Advance java session 20
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AJAX allows for asynchronous data retrieval and dynamic display. It uses technologies like XML, XSLT, DOM, and JavaScript. Servlet 3.0 includes annotations and methods to support asynchronous processing, allowing requests to be processed asynchronously without blocking the original thread. The AsyncContext class provides an execution context for asynchronous operations and wraps the request and response.
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Advance java session 20
- 1. AJAX
- 2. Agenda • Asynchronous web applications • Understand the interactions that are essential to asynchronous web pages • Understand the role of AJAX-style client side programming • Implement asynchronous servlets using the facilities of Java EE 6
- 3. AJAX • AJAX stands for Asynchronous Javascript and XML - It Incorporates • Standard based presentation technology using xhtml and css • Dynamic display and interaction using DOM • Data interchange and manipulation using XML and XSLT • Asynchronous data retrieval using XMLHttpRequest • And Javascript binding everything together
- 5. AJAX web application model
- 6. Asynchronous Support in JEE 6 • Servlet 3.0 Specs has included asynchronous support • Annotation Attributes - @WebServlet(url="/foo" asyncSupported=true) - @WebFilter(url="/foo" asyncSupported=true) • Normal Servlet runs in a Synchronous Context • Asynchcronous Servlet run in a Asynchronous Context
- 7. Asynchronous Support in JEE 6 • ServletRequest Methods - startAsync(ServletRequest, ServletResponse) - startAsync() - getAsyncContext() • Eg - AsyncContext aCtx= req.startAsync(req,res)
- 8. AsyncContext Class • AsyncContext class is a new Servlet 3.0 - Provides the execution context for async operation - It wraps the request and response Objects - Methods • AsyncContext.dispatch() • AsyncContext.dispatch(path) • AsyncContext.dispatch(ServletContext,path) - Using any of the above methods enables the processing to return to the container after async operation that was started
- 9. AsyncContext Class • AsyncContext class is a new Servlet 3.0 - Provides the execution context for async operation - It wraps the request and response Objects - Methods • AsyncContext.dispatch() • AsyncContext.dispatch(path) • AsyncContext.dispatch(ServletContext,path) - Using any of the above methods enables the processing to return to the container after async operation that was started
- 10. Async Servlet Example <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1> <title>Asynchronous Servlet 3.0 Example</title> </head> <body> <h3>Hi this is a demo example of Asynchronous Servlet 3.0 Example.</h3> </body> </html> <!– asyncExample.html
- 11. Async Servlet Example import java.io.IOException; import java.util.Date; import java.io.PrintWriter; import javax.servlet.AsyncContext; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; @WebServlet( urlPatterns = "/Servlet3AsyncExample“,asyncSupported=true)
- 12. Async Servlet Example public class Servlet3AsyncExample extends HttpServlet{ public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException{ Date date= new Date(); response.setContentType("text/html"); PrintWriter out= response.getWriter(); request.setAttribute("receivedAt", date); out.println(request.getAttribute("receivedAt")); AsyncContext asyncCtx = request.startAsync(); ServletRequest req = asyncCtx.getRequest(); boolean bol= req.isAsyncStarted(); //Will return true out.println("<br>AsyncStarted : "+bol);
- 13. Async Servlet Example asyncCtx.dispatch("/asyncExample.html"); boolean bol1= req.isAsyncStarted(); //Will return false out.println("<br>AsyncStarted : "+bol1); boolean bol2= req.isAsyncSupported(); //Will return true out.println("<br>AsyncSupported : "+bol2); } public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { doGet(request, response); } }
- 14. Summary • AJAX comprises multiple Technology • AJAX is extensively used in WEB 2.0 • AJAX is based on Standard technologies • AyncSupported servlet features enables us to process incoming request and response without being bound to original thread that initiated the request