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Friday, August 23, 2019
Kunal Bhowmick - IT Professional with more than 9 years of experience in the IT industry....
Kunal Bhowmick - IT Professional with more than 11 years of experience in the IT industry....: Kunal Bhowmick - IT Professional with more than 11 years of experience in the IT industry. - in Nagavara, Bangalore for Java Training and Python Training. Kunal Bhowmick profile - 1) I am an IT Professional with more than...
Friday, November 21, 2014
How to implement an interface in a class but prohibit the class from implementing the interface methods in that class ?
Hi Friends,
Today I will present an interesting scenario in front of you . Normally we , most of the time will not come across such a scenario while coding . But there are exceptions and this happens to be ab exceptional exception that we should get to know.
Scenario : Consider an interface K which has 2 methods in it : methA(), methB(). Now we need to have two classes A and B in such a way that they will implement the interface K . But Class A will only over ride methA() and Class B will implement methB() . How can we achieve that ?
Solution :
Normally when you implement an interface in a concrete class you will have to override the methods present in the interface otherwise the compiler will give an error . So how we accomplish the un accomplish-able like scenario stated above .
The answer is an Abstract Class . Yes , you heard it right : abstract class. An abstract class can implement an interface but it is not obliged to override any of the methods in the interface .
So for our scenario , we can do it the following way :
public interface K {
public void methA();
public void methB();
}
Now we can write our abstract class like this :
public abstract class A implements K{
}
You can check the above piece of code by running it in IDE of your choice (Eclipse, Netbeans etc). It will not throw any compiler error, because, an abstract class is not required to override any method in the interface , but it can if you want it to .
Hence, in this case, as we want to override methA() in class A, we can re organize Class A as :
public abstract class A implements K{
@Override
public void methA(){
System.out.println("methA");
}
}
Now we can use the class B as a concrete class and have it extend B, like below :
public class B extends A{
}
If you write just the above piece of code , the compiler will throw error and ask you to implement the un-implemented method methB(). That's because B is a concrete class and it implements K via A. Since, methA() is already overidden in class A , so the compiler asks the developer to override and implement methB() in class B.
In light of the above explanation we can organize the class B as :
public class B extends A{
@Override
public void methB(){
System.out.println("methB");
}
}
You can refer this stack overflow thread for more details : http://stackoverflow.com/questions/197893/why-an-abstract-class-implementing-an-interface-can-miss-the-declaration-impleme
That's it for today. Hopefully this will enlighten people who are not aware of this concept .
Today I will present an interesting scenario in front of you . Normally we , most of the time will not come across such a scenario while coding . But there are exceptions and this happens to be ab exceptional exception that we should get to know.
Scenario : Consider an interface K which has 2 methods in it : methA(), methB(). Now we need to have two classes A and B in such a way that they will implement the interface K . But Class A will only over ride methA() and Class B will implement methB() . How can we achieve that ?
Solution :
Normally when you implement an interface in a concrete class you will have to override the methods present in the interface otherwise the compiler will give an error . So how we accomplish the un accomplish-able like scenario stated above .
The answer is an Abstract Class . Yes , you heard it right : abstract class. An abstract class can implement an interface but it is not obliged to override any of the methods in the interface .
So for our scenario , we can do it the following way :
public interface K {
public void methA();
public void methB();
}
Now we can write our abstract class like this :
public abstract class A implements K{
}
You can check the above piece of code by running it in IDE of your choice (Eclipse, Netbeans etc). It will not throw any compiler error, because, an abstract class is not required to override any method in the interface , but it can if you want it to .
Hence, in this case, as we want to override methA() in class A, we can re organize Class A as :
public abstract class A implements K{
@Override
public void methA(){
System.out.println("methA");
}
}
Now we can use the class B as a concrete class and have it extend B, like below :
public class B extends A{
}
If you write just the above piece of code , the compiler will throw error and ask you to implement the un-implemented method methB(). That's because B is a concrete class and it implements K via A. Since, methA() is already overidden in class A , so the compiler asks the developer to override and implement methB() in class B.
In light of the above explanation we can organize the class B as :
public class B extends A{
@Override
public void methB(){
System.out.println("methB");
}
}
You can refer this stack overflow thread for more details : http://stackoverflow.com/questions/197893/why-an-abstract-class-implementing-an-interface-can-miss-the-declaration-impleme
That's it for today. Hopefully this will enlighten people who are not aware of this concept .
Wednesday, November 19, 2014
Java 8 : Interfaces and Default Methods
Hi ,
Today I am going to post a bit about some of the exciting features of Java 8.
Pre-requisites :
1> Install java 8 SDK
2> Install Eclipse Luna (Eclipse 4.4.1)
Without Eclipse Luna 4.4.1 , it will be very difficult to run programs in Java 8. So please download and install the Eclipse Luna Build .
So, let's get started with the good stuff .
Default Methods :
Now in java 8 , we can have methods with default signature in interface, which will have body logic or implementation logic .
So, let's say I have an interface called Person below :
public interface Person {
default void sayHello() {
System.out.println("Hello there in Person!");
}
}
As you can see if encapsulate a method name in the interface with default signature, you can add your logic in it.
Now what happens , when I have another interface with same method name but different implementation logic and I try to implement both of them in a single class ?
public interface Male {
default void sayHello() {
System.out.println("Hi there in Male ");
}
}
My implementation class(Sample.java) is shown below :
As you can see, here the compile time error is thrown because the compiler is not understanding which "sayHello()" method it should implement.
So to resolve this ambiguity, we can override the sayHello() method in the implementation class itself like this :
public class Sample implements Person, Male {
//override the sayHello to resolve ambiguity
public void sayHello() {
}
}
OR
We can just call the appropriate / desired interface method directly inside .
To do this, we have to use the syntax : "Interface.super.methodname()"
public class Sample implements Person, Male {
//override the sayHello to resolve ambiguity
public void sayHello() {
Person.super.sayHello();
Male.super.sayHello();
}
}
So a default method looks a lot like an abstract class implementation , does n't it ?
However, there is a subtle difference : An abstract class holds the state of its object as it can have constructors .But interfaces in java 8 with default methods cannot have constructors and as such cannot hold the state of an object. Default method should be used for backward compatibility. Whenever you want to add additional functionality in an existing legacy interface you can use default methods without breaking any existing implement or classes.
That's all on interfaces from java 8 perspective . I will come up with a new feature of Java 8 on my next post which will be related to Lambda Expressions .
Today I am going to post a bit about some of the exciting features of Java 8.
Pre-requisites :
1> Install java 8 SDK
2> Install Eclipse Luna (Eclipse 4.4.1)
Without Eclipse Luna 4.4.1 , it will be very difficult to run programs in Java 8. So please download and install the Eclipse Luna Build .
So, let's get started with the good stuff .
Default Methods :
Now in java 8 , we can have methods with default signature in interface, which will have body logic or implementation logic .
So, let's say I have an interface called Person below :
public interface Person {
default void sayHello() {
System.out.println("Hello there in Person!");
}
}
As you can see if encapsulate a method name in the interface with default signature, you can add your logic in it.
Now what happens , when I have another interface with same method name but different implementation logic and I try to implement both of them in a single class ?
public interface Male {
default void sayHello() {
System.out.println("Hi there in Male ");
}
}
My implementation class(Sample.java) is shown below :
As you can see, here the compile time error is thrown because the compiler is not understanding which "sayHello()" method it should implement.
So to resolve this ambiguity, we can override the sayHello() method in the implementation class itself like this :
public class Sample implements Person, Male {
//override the sayHello to resolve ambiguity
public void sayHello() {
}
}
OR
We can just call the appropriate / desired interface method directly inside .
To do this, we have to use the syntax : "Interface.super.methodname()"
public class Sample implements Person, Male {
//override the sayHello to resolve ambiguity
public void sayHello() {
Person.super.sayHello();
Male.super.sayHello();
}
}
So a default method looks a lot like an abstract class implementation , does n't it ?
However, there is a subtle difference : An abstract class holds the state of its object as it can have constructors .But interfaces in java 8 with default methods cannot have constructors and as such cannot hold the state of an object. Default method should be used for backward compatibility. Whenever you want to add additional functionality in an existing legacy interface you can use default methods without breaking any existing implement or classes.
That's all on interfaces from java 8 perspective . I will come up with a new feature of Java 8 on my next post which will be related to Lambda Expressions .
Sunday, November 2, 2014
Different types of Locking in a threaded(multi or Uni) environment in Java
Hi friends,
I am back after a long hiatus. I became so wrapped up in several things that I forgot to share my experience here for a long time. Anyways, let's move forward with today's post.
Recently I delved into Java threading. In my experience , I did not come across a single web application that makes use of the java threading utilities(which is a shame really, since they are so versatile and useful; the other reason may be that they are bit tough to understand and implement). So , while going through different threading techniques, I stumbled upon a concept of threading called as locking. The more I read, the more confused I became. At last I was able to get myself out of such a tangled mess with some help. So here I will post about locking in a way that it's easy to understand .
What is Locking ?
Locking is a way in which a thread accesses a resource and tells other threads that they cannot access the same resource until he is done using it. So , that means when we use the synchronized keyword on a method or a code block , only one thread at a time can access it. Other threads will wait until the thread accessing it is finished with it's operation. That's called locking; means the resource is locked and no one else can access it unless it's unlocked for future use.
Types of Locking
There are actually two types of locking:
1> Intrinsic Locking
2> Explicit Locking
Intrinsic locking are of different types like : Object level locking, class level locking and re entrant locking.
Object Level Locking :
Object level locking is using the synchronized key word on a non static method or a non static code block.So in such a type of locking, multiple threads will enter the class using different instances or objects of the class, but only one thread will have a lock on the method or the code block for a particular instance . This makes instance level data thread safe .
public class Death
{
public synchronized void deathEaters(){} //non static method
}
or
public class Harbinger
{
public void War(){
synchronized (this) //non static code block
{
}
}
}
Class Level Locking :
Class level locking comes into play when synchronized key word is used on a static method or a static code block. That means at a given instance , if there are 100 threads, then only one thread can enter the method or code block. Other threads will be waiting . This comes into play because of the nature of a static method. A static method is always available at class level and it is shared by all instances. Hence the need to have this type of locking here .
public class Death
{
public synchronized static void deathEaters(){} // static method
}
or
public class Harbinger
{
public static void War(){
synchronized (Harbinger.class) //static code block
{
}
}
}
Re entrant locking :
This is an interesting concept. Synchronized methods are re entrant in nature .If a thread has lock on the monitor object using one synchronized method and if another synchronized method requires to have the lock on the same monitor object then the thread can enter that method . That's why it is called re entrant ( the ability to re enter ) . Consider the following :
public class Famine{
public synchronized death(){
plague();
}
public synchronized plague(){
}
}
If a thread enters death(), it has the lock on Famine object, so when it tries to execute plague() method, the thread is allowed to execute plague() method since it’s already holding the lock on the Famine object.
Explicit Locking :
Explicit locking is a way of introducing thread safety without using synchronized keyword. Instead we can use the Lock API present in java.util.concurrent package to introduce locking.
public class Resource {
public void doResourcing(){
}
public void dologging(){
}
}
public class ExplicitLockingUsingSynchronized implements Runnable{
private Resource resource;
public ExplicitLockingUsingSynchronized(Resource r){
this.resource = r;
}
@Override
public void run() {
synchronized (resource) {
resource.doResourcing();
}
resource.dologging();
}
}
Now let's try this using the Lock API and we will remove the synchronized keyword.
public class ExplicitLockingImplementation implements Runnable{
private Resource resource;
private Lock lock;
public ExplicitLockingImplementation(Resource r){
this.resource = r;
this.lock = new ReentrantLock();
}
@Override
public void run() {
try {
if(lock.tryLock(10, TimeUnit.SECONDS)){
resource.doResourcing();
}
} catch (InterruptedException e) {
e.printStackTrace();
}finally{
lock.unlock(); //release lock
}
resource.doLogging();
}
I am back after a long hiatus. I became so wrapped up in several things that I forgot to share my experience here for a long time. Anyways, let's move forward with today's post.
Recently I delved into Java threading. In my experience , I did not come across a single web application that makes use of the java threading utilities(which is a shame really, since they are so versatile and useful; the other reason may be that they are bit tough to understand and implement). So , while going through different threading techniques, I stumbled upon a concept of threading called as locking. The more I read, the more confused I became. At last I was able to get myself out of such a tangled mess with some help. So here I will post about locking in a way that it's easy to understand .
What is Locking ?
Locking is a way in which a thread accesses a resource and tells other threads that they cannot access the same resource until he is done using it. So , that means when we use the synchronized keyword on a method or a code block , only one thread at a time can access it. Other threads will wait until the thread accessing it is finished with it's operation. That's called locking; means the resource is locked and no one else can access it unless it's unlocked for future use.
Types of Locking
There are actually two types of locking:
1> Intrinsic Locking
2> Explicit Locking
Intrinsic locking are of different types like : Object level locking, class level locking and re entrant locking.
Object Level Locking :
Object level locking is using the synchronized key word on a non static method or a non static code block.So in such a type of locking, multiple threads will enter the class using different instances or objects of the class, but only one thread will have a lock on the method or the code block for a particular instance . This makes instance level data thread safe .
public class Death
{
public synchronized void deathEaters(){} //non static method
}
or
public class Harbinger
{
public void War(){
synchronized (this) //non static code block
{
}
}
}
Class Level Locking :
Class level locking comes into play when synchronized key word is used on a static method or a static code block. That means at a given instance , if there are 100 threads, then only one thread can enter the method or code block. Other threads will be waiting . This comes into play because of the nature of a static method. A static method is always available at class level and it is shared by all instances. Hence the need to have this type of locking here .
public class Death
{
public synchronized static void deathEaters(){} // static method
}
or
public class Harbinger
{
public static void War(){
synchronized (Harbinger.class) //static code block
{
}
}
}
Re entrant locking :
This is an interesting concept. Synchronized methods are re entrant in nature .If a thread has lock on the monitor object using one synchronized method and if another synchronized method requires to have the lock on the same monitor object then the thread can enter that method . That's why it is called re entrant ( the ability to re enter ) . Consider the following :
public class Famine{
public synchronized death(){
plague();
}
public synchronized plague(){
}
}
If a thread enters death(), it has the lock on Famine object, so when it tries to execute plague() method, the thread is allowed to execute plague() method since it’s already holding the lock on the Famine object.
Explicit Locking :
Explicit locking is a way of introducing thread safety without using synchronized keyword. Instead we can use the Lock API present in java.util.concurrent package to introduce locking.
public class Resource {
public void doResourcing(){
}
public void dologging(){
}
}
public class ExplicitLockingUsingSynchronized implements Runnable{
private Resource resource;
public ExplicitLockingUsingSynchronized(Resource r){
this.resource = r;
}
@Override
public void run() {
synchronized (resource) {
resource.doResourcing();
}
resource.dologging();
}
}
Now let's try this using the Lock API and we will remove the synchronized keyword.
public class ExplicitLockingImplementation implements Runnable{
private Resource resource;
private Lock lock;
public ExplicitLockingImplementation(Resource r){
this.resource = r;
this.lock = new ReentrantLock();
}
@Override
public void run() {
try {
if(lock.tryLock(10, TimeUnit.SECONDS)){
resource.doResourcing();
}
} catch (InterruptedException e) {
e.printStackTrace();
}finally{
lock.unlock(); //release lock
}
resource.doLogging();
}
Now do you see the difference : There a lot of API related methods to help us with locking in the Lock API(for eg, usage of time out as I have shown here). It makes our job much, much easier . We can use a lot of conditions and options using the lock API.
That's all on thread locking. I hope this will be very informative for people who are trying to understand the concept of locking in threads .
Tuesday, September 24, 2013
JAX WS SSL Configuration to solve wsdl certificate problems
Hi friends,
Back to you after a long time. This past 2 months , i had been crazy busy and hence, did not have enough time to discuss anything.
Today , i am going to discuss a very important topic. This is regarding the invocation of a JAX-WS or JAX-RPC service.
PROBLEM :
Some time back i was trying to invoke a JAX WS service from a stand alone java application (an application having a java class with the main method and having no application server at all). The problem was, every time i was trying to invoke any service operation, it was giving me a SSL CONFIGURATION EXCEPTION .
REASON :
Now the reason behind it was that, every service call requires to validated . So how is that done ? It's done with the help of certificates. So what i did was that, i got a hold of those certificates(the service i was using needed 2 of them) and integrated them with my java environment to make the WSDL hoster realize that it was a valid invocation.
SOLUTION (THE JAVA WAY):
My certificate names were cert1.cer and cert2.cer . And this how i integrated them in my java environment(In use RAD-Rational Application Developer) :
1. Place the below cry certificates in the path "C:\Program Files\IBM\SDP\jdk\jre\lib\security"
cert1.cer, cert2.cer
2. cacerts is the trusStore file. It's present in :
C:/Program Files/IBM/SDP/jdk/jre/lib/security/cacerts
3. In command prompt perform the below execution :
C:\Program Files\IBM\SDP\jdk\jre\lib\security>"C:\Program Files\IBM\SDP\jdk\jre\bin\keytool" -import -alias cert1 -file cert1.cer -keystore cacerts
4. If it asks keystore password, mention changeit, which is the default keystore password
Enter keystore password: changeit
Trust this certificate? [no]: yes
Certificate was added to keystore
5. Peform the steps 3 and 4 for the second certificate(cert2.cer).
And , i thought that was the end of it, but apparently it was not to be so. It seems , you have to configure the
"javax.net.ssl" in your program to make it work, and this is how you have got to do it :
System.setProperty("javax.net.ssl.trustStore", "C:\\Program Files\\IBM\\SDP\\jdk\\jre\\lib\\security\\cacerts");
System.setProperty("javax.net.ssl.trustStorePassword", "changeit");
Now,the problem will be that the above piece of code will configure only the truststore, but that's not all; you have got to configure the keystore as well. So for this , you have gotta add the following lines of code :
System.setProperty("javax.net.ssl.keyStore", "C:\\Program Files\\IBM\\SDP\\jdk\\jre\\lib\\security\\cacerts");
System.setProperty("javax.net.ssl.keyStorePassword", "changeit");
And voila, everything will start working for you.
In case you are wondering how to add the certificates pro grammatically instead of adding them manually, then you can use this link : http://stackoverflow.com/questions/18764122/how-to-integrate-wsdl-certificates-to-the-cacerts-file-in-jdk-jre-security-folde
THE UNIX WAY( no--check--certificates) :
Now if you are writing a shell script and you are invoking a particular operation of the web service , then you can actually tell the host not to validate the invocation for any certificates.
In my case, i normally use the CURL command to do my bidding , though other times it's the WGET command. So for example , my invocation of a service operation using a schell script will look something like this :
#! /bin/sh
ENDPOINT="http://mathertel.de/AJAXEngine/S01_AsyncSamples/CalcService.asmx"
VALUE=1234567890
if [ -n "${1}" ]; then
VALUE=${1}
fi
curl --silent \
--data \
@- \
--header 'Content-Type: application/soap+xml; charset=utf-8' \
--user-agent "" \
${ENDPOINT} <<EOF | xmllint --format -
<?xml version="1.0" encoding="utf-8"?>
<soap12:Envelope
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap12="http://www.w3.org/2003/05/soap-envelope">
<soap12:Body>
<CalcPrimeFactors xmlns="http://www.mathertel.de/S01_AsyncSamples/">
<inputText>${VALUE}</inputText>
</CalcPrimeFactors>
</soap12:Body>
</soap12:Envelope>
EOF
DON'T BE AFRAID or alarmed , this is not a complicated code. Curl's just a command(you have to have it installed though in your linux distro), where you pass the end point and the request structure . Once that is done , this will give an out put , which for brevity , we can parse it using XMLLINT, which is a command that parses the response in XML format. In case, you do not want to be validated for certificates, you just need to add the option no--check--certificates to the command invocation and you will get the response without any certificate hassles .
In my case, the output looks like this :
RESPONSE FROM THE SERVICE :
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<soap:Body>
<CalcPrimeFactorsResponse xmlns="http://www.mathertel.de/S01_AsyncSamples/">
<CalcPrimeFactorsResult>2 3 3 5 3607 3803</CalcPrimeFactorsResult>
</CalcPrimeFactorsResponse>
</soap:Body>
</soap:Envelope>
Hope this will be fun to know for you all as it was for me.
Good bye.
Back to you after a long time. This past 2 months , i had been crazy busy and hence, did not have enough time to discuss anything.
Today , i am going to discuss a very important topic. This is regarding the invocation of a JAX-WS or JAX-RPC service.
PROBLEM :
Some time back i was trying to invoke a JAX WS service from a stand alone java application (an application having a java class with the main method and having no application server at all). The problem was, every time i was trying to invoke any service operation, it was giving me a SSL CONFIGURATION EXCEPTION .
REASON :
Now the reason behind it was that, every service call requires to validated . So how is that done ? It's done with the help of certificates. So what i did was that, i got a hold of those certificates(the service i was using needed 2 of them) and integrated them with my java environment to make the WSDL hoster realize that it was a valid invocation.
SOLUTION (THE JAVA WAY):
My certificate names were cert1.cer and cert2.cer . And this how i integrated them in my java environment(In use RAD-Rational Application Developer) :
1. Place the below cry certificates in the path "C:\Program Files\IBM\SDP\jdk\jre\lib\security"
cert1.cer, cert2.cer
2. cacerts is the trusStore file. It's present in :
C:/Program Files/IBM/SDP/jdk/jre/lib/security/cacerts
3. In command prompt perform the below execution :
C:\Program Files\IBM\SDP\jdk\jre\lib\security>"C:\Program Files\IBM\SDP\jdk\jre\bin\keytool" -import -alias cert1 -file cert1.cer -keystore cacerts
4. If it asks keystore password, mention changeit, which is the default keystore password
Enter keystore password: changeit
Trust this certificate? [no]: yes
Certificate was added to keystore
5. Peform the steps 3 and 4 for the second certificate(cert2.cer).
And , i thought that was the end of it, but apparently it was not to be so. It seems , you have to configure the
"javax.net.ssl" in your program to make it work, and this is how you have got to do it :
System.setProperty("javax.net.ssl.trustStore", "C:\\Program Files\\IBM\\SDP\\jdk\\jre\\lib\\security\\cacerts");
System.setProperty("javax.net.ssl.trustStorePassword", "changeit");
Now,the problem will be that the above piece of code will configure only the truststore, but that's not all; you have got to configure the keystore as well. So for this , you have gotta add the following lines of code :
System.setProperty("javax.net.ssl.keyStore", "C:\\Program Files\\IBM\\SDP\\jdk\\jre\\lib\\security\\cacerts");
System.setProperty("javax.net.ssl.keyStorePassword", "changeit");
And voila, everything will start working for you.
In case you are wondering how to add the certificates pro grammatically instead of adding them manually, then you can use this link : http://stackoverflow.com/questions/18764122/how-to-integrate-wsdl-certificates-to-the-cacerts-file-in-jdk-jre-security-folde
THE UNIX WAY( no--check--certificates) :
Now if you are writing a shell script and you are invoking a particular operation of the web service , then you can actually tell the host not to validate the invocation for any certificates.
In my case, i normally use the CURL command to do my bidding , though other times it's the WGET command. So for example , my invocation of a service operation using a schell script will look something like this :
#! /bin/sh
ENDPOINT="http://mathertel.de/AJAXEngine/S01_AsyncSamples/CalcService.asmx"
VALUE=1234567890
if [ -n "${1}" ]; then
VALUE=${1}
fi
curl --silent \
--data \
@- \
--header 'Content-Type: application/soap+xml; charset=utf-8' \
--user-agent "" \
${ENDPOINT} <<EOF | xmllint --format -
<?xml version="1.0" encoding="utf-8"?>
<soap12:Envelope
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap12="http://www.w3.org/2003/05/soap-envelope">
<soap12:Body>
<CalcPrimeFactors xmlns="http://www.mathertel.de/S01_AsyncSamples/">
<inputText>${VALUE}</inputText>
</CalcPrimeFactors>
</soap12:Body>
</soap12:Envelope>
EOF
DON'T BE AFRAID or alarmed , this is not a complicated code. Curl's just a command(you have to have it installed though in your linux distro), where you pass the end point and the request structure . Once that is done , this will give an out put , which for brevity , we can parse it using XMLLINT, which is a command that parses the response in XML format. In case, you do not want to be validated for certificates, you just need to add the option no--check--certificates to the command invocation and you will get the response without any certificate hassles .
In my case, the output looks like this :
RESPONSE FROM THE SERVICE :
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<soap:Body>
<CalcPrimeFactorsResponse xmlns="http://www.mathertel.de/S01_AsyncSamples/">
<CalcPrimeFactorsResult>2 3 3 5 3607 3803</CalcPrimeFactorsResult>
</CalcPrimeFactorsResponse>
</soap:Body>
</soap:Envelope>
Hope this will be fun to know for you all as it was for me.
Good bye.
Saturday, July 13, 2013
The magic of CSSPIE3 library
Hi friends,
Today i am gonna talk about an interesting tidbit that i came to know very recently.
The Problem :
I was working on installing a gradient for a page. For mozilla, the gradient was written as :
background: linear-gradient(to bottom, #ffffff 18%,#ecedeb 18%,#d1d5d0 100%);
And the pictorial view of that block of code comes up as something like this :
Now linear gradient cannot be used for the browser like IE8, as IE8 does not understand what it is. Hence we need to use filter here like :
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ffffff', endColorstr='#d1d5d0',GradientType=0 );
The element gradientType = 0 signifies that we here are talking about a linear gradient. That's how IE understands a linear gradient. Now the problem with that is, once such a style is implemented, IE super imposes that with it's own styles, thus marring the whole effect , like in here :
As you can see from the picture above we get discontinuous red lines even after applying the filter.
So for a long time i was languishing under the knowledge that IE 8 is not letting me bring up the gradient properly.
Reason :
The problem with using filters is that they are old pieces of code of a bygone era. They are not very reliable/good. No one really used them until recently when we got first class gradients/opacity etc. IE's old
filter styles are well known for having major bugs and quirks. Hence i was pondering on the possible solutions when i suddenly came across the CSSPIE3 library.The way out :
CSS3Pie library is a little Javascript lib that tries to add a few standard CSS features to old IE versions, including CSS gradients. It works internally by using VML graphics, not
filter styles, which means that you don't get the bugs thatfilter causes . Hence all i needed to do here was use the linear gradient and couple it to PIE.js. I downloaded the PIE.js from : http://css3pie.com/ .
Now to use it , first i described my style in jsp inside a class like :
<Style type="text/css">
.ieMasterStyle{
background: linear-gradient(to bottom, #ffffff 18%,#ecedeb 18%,#d1d5d0 100%);
}
<Style>
In my jsp , i referred to it as :
<td class='ieMasterStyle'>Border</td>
Now calling this one is a bit tricky and it is a two step process :
STEP 1 :
Include the PIE.js script in your page, surrounded by a conditional comment to prevent it from being downloaded in other browsers:
<script type="text/javascript" src="path/to/PIE.js"></script>
<![endif]-->
or, in case, you don't want to download it , but just want to refer it from a CDN than do this :
<!--[if IE]>
<script type="text/javascript" src="http://cdn.jsdelivr.net/css3pie/1.0.0/PIE.js"></script>
<![endif]-->
NOTE : Remeber to use PIE.js version 1.0 as it's the most stable version around.
STEP 2 :
Invoke the
PIE.attach(el) function for each element that needs CSS3 styling. Make sure you do this after the page's DOM has been fully loaded. For example, using jQuery:$(function() {
if (window.PIE) {
$('.ieMasterStyle').each(function() {
PIE.attach(this);
});
}
});
As you can see from above , i have fed the ieMasterStyle that i created directly o PIE.js, where in the PIE.js will do it's magic and apply the linear gradient for us . Hence the finished product in IE 8 looks like this :
And thus i achieved browser consitency and PIE.js saved my bacon.
That's it guys. Bye .
Thursday, July 4, 2013
Android : Layouts
Back to you guys after a long time. From today we will go inside in depth of android features and try to learn some new stuff along the way . The next few days, we will feverishly try to cover a lot of topics pertaining to android. So let's get cracking .
What's an android layout ?
Well, a lay out is what it actually means. It's the main UI of your app and will contain several UI controls of your app. You can define your lay out height, width and orientation , add text views , buttons etc and when you run the app , all of them will come up in your app UI . Layouts are presented in XML. When you first create a layout, the main.xml is created. In case you are wondering that's your lay out .
This is how a typical layout is created :
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
</LinearLayout >
I know, i know, you are very confused . Let's break it up then :
1> fill_parent --> means fill the parent window
2> vertical --> That's your typical orientation , you can specify 'horizontal' as well and no one will kill you.
3> wrap_content --> means wrap the content , kind of works like html wrap attribute, quite cool , huh !
Okay, kidding aside, these are very important attributes that define your layout, which means they tell your mobile / tablet that this is the way you want the app to be shown .
So let's run this one in eclipse, once we do that , this is what we will get in the emulator :
If you look clearly up above , you will see the hello world string is coming twice and vertically one below the other. It's coming twice because we have two text views and vertically because the orientation is vertical, duh......
So there you go....it's been laid out for you. Till next time ....
What's an android layout ?
Well, a lay out is what it actually means. It's the main UI of your app and will contain several UI controls of your app. You can define your lay out height, width and orientation , add text views , buttons etc and when you run the app , all of them will come up in your app UI . Layouts are presented in XML. When you first create a layout, the main.xml is created. In case you are wondering that's your lay out .
This is how a typical layout is created :
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
</LinearLayout >
I know, i know, you are very confused . Let's break it up then :
1> fill_parent --> means fill the parent window
2> vertical --> That's your typical orientation , you can specify 'horizontal' as well and no one will kill you.
3> wrap_content --> means wrap the content , kind of works like html wrap attribute, quite cool , huh !
Okay, kidding aside, these are very important attributes that define your layout, which means they tell your mobile / tablet that this is the way you want the app to be shown .
So let's run this one in eclipse, once we do that , this is what we will get in the emulator :
If you look clearly up above , you will see the hello world string is coming twice and vertically one below the other. It's coming twice because we have two text views and vertically because the orientation is vertical, duh......
So there you go....it's been laid out for you. Till next time ....
Saturday, April 27, 2013
How to Set up an environment for Android Development
Hi friends,
Back to you after a long time. Today we are going to look into a very important technology namely : Android.
Now the android programming language is very useful for app development . A lot of us want to be app developers but we are not sure about how to progress. Well the upcoming few weeks , we will look deeply into this technology and try to learn a lot of things.
However, what good is this , if we don't have an application development environment to test what we have learnt ? So i am gonna tell you how how to set up a local work space for Android . Hang tight.
Back to you after a long time. Today we are going to look into a very important technology namely : Android.
Now the android programming language is very useful for app development . A lot of us want to be app developers but we are not sure about how to progress. Well the upcoming few weeks , we will look deeply into this technology and try to learn a lot of things.
However, what good is this , if we don't have an application development environment to test what we have learnt ? So i am gonna tell you how how to set up a local work space for Android . Hang tight.
For the most part, you'll figure out pretty quickly through trial and error what you'll need. If you're using Eclipse, it will yell at you when you're missing things, and you simply find what you're missing in the SDK Manager and install it.
That said, here's what I needed to get up and running with a very basic setup (this assumes using Android 4.1, if you plan on building for an earlier version, then you'll need to download the corresponding libraries from that version):
- SDK Platform
- ARM EABI v7a System Image (optional, you can also grab the Intel x86 Atom and/or Mips System images if you plan on developing for one of those platforms; ARM is the default, from what I've seen)
- Android SDK Platform-tools
You get these simply by going to the Android SDK Manager (your SDK folder/tools/android; or click the "SDK Manager" button in Eclipse), selecting what you need, and clicking "Install Packages". Once you do that, you can follow the rest of the guide that you linked for building your first app (I highly recommend it, it's extraordinarily beneficial), and your app should run with no problem.
Here's a snapshot to get you started :
Now all you gotta do , is install the packages that I have checked in and that creates your basic set up. The other stuff you can install later.
Hope that was useful. Very soon we will dive in to the world of Android.
Good Bye .
Sunday, April 7, 2013
BASH COMMANDS - PART 1
Hi friends,
Today we are gonna go in a different direction . After some time , i thought of coming out with a series of tutorials on BASH scripting , which is a must if you wanna write complex scripts. My try outs here will
consist of commands written in UBUNTU 12.04 PP LTS as this is what i am using right now. So let us open up our terminal and begin our wonderful journey :
Finding out where the inbuilt commands lie :
Type :
bash$ : cd /bin
bash$/bin : ls
Creating my own directory and seeing the permissions it has :
mkdir kunal
ls -ld kunal → drwxrwxr-x 2 atri atri 4096 Apr 3 02:00 kunal
Consider these shell operations :
Consider the next set of shell commands :
How to make use of manual in Unix :
bash$ : man man
O/P :
What if we give :
bash$ : man cp
What is Shebang ? :
The shebang is the first line in a script because it is interpreted by the kernel, which looks at the two bytes at the start of an executable file. If these are
#! the rest of the line is interpreted as the executable to run and with the script file available to that program on stdin. Since the kernel will only look at the first two characters and has no notion of further lines, you must place the hash bang in line 1.Let us consider the script below :
This script does a listing of files and in between the first and last listing , it tries to read a file. So if you try to execute the file without changing its permissions it won't run. Hence first you gotta do this :
bash $ : ls -lrt yourFile --> get the available permissions
bash $ : chmod a+x yourFile --> make the file executable.
Voila, now you are ready to run it. Just do :
bash $ : ./yourFile
or
bash $: sh yourFile.sh
That's all for today. Next time we will delve deeper .
Good Bye .
Wednesday, March 13, 2013
Keeping a healthy Mind and Body
Hi Friends,
I am back again. These upcoming weeks we will look into various aspects of different technologies.
However, before doing that i thought i will publish this article.
The last few weeks had been the worst days of my life. Why ? Because I had been ill. So here goes :
I know all of us are busy doing this and that. But if we do not keep a healthy body, none of this will matter. So listen to what i have got to say here as it is more important than all the articles that i have published during my life time.
As we get older the body’s tissues and organs start to work less efficiently. We have to work harder and harder to stay fit and active. But keeping well is also about anticipating what’s increasingly likely to go wrong, and taking steps to prevent harmful events from happening. This may mean not just eating the right foods and taking regular exercise, but also changing your living environment and watching out for possible dangers.
Preventative tactics are particularly important because our health doesn't just decline in a gradual way. Instead what’s often more important is a step-by-step decline on top of a slow deterioration in health. Every so often we have a major illness or event from which we never quite recover to previous levels of fitness. The most common causes include:
- Infections.
- Broken bones.
- Cancers.
- Conditions or diseases requiring an operation.
Listed below are ten essential elements of good health. If you take all of the actions listed below, you will be much healthier.
- Eat a Healthy Breakfast
- Drink at Least 8 Glasses of Water
- Take a Good Quality Multiple Vitamin/Mineral
- Connect with Other People
- Express Your Emotions Appropriately
- Eat Fruits and Vegetables
- Spend at Least 30 Minutes Outdoors
- Do Something Physically Active
- Take Some Quiet Time for Yourself
- Keep Regular Sleep Hours
- Establish a Relationship with a Doctor You Can Trust
Lastly, this is helping me a lot : Meditate properly for at least half an hour.
Hence try to keep yourself healthy folks. This is the primary wealth for which you are fighting with the world.
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