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Java servlet technology

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Minal Maniar
Minal Maniar

This document provides an introduction to Java servlet technology. It discusses how servlets address limitations of CGI scripts by providing a portable way to generate dynamic web content from the server side using Java. Key topics covered include the servlet interface, lifecycle, and advantages over CGI such as improved performance and portability. Configuration and use of servlets within Eclipse and Tomcat are also explained.

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JAVA SERVLETTECHNOLOGY PREPARED BY: MINAL MANIAR,ASSISTANT PROFESSOR, CSPIT, CHARUSAT
INTRODUCTION  Shortly after the Web began to be used for delivering services, service providers recognized the need for dynamic content.  Applets, one of the earliest attempts toward this goal.  At the same time, developers also investigated using the server platform for the same purpose. Initially, Common Gateway Interface (CGI) server-side scripts were the main technology used to generate dynamic content.  Although widely used, CGI scripting technology had many shortcomings.
CGI(COMMMON GATEWAY INTERFACE)
DISADVANTAGES OF CGI TECHNOLOGY  Platform Dependent  If number of clients increases, it takes more time for sending response. – Lack of Scalability  For each request, it starts a process and Web server is limited to start processes.  It uses platform dependent language e.g. C, C++, perl.  To address these limitations, Java Servlet technology was created as a portable way to provide dynamic, user-oriented content.
INTRODUCTION TO SERVLET
JAVA SERVLETTECHNOLOGY  Servlet technology is used to create web application (resides at server side and generates dynamic web page).  Servlet can be described in many ways, depending on the context.  Servlet is a technology i.e. used to create web application.  Servlet is an API that provides many interfaces and classes including documentations.  Servlet is an interface that must be implemented for creating any servlet.  Servlet is a class that extends the capabilities of the servers and responds to the incoming requests. It can respond to any type of requests.  Servlet is a web component that is deployed on the server to create dynamic web page.
WHAT IS A SERVLET ?  “A servlet is a Java programming language class used to extend the capabilities of servers that host applications accessed by means of a request-response programming model.”  Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by web servers. For such applications, Java Servlet technology defines HTTP-specific servlet classes.
WHAT IS A SERVLET ?  javax .servlet and javax.servlet.http packages provide interfaces and classes for writing Servlet  All Servlets must implement the Servlet interface, which defines lifecycle methods.  Javax.servlet package contains many interfaces and classes that are used by the servlet or web container.  javax.servlet.http package contains interfaces and classes that are responsible for http requests only.
ADVANTAGES OF SERVLET OVER CGI  Better Performance  Portability  Robust  Secure
WEB TERMINOLOGY  Website – Static and Dynamic  HTTP, HTTP Request  GET, POST  Servlet Container  Web Server and Application Server
SERVLET CONTAINER  The Servlet Container performs many operations that are given below:  Life Cycle Management  Multithreaded support  Object Pooling  Security
WEB SERVER  Web server contains only web or servlet container. It can be used for servlet, jsp, struts, jsf etc. It can't be used for EJB.  It is a computer where the web content can be stored.  web server can be used to host the web sites but there also used some other web servers also such as FTP, email, storage, gaming etc.  Examples of Web Servers are: ApacheTomcat, IIS  It can respond to the client request in either of the following two possible ways:  Generating response by using the script and communicating with database.  Sending file to the client associated with the requested URL.
ENVIRONMENT SETUP - ECLIPSE  Configure dynamic Web Project in Eclipse IDE  Set up Apache Tomcat Server instance in Eclipse IDE  Set up build path of project; add all Servlet and JSP Libraries (Add Library – servlet- api.jar)  Add JDBC driver JAR for MySQL – Paste Under Lib folder of your workspace and Add JAR from Properties  https://dev.mysql.com/downloads/connector/j/5.1.html  Deploy and run the Project on the Server – Right click Run As Server  WAR file - tomcat understands onlyWAR  Deploy WAR external to Eclipse IDE
DEPLOY EXTERNAL TO ECLIPSE  Right click project and export it to generateWAR file  PutWAR file inTomcat – webapps folder to deploy your project  Go to <Tomcat_Home>bin in command prompt  Start Server : startup.bat
ALTERNATIVESTO SETUP APPLICATION  Maven or Gradle – Set up the entire project structure and configure build path with all necessary Library  JBoss,WebLogic, GlassFish or ant Java EE – Compliant contianers/servers for hosting the application  Ask build tool itself to deploy and run the project on server  NetBeans or IntelliJ IDE for development  Any other relational database
PROJECT APPLICATION SETUP  Implements Model->View-> Controller(MVC) architecture  View – JSP or HTML files  Controller – Servlet classes that intercept request and prepare response  Model – data access object (DAO) classes that talk to the database  Copy css , html and images folder under Web Content in your project
PROJECT APPLICATION SETUP : DATABASE SETUP FOR APPLICATION  Schema name of your choice – hplus  MySQL database server  Following tables have been used:  Users – to store all user information  Products – to store all product related information  Orders - to store order history of a particular user  hplus.sql :You can import – run this script in MySQL server
TYPES OF HTTP REQUEST GET – gets information from server:Idempotent – Wouldn’t change anything on server side if request is sent out multiple times POST – processes information on server PUT – Uploads a resource on server DELETE - deletes a resource on server HEAD – same as GET , but returns only the headers OPTIONS – helps trace what HTTP methods work on server
FORWARDING IN SERVLET  The RequestDispatcher interface provides the facility of dispatching the request to another resource it may be html, servlet or jsp.  This interface can also be used to include the content of another resource also.  There are two methods defined in the RequestDispatcher interface.
FORWARD() METHOD  Response of second servlet is sent to the client. Response of the first servlet is not displayed to the user.
FORWARD() METHOD  Response of second servlet is included in the response of the first servlet that is being sent to the client.
SEND REDIRECT IN SERVLET  This method is used to redirect response to another resource,  It may be servlet  JSP or  html file.  This interface can also be used to include the content of another resource.
FORWARD()VS SENDREDIRECT()  comparison
SERVLETCONFIG INTERFACE  An object of ServletConfig is created by the web container for each servlet.  This object can be used to get configuration information from web.xml file.  The core advantage of ServletConfig is that you don't need to edit the servlet file if information is modified from the web.xml file.  public ServletConfig getServletConfig(); //syntax
SERVLETCONFIG INTERFACE  ServletConfig config=getServletConfig();
EXAMPLE OF SERVLETCONFIG TO GET INITIALIZATION PARAMETER
WEB.XML
EXAMPLE OF SERVLETCONFIG TO GET ALL THE INITIALIZATION PARAMETERS
SERVLETCONTEXT INTERFACE  An object of ServletContext is created by the web container at time of deploying the project.  This object can be used to get configuration information from web.xml file.  There is only one ServletContext object per web application.  If any information is shared to many servlet, it is better to provide it from the web.xml file using the <context-param> element.  The object of ServletContext provides an interface between the container and servlet.  The ServletContext object can be used to get configuration information from the web.xml file.  The ServletContext object can be used to set, get or remove attribute from the web.xml file.  The ServletContext object can be used to provide inter-application communication.
TO GET THE OBJECT OF SERVLETCONTEXT INTERFACE  getServletContext() method of ServletConfig interface returns the object of ServletContext.  getServletContext() method of GenericServlet class returns the object of ServletContext.  Examples  //We can get the ServletContext object from ServletConfig object  ServletContext application=getServletConfig().getServletContext();  //Another convenient way to get the ServletContext object  ServletContext application=getServletContext();
EXAMPLE OF SERVLETCONTEXT TO GETTHE INITIALIZATION PARAMETER Web.xml
COMPARISON
COMPARISON
REFERENCES  https://docs.oracle.com/javaee/7/tutorial/  https://www.java4s.com  https://www.lynda.com  https://javarevisited.blogspot.com  https://www.javatpoint.com/

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Java servlet technology

  • 1. JAVA SERVLETTECHNOLOGY PREPARED BY: MINAL MANIAR,ASSISTANT PROFESSOR, CSPIT, CHARUSAT
  • 2. INTRODUCTION  Shortly after the Web began to be used for delivering services, service providers recognized the need for dynamic content.  Applets, one of the earliest attempts toward this goal.  At the same time, developers also investigated using the server platform for the same purpose. Initially, Common Gateway Interface (CGI) server-side scripts were the main technology used to generate dynamic content.  Although widely used, CGI scripting technology had many shortcomings.
  • 4. DISADVANTAGES OF CGI TECHNOLOGY  Platform Dependent  If number of clients increases, it takes more time for sending response. – Lack of Scalability  For each request, it starts a process and Web server is limited to start processes.  It uses platform dependent language e.g. C, C++, perl.  To address these limitations, Java Servlet technology was created as a portable way to provide dynamic, user-oriented content.
  • 6. JAVA SERVLETTECHNOLOGY  Servlet technology is used to create web application (resides at server side and generates dynamic web page).  Servlet can be described in many ways, depending on the context.  Servlet is a technology i.e. used to create web application.  Servlet is an API that provides many interfaces and classes including documentations.  Servlet is an interface that must be implemented for creating any servlet.  Servlet is a class that extends the capabilities of the servers and responds to the incoming requests. It can respond to any type of requests.  Servlet is a web component that is deployed on the server to create dynamic web page.
  • 7. WHAT IS A SERVLET ?  “A servlet is a Java programming language class used to extend the capabilities of servers that host applications accessed by means of a request-response programming model.”  Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by web servers. For such applications, Java Servlet technology defines HTTP-specific servlet classes.
  • 8. WHAT IS A SERVLET ?  javax .servlet and javax.servlet.http packages provide interfaces and classes for writing Servlet  All Servlets must implement the Servlet interface, which defines lifecycle methods.  Javax.servlet package contains many interfaces and classes that are used by the servlet or web container.  javax.servlet.http package contains interfaces and classes that are responsible for http requests only.
  • 9. ADVANTAGES OF SERVLET OVER CGI  Better Performance  Portability  Robust  Secure
  • 10. WEB TERMINOLOGY  Website – Static and Dynamic  HTTP, HTTP Request  GET, POST  Servlet Container  Web Server and Application Server
  • 11. SERVLET CONTAINER  The Servlet Container performs many operations that are given below:  Life Cycle Management  Multithreaded support  Object Pooling  Security
  • 12. WEB SERVER  Web server contains only web or servlet container. It can be used for servlet, jsp, struts, jsf etc. It can't be used for EJB.  It is a computer where the web content can be stored.  web server can be used to host the web sites but there also used some other web servers also such as FTP, email, storage, gaming etc.  Examples of Web Servers are: ApacheTomcat, IIS  It can respond to the client request in either of the following two possible ways:  Generating response by using the script and communicating with database.  Sending file to the client associated with the requested URL.
  • 13. ENVIRONMENT SETUP - ECLIPSE  Configure dynamic Web Project in Eclipse IDE  Set up Apache Tomcat Server instance in Eclipse IDE  Set up build path of project; add all Servlet and JSP Libraries (Add Library – servlet- api.jar)  Add JDBC driver JAR for MySQL – Paste Under Lib folder of your workspace and Add JAR from Properties  https://dev.mysql.com/downloads/connector/j/5.1.html  Deploy and run the Project on the Server – Right click Run As Server  WAR file - tomcat understands onlyWAR  Deploy WAR external to Eclipse IDE
  • 14. DEPLOY EXTERNAL TO ECLIPSE  Right click project and export it to generateWAR file  PutWAR file inTomcat – webapps folder to deploy your project  Go to <Tomcat_Home>bin in command prompt  Start Server : startup.bat
  • 15. ALTERNATIVESTO SETUP APPLICATION  Maven or Gradle – Set up the entire project structure and configure build path with all necessary Library  JBoss,WebLogic, GlassFish or ant Java EE – Compliant contianers/servers for hosting the application  Ask build tool itself to deploy and run the project on server  NetBeans or IntelliJ IDE for development  Any other relational database
  • 16. PROJECT APPLICATION SETUP  Implements Model->View-> Controller(MVC) architecture  View – JSP or HTML files  Controller – Servlet classes that intercept request and prepare response  Model – data access object (DAO) classes that talk to the database  Copy css , html and images folder under Web Content in your project
  • 17. PROJECT APPLICATION SETUP : DATABASE SETUP FOR APPLICATION  Schema name of your choice – hplus  MySQL database server  Following tables have been used:  Users – to store all user information  Products – to store all product related information  Orders - to store order history of a particular user  hplus.sql :You can import – run this script in MySQL server
  • 18. TYPES OF HTTP REQUEST GET – gets information from server:Idempotent – Wouldn’t change anything on server side if request is sent out multiple times POST – processes information on server PUT – Uploads a resource on server DELETE - deletes a resource on server HEAD – same as GET , but returns only the headers OPTIONS – helps trace what HTTP methods work on server
  • 19. FORWARDING IN SERVLET  The RequestDispatcher interface provides the facility of dispatching the request to another resource it may be html, servlet or jsp.  This interface can also be used to include the content of another resource also.  There are two methods defined in the RequestDispatcher interface.
  • 20. FORWARD() METHOD  Response of second servlet is sent to the client. Response of the first servlet is not displayed to the user.
  • 21. FORWARD() METHOD  Response of second servlet is included in the response of the first servlet that is being sent to the client.
  • 22. SEND REDIRECT IN SERVLET  This method is used to redirect response to another resource,  It may be servlet  JSP or  html file.  This interface can also be used to include the content of another resource.
  • 24. SERVLETCONFIG INTERFACE  An object of ServletConfig is created by the web container for each servlet.  This object can be used to get configuration information from web.xml file.  The core advantage of ServletConfig is that you don't need to edit the servlet file if information is modified from the web.xml file.  public ServletConfig getServletConfig(); //syntax
  • 25. SERVLETCONFIG INTERFACE  ServletConfig config=getServletConfig();
  • 26. EXAMPLE OF SERVLETCONFIG TO GET INITIALIZATION PARAMETER
  • 28. EXAMPLE OF SERVLETCONFIG TO GET ALL THE INITIALIZATION PARAMETERS
  • 29. SERVLETCONTEXT INTERFACE  An object of ServletContext is created by the web container at time of deploying the project.  This object can be used to get configuration information from web.xml file.  There is only one ServletContext object per web application.  If any information is shared to many servlet, it is better to provide it from the web.xml file using the <context-param> element.  The object of ServletContext provides an interface between the container and servlet.  The ServletContext object can be used to get configuration information from the web.xml file.  The ServletContext object can be used to set, get or remove attribute from the web.xml file.  The ServletContext object can be used to provide inter-application communication.
  • 30. TO GET THE OBJECT OF SERVLETCONTEXT INTERFACE  getServletContext() method of ServletConfig interface returns the object of ServletContext.  getServletContext() method of GenericServlet class returns the object of ServletContext.  Examples  //We can get the ServletContext object from ServletConfig object  ServletContext application=getServletConfig().getServletContext();  //Another convenient way to get the ServletContext object  ServletContext application=getServletContext();
  • 31. EXAMPLE OF SERVLETCONTEXT TO GETTHE INITIALIZATION PARAMETER Web.xml
  • 34. REFERENCES  https://docs.oracle.com/javaee/7/tutorial/  https://www.java4s.com  https://www.lynda.com  https://javarevisited.blogspot.com  https://www.javatpoint.com/