Advanced Java Session 6 New York University School of Continuing and Professional Studies

2 Objectives Java Servlets –BasicServlet –Accessing Form Data, HTTP Headers, CGI Variables –Cookies and Sessions Java Server Pages –Overview of Java Server Pages –Using Java Beans in JSP Integrating Java Servlets and JSP

3 Web Applications Architecture client Web server App server Backend Services such as db, quote server

4 Java Servlets Modern replacement for CGIs Server components written in Java Advantages of Servlets –Efficient –State Management –Portable –Robust –Extensible –Quick Development –Widespread Acceptance

5 Application Server Model services Servlet container servlets

6 Classes and Interfaces Servlet ServletConfig ServletContext GenericServlet ServletRequest ServletResponse HttpServlet HttpServletRequest HttpServletResponse HttpSession Cookie

7 GenericServlet Abstract class public void init() throws ServletException public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException public void destroy()

8 HttpServlet Abstract class protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException

9 BasicServlet example tomcat env javac BasicServlet.java servit BasicServlet.class tomcat start

10 Accessing Form Data String getParameter(String) Enumeration getParameterNames() ShowParameters.java

11 Accessing HTTP Headers String getMethod() String getRequestURI() String getProtocol() Enumeration getHeaderNames() ShowRequestHeader.java

12 Accessing CGI Variables String getAuthType() String getContentLength() String getContentType() ……. More complete list is in the handout. ShowCGIVariables.java

13 Generating Response setContentType() getWriter() …… More in the handout.

14 Handling Sessions Object getAttribute(String name) void setAttribute(String name, Object value) Enumeration getAttributeNames() void removeAttribute(String name) void Invalidate() ShowSession.java

15 Java Server Pages Use embedded java code in HTML files “automatically generated” servlet Part of the J2EE framework Supported by most Application Servers

16 Jsp Servlet Java Server Pages turn into a servlet Engine translates JSP into a java servlet, compiles it and executes it. HttpJspPage interface is a subclass of Servlet JSP engine provides a class that implements HttpJspPage interface _jspService method is the main entry point

17 Embedded Tags

18 Embedded Java code hello item number

19 page directives Language Import contentType errorPage Extends isErrorPage isThreadSafe Session autoFlush Buffer

20 Using Java Beans in Java Server Pages Basic Bean Use

21 Accessing Bean Properties <jsp:setProperty name=“book1” property=“title” value=“Developing Applications in J2EE”/>

22 Associating properties with HTML input parameters BookEntry example

23 Extending JSP with custom tags body text TagSupport class implements Tag BodyTagSupport class implements BodyTag Tag Library Descriptor

24 Integrating Servlets and Java Server Pages Use servlets for presentation logic User jsp for layout Jsp can also generate XML Examples: ShowPage.java ShowError.java

25 Thank you