Saturday, 29 March 2014

Servlets : Webserver vs Application Server


Click here to watch in Youtube : https://www.youtube.com/watch?v=WkaLSZ888as

 Click the below Image to Enlarge
Webserver vs Application Server
See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at No comments:

    Servlets : Application Server



    Click here to watch in Youtube : https://www.youtube.com/watch?v=ntQlB2fWyE0

     Click the below Image to Enlarge
    Application Server
    Application Server
    See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at No comments:

    Servlets : ServletLifeCycle - Example

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    Understanding the Servlet Life Cycle in Java

    In Java web development, understanding the life cycle of a Servlet is fundamental. The entire life cycle of a Servlet is managed by the Servlet Container (such as Apache Tomcat) and consists of three core methods: init(), service(), and destroy().

    1. Initialization Phase: init()

    The init() method is invoked by the container strictly once when the Servlet instance is first loaded and instantiated. This phase initializes necessary resources, configurations, or database connections before handling client requests.

    2. Request Processing Phase: service()

    Once initialized, the service() method is executed multiple times—each time a client sends a request to the mapped URL pattern. It reads incoming client requests and generates dynamic responses back to the browser.

    3. Destruction Phase: destroy()

    The destroy() method is called by the container strictly once when the Servlet is taken out of service or the server is shutting down. This allows clean-up operations like closing database connections or releasing system memory.

    Related Tutorials from the Channel

    Click here to watch in Youtube : https://www.youtube.com/watch?v=6AcVTFcZkCk

    Click the below Image to Enlarge

     ServletInterface Project Dir Structure
    ServletLifeCycle - Example

     ServletsLifeCycle.java
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    import java.io.IOException;
import java.io.PrintWriter;

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

// Extend HttpServlet class
public class ServletsLifeCycle extends HttpServlet
{

  private static final long serialVersionUID = 1L;
  private int i;

  public void init() throws ServletException
  {
    System.out.println("------------------------------------------------------");
    System.out.println(" Init method is called ");
    System.out.println("------------------------------------------------------");
  }

  public void service( HttpServletRequest request, HttpServletResponse response ) throws ServletException,
                  IOException
  {
    ++i;
    System.out.println(" service method is called "+i+ " time");
    // Set response content type
    response.setContentType("text/html");

    // Actual logic goes here.
    PrintWriter out = response.getWriter();
    out.println("<h1>" + " service method is called "+i+ " time" + "</h1>");
  }

  public void destroy()
  {
    System.out.println("------------------------------------------------------");
    System.out.println(" destroy method is called ");
    System.out.println("------------------------------------------------------");
  }
}

    web.xml
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    <?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
                      http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
  version="3.0"
  metadata-complete="true">

    <display-name>ServletsLifeCycle Application</display-name>
    <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>

     <servlet>
        <servlet-name>ServletsLifeCycle</servlet-name>
        <servlet-class>ServletsLifeCycle</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>ServletsLifeCycle</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
    
</web-app>


    index.html
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    <!DOCTYPE HTML><html lang="en"><head>
<meta charset="UTF-8">
<title>ServletsLifeCycle</title>
</head>
<body>
<p>
<h3>ServletsLifeCycle</H3>
<p></p>
<ul>
<li><a href="hello">ServletsLifeCycle Test</a></li>

</ul>
</body></html>

    Environment Used

    JDK version :1.6.0_30
    Tomcat version : 7.0.50 

    To Download HelloworldApp Project Click the below link

    https://sites.google.com/site/javaee4321/servlets/ServletsLifeCycleApp.zip?attredirects=0&d=1

    See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at No comments:

    Servlets : Webserver


    Click here to watch in Youtube : https://www.youtube.com/watch?v=ZY6SO-qeb08

    Click the below Image to Enlarge
    Webserver
    Webserver
    Webserver

    See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at No comments:

    Tuesday, 25 March 2014

    Servlets : ServletConfig


    Click here to watch in Youtube : https://www.youtube.com/watch?v=cfwI_bdwQa4

     Click the below Image to Enlarge
    ServletConfig
    ServletConfig
    ServletConfig

    ServletConfig Project Dir Structure
    ServletConfig

    ServletConfigServlet.java
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    import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

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

public class ServletConfigServlet extends HttpServlet
{

  private static final long serialVersionUID = 1L;

  ServletConfig             servletConfig           = null;

  public void init( ServletConfig servletConfig )
  {
    this.servletConfig = servletConfig;
    System.out.println("\n-----------------------------------------------------");
    System.out.println("init method has been called and servlet is initialized");
    System.out.println("-----------------------------------------------------");

    System.out.println("Using 'getInitParameter(String name)' method get the value");
    String driverName = servletConfig.getInitParameter("driverName");
    System.out.println("Driver Name : " + driverName);

    System.out.println("\nUsing 'getInitParameterNames()'  method get the value");
    Enumeration<String> paramNames = servletConfig.getInitParameterNames();

    while( paramNames.hasMoreElements() )
    {
      String paramName = paramNames.nextElement();

      String value = servletConfig.getInitParameter(paramName);

      System.out.println("paramName : " + paramName + ", Value: " + value);

    }

  }

  public void doGet( HttpServletRequest request, HttpServletResponse response ) throws ServletException,
                  IOException
  {

    System.out.println("\n-----------------------------------------------------");
    System.out.println("doGet method has been called");
    System.out.println("-----------------------------------------------------");

    ServletConfig servletConfig = getServletConfig();
    System.out.println("Got servletconfig object using getServletConfig() method : " + servletConfig);
    System.out.println("Servlet Name : " + servletConfig.getServletName());
    System.out.println("ServletContext Object : " + servletConfig.getServletContext());

    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    out.print("<html><body>");
    out.print("<b>hello HTTP servlet</b>");
    out.print("</body></html>");
  }

  public void destroy()
  {
    System.out.println("-----------------------------------------------------");
    System.out.println("destroy method has been called and servlet is destroyed");
    System.out.println("-----------------------------------------------------");
  }

  public ServletConfig getServletConfig()
  {
    return servletConfig;
  }
}

    web.xml
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    <?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" metadata-complete="true" version="3.0">
  <display-name>ServletConfigServlet</display-name>
  <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>
  <servlet>
    <servlet-name>ServletConfigServlet</servlet-name>
    <servlet-class>ServletConfigServlet</servlet-class>
    
     <init-param>  
      <param-name>driverName</param-name>  
      <param-value>oracle.jdbc.driver.OracleDriver</param-value>  
    </init-param>
    
     <init-param>  
      <param-name>username</param-name>  
      <param-value>ram</param-value>  
    </init-param>
    
    <init-param>  
      <param-name>password</param-name>  
      <param-value>ram</param-value>  
    </init-param>   
    
  </servlet>
  
  <servlet-mapping>
    <servlet-name>ServletConfigServlet</servlet-name>
    <url-pattern>/servletConfig</url-pattern>
  </servlet-mapping>
</web-app>

    index.html
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    <!DOCTYPE HTML><html lang="en"><head>
<meta charset="UTF-8">
<title>ServletConfigServlet</title>
</head>
<body>
<p>
<h3>ServletConfigServlet</H3>
<p></p>
<ul>

<li><a href="servletConfig">ServletConfigServlet</a></li>

</ul>
</body></html>

    Environment Used: 

    JDK version :1.6.0_30
    Tomcat version : 7.0.50 

    To Download ServletConfigApp Project Click the below link

    https://sites.google.com/site/javaee4321/servlets/ServletConfigApp.zip?attredirects=0&d=1

    See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at 1 comment:

    Monday, 24 March 2014

    Servlets : HTTPServlet


    Click here to watch in Youtube : https://www.youtube.com/watch?v=JUFBrXOgAlk

     Click the below Image to Enlarge
    HTTPServlet

     HTTPServlet Project Dir Structure

    HTTPServlet

     HelloHttpServlet.java
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    import java.io.IOException;
import java.io.PrintWriter;

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

public class HelloHttpServlet extends HttpServlet
{

  private static final long serialVersionUID = 1L;

  ServletConfig             config           = null;

  public void init( ServletConfig config )
  {
    this.config = config;
    System.out.println("-----------------------------------------------------");
    System.out.println("init method has been called and servlet is initialized");
    System.out.println("-----------------------------------------------------");
  }

  public void doGet( HttpServletRequest request, HttpServletResponse response ) throws ServletException,
                  IOException
  {

    System.out.println("-----------------------------------------------------");
    System.out.println("doGet method has been called");
    System.out.println("-----------------------------------------------------");

    response.setContentType("text/html");

    PrintWriter out = response.getWriter();
    out.print("<html><body>");
    out.print("<b>hello HTTP servlet</b>");
    out.print("</body></html>");
  }

  public void destroy()
  {
    System.out.println("-----------------------------------------------------");
    System.out.println("destroy method has been called and servlet is destroyed");
    System.out.println("-----------------------------------------------------");
  }

}

    web.xml
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    <?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" metadata-complete="true" version="3.0">
  <display-name>HelloHttpServlet</display-name>
  <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>
  <servlet>
    <servlet-name>HelloHttpServlet</servlet-name>
    <servlet-class>HelloHttpServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>HelloHttpServlet</servlet-name>
    <url-pattern>/helloHttpServlet</url-pattern>
  </servlet-mapping>
</web-app>

    index.html
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    <!DOCTYPE HTML><html lang="en"><head>
<meta charset="UTF-8">
<title>HelloHttpServlet</title>
</head>
<body>
<p>
<h3>HelloHttpServlet</H3>
<p></p>
<ul>

<li><a href="helloHttpServlet">HelloHttpServlet</a></li>

</ul>
</body></html>

    Environment Used: 

    JDK version :1.6.0_30
    Tomcat version : 7.0.50 

    To Download HTTPServletApp Project Click the below link

    https://sites.google.com/site/javaee4321/servlets/HTTPServletApp.zip?attredirects=0&d=1 

    See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at 1 comment:

    Sunday, 23 March 2014

    Servlets : GenericServlet


    Click here to watch in Youtube : https://www.youtube.com/watch?v=ieweBKuDVe8

     Click the below Image to Enlarge
    GenericServlet

    GenericServlet Project Dir Structure
    GenericServlet
    HelloGenericServlet.java

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    import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.GenericServlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class HelloGenericServlet extends GenericServlet
{

  private static final long serialVersionUID = 1L;

  ServletConfig             config           = null;

  public void init( ServletConfig config )
  {
    this.config = config;
    System.out.println("-----------------------------------------------------");
    System.out.println("init method has been called and servlet is initialized");
    System.out.println("-----------------------------------------------------");
  }

  public void service( ServletRequest req, ServletResponse res ) throws IOException, ServletException
  {
    System.out.println("-----------------------------------------------------");
    System.out.println("service method has been called");
    System.out.println("-----------------------------------------------------");

    res.setContentType("text/html");  
      
    PrintWriter out=res.getWriter();  
    out.print("<html><body>");  
    out.print("<b>hello generic servlet</b>");  
    out.print("</body></html>");  

  }

  public void destroy()
  {
    System.out.println("-----------------------------------------------------");
    System.out.println("destroy method has been called and servlet is destroyed");
    System.out.println("-----------------------------------------------------");
  }

}

    web.xml

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    <?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" metadata-complete="true" version="3.0">
  <display-name>HelloGenericServlet</display-name>
  <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>
  <servlet>
    <servlet-name>HelloGenericServlet</servlet-name>
    <servlet-class>HelloGenericServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>HelloGenericServlet</servlet-name>
    <url-pattern>/helloGenericServlet</url-pattern>
  </servlet-mapping>
</web-app>

    index.html

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    <!DOCTYPE HTML><html lang="en"><head>
<meta charset="UTF-8">
<title>HelloGenericServlet</title>
</head>
<body>
<p>
<h3>HelloGenericServlet</H3>
<p></p>
<ul>

<li><a href="helloGenericServlet">HelloGenericServlet</a></li>

</ul>
</body></html>

    Environment Used: 

    JDK version :1.6.0_30
    Tomcat version : 7.0.50

    To Download GenericServletApp Project Click the below link

    https://sites.google.com/site/javaee4321/servlets/GenericServletApp.zip?attredirects=0&d=1 

     See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at No comments:

    Servlets : Client Server Architecture of the Internet | Client--server Model


    Click here to watch in Youtube :  https://www.youtube.com/watch?v=b5l8D3YBcdI

     Click the below Image to Enlarge
    Client Server Architecture of the Internet | Client--server Model
    Client Server Architecture of the Internet | Client--server Model

    See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at No comments:

    Servlets : Client Server Architecture | Client--server Model


    Click here to watch in Youtube :  https://www.youtube.com/watch?v=6g62gt5f0TI

     Click the below Image to Enlarge
    Client Server Architecture | Client--server Model
    See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at No comments:

    Servlets : What is Server


    Click here to watch in Youtube : https://www.youtube.com/watch?v=WovjF_nTJdY

     Click the below Image to Enlarge
    What is Server

    See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at No comments:

    Servlets : Servlet Interface


    Click here to watch in Youtube :  https://www.youtube.com/watch?v=X9AheaJGMBI

     Click the below Image to Enlarge
    Servlet Interface

    ServletInterface Project Dir Structure
    Servlet Interface

     FirstServlet.java

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    import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class FirstServlet implements Servlet
{
  ServletConfig config = null;

  public void init( ServletConfig config )
  {
    this.config = config;
    System.out.println("-----------------------------------------------------");
    System.out.println("init method has been called and servlet is initialized");
    System.out.println("-----------------------------------------------------");
  }

  public void service( ServletRequest req, ServletResponse res ) throws IOException, ServletException
  {
    System.out.println("-----------------------------------------------------");
    System.out.println("service method has been called");
    System.out.println("-----------------------------------------------------");

    res.setContentType("text/html");

    PrintWriter out = res.getWriter();
    out.print("<html><body>");
    out.print("<b>hello simple servlet</b>");
    out.print("<br>");
    out.print("<b>Servlet Info :</b> "+getServletInfo());
    out.print("<br>");
    out.print("<b>Get Servlet config object :</b> "+getServletConfig());
    
    out.print("</body></html>");

  }

  public void destroy()
  {
    System.out.println("-----------------------------------------------------");
    System.out.println("destroy method has been called and servlet is destroyed");
    System.out.println("-----------------------------------------------------");
  }

  public ServletConfig getServletConfig()
  {
    return config;
  }

  public String getServletInfo()
  {
    return "copyright 2014-01-01 version : 3.0";
  }

}

    Web.xml

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    <?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns="http://java.sun.com/xml/ns/javaee"
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
 metadata-complete="true" version="3.0">
 <display-name>Servlet Interface</display-name>
 <description>
        This is a simple web application with a source code organization
        based on the recommendations of the Application Developer's Guide.
    </description>
 <servlet>
  <servlet-name>FirstServlet</servlet-name>
  <servlet-class>FirstServlet</servlet-class>

 </servlet>
 <servlet-mapping>
  <servlet-name>FirstServlet</servlet-name>
  <url-pattern>/firstServlet</url-pattern>
 </servlet-mapping>

</web-app>

    index.html

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    <!DOCTYPE HTML><html lang="en"><head>
<meta charset="UTF-8">
<title>ServletInterface</title>
</head>
<body>
<p>
<h3>ServletInterface</H3>
<p></p>
<ul>

<li><a href="firstServlet">FirstServlet</a></li>

</ul>
</body></html>

    Environment Used:

    JDK version :1.6.0_30
    Tomcat version : 7.0.50 

    To Download ServletInterfaceApp Project Click the below link

    https://sites.google.com/site/javaee4321/servlets/ServletInterfaceApp.zip?attredirects=0&d=1 
     
    See also:

  • Servlets Tutorial
  • All Design Patterns Links
    • at 1 comment: