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JavaServer Page

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).

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JavaServer Page

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  1. JavaServer Page by Antonio Ko

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

  3. 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

  4. 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.

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

  6. 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!”

  7. 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("<HTML>"); out.println("<HEAD><TITLE>Hello World</TITLE></HEAD>"); out.println("<BODY>"); out.println("<BIG>Hello World</BIG>"); out.println("</BODY></HTML>"); } }

  8. <html> <head> <title>Hello, World JSP Example</title> </head> <body> <h2> Hello, World! The current time in milliseconds is <%= System.currentTimeMillis() %> </h2> </body> </html>

  9. Syntax • Three main types of JSP constructs embed in a HTML page: • Scripting elements • Directives • actions

  10. Scripting Element • Three forms available: • <%= expression %>, for output • <% code %>, for a block of Java code • <%! code %>, for declaration

  11. Directives • A JSP directive affects the overall structure of the servlet that results from the JSP page. • Syntax: <%@ directive attribute =“value” %> • Three types of directives: • page • include • taglib

  12. 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” />

  13. Sample1 <html> <head> <title>Untitled Document</title> </head> <body> <%= "hello world"%> </body> </html>

  14. Sample2 <html> <head> <title>Untitled Document</title> </head> <body> <% if(Math.random()<0.5) {%> Have a <BR>nice<BR>day <% }else {%> Have a <BR>lousy<BR>day <%}%> </body> </html>

  15. Sample 3 <%@ page import="java.util.*" %> <HTML> <BODY> <%! Date theDate = new Date(); Date getDate() { System.out.println( "In getDate() method" ); return theDate; } %> Hello! The time is now <%= getDate() %> </BODY> </HTML>

  16. 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; } }

  17. 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

  18. Tag Example <!—TagExample --><html> <head> <title>Get Name and Course with DropList tag</title> </head> <body> <%@ taglib uri="mytags" prefix ="mytag" %> <mytag:tagExample name = "Joe " lname="Doe" /> </body> </html>

  19. // 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!" */ public class myTagExample.java extends SimpleTagSupport { protected String name=""; protected String lastName=""; public void doTag() throws JspException, IOException { getJspContext().getOut().write(name+ " :Hello world: “ +lastName); } public void setName(String name){ this.name = name; } public void setLname(String lname){ this.lastName = lname; } }

  20. Tag Library Descriptor <tag> <name>tagExample</name> <tag-class>tony.myTagExample </tag-class> <body-content>EMPTY</body-content> <description> perform </description> <attribute> <name>name</name> <required>true</required> </attribute> <attribute> <name>lname</name> <required>true</required> </attribute> </tag>

  21. Conclusion

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