Servlet.pptx
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The document discusses servlets and provides information about: - Servlets are Java programs that run on a web or application server and act as a middle layer between HTTP requests and databases or applications. - Servlets have advantages over CGI like better performance, portability, robustness, and security since they are implemented in Java. - The servlet lifecycle includes initialization via init(), processing requests via service(), and termination via destroy(). - The javax.servlet and javax.servlet.http packages contain interfaces and classes for the servlet API.
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Servlet.pptx
- 1. U18CSI6201 INTERNET & WEB PROGRAMMING SERVLETS V.SENTHIL KUMAR Department of CSE
- 2. COURSE OUTCOMES CO1: DESIGN A WEBSITE USING HTML (K5, S3) CO2: Apply Cascading Style Sheet to design a HTML Webpage (K3, S2) CO3: Develop a HTML form and validate it using Java Script (K5, S2) CO4: Develop web application using JSP, Servlet (K5, S3) CO5: Develop an XML document and validate it using SCHEMA (K5, S2)
- 3. AGENDA WHAT IS SERVLET? ADVANTAGES SERVLET ARCHITECTURE SERVLET TASKS SERVLET PACKAGE SERVLET LIFE CYCLE
- 4. What are Servlets? • Java Servlets are programs that run on a Web or Application server. • Act as a middle layer between a requests coming from a Web browser or other HTTP client and databases or applications on the HTTP server. • Implemented using the Common Gateway Interface (CGI).
- 5. Servlet
- 7. Disadvantages of CGI • There are many problems in CGI technology: 1.If the number of clients increases, it takes more time for sending the response. 2.For each request, it starts a process, and the web server is limited to start processes. 3.It uses platform dependent language e.g. C, C++, perl.
- 9. Advantages of servlet Better performance: because it creates a thread for each request, not process. Portability: because it uses Java language. Robust: JVM manages Servlets, so we don't need to worry about the memory leak, garbage collection, etc. Secure: because it uses java language.
- 10. Servlets offer several advantages • Performance is significantly better. • Servlets execute within the address space of a Web server. • Servlets are platform-independent • Java security manager on the server enforces a set of restrictions to protect the resources on a server machine. • The full functionality of the Java class libraries is available to a servlet.
- 13. Servlet Container • It provides the runtime environment for JavaEE (j2ee) applications. • The client/user can request only a static WebPages from the server. If the user wants to read the web pages as per input then the servlet container is used in java.
- 15. Servlet Container States Standalone: It is typical Java-based servers in which the servlet container and the web servers are the integral part of a single program. For example:- Tomcat running by itself In-process: It is separated from the web server, because a different program runs within the address space of the main server as a plug-in. For example:- Tomcat running inside the JBoss. Out-of-process: The web server and servlet container are different programs which are run in a different process. For performing the communications between them, web server uses the plug-in provided by the servlet container.
- 16. Server: Web vs. Application • Server is a device or a computer program that accepts and responds to the request made by other program, known as client. It is used to manage the network resources and for running the program or software that provides services. • There are two types of servers: 1.Web Server 2.Application Server
- 17. 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. In general 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: Apache Tomcat and Resin. Generating response by using the script and communicating with database. Sending file to the client associated with the requested URL.
- 18. Web Server
- 19. Application Server • Application server contains Web and EJB containers. It can be used for servlet, jsp, struts, jsf, ejb etc. It is a component based product that lies in the middle-tier of a server centric architecture. • It provides the middleware services for state maintenance and security, along with persistence and data access. It is a type of server designed to install, operate and host associated services and applications for the IT services, end users and organizations.
- 21. Servlets Tasks Read the explicit data sent by the clients (browsers). 1 Read the implicit HTTP request data sent by the clients (browsers). 2 Process the data and generate the results. 3 Send the explicit data (i.e., the document) to the clients (browsers). 4 Send the implicit HTTP response to the clients (browsers). 5
- 22. Servlet API • The javax.servlet and javax.servlet.http packages represent interfaces and classes for servlet api. • The javax.servlet package contains many interfaces and classes that are used by the servlet or web container. These are not specific to any protocol. • The javax.servlet.http package contains interfaces and classes that are responsible for http requests only.
- 27. Servlets - Life Cycle A servlet life cycle can be defined as the entire process from its creation till the destruction. The following are the paths followed by a servlet. The servlet is initialized by calling the init() method. The servlet calls service() method to process a client's request. The servlet is terminated by calling the destroy() method. Finally, servlet is garbage collected by the garbage collector of the JVM.
- 28. The init() Method • The init method is called only once. It is called only when the servlet is created, and not called for any user requests afterwards. So, it is used for one-time initializations, just as with the init method of applets.
- 29. The service() Method • The service() method is the main method to perform the actual task. The servlet container (i.e. web server) calls the service() method to handle requests coming from the client( browsers) and to write the formatted response back to the client. • The service() method checks the HTTP request type (GET, POST, PUT, DELETE, etc.) and calls doGet, doPost, doPut, doDelete, etc. methods as appropriate.
- 32. The destroy() Method • The destroy() method is called only once at the end of the life cycle of a servlet. • This method gives your servlet a chance to close database connections, halt background threads, write cookie lists or hit counts to disk, and perform other such cleanup activities.
- 34. Architecture First the HTTP requests coming to the server are delegated to the servlet container. 1 The servlet container loads the servlet before invoking the service() method. 2 Then the servlet container handles multiple requests by spawning multiple threads, each thread executing the service() method of a single instance of the servlet. 3