Lexical scoping in JavaScript

If you are familiar with JavaScript you might be aware that JavaScript uses lexical scoping . Now what really is lexical scoping and how is it different than other languages like java ?
What is actually a scope ? A scope is the visibility and accessibility of the variable . So when a JavaScript function tries to refer to a variable , the scope of the variable comes into play . Now lexical scoping means the variable will be accessible to the function only if it was in scope when it was defined.
The key point is variable does have different scopes while definition and execution.

Angular Js

Angular js is mainly used to build single page application . It is based on MVC architecture.

1. model The form fields act as model , we need to use ng-model attribute to specify the model name.
   
2. view The HTML page is the view , which is being displayed to the user
   
3. controller We can create a JavaScript function which will be the controller
   

There are 3 most important components of angular js.

1. application
2. controller
3. service

Common Errors:
Error: [$injector:unpr] Unknown provider: myServiceProvider
 When you see this error you need to check if have my service defined for your application.

Click on the buttons inside the tabbed menu:

angular.module("home",home); var home=function (){ }

Gradle

Hi Guys,
I have started learning cradle and this blog will help you getting familiar with gradle.

Gradle is a build tool where in you can have a project comprising of tasks.
Your build related details will be mentioned in build.gradle file .
By default the folder name is the rootProject  name if you want to configure it change in settings.gradle file.
End.

rootProject=org.myProject

The project inside the root project will be the subProject .
You can specify the dependency in build.gradle as

If you want to use a repository you can use the repository to define it.

repository {
maven{

url "http://testRepo.org"
}

}

Wildfly 10

Hi Guys, I have started using Wildfly 10 sometime back and here is my guide on how to successfully configure wildfly 10. First of all download it from site.

http://wildfly.org/downloads/

Now, check if you have JAVA in the environment variables .Make sure it is pointed to Java 8.

echo %JAVA%
C:\Program Files\Java\jdk1.8.0_91\jre\bin\java.exe

open command prompt ,goto Wildfly\bin and type the following command

standalone.bat -Djboss.home.dir=\softwares\wildfly_10\wildfly-10.1.0.Final -Djboss.server.config.dir=\softwares\wildfly_10\wildfly-10.1.0.Final\standalone\configuration

If you are using powershell type the following command

.\standalone.bat -Djboss.home.dir=\softwares\wildfly_10\wildfly-10.1.0.Final -Djboss.server.config.dir=\softwares\wildfly_10\wildfly-10.1.0.Final\standalone\configuration

Note : you need to change the path to the path where wildfly installation is.

If you face the following error while starting

Unable to read the logging configuration from 'file:F:\shahbaz\softwares\wildfly_10\wildfly-10.1.0.Final\standalone/logging.properties' (java.io.FileNotFoundException: F:\shahbaz\softwares\wildfly_10\wildfly-10.1.0.Final\standalone\logging.properties (The system cannot find the file specified))

change the -Djboss.server.config.dir to the proper config path.

To find out which port number the http server is running , open standalone.xml and check the following attribute.

<socket-binding name="http" port="${jboss.http.port:8090}"/>

Once you start wildfly hit the following URL http://localhost:8090

Click on admin console and then you might see the following screen.

Run add-user.bat and set the username and password for application as well as management realm

Goto the home page after adding the users

Done with the server configuration . Now you can start playing with the server. So,Lets create a simple application and deploy .We will have a index page which will display a message on load.

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">

    <display-name>My App </display-name>
</web-app>

<html>
<body>
Hi ,
This is my app.
</body>
</html>

Now build the war file which will be deployed . Type the following command in the console.

"C:\Program Files\Java\jdk1.8.0_91\bin\jar" -cvf myApp.war *

Once you have the war file ready you can deploy it using wildfly admin console.Follow the steps to deploy a war file.

Deploy the selected war file

Lets create servlet jsp project and deploy it.

package org.myApp;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.myApp.TempConvertor;

public class Converter extends HttpServlet
{
public void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException,ServletException{
try{
String farenhiet=request.getParameter("farenhiet");
if(farenhiet != null ){
String celcius=TempConvertor.farenhietToCelcius(Float.parseFloat(farenhiet));
request.setAttribute("celcius",celcius);
RequestDispatcher requestDispatcher=request.getRequestDispatcher("/conv/result.jsp");
requestDispatcher.forward(request,response);
}
}catch(Exception e){
e.printStackTrace();
RequestDispatcher requestDispatcher=request.getRequestDispatcher("/conv/error.jsp");
requestDispatcher.forward(request,response);
}

}
public void doPost(HttpServletRequest request,HttpServletResponse response){
}
}

public class TempConvertor
{
public static String farenhietToCelcius(float farenhiet){
float celcius =(farenhiet -32 )*5/9;
return String.valueOf(celcius);
}
}

Your code here.

you can start it using eclipse, if you face the following error you need to change the Java installations.

Exception in thread "main" java.lang.UnsupportedClassVersionError: org/jboss/modules/Main : Unsupported major.minor version 52.0 at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:800) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) at java.net.URLClassLoader.defineClass(URLClassLoader.java:449) at java.net.URLClassLoader.access$100(URLClassLoader.java:71) at java.net.URLClassLoader$1.run(URLClassLoader.java:361) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:425) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) at java.lang.ClassLoader.loadClass(ClassLoader.java:358) at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)

org.dom4j.DocumentFactory cannot be cast to org.dom4j.DocumentFactory

Hi Guys , You might face this exception when using wildfly 10 with hibernate. This exception is linked with the classloader since the same class is loaded by two different class loaders. You can the following solution

 <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.1.0.Final</version>
            <scope>provided</scope>
        </dependency>

Uncaught TypeError: Converting circular structure to JSON

Hi Guys

You will see this error on converting a json to string using JSON.stringify .

Full stacktrace is like

Uncaught TypeError: Converting circular structure to JSON
at JSON.stringify (<anonymous>)
at <anonymous>:1:6

Below is the sample code that can cause this exception. You can see that we have created an element object in line number 1 and in line number 2 we are assigning the same element object to the node attribute of the element. This is having a circular reference . Hence you will experience the exception.

var element={"node":{}};
element.node=element;

JSON.stringify(element);

You might also face the error for the following block of code :

var element={"node":{}};
element.node=element;

angular.toJson(element);

Uncaught is added since the exception is not catched by a catch block . According to MSDN, A TypeError is thrown when an operand or argument passed to a function is incompatible with the type expected by that operator or function .So here it is explicitly thrown by stringify method.It is also possible that a common utility method is throwing this exception. Check if your code has the following statement .

new TypeError("Converting circular structure to JSON");

The integer literal does not conform to the expected type String

Hi Guys ,

There are multiple reasons for getting this error .

1. If you have a class for which you are trying to create an object and you have missed to specify any of the class variables while creating the object, you might face the exception like :
The boolean literal does not conform to the expected type String .

Take a look at the program below :

class Student(
    val name: String,
    var age: Int
)

fun main(args: Array<String>) {
    val student= Student(1)
    println(student.name)
    println(student.age)
}

If you try to run the above program you might face an error like .

• • Error:(8, 25) The integer literal does not conform to the expected type String
  • Error:(8, 26) No value passed for parameter age

Click here to run this test.