Access Specifiers in Java


An access specifier is a keyword that specifies how to access or read the members of a class or the class itself.

There are four access specifiers in Java as mentioned below:

  1. private
  2. public
  3. protected
  4. default

1. Private : Private members of a class are not accessible in other class either in the same package or in another package. The scope of private specifier is class scope.

2. Public : Public members of a class are accessible any where in the same package or another package. The scope of public specifier is Global.

3.Protected : Protected members are available in the same package. They are not available in the class of another package. You can access the protected members in sub class of same package or another package.

4. Default : Default members are available in the class of same package but they are not available in another package. The scope of default specifier is Package level.

Other Useful Links:

Avoid nested loops using Collection Framework in Java

Replace special characters in a String using java

Singleton Design pattern in JAVA

Convert Array to Vector in Java

Marker or Tag Interface in Java

equals() and hashCode() methods of Object Class

Difference between Iterator and ListIterator

Inner classes in Java

Difference between Abstract Class and Interface:

List of View Resolvers in Spring MVC


In Spring MVC, view resolvers enable you to render models in a browser without tying you to a specific view technology like JSP, Velocity, XML…etc.

There are two interfaces that are important to the way Spring handles views are ViewResolver and View. The ViewResolver provides a mapping between view names and actual views. The View interface addresses the preparation of the request and hands the request over to one of the view technologies.

Below are the important view resolvers provided by spring framework:

  1. AbstractCachingViewResolver : Abstract view resolver that caches views. Often views need preparation before they can be used; extending this view resolver provides caching.
  2. XmlViewResolver : Implementation of ViewResolver that accepts a configuration file written in XML with the same DTD as Spring’s XML bean factories. The default configuration file is /WEB-INF/views.xml.
  3. ResourceBundleViewResolver : Implementation of ViewResolver that uses bean definitions in a ResourceBundle, specified by the bundle base name. Typically you define the bundle in a properties file, located in the classpath. The default file name is views.properties.
  4. UrlBasedViewResolver : Simple implementation of the ViewResolver interface that effects the direct resolution of logical view names to URLs, without an explicit mapping definition. This is appropriate if your logical names match the names of your view resources in a straightforward manner, without the need for arbitrary mappings.
  5. InternalResourceViewResolver :  Convenient subclass of UrlBasedViewResolver that supports InternalResourceView (in effect, Servlets and JSPs) and subclasses such as JstlView and TilesView. You can specify the view class for all views generated by this resolver by using setViewClass(..).
  6. VelocityViewResolver/FreeMarkerViewResolver : Convenient subclass of UrlBasedViewResolver that supports VelocityView (in effect, Velocity templates) or FreeMarkerView ,respectively, and custom subclasses of them.
  7. ContentNegotiatingViewResolver : Implementation of the ViewResolver interface that resolves a view based on the request file name or Accept header.

Other Useful Links:

Basic Spring MVC Application

Spring MVC with Tiles framework sample application

Basic Spring MVC Application


This post explains how to create spring based web application.

Folder Structure:

Typical folder structure of the spring web application contains as below.

Folder Structure

web.xml:

Below is the web.xml file which contains the spring configuration. DispatcherServlet is controller of the spring mvc application, all the requests which coming to the application will be passed through it.  DispatcherServlet loads the spring-context.xml file during server start up and keeps the all the configurations in servlet context. Action path configured for this applications is *.html.

<?xml version=”1.0″ encoding=”UTF-8″?>
<web-app xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance&#8221;
xmlns=”http://java.sun.com/xml/ns/javaee&#8221;
xmlns:web=”http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd&#8221;
xsi:schemaLocation=”http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd&#8221;
id=”WebApp_ID” version=”2.5″>

<display-name>Spring Hello World</display-name>

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

<servlet>
<servlet-name>springDispatcher</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/config/spring-context.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springDispatcher</servlet-name>
<url-pattern>*.html</url-pattern>
</servlet-mapping>
</web-app>

index.jsp:

index.jsp file configured in web.xml as a welcome file, so this file will be loaded when user hit the http://localhost:8080/SpringMVC/ url in the browser.

<jsp:forward page=”sayhello.html”></jsp:forward>

HelloWorldController.java:

When ever index.jsp loaded into the browser, it will forward the request to sayhello.html. This sayhello request is mapped to sayHello() method in HelloWorldController class. So, sayHello() method will be executed and it will return the ‘hello’ string after completion of method execution.

package in.javatutorials.spring.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
*
* @author Javatutorials
*
*/
@Controller
public class HelloWorldController {

/**
* Controls the ‘sayhello’ and return to hello.jsp
* @return
*/
@RequestMapping(value = “/sayhello”, method = RequestMethod.GET)
public String sayHello() {

System.out.println(“Sample Spring Application”);

return “hello”;
}

}

spring-context.xml:

Package of HelloWorldController  class is configured as a controller package in the spring-context file as mentioned below. This sample application is configured with the InternalResourceViewResolver, when ever sayHello() method returns the hello string, request will be redirected to hello.jsp based upon the InternalResourceViewResolver configuration as mentioned in the below file.

<?xml version=”1.0″ encoding=”UTF-8″?>
<beans xmlns=”http://www.springframework.org/schema/beans&#8221;
xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance&#8221; xmlns:mvc=”http://www.springframework.org/schema/mvc&#8221;
xmlns:context=”http://www.springframework.org/schema/context&#8221;
xsi:schemaLocation=”
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd”&gt;

<context:component-scan base-package=”in.javatutorials.spring.controller” />
<mvc:annotation-driven />

<bean
class=”org.springframework.web.servlet.view.InternalResourceViewResolver”>
<property name=”prefix” value=”/jsp/” />
<property name=”suffix” value=”.jsp” />
</bean>

</beans>

hello.jsp:

Finally ‘Hi, This is Sample Spring MVC Application’ message will be shown to the user as it is mentioned in the below jsp.

<%@ page language=”java” contentType=”text/html; charset=ISO-8859-1″
pageEncoding=”ISO-8859-1″%>
<!DOCTYPE html PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN” “http://www.w3.org/TR/html4/loose.dtd”&gt;
<html>
<head>
<meta http-equiv=”Content-Type” content=”text/html; charset=ISO-8859-1″>
<title>Sample Spring MVC Application</title>
</head>
<body>Hi, This is Sample Spring MVC Application
</body>
</html>

Access the application in Browser:

http://localhost:8080/SpringMVC/

Application Browser

Please click on the below link to download the complete application : Click here

Other Useful links:

Spring MVC with Tiles framework sample application

differences between DispatchAction and LookupDispatchAction in Struts Framework

Create a Java web service using top down approch

Example programs for SOAP webservice client

Spring MVC with Tiles framework sample application


Below post talks about the Spring MVC integration with the tiles framework.

You can build developer friendly and user friendly web applications using the tiles framework.

Basic Folder structure of the application:

Typical folder structure of the Spring MVC application has mentioned below:

Spring MVC Application folder structure
Spring MVC Application folder structure

 

Web.xml:

Below is the web.xml file which contains the spring configuration. DispatcherServlet is controller of the spring mvc application, all the requests which coming to the application will be passed through it. DispatcherServlet loads the spring-context.xml file during server start up and keeps the all the configurations in servlet context. Action path configured for this applications is *.html.

<?xml version=”1.0″ encoding=”UTF-8″?>
<web-app xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance&#8221;
xmlns=”http://java.sun.com/xml/ns/javaee&#8221;
xmlns:web=”http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd&#8221;
xsi:schemaLocation=”http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd&#8221;
id=”WebApp_ID” version=”2.5″>
<display-name>Spring Hello World</display-name>
<welcome-file-list>
<welcome-file>/</welcome-file>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>

<servlet>
<servlet-name>springDispatcher</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/config/spring-context.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springDispatcher</servlet-name>
<url-pattern>*.html</url-pattern>
</servlet-mapping>
</web-app>

index.jsp:

index.jsp file configured in web.xml as a welcome file, so this file will be loaded when user hit the http://localhost:8080/SpringMVC/ url in the browser.

<jsp:forward page=”contacts.html”></jsp:forward>

HelloWorldController .java:

When ever index.jsp loaded into the browser, it will forward the request to contacts.html. This contacts request is mapped to contollContacts() method in HelloWorldController class. So, contollContacts() method will be executed and it will return the ‘contact’ string after completion of method execution.

package in.javatutorials.spring.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
*
* @author Javatutorials
*
*/
@Controller
public class HelloWorldController {

/**
* Controls the ‘contacts’ and return to respective layout page
* @return
*/
@RequestMapping(value = “/contacts”, method = RequestMethod.GET)
public String contollContacts() {

String message = “Hi, You are in Controller !!!”;
System.out.println(message);

return “contact”;
}

}

 

spring-context.xml:

As the Tiles framework has been configured in the spring-context file as below with UrlBasedViewResolver, whenever contact will be returned by contollContacts() methods, request will be reached to tiles.xml and contact tile configuration will be loaded.

<?xml version=”1.0″ encoding=”UTF-8″?>
<beans xmlns=”http://www.springframework.org/schema/beans&#8221;
xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance&#8221; xmlns:mvc=”http://www.springframework.org/schema/mvc&#8221;
xmlns:context=”http://www.springframework.org/schema/context&#8221;
xsi:schemaLocation=”
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd”&gt;

<context:component-scan base-package=”in.javatutorials.spring.controller” />
<mvc:annotation-driven />

<bean id=”viewResolver”
class=”org.springframework.web.servlet.view.UrlBasedViewResolver”>
<property name=”viewClass”>
<value>
org.springframework.web.servlet.view.tiles2.TilesView
</value>
</property>
</bean>
<bean id=”tilesConfigurer”
class=”org.springframework.web.servlet.view.tiles2.TilesConfigurer”>
<property name=”definitions”>
<list>
<value>/config/tiles.xml</value>
</list>
</property>
</bean>

</beans>

 

tiles.xml:

Below will be the tiles configuration made for our sample application. contact tiles definition is extending to base.definition and base definition will be using layout.jsp as the layout file for our application.

<?xml version=”1.0″ encoding=”UTF-8″ ?>
<!DOCTYPE tiles-definitions PUBLIC
“-//Apache Software Foundation//DTD Tiles Configuration 2.0//EN”
http://tiles.apache.org/dtds/tiles-config_2_0.dtd”&gt;

<tiles-definitions>
<definition name=”base.definition” template=”/jsp/layout.jsp”>
<put-attribute name=”title” value=”” />
<put-attribute name=”header” value=”/jsp/header.jsp” />
<put-attribute name=”menu” value=”/jsp/menu.jsp” />
<put-attribute name=”body” value=”” />
<put-attribute name=”footer” value=”/jsp/footer.jsp” />
</definition>

<definition name=”contact” extends=”base.definition”>
<put-attribute name=”title”
value=”Sample Spring MVC With Tiles Appliacation” />
<put-attribute name=”body” value=”/jsp/contact.jsp” />
</definition>

</tiles-definitions>

layout.jsp:

This layout.jsp is divided the complete application page as header, menu, body, footer. So, once the layout.jsp called, all the other jsps will be included as per the configuration mentioned in the tiles.xml file.

<%@ taglib uri=”http://tiles.apache.org/tags-tiles&#8221; prefix=”tiles”%>
<!DOCTYPE HTML PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN”
http://www.w3.org/TR/html4/loose.dtd”&gt;
<html>
<head>
<meta http-equiv=”Content-Type” content=”text/html; charset=UTF-8″>
<title><tiles:insertAttribute name=”title” ignore=”true” /></title>
</head>
<body>
<table border=”1″ cellpadding=”2″ cellspacing=”2″ align=”center”>
<tr>
<td height=”30″ colspan=”2″><tiles:insertAttribute name=”header” />
</td>
</tr>
<tr>
<td height=”250″><tiles:insertAttribute name=”menu” /></td>
<td width=”350″><tiles:insertAttribute name=”body” /></td>
</tr>
<tr>
<td height=”30″ colspan=”2″><tiles:insertAttribute name=”footer” />
</td>
</tr>
</table>
</body>
</html>

 

header.jsp:

<h1>Header</h1>

 

menu.jsp:

<p>Menu</p>

 

footer.jsp:

<h1>Footer page</h1>

 

contact.jsp:

<%@taglib uri=”http://www.springframework.org/tags/form&#8221; prefix=”form”%>
<html>
<head>
<title>Sample Spring MVC With Tiles Appliacation</title>
</head>
<body>
<h2>Sample Spring MVC With Tiles Appliacation</h2>
<%
System.out.println(“Contact jsp”);
%>

</body>
</html>

 

Final Output of the Application:

When ever user hits the below url in the browser, application will be loaded as mentioned in the below screenshot.

http://localhost:8080/SpringMVC/

Sample Spring MVC With Tiles framework application
Sample Spring MVC With Tiles framework application

 

To download complete application , please click on the link below : Click here

Other Useful links:

Basic Spring MVC Application

JDBC Type Driver connection for MS SQL Server


Below is the sample program to connect to MS SQL Sever using JDBC type 4 driver:

package in.javatutorials;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

/**
* @author JavaTutorials.in
*
*/
public class MSSqlDBConnection {

/**
* initialize the connection object
*/
private static Connection connection = null;

/**
* Create the database connection and return the same
*
* @return connection Connection
*/
public static Connection getDbConnection() {

// if required, below variables can be read from properties file
String username = "sqlusr";
String password = "sqlpasswrd";
String connStr = "jdbc:sqlserver://:1433;instanceName=SQLEXPRESS;databaseName=test";
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");

connection = DriverManager.getConnection(connStr, username,
password);
} catch (ClassNotFoundException classNotFoundExcep) {
classNotFoundExcep.printStackTrace();
} catch (SQLException sqlExcep) {
sqlExcep.printStackTrace();
}
return connection;
}

/**
* Close the connection if exists, this method can be called once
* transaction is completed, so that it will close the connection
*/
public static void closeConnection() {
if (connection != null) {
try {
connection.close();
} catch (SQLException sqlExcep) {
sqlExcep.printStackTrace();
}
}
}

public static void main(String[] args) {
System.out.println("Print the Database conn object : "
+ getDbConnection());
}
}