  
                out = new PrintWriter(new BufferedWriter(fosStream));  
                out.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");  
                for (int j = 0; j < sheet.getColumns(); j++) {  
                     for (int i = 0; i < sheet.getRows(); i++) {  
                          Cell cell = sheet.getCell(j, i);  
                          CellType type = cell.getType();  
                          if (cell.getContents() == null  
                                    || cell.getContents().equals("")) {  
                          out.println("<" + cell.getColumn() + "" + cell.getRow()  
                                    + ">");  
                          out.println("</" + cell.getColumn() + "" + cell.getRow()  
                                    + ">");  
           } catch (BiffException e) {  
      public static void main(String[] args) throws IOException {  
           Convertor test = new Convertor();  

Just a mini pragmatical example of how to pass parameters from a composite component back to a template

The template layout:
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"  
 <html xmlns=""  
  <title><ui:insert name="pagetitle">Default page title</ui:insert></title>  
  <ui:insert name="content">  
                 Default page content  
 The composite component  
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"   
 <html xmlns=""  
 <ui:composition template="WEB-INF/templates/masterLayout.xhtml">  
      <ui:define name="pagetitle">  
                     This is the index page  
      <ui:define name="content">  
           <p>A value can be passed from the composition to a template using the ui:param tag</p>  
           <ui:param name="someParam" value="#{someBB.something}"/>  
And now the backing bean that holds the value:
 package backingbeans;  
 import javax.enterprise.context.RequestScoped;  
 import javax.inject.Named;  
 public class SomeBB {  
      private String something;  
      public SomeBB() {  
           something = "THIS IS SOME DEFAULT VALUE";  
      public String getSomething() {  
           return something;  
      public void setSomething(String something) {  
           this.something = something;  

Wednesday, June 15, 2011

Connecting to a database using JDBC

Two college friends asked me to create a "Hello World" level pragmatical explanation of how a java system can connect to a database and interact with data. Also i've been told, to use any java api or tool i wish to achieve this task.

I think the easiest way to make a demo of how to connect to a database, is to use the JDBC api, that is included in the JSE-SDK since years. Also i think that for a learning purposes and better understanding of how java works with databases, this would be the best(Instead of using ORM tools like Hibernate or JPA)

Ok, lets get started:

-The java SE JDK
An IDE(I suggest you eclipse)
-A database driver(More info about JDBC drivers )
-A database server(For its simplicity to use, i would recommend you  Microsoft SQL 2005)

The source code:

1:  import java.sql.Connection;  
2:  import java.sql.DriverManager;  
3:  import java.sql.ResultSet;  
4:  import java.sql.SQLException;  
5:  import java.sql.Statement;  
6:  public class DB {  
7:   public void dbConnect() {  
8:   Connection con = null;  
9:   Statement stmt = null;  
10:   ResultSet rs = null;  
11:   String connectionURL = "jdbc:sqlserver://;databaseName=forJDBC;user=george;password=george;";  
12:   try {  
13:    Class.forName("");  
14:    con = DriverManager.getConnection(connectionURL);  
15:    System.out.println("Connected!");  
16:    String SQL = "SELECT * FROM Samples";  
17:    stmt = con.createStatement();  
18:    rs = stmt.executeQuery(SQL);  
19:    while ( {  
20:    System.out.println();  
21:    System.out.println(rs.getString(1) + "-" + rs.getString(2));  
22:    }  
23:   } catch (SQLException e) {  
24:    e.printStackTrace();  
25:   } catch (ClassNotFoundException e) {  
26:    e.printStackTrace();  
27:   } finally {  
28:    if (rs != null) {  
29:    try {  
30:     rs.close();  
31:    } catch (Exception e2) {  
32:     e2.printStackTrace();  
33:    }  
34:    if (stmt != null) {  
35:     try {  
36:     rs.close();  
37:     } catch (Exception e2) {  
38:     e2.printStackTrace();  
39:     }  
40:    }  
41:    if (con != null) {  
42:     try {  
43:     rs.close();  
44:     } catch (Exception e2) {  
45:     e2.printStackTrace();  
46:     }  
47:    }  
48:    }  
49:   }  
50:   }  
51:  }  

1- The first thing we need is to add the JDBC driver that will allow us to connect to the database into the projects builth path:

2.1-Make sure the database server is started.(Make sure you have logged in as an administrator)

2.2- Create a table in the database and add some data.
In this example i will not create the tables programatically. You can do it your selves with SQL Management Studio or similar tool. Just create a Database that meets the configuration above, and add two it a table called Sample with to VARCHAR fields. If you want to know more about how to programatically create tables with JDBC follow this link:

3-Create a connection URL:

1:  String connectionURL = "jdbc:sqlserver://;databaseName=forJDBC;user=djoleP;password=djoleP;";  

4-Find the driver located path the ClassPath (if needed)


5-Connect to the database

 con = DriverManager.getConnection(connectionURL);  

6-Create a SQL Querry and an Statement, to be able to execute the query

1:  String SQL = "SELECT * FROM Samples";  
2:    stmt = con.createStatement();  
3:    rs = stmt.executeQuery(SQL); 

6-Extract data until the result set is empty

1:  while ( {  
2:    System.out.println();  
3:    System.out.println(rs.getString(1) + "-" + rs.getString(2));  
4:    }  

7-Close the result set, connection and other streams that you might open(The transaction is finished!)

1:  finally {  
2:    if (rs != null) {  
3:    try {  
4:     rs.close();  
5:    } catch (Exception e2) {  
6:     e2.printStackTrace();  
7:    }  
8:    if (stmt != null) {  
9:     try {  
10:     rs.close();  
11:     } catch (Exception e2) {  
12:     e2.printStackTrace();  
13:     }  
14:    }  
15:    if (con != null) {  
16:     try {  
17:     rs.close();  
18:     } catch (Exception e2) {  
19:     e2.printStackTrace();  
20:     }  
21:    }  
22:    }  

Download the source codes(The database driver is included in the project):

This post goes dedicated to my two good colleges from college Tripo and Zoran.

Sunday, June 12, 2011

Using apache POI to write to word documents

A simple Hello World example for writing  into word files with apache POI
If you use maven add this 2 dependencies(Otherwise download and necessary libraries and add them to your build path):

Here a simple Hello World! program:

 package com.djordje;   
  import org.apache.poi.xwpf.usermodel.XWPFDocument;   
  import org.apache.poi.xwpf.usermodel.XWPFParagraph;   
  import org.apache.poi.xwpf.usermodel.XWPFRun;   
  public class App {   
    public void newWordDoc(String filename, String fileContent)   
         throws Exception {   
       XWPFDocument document = new XWPFDocument();   
       XWPFParagraph tmpParagraph = document.createParagraph();   
       XWPFRun tmpRun = tmpParagraph.createRun();   
       FileOutputStream fos = new FileOutputStream(new File(filename + ".doc"));   
    public static void main(String[] args) throws Exception {   
         App app = new App();   
         app.newWordDoc("testfile", "Hello World!");   

Printing any text file in java(Trick)

If you want to find an easy way and fast way to print in using java any text file, you can use the desktop api to do it.(Note this is not the best approach, but can get you unstuck in certain occasions).

1:  public void print() {  
2:    //The desktop api can help calling other applications in our machine  
3:    //and also many other features...  
4:    Desktop desktop = Desktop.getDesktop();  
5:    try {  
6:    //desktop.print(new File("DocXfile.docx"));  
7:      desktop.print(new File("Docfile.pdf"));  
8:    } catch (IOException e) {        
9:      e.printStackTrace();  
10:    }  
11:  }  

Friday, June 10, 2011

HOW TO USE IMAGES IN A JEE6 PROJECT?(Most common approaches)

<h:graphicImage id="img" value="/images/download.gif" alt="The image could not be found."/> 

A browser loads each image by sending an HTTP request for the resource.
Resources that are under the WEB-INF directory can not be directly retrieved via an HTTP request.

You have several options:
1. Move the images directory such that it is under the WebContent directory, but is not under the WEB- INf directory. For example, *WebContent/images*

2.    Intercept requests for images in a servlet or filter, read the file from within the servlet or filter, then return the file. There are 3rd party implementations of this.If you dont want to write your own servlet for this, Im sure with a bit of search you can find a servlet that suits your needs in google.


1-Create a servlet

//This can be located at a package called servlets(next to entities and managed beans)
class MyCaptcha extends HttpServlet{

      private int height = 0;

    private int width = 0;

    public static final String CAPTCHA_KEY = "captcha_key_name";


    public void init(ServletConfig config) throws ServletException {


        height = Integer.parseInt(getServletConfig().getInitParameter("height"));
        width = Integer.parseInt(getServletConfig().getInitParameter("width"));

    protected void doGet(HttpServletRequest req, HttpServletResponse response) throws IOException, ServletException {
        //Expire response
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        response.setHeader("Pragma", "no-cache");
        response.setDateHeader("Max-Age", 0);

        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D graphics2D = image.createGraphics();
        Hashtable<TextAttribute, Object> map = new Hashtable<TextAttribute, Object>();
        Random r = new Random();
        String token = Long.toString(Math.abs(r.nextLong()), 36);
        String ch = token.substring(0, 6);
        Color c = new Color(0.6662f, 0.4569f, 0.3232f);
       GradientPaint gp = new GradientPaint(30, 30, c, 15, 25, Color.white, true);
        Font font = new Font("Verdana", Font.CENTER_BASELINE, 26);
        graphics2D.drawString(ch, 2, 20);

        HttpSession session = req.getSession(true);
        session.setAttribute(CAPTCHA_KEY, ch);

        OutputStream outputStream = response.getOutputStream();
            ImageIO.write(image, "jpeg", outputStream);


2-Add the following settings to your web.xml:
                  <description>passing height</description>
                  <description>passing height</description>

3- Add the captcha markup at the front page
<h:graphicImage id="capimg"
                                    value="#{facesContext.externalContext.requestContextPath}/../Captcha.jpg" />
                              <br />
                              <h:outputText value="*Napisite text koj vidite u slici " />
                              <h:inputText id="captchaSellerInput"
                                    value="#{registrationControllerSeller.captchaSellerInput}" />

4- Add the backing bean logic of the captha:

HttpServletRequest request = (HttpServletRequest) FacesContext
            Boolean isResponseCorrect = Boolean.FALSE;
            javax.servlet.http.HttpSession session = request.getSession();
            String parm = captchaSellerInput;
            String c = (String) session.getAttribute(MyCaptcha.CAPTCHA_KEY);
            if (parm.equals(c)) {
                 //CAPTCHA CORRECT INPUT
else {
                //CAPTCHA INCORRECT INPUT  

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