JavaServer Page by Antonio Ko

Overview ► Introduction ► What is a servlet? ► What can servlets do? ► Servlets Vs JSP ► Syntax ► Samples ► JavaBean ► Tag Library ► Conclusion

Introduction ► Java Server Pages (JSP) is basically Sun's answer to Microsoft's Active Server Pages (ASP). ► Advantages over other technologies:  It is in Java  No tied to a particular server product ► JSP is actually based on Java Servlet

What is Servlet ► Java’s answer to the Common Gateway Interface (CGI). ► Applet: a java program that runs within the web browser. ► Servlet: a java program that runs within the web server.

What can Servlets do  Search Engines  Personalization Systems  E-Commerce Applications  Shopping Carts  Product Catalogs  Intranet Applications  Groupware Applications: bulletin boards, file sharing, etc.

Servlets vs JSP  Servlets  code looks like a regular Java program.  JSP  embed Java commands directly within HTML  Let’s examine a Servlet program next to a JSP program…  Each of these prints, “Hello, World!”

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloWorld extends HttpServlet { public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType("text/html"); PrintWriter out = res.getWriter(); out.println(" "); out.println(" Hello World "); out.println(" "); out.println(" Hello World "); out.println(" "); }

Hello, World JSP Example Hello, World! The current time in milliseconds is

Syntax ► Three main types of JSP constructs embed in a HTML page:  Scripting elements  Directives  actions

Scripting Element ► Three forms available: 1., for output 2., for a block of Java code 3., for declaration

Directives ► A JSP directive affects the overall structure of the servlet that results from the JSP page. ► Syntax: ► Syntax: ► Three types of directives: 1.page 2.include 3.taglib

Action ► JSP actions are XML tags that invoke built-in web server functionality.  e.g. <jsp:setProperty name = “myBean” property = “message” value = “This is my message” />

Sample1 Untitled Document

Sample2 Untitled Document Have a nice day Have a lousy day

Sample 3 <%! Date theDate = new Date(); Date getDate() { System.out.println( "In getDate() method" ); return theDate; } %> Hello! The time is now

JavaBean ► An object that holds data with setter and getter methods. ► Can be used to store data through out the session. public class SimpleBean { private String message = "No message specified"; public String getMessage() { return(message); } public void setMessage(String message) { this.message = message; }

Tag Library ► One of the features of JSP ► Simplify complex server-side behavior into simple elements ► Creates custom JSP tags into a library. ► Each tag library has a tag library descriptor  TLD describes each tag information ► Hide underlying implementation

Tag Example Get Name and Course with DropList tag

// This is myTagExample.java package tony; import javax.servlet.jsp.JspException; import javax.servlet.jsp.tagext.SimpleTagSupport; import java.io.IOException; /** * SimpleTag handler that prints "Hello, world!" * SimpleTag handler that prints "Hello, world!" */ */ public class myTagExample.java extends SimpleTagSupport { protected String name=""; protected String name=""; protected String lastName=""; protected String lastName=""; public void doTag() throws JspException, IOException { public void doTag() throws JspException, IOException { getJspContext().getOut().write(name+ " :Hello world: “ +lastName); getJspContext().getOut().write(name+ " :Hello world: “ +lastName); } public void setName(String name){ public void setName(String name){ this.name = name; this.name = name; } public void setLname(String lname){ public void setLname(String lname){ this.lastName = lname; this.lastName = lname; }}

Tag Library Descriptor <tag><name>tagExample</name> tony.myTagExample tony.myTagExample EMPTY EMPTY perform name name true true lname lname true true

Conclusion