Manipulating PDF document using iText library

There are several libraries that can be used to manipulate a PDF document like PDFBox, iText, PDFClows etc. I also have to do some PDF manipulation stuff and I decided to go with iText. I choose iText because it supports low level PDF manipulation, its community is very strong, lots of helping hands are available and it is also open source and available in both Java and C#.

iText allows you to create a PDF doument, add content in it, update content and save it. I have tried following basic features so far and found it really interesting:

• With low level support one can add a text chunk, paragraph, phrase, link, chapter, section, image, set text color and other attributes into the document. 
• You can also create a table/grid inside a PDF document and play with each cell of the table.
• It is also easy to read an existing PDF document. You can retrieve existing information related to document and pages.
• Using iText one can also fill up an empty PDF template.
• It allows to set javascript in a PDF document to make a document interactive. Document can be also be navigated to a particular page. Creating bookmarks, annotations and triggering javascirpt from a button can also be done using iText.
• Document can also be password encrypted to allow/disallow certain actions that can be done the document.
• Whole PDF document can also be signed using a certificate to make the document secure.

There is also a book on how to play with PDFs using iText in Action. He is the author of iText in Action and is very supportive on stackoverflow. I also have some questions regarding iText on stackoverflow on this link.

rizzz86

My Experience of Installing MongoDB on Ubuntu

In my last post I have write some very basic and initial points related to MongoDB. That was my initial observation of what MongoDB is and what are its basic features.

This article does not contains the detailed step by step tutorial of how to install MongoDB on Ubuntu. There are already lots of articles available on the installation of MongoDB on Ubuntu &Windows operating systems. In this post I am going to write my experience of Installing MongoDB on Ubuntu.

There are two common ways of installing any kind of software on Ubuntu. One is by using the "Ubuntu Software Center" and other is to download the package and install it manually. Option one is commonly used by users as it is very simple and it automatically download and install the target software on Ubuntu. In the case of MongoDB both option can be used for installation.

For testing purpose I have installed MongoDB using the Software Center (you can also use apt-get command that also download and install package from Software Center). Initially it works good by using it from terminal. I can able to start and stop MongoDB and execute different types of queries. The problem begins when I try to use MongoDB programmaticaly. I cannot able to connect with MongoDB using Java and Eclipse IDE even MongoDB is running and can be used from terminal. So, I have removed all the packages of MongoDB and install it manually. After that I am able to use it via terminal as well as programmatically.

This seems to be something related to version issue as also mentioned on this link. If someone knows what is the actual reason of this different behavior on different installation options do comment here. This is what I have experienced when installing and using MongoDB on Ubuntu.

rizzz86

JAVA: Date and Calendar

This is not something new but something of very common use in most of the projects. In this post I am going to write some date, time and calendar functions that are commonly used as utility. From next time I will copy them from this post rather than code them again.

To get a Date in any Format the SimpleDateFormat Class is used. Following snippet will return current date in provided format in SimpleDateFormat argument.

Date date = new Date();    
DateFormat dateFormatter = new SimpleDateFormat("dd");    
String formattedDate = dateFormatter.format(date);

Format "dd" is used to get the date number from date

Format "yyyy" is used to get the year number from date

Format "MM" is used to get the month number from date

Format "MMMM" is used to get the month name from date

This method will return the date of targeted format from source format.

    String dt = dateString;  // Start date
    SimpleDateFormat sdf = null;
    try {
            sdf = new SimpleDateFormat(sourceFormat);
            Date date = sdf.parse(dt);
    
            sdf  = new SimpleDateFormat(targetFormat);
            dt = sdf.format(date);  // dt is now in the new date format            
    } catch (ParseException e) {
        e.printStackTrace();
    }

To get Number of Days in a Month we will take help from Calendar Class here. Following method will be usd to get number of days in a month.

public static int getNumberOfDaysInMonth(int screenMonth){
      Calendar calendar = Calendar.getInstance();
      int year = Integer.valueOf(getYearNumber());
      int month = screenMonth;
      int date = 1;
      calendar.set(year, month, date);
      int days = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);        
      
      return days;
}

This method will return Month Name from month number. Calendar is used here as well.

public static String getMonthNameByMonthNumber(int currentMonthNumber) {
    String dt;
    Calendar c = Calendar.getInstance();
    c.set(Calendar.MONTH, currentMonthNumber);
    c.add(Calendar.MONTH, 0);  // number of days to add
    
    SimpleDateFormat sdf  = new SimpleDateFormat("MMMM");
    dt = sdf.format(c.getTime());  // dt is now the new date        
    return dt;
}

To get the First Day of month following method can be used.

public static String getFirstDayOfMonth(int month) {
    Calendar c = Calendar.getInstance();
    c.set(Calendar.MONTH, month);
    c.set(Calendar.DATE, 1);

    DateFormat f = new SimpleDateFormat("EEE");        
    return f.format(c.getTime());
}

Similarly to get the first date of week Calendar Class is used.

public static int getFirstDateOfWeek() {
    Calendar c = Calendar.getInstance();
    c.set(Calendar.WEEK_OF_YEAR, Calendar.WEEK_OF_MONTH);
    c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek());

    DateFormat f = new SimpleDateFormat("dd");
    String cc = f.format(c.getTime());

    // Plus 1 is done to get the Monday Date instead of Sunday
    return Integer.valueOf(cc) + 1;
}

There are many other methods that can be used commmonly. I will keep updating this post when ever I got something new. Also do comment If there is any method you want to add here or If any of them can be implemented in much better way.

rizzz86

Split a String with Dot "." in JAVA

In JAVA we can split a String with Dot "." using a split() function. But it can be done in a different way as compared to other characters. Dot "." is a reserved character in regular expression, hence it will not treat the split on dot the same way.

Following code can be used to split a string by dot.

String stringWithDot = "rizzz86.blogspot.com"; 
String[] stringArray = stringWithDot.split("\\.");

Double backslash will do the work where one slash is work as a escape character.

rizzz86

Iterate over JAVA HashMap in FreeMarker

Java HashMap can be iterated in FreeMarker by using a <#list> tag as follows:

<#list hashMap?keys as key>

        ${key}=${hashMap[key]}

<#list>

If you are using the above code with default FreeMarker Configuration then there would be some different behavior during iteration. For example if the HashMap is:

HashMap hashMap = new HashMap();

hashMap.put("1","one");

hashMap.put("2","two"); 

By iterating on hashMap with default Configuration it will output following keys in result:

put
remove
entrySet
hashCode
productElement
clear
isEmpty
1
values
empty
underlying
productElements
copy
getClass
get
copy$default$1
equals
productPrefix
class
canEqual
keySet
size
2
containsKey
productArity
containsValue
productIterator
toString
putAll        

This result shows that the iteration is done on all the available hashMap properties.

To get rid of this you have to set the FreeMarker Configuration as follows:

Configuration configuration = new Configuration();
BeansWrapper wrapper = (BeansWrapper) this.configuration.getObjectWrapper();
wrapper.setSimpleMapWrapper(true);
this.configuration.setObjectWrapper(wrapper);

Here the BeanWrapper's simpleMapWrapper property is set as 'true'. After setting this configuration the results over iterating on hashMap will give only the defined key-value pair.

rizzz86

MD5 Hashing in J2ME

MD5 (Message Digest) is a hashing algorithm that can be used to ensure data integrity, save and protect passwords/codes, generate unique keys of limited length against a long literal etc. It takes input as String and generates the Hash of that string.

In JAVA there is a built-in MD5 support in its Standard Edition (J2SE). But if we talk about its Micro Edition (J2ME) their is no support for MD5. The package of JAVA Standard Edition can also be used in Micro Edition if and only if the platform supports the SATSA-Crypto Optional Package (How to know that your platform supports SATSA-Crypto).

I have found and tested the Third-Party implementation that can generate MD5 hash and can be used in JAVA Micro Edition. You can get the MD5 source files from here.

rizzz86

J2ME Default Emulator without asking for Permission

While running J2ME project with Default Emulator it will ask for Permissions in case of File Read/Write, HTTP Connectivity etc. To get rid of this Permission on every access you have to change the Security options of Emulator. In my case I am using NetBeans IDE, so to change these options I will go through following steps:

1. Open Project Properties
2. Click on Manage Emulators Button
3. Go to Tools & Extension Tab and Click Open Preferences Option
4. On Preferences Window click on Security option
5. Select Security Policy to 'JTWI'
6. Select Security Domain as 'trusted'
7. Now run the project it will not ask for access Permissions

 rizzz86

Unit Testing for J2ME - JMUnit

In professional development environment it is a common practice to create Unit Tests. On Java platform there are lots of research and development done on Unit Tests for Enterprise Edition. As far as Java Micro Edition is concerned one of the framework available is JMUnit.

Creating and executing a test case using jmunit is quite simple and can be done without wasting much time to explore it. Following steps will guide you how to work with jmunit:

•  In your mobile application right click on package (where you want to create a unit test) and select option 'New > Empty JMUnit Test'.
• It will create a unit test class for you that will look like this:

/*
 * ABCTest.java
 * JMUnit based test
 *
 */

package hello;


import jmunit.framework.cldc10.*;

/**
 * @author rizwan
 */
public class ABCTest extends TestCase {
    
    public ABCTest() {
        //The first parameter of inherited constructor is the number of test cases
        super(0,"ABCTest");
    }            

    public void test(int testNumber) throws Throwable {
    }    
}  

• Next you will create a test method in same class and call it in test() using switch cases.
• Total count of test cases will also be mentioned in unit class constructor.
• Now the code will look like this:

/*
 * ABCTest.java
 * JMUnit based test
 *
 */

package hello;


import jmunit.framework.cldc10.*;

/**
 * @author rizwan
 */
public class ABCTest extends TestCase {
    
    public ABCTest() {
        //The first parameter of inherited constructor is the number of test cases
        super(1,"ABCTest");
    }            

    public void test(int testNumber) throws Throwable {
        switch(testNumber){
            case 0: 
                testOne();
                break;
        }
    }    

    private void testOne() throws Exception{
        String tmp = "Hello Rizwan";
        assertEquals(tmp, "Hello Rizwan");
    }
} 

• After that you have to mention 'ABCTest' as your Midlet.
• Go into 'project properties > Application Descriptor > MIDlets' and define unit test name and package here.
• Run application and you will also get Test option on screen:  
• Test the project and it will show you the results

Your mobile test case is ready !

rizzz86

Add External JAR in j2me-polish Project

To use any external jar in a j2me-polish project following steps need to be taken:

• Copy jar file in j2me-polish/import/ folder
• Add jar file in project libraries
• Update build.xml file by adding attribute 'binarylibraries="jarname1.jar;jarname2.jar"' inside < build > tag. (Multiple jars can be defined by placing semi-colon between jars)

rizzz86

Class.forName("classname").newInstance()

Don't do this foolish mistake again :|

I was trying to get the class instance using Class.forname(...) but continuosly getting IllegalAccessException.

At the end I found that the class I am trying to call has a private constructor in it. So it cannot be possible to create an instance of class with private constructor.


rizzz86

Maven j2me-Archetype

I am using Netbeans6.7 for mobile project development and want to make that project a 'maven project'. I have maven configured on my machine.

To make maven based j2me project I have created a new project from File > New Project > Maven > Maven Project > j2me Archetype (2.0.4). The project created successfully and showing the properties of maven as well . . .  BUT !!

I cannot able to view the properties of mobile project (i.e. Platform Type, Device Profile and Configuration, Midlet Information etc). To execute that project it requires a class with main() method. So I have posted all that on forum and finally got the following answer:

j2me development is not supported for maven projects in netbeans :(

rizzz86

JSON source for J2ME (mobile applications)

Javascript Object Notation (JSON) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. I am trying to use it in for mobile application development.

Today I was looking for a JSON source code for Java Micro Edition (J2ME). After lots of googling I have found it from the following link:

https://meapplicationdevelopers.dev.java.net/source/browse/meapplicationdevelopers/demobox/mobileajax/lib/json/src/org/json/me/



rizzz86

Share Common Code Between J2ME and J2SE Project -- Problem/Solution

Statement:
If you are creating a client/server project on Java, where client is a mobile device and server is a web application. Also if there is a common code between client and server then where do you place that common code ?

I also faces the same and go through the following phases before deciding what to do. The two points that came in mind right away are:

• Create a J2SE Project and place common code there. Make your client and server project dependant on that common project.
• Create a J2ME Project and place common code there. Make your client and server project dependant on that common project.
  

First I have created J2SE as a Common Project:

When I execute the client (J2ME) project with a dependency of common project (J2SE), I got the following error:

Running with storage root DefaultColorPhone
Method............: 100d2aa8 'com/sun/midp/midlet/MIDletState.createMIDlet (stat
ic)'
Stack Chunk.......: e58cd4
Frame Pointer.....: e58d30
Current IP........: 10128592 = 10128584 + offset 14
Previous Frame....: e58cf4
Previous IP.......: 1012052b (offset 22)
Frame size........: 8 (1 arguments, 7 local variables)
Argument[0].......: e59a9c
Local[1]..........: 0
Local[2]..........: e58cf4
Local[3]..........: e68858
Local[4]..........: e58d08
Local[5]..........: 100dcdd0
Local[6]..........: e58cd4
Local[7]..........: 1015f0a0
Operand[1]........: e59a9c

Method............: 100cd0e4 'com/sun/midp/midlet/Selector.run (virtual)'
Stack Chunk.......: e58cd4
Frame Pointer.....: e58cf4
Current IP........: 1012052b = 10120515 + offset 22
Previous Frame....: 0
Previous IP.......: 1
Frame size........: 6 (1 arguments, 5 local variables)
Argument[0].......: e59d10
Local[1]..........: e68a68
Local[2]..........: e59a9c
Local[3]..........: 0
Local[4]..........: 0
Local[5]..........: 0
Operand[1]........: e68a68

VM status:
Instruction pointer.: 10128592 (offset within invoking method: 14)
Next instruction....: 0x4c
Frame pointer.......: e58d30
Local pointer.......: e58d10
Stack size..........: 128; sp: e58d48; ranges: e58cdc-e58edc;
Contents of the current stack frame:
e58d10: e59a9c (lp)
e58d14: 0
e58d18: e58cf4
e58d1c: e68858
e58d20: e58d08
e58d24: 100dcdd0
e58d28: e58cd4
e58d2c: 1015f0a0
e58d30: e58cf4 (fp)
e58d34: 1012052b
e58d38: e58d0c
e58d3c: 100d2aa8
e58d40: e58cd4
e58d44: 0 (end of frame)
e58d48: e59a9c (sp)
Execution stack contains 112 items:
e59d10
e68a68
e59a9c
0
0
0
0
1
e58cd8
100cd0e4
e58cd4
0
e68a68
e59a9c
0
e58cf4
e68858
e58d08
100dcdd0
e58cd4
1015f0a0
e58cf4
1012052b
e58d0c
100d2aa8
e58cd4
0
e59a9c

Execution completed.
429584 bytecodes executed
10 thread switches
486 classes in the system (including system classes)
2380 dynamic objects allocated (72064 bytes)
1 garbage collections (0 bytes collected)
ALERT: java/lang/ClassFormatError: Bad version information.
Execution completed.
429584 bytecodes executed
10 thread switches
486 classes in the system (including system classes)
2380 dynamic objects allocated (72064 bytes)
1 garbage collections (0 bytes collected)

After reading some forums I recompile my common project (J2SE) on jdk1.4 and add it as a dependency in client project (J2ME) again (previously I have compiled it on jdk1.5). This time the client (J2ME) executes and works successfully.


ISSUES:

In Java the development toolkit for mobile (J2ME) contains limited features as compared to the standard edition (J2SE). If you are creating your project on J2SE then you must not use any feature of J2SE in project that is not provided by J2ME (mobile edition have limited features).

In jdk1.5 there are some major specification changes due to which it generates different byte-code number that results in "ALERT: java/lang/ClassFormatError: Bad version information". So you need to run/compile your common (J2SE) project on jdk1.3/1.4




Next I have created J2ME as a Common Project:

I am using Netbeans 6.7 for development, so I have created 'Java ME > Mobile Class Library' project for common code. The Mobile Class Library is a mobile project but does not contain any Midlets. It uses IDE-generated Ant build scripts and special tasks to pre-process, build, obfuscate, preverify, debug, run and depoly your library in JAVA ME Environment.

I moved all my common code in this mobile project and then use it as a dependency for both client (J2ME) and server (J2SE) projects and it works properly for both editions. Doing this ensures the compatability of both versions because mobile edition features are already supported by standard edition. Also you will be free from jdk-versioning issue that was faced in previously.

Conclusion:
So create 3 different projects, one is a client (J2ME), another is a server (J2SE) and a common project (J2ME) that will be used by client and server.



rizzz86

Set JAVA_HOME Path

Helpful link for setting up JAVA_HOME and PATH in Linux OS.

http://www.cyberciti.biz/faq/linux-unix-set-java_home-path-variable/


rizzz86