Vikas Java Notes: September 2014

Saturday, September 27, 2014

Execute and Wait Interface in Struts2

The Execute and Wait Interceptor (execAndWait) is great for running long-lived actions in the background while showing the user a nice progress meter. This also prevents the HTTP request from timing out when the action takes more than 5 or 10 minutes. Click Here for more info.

Let’s see how we can use it –

1. Welcome.jsp -
This is the initial jsp which will request for some processing.

<%@page contentType="text/html" pageEncoding="UTF-8"%>

<%@taglib uri="/struts-tags" prefix="s" %>

<!DOCTYPE html>

<html>

<head>

</head>

<body>

<h1>execAndWait interceptor</h1>

<h2>

This Web app shows how to use execAndWait Interface <br/>

to show a page when business logic taking long time <br/>

and you want to show another page, till the execution<br/>

is not completed successfully.

</h2>

<br/>

<s:form name="frm" action="waitAction.action">

<s:submit value="Process ..."/>

</s:form>

</body>

</html>

2. Wait.jsp
The page which will shows when user is waiting for server response.

<%@ taglib prefix="s" uri="/struts-tags" %>

<head>

<meta http-equiv="refresh" content="2;"/>

<title>Please Wait ...</title>

</head>

<body>

Please wait...

</div>

</body>

</html>

3. Done.jsp
This is the jsp will be displayed after processing

<%@page contentType="text/html" pageEncoding="UTF-8"%>

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>Thanks for waiting ...</title>

</head>

<body>

<h1>Process completed!!!</h1>

<h2>Thanks for waiting!! </h2>

</body>

</html>

4. Action Class:

This Action is called from the welcome.jsp file. It will process the actual business logic. Name it as “WaitAction.java”

package action;

import com.opensymphony.xwork2.ActionSupport;

public class WaitAction extends ActionSupport {

/* default constructor */

public WaitAction() {

}

@Override

public String execute() {

try {

/* wait for 12000 ms */

Thread.sleep(12000);

} catch (Exception e) {

System.out.println(e);

}

return SUCCESS;

}

} // end of class

5. Make an entry in struts.xml file for action class –

This interceptor is already configured but is not part of any of the default stacks. Because of the nature of this interceptor, it must be the last interceptor in the stack.

Important: Because the action will be running in a separate thread, you can't use ActionContext because it is a ThreadLocal. This means if you need to access, for example, session data, you need to implement SessionAware rather than calling ActionContext.getSession().

Parameters for execAndWait Interceptor:

threadPriority (optional) - the priority to assign the thread. Default is Thread.NORM_PRIORITY.

delay (optional) - an initial delay in millis to wait before the wait page is shown (returning wait as result code). Default is no initial delay.

delaySleepInterval (optional) - only used with delay. Used for waking up at certain intervals to check if the background process is already done. Default is 100 millis.

<interceptor-ref name="defaultStack"/>

<interceptor-ref name="execAndWait">

<param name="delay">1500</param>

</interceptor-ref>

<result name="wait">/jsp/Wait.jsp</result>

<result name="success">/jsp/Done.jsp</result>

</action>

</package>

6. Entry in web.xml file –

<filter-name>struts2</filter-name>

<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>

</filter>

<filter-mapping>

<filter-name>struts2</filter-name>

<url-pattern>/*</url-pattern>

</filter-mapping>

<welcome-file-list>

<welcome-file>jsp/welcome.jsp</welcome-file>

</welcome-file-list>

This would be folder structure of your project, after developing all the necessary files

Now deploy and run the webapp.

Welcome.jsp

Wait .jsp

Done.jsp

Thanks for reading ....Namaste ....

How to write a Simple Spring Program ?

This is one of the simplest program, which uses DI (Dependency Injection) feature of Spring.

For this tutorial you need Spring_2.5.jar and commons-logging-1.1.1.jar file.

I am using NetBeans 7.2 for this tutorial..

Lets Start -

1. Create a class with main function, in my example i am creating class FirstSpringProgram.java containing main class.

FirstSpringProgram.java

/**

* @author Vikas Kumar Verma

public class FirstSpringProgram {

/**

* @param args the command line arguments

public static void main(String[] args) {

System.out.println("JSR");

/**

* Create and dispense bean, It load Bean Definition and wire bean

* together.

ApplicationContext applicationContext

= new FileSystemXmlApplicationContext(

"E:\\vikas\\rnd\\FirstSpringProgram\\Spring.xml");

/**

* Get Bean using Bean ID declred in Spring.xml file.

SpringBean springBean = (SpringBean) applicationContext.getBean("SpringBean");

/**

* Executing the bean method.

System.out.println("Out put from Spring Bean: " + springBean.callSpring());

System.out.println("Thanks");

}

} /* End of class */

2. Now we need to create Interface which represent the Spring Bean, Name this file as

SpringBean.java -

* Interface declaring prototype of Spring Bean

package firstspringprogram.bean;

/**

* @author Vikas Kumar Verma

public interface SpringBean {

/**

* Bean Method return bean message.

* @return String

public String callSpring();

}

/* End of class */

3. Create a Bean class implimenting SpringBean Interface, as SpringBeanImpl.java

SpringBeanImpl.java -

package firstspringprogram.bean;

/**

* @author : Vikas Kumar Verma

public class SpringBeanImpl implements SpringBean {

/**

* Bean Method return bean message.

* @return String

@Override

public String callSpring() {

/**

* Return Bean Message

return "Thank You for Calling Me ... ";

}

/* End of class */

4. Now we have to map the bean with spring container, to do this

you need to create and xml config file which register the bean(interface)

with its implimentation.

Spring.xml -

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">

</bean>

</beans>

Now you have done with it, just compile the program.

The output should be like this -

Output from Spring Bean:

Thank You for Calling Me …

Thanks

Monday, September 22, 2014

How to set max length of a TextField in fxml ?

Sometime it required to set max length of a TextField, but unfortunately, fxml does not provide this functionality.

So how to do this ?

To set the max length, there are two ways.

1. Create a Change Listener class and register it , with TextField Object, for which you want to set max length.

2. Create a concrete class, and extend it with TextField class.

Here we are going to see how to implement first options that is -

1. Create a Change Listener class and register it , with TextField Object, for which you want to set max length.

Change Listener -

Implement ChangeListner and add it to the TextField, for which you want to set max character length.

To do that, create a concrete class, and implement it with javafx.beans.value.ChangeListener

This listener notice whenever state of text field (its observable) is changed (Here in this case a text field).

public class ChangeListener implements javafx.beans.value.ChangeListener<String>

Interface ChangeListener, have a method changed; this method is called whenever stated of observable text field is changed.

public void changed(ObservableValue<? extends String> observableValuem, String oldValue, String newValue)

In above method signature, parameter oldValue contains the old value of text field, and newValue parameter contains the changed value (new value).

We can add our code to control the max length of TextField like this -

public void changed(ObservableValue<? extends String> observableValue,

String oldValue, String newValue) {

/* To check if the value is null then return */

if (newValue == null){

return;

}

/* Check the length of new value length is less then defined max length then set the new value to the text field, else keep old value in text field. */

if (newValue.length() > maxLength) {

TextField.setText(oldValue);

} else {

TextField.setText(newValue);

}

} // End of Method

In 'initialize' method of controller class, add listener like this -

textField.textProperty().addListener(new ChangeListener(TextField, maxLength));

In the above code snippet, textField is the text filed in which you want to add listener, and ‘maxLength’ is max length of text field.

Example -

fxml file -

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>

<?import java.util.*?>

<?import javafx.scene.*?>

<?import javafx.scene.control.*?>

<?import javafx.scene.layout.*?>

<AnchorPane id="AnchorPane" prefHeight="200" prefWidth="320" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8"

fx:controller="com.fxml.FXMLDocumentController">

<Label fx:id="label" layoutX="46.0" layoutY="51.0" minHeight="16"

minWidth="69" text="User Name" />

<TextField fx:id="userName" layoutX="142.0" layoutY="50.0"

prefHeight="25.0" prefWidth="139.0" promptText="Max Size is 5 Char" />

</children>

</AnchorPane>

Controller Class -

* This is my controller class.

package com.fxml;

import java.net.URL;

import java.util.ResourceBundle;

import javafx.event.ActionEvent;

import javafx.fxml.FXML;

import javafx.fxml.Initializable;

import javafx.scene.control.Label;

import javafx.scene.control.TextField;

import com.listener.ChangeListener;

/**

* @author vikas

public class FXMLDocumentController implements Initializable {

@FXML

private Label label;

@FXML

private TextField userName;

@FXML

private void handleButtonAction(ActionEvent event) {

}

@Override

public void initialize(URL url, ResourceBundle rb) {

/* max length of text field user name */

int maxLength = 5;

/* add ChangeListner to TextField */

userName.textProperty().addListener(new ChangeListener(userName, maxLength));

}

} // End of class

Change Listener Class -

package com.listener;

This listener calass is called to set maximum length of any text field.

Example -

TextField textField;

ChangeListener listener = new ChangeListener(TextField, 5); // set max length as 5

textField.textProperty().addListener(listener);

import javafx.beans.value.ObservableValue;

import javafx.scene.control.TextField;

/**

* @author vikas

public class ChangeListener implements javafx.beans.value.ChangeListener<String> {

private int maxLength;

private TextField textField;

public ChangeListener(TextField textField, int maxLength) {

this.textField= textField;

this.maxLength = maxLength;

}

public int getMaxLength() {

return maxLength;

}

@Override

public void changed(ObservableValue<? extends String> ov, String oldValue,

String newValue) {

if (newValue == null) {

return;

}

if (newValue.length() > maxLength) {

textField.setText(oldValue);

} else {

textField.setText(newValue);

}

}// End of Class

Main class -

* Main class to load fxml class.

package com.fxml;

import javafx.application.Application;

import javafx.fxml.FXMLLoader;

import javafx.scene.Parent;

import javafx.scene.Scene;

import javafx.stage.Stage;

/**

* @author vikas

public class Main extends Application {

@Override

public void start(Stage stage) throws Exception {

Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

Scene scene = new Scene(root);

stage.setScene(scene);

stage.show();

}

/**

* @param args the command line arguments

public static void main(String[] args) {

launch(args);

}

} // End of Class

Output -

Input Maximum value in text field -

Thank You ...