Strait Fram Singapuur

In almost all real world projects (non Spring + We are not considering Arquillian or any similar framework) where you are using JPA (Hibernate implementation), the data source binding happens by JNDI and the services are provided by EJBs, which means to test your entities for any CRUD operation you have to deploy the bundle (ear, ejb or war) into the application server which adds time to your development efforts each time you make any change. So in this post we will see how we can temporarily inject entity manager into your business class so that you can test all the operations you want to perform on entities without deploying the application or restarting server quite often.

persistence.xml: The configuration for entity managers both inside an application server and in a standalone application reside in a persistence archive. In the next section we focus on standalone configuration.

 
  org.hibernate.ejb.HibernatePersistence
  com.gognamunish.test.Entity
  
   
   
   
   
   
  
 

Please Note:

• The database dialect we have chosen is MySQL for obvious reasons.
• Persistence unit has name test_unit and the type is RESOURCE_LOCAL and not JTA.
• com.gognamunish.test.Entity is the entity which we want to test later.
• As we are running without a JNDI available datasource, we must specify JDBC connections with Hibernate specific properties

Next in your business class you can get reference to the entity manager as follow:

EntityManagerFactory factory ;
factory = Persistence.createEntityManagerFactory("test_unit");
EntityManager manager = factory.createEntityManager();

That's all you need , after obtaining the reference focus only on your entity and the operation you want to perform on it.
Let's try one sample example:

/* Sample Entity class */
@javax.persistence.Entity
@Table(name = "Entity")
public class Entity {
 @Id
 private Long id;
 @Column
 private String value;
}

package com.gognamunish.test;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

/**
 * Sample Test - nothing fancy.
 * 
 * @author Munish Gogna
 * 
 */
public class LocalEntityManager {
 static EntityManager manager;
 static {
  EntityManagerFactory factory = Persistence
    .createEntityManagerFactory("test_unit");
  manager = factory.createEntityManager();
 }

 public static void main(String[] args) {

  System.out.println("Before Entities: " + getEntities());

  manager.getTransaction().begin();
  Entity entity = new Entity();
  entity.setId(1l);
  entity.setValue("my first value");
  saveOrUpdate(entity);
  manager.getTransaction().commit();

  System.out.println("After Entities: " + getEntities());

 }

 private static Entity saveOrUpdate(Entity entity) {
  return manager.merge(entity);
 }

 @SuppressWarnings("unchecked")
 private static List<Entity> getEntities() {
  return manager.createQuery("from Entity").getResultList();
 }
}

LOGS:
Hibernate: select entity0_.id as id0_, entity0_.value as value0_ from Entity entity0_
Before Entities: []
Hibernate: select entity0_.id as id0_0_, entity0_.value as value0_0_ from Entity entity0_ where entity0_.id=?
Hibernate: insert into Entity (value, id) values (?, ?)
Hibernate: select entity0_.id as id0_, entity0_.value as value0_ from Entity entity0_
After Entities: [Id:1, Value:my first value]

One of the frequently asked questions in interviews, let's try few ways available in JDK to reverse a string:

import java.util.Stack;
public class StringReverse {

 public static String reverse1(String s) {
  int length = s.length();
  if (length <= 1)
   return s;
  String left = s.substring(0, length / 2);
  String right = s.substring(length / 2, length);
  return reverse1(right) + reverse1(left);
 }

 public static String reverse2(String s) {
  int length = s.length();
  String reverse = "";
  for (int i = 0; i < length; i++)
   reverse = s.charAt(i) + reverse;
  return reverse;
 }

 public static String reverse3(String s) {
  char[] array = s.toCharArray();
  String reverse = "";
  for (int i = array.length - 1; i >= 0; i--)
   reverse += array[i];

  return reverse;
 }

 public static String reverse4(String s) {
  return new StringBuffer(s).reverse().toString();
 }

 public static String reverse5(String orig) {
  char[] s = orig.toCharArray();
  int n = s.length - 1;
  int halfLength = n / 2;
  for (int i = 0; i <= halfLength; i++) {
   char temp = s[i];
   s[i] = s[n - i];
   s[n - i] = temp;
  }
  return new String(s);
 }

 public static String reverse6(String s) {

  char[] str = s.toCharArray();

  int begin = 0;
  int end = s.length() - 1;

  while (begin < end) {
   str[begin] = (char) (str[begin] ^ str[end]);
   str[end] = (char) (str[begin] ^ str[end]);
   str[begin] = (char) (str[end] ^ str[begin]);
   begin++;
   end--;
  }

  return new String(str);
 }

 public static String reverse7(String s) {
  char[] str = s.toCharArray();
  Stack<Character> stack = new Stack<Character>();
  for (int i = 0; i < str.length; i++)
   stack.push(str[i]);

  String reversed = "";
  for (int i = 0; i < str.length; i++)
   reversed += stack.pop();

  return reversed;
 }

}

Feel free to suggest other ways if you have.

My previous post was about merging the PDF files into single file using PDFBox, the limitation of that approach was if you had fill able form inside any PDF file it was lost, to over come that issue here is an updated version of the same post using iText library.

import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;

import com.lowagie.text.pdf.AcroFields;
import com.lowagie.text.pdf.PdfCopyFields;
import com.lowagie.text.pdf.PdfReader;

/**
 * Merges the PDF files while retaining the fillable forms within them. It also
 * renames form field (to avoid conflicts) which can have an impact if form is
 * submitted to server but for printing purpose should be OK.
 * 
 * @author Munish Gogna
 * 
 */
public class PDFMerge {
 private static int counter = 0;

 public static void merge(List<InputStream> sourcePDFs,
   OutputStream targetPDF) throws Exception {
  if (sourcePDFs != null && targetPDF != null) {
   PdfCopyFields copy = new PdfCopyFields(targetPDF);

   for (InputStream stream : sourcePDFs) {
    PdfReader pdfReader = new PdfReader(stream);
    renameFields(pdfReader.getAcroFields());
    copy.addDocument(pdfReader);
    stream.close();
   }
   copy.close();
  }
 }

 private static void renameFields(AcroFields fields) {
  Set<String> fieldNames = fields.getFields().keySet();
  String prepend = String.format("_%d.", counter++);

  for (String fieldName : fieldNames) {
   fields.renameField(fieldName, prepend + fieldName);
  }
 }

 public static void main(String[] args) {
  try {
   List<InputStream> pdfs = new ArrayList<InputStream>();
   pdfs
     .add(new URL(
       "http://thewebjockeys.com/TheWebJockeys/Fillable_PDF_Sample_from_TheWebJockeys_vC5.pdf")
       .openStream());
   pdfs
     .add(new URL(
       "http://help.adobe.com/en_US/Acrobat/9.0/Samples/interactiveform_enabled.pdf")
       .openStream());
   OutputStream output = new FileOutputStream("merged.pdf");

   merge(pdfs, output);

  } catch (Exception e) {
   e.printStackTrace();
  }
 }

}

The iText jar can be downloaded here

Thanks.

I was just looking for some way to merge PDFs generated from different sources to one final deck. iText library was one obvious choice but when I looked into PDFBox library I was stunned with the simplicity and ease with which PDFs can be merged. I tried merging three different PDF files and to my surprise it took less than 15 lines of code as shown below:

package com.gognamunish.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import org.apache.pdfbox.util.PDFMergerUtility;

/**
 * Merges pdf files into one final pdf.
 * 
 * @author Munish Gogna
 */
public class PDFMerge {

 public static void main(String[] args) throws Exception {
  // Get the byte streams from any source (maintain order)
  List<InputStream> sourcePDFs = new ArrayList<InputStream>();
  sourcePDFs.add(new FileInputStream(new File("pdf1.pdf")));
  sourcePDFs.add(new FileInputStream(new File("pdf2.pdf")));
  sourcePDFs.add(new FileInputStream(new File("pdf3.pdf")));

  // initialize the Merger utility and add pdfs to be merged
  PDFMergerUtility mergerUtility = new PDFMergerUtility();
  mergerUtility.addSources(sourcePDFs);
  // set the destination pdf name and merge input pdfs
  mergerUtility.setDestinationFileName("merged.pdf");
  mergerUtility.mergeDocuments();
 }
}

The library is rich and provides many options out of the box that can be useful when it comes to playing with PDFs, worth a try !!!

http://pdfbox.apache.org/index.html
 cheers, Munish Gogna

Do you wish to keep notes where the notes keep the date automatically? Well here is an awesome trick for you. All you need is notepad.


1) Open a blank notepad file.
2) Type .LOG in all caps at the top and hit enter.
3) Now save the file.
4) After closing the file, reopen it and notice that the date & time is now listed on the second line.
5) Also notice that the cursor is ready for you to start typing on the very next line.
6) Now every time you open it, type something on the next line and then save it, when you reopen it, it will have automatically saved the date and time on the last line.

It keeps a running record of date and time for each save. Now you have a cheap diary! Congrats!

source:centralbeat

First thing I would like to admit is - Sorry for being away for so long !!!
Next let's quickly move to second thing which is the topic of today's very simple post - scheduling jobs in JBoss :)

In many projects there is a requirement for cron-like task scheduling, be it for batch processing, automatic system maintenance or some other regular job. Few days back I had to create a cron job to sync data from external source to the local database. I was having so many options to implement the functionality like:

• java.util.Timer
  
• EJB Timers
  
• Unix Cron jobs
  
• Quartz Scheduler
  
• Custom Timer
  

But in the end I settled for a very simple solution (in terms of time it took to implement the whole stuff) that is as effective as anything mentioned above.

org.jboss.varia.scheduler.Scheduler
----------------------------------------
The good thing is, this Scheduler directly invokes a callback on an instance of a user defined class, or an operation of a user specified MBean. Let's say we want to print 'Hello World!' (our so called task) after every 30 seconds from the the time of deployment.

package com.gognamunish.test;
import org.jboss.varia.scheduler.Schedulable;
/**
* Implement Schedulable interface and override perform() function. 
* @author Munish Gogna
*/
public class HelloWorld implements Schedulable
{
    public void perform( Date now, long remainingRepetitions ) {
        System.out.println("Hello World");
    }
}

Next just copy the following mbean definition in /deploy/scheduler-service.xml file of the Jboss profile.

      true
      com.gognamunish.test.HelloWorld
      0
      30000
      -1
      true    

      
   

Once the deployment is done, this task will be called after every 30 seconds, so easy and simple right? We can also pass input parameters to our target class using 'SchedulableArguments' attribute, just make sure you define the right constructor in the class that implements Schedulable interface. e.g If we want to pass the location and environment of the server, we have to add following lines to the mbean definition:

Singapore,Test
 java.lang.String,java.lang.String

HelloWorld class now has to define a constructor as follow:

public HelloWorld (String location, String environment){
 this.location=location;
 this.environment=environment;
}

Note: This example has dependency on scheduler-plugin.jar which can be obtained from /common/lib folder of $JBOSS_HOME (it is sad that it's not available in maven or jboss repository)

Give it a Try !!!!