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Core web application development
 

Core web application development

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    Core web application development Core web application development Presentation Transcript

    • Core Web ApplicationDevelopment Using Servlet &JSPBahaa Farouk Organized By
    • Agenda• Servlet – What is Java Servlet? – Servlet Life Cycle – Client Interaction & Session• JSP – What’s JSP? – JSP Life Cycle – What’s JSP Contains? – JSP Scope & Implicit Objects• Why Servlet & JSP?
    • Web Application Development?
    • Agenda• Servlet – What is Java Servlet? – Servlet Life Cycle – Client Interaction & Session• JSP – What’s JSP? – JSP Life Cycle – What’s JSP Contains? – JSP Scope & Implicit Objects• Why Servlet & JSP?
    • What is Java Servlet?• An alternate form of server-side computation that uses Java• The Web server is extended to support an API, and then Java programs use the API to create dynamic web pages• Using Java servlets provides a platform-independent replacement for CGI scripts.• Servlets can be embedded in many different servers because the servlet API, which you use to write servlets, assumes nothing about the servers environment or protocol.
    • Servlet Life Cycle• Initialization – the servlet engine loads the servlet’s *.class file in the JVM memory space and initializes any objects• Execution – when a servlet request is made, • a ServletRequest object is sent with all information about the request • a ServletResponse object is used to return the response• Destruction – the servlet cleans up allocated resources and shuts down
    • Client Interaction• When a servlet accepts a call from a client, it receives two objects: – A ServletRequest, which encapsulates the communication from the client to the server. – A ServletResponse, which encapsulates the communication from the servlet back to the client.• ServletRequest and ServletResponse are interfaces defined by the javax.servlet package.
    • Request Header Example
    • Request Parameters
    • Cookies
    • Session Capabilities• Session tracking is a mechanism that servlets use to maintain state about a series of requests from the same user(that is, requests originating from the same browser) across some period of time.• Session tracking capabilities. The servlet writer can use these APIs to maintain state between the servlet and the client that persists across multiple connections during some time period.
    • Sessions
    • Agenda• Servlet – What is Java Servlet? – Servlet Life Cycle – Client Interaction & Session• JSP – What’s JSP? – JSP Life Cycle – What’s JSP Contains? – JSP Scope & Implicit Objects• Why Servlet & JSP?
    • What is JSP?• A Java Servlet is a Java program that is run on the server – There are Java classes for retrieving HTTP requests and returning HTTP responses – Must return an entire HTML page, so all tuning of the page must be done in a Java program that needs to be re- compiled• Java Server Pages (JSP) – use HTML and XML tags to design the page and JSP scriplet tags to generate dynamic content (Easier for separation between designer & developer) – use Java Beans and useful built-in objects for more convenience
    • JSP Life Cycle• JSP page (MyFirstJSP.jsp) – Translated to Servle (MyFirstJSP.servlet) – Compiled to class (MyFirstJSP.class) – Loaded into memory (Initialization) – Execution (repeats) – Destruction• Any change in JSP page automatically repeats the whole life cycle.
    • Introduction • A Java Servlet is a Java program that is run on the server – There are Java classes for retrieving HTTP requests and returning HTTP responses • Java Server Pages (JSP) – use HTML and XML tags to design the page and JSP scriplet tags to generate dynamic content – use Java Beans, which are reusable components that are invoked by scriplets
    • What do JSPs contain?• Template data – Everything other than elements (eg. Html tags)• Elements – based on XML syntax • <somejsptag attribute name=“atrribute value”> BODY </somejsptag> – Directives – Scripting • Declarations • Scriptles • Expressions – Standard Actions
    • Directives • <%@ directivename attribute=“value” attribute=“value” %> • The page directive – <%@ page ATTRIBUTES %> – language, import, Buffer, errorPage,… – <%@ page languange=“java” import=“java.rmi.*,java.util.*” %> • The include directive – <%@ include file=“Filename” %> – the static file name to include (included at translation time) • The taglib directive – <% taglib uri=“taglibraryURI” prefix=“tagPrefix” %>
    • Scripting(Declaration, Expressions, Scriptlets) • <%! . . %> declares variables or methods – define class-wide variables – <%! int i = 0; %> – <%! int a, b; double c: %> – <%! Circle a = new Circle(2.0); %> – You must declare a variable or method in a jsp page before you use it – The scope of a declaration is the jsp file, extending to all includes • <%= . . %> defines an expression and casts the result as a string
    • Scripting II • <%= . . %> can contain any language expression, but without a semicolon, e.g. • <%= Math.sqrt(2) %> • <%= items[I] %> • <%= a + b + c %> • <%= new java.util.Date() %> • <% . . %> can handle declarations (page scope), expressions, or any other type of code fragment • <% for(int I = 0; I < 10; I++) { out.println(“<B> Hello World: “ + I); } %>
    • JSP and Scope• Page - objects with page scope are accessible only within the page where they are created• Request - objects with request scope are accessible from pages processing the same request where they were created• Session - ojbects with session scope are accessible from pages processing requests that are in the same session as the one in which they were created• Application - objects with application scope are accessible from pages processing requests that are in the same application as the one in which they were created• All the different scopes behave as a single name space
    • Implicit Objects• These objects do not need to be declared or instantiated by the JSP author, but are provided by the container (jsp engine) in the implementation class• request Object (javax.servlet.ServletRequest)• response Object (javax.servlet.ServletResponse)• session Object (javax.servlet.http.HttpSession)• application Object• out Object• config Object• page Object• pageContext Object (javax.servlet.jsp.PageContext)• exception
    • Number guess - Browser Output
    • Agenda• Servlet – What is Java Servlet? – Servlet Life Cycle – Client Interaction & Session• JSP – What’s JSP? – JSP Life Cycle – What’s JSP Contains? – JSP Scope & Implicit Objects• Why Servlet & JSP?
    • Why Servlet/JSP?What is an Enterprise Application? • Reliable • Scalable • Maintainable • Manageable – If you are developing an Enterprise Application for whose daily transactions are millions? • Performance? Scalability? Reliability?
    • Questions ?