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  1. 1.  Servlets are part of the Java2EE specification.  Servlets are modules that run on the server, enabling you to extend the server’s functionality.  Servlets work within a Web server environment, and they are a key component of server side  Java development. Servlets are an effective replacement for CGI scripts.
  2. 2.  Can be deployed into distributed server environments.  Servlets are platform- and server-independent.  Servlets are easy to develop and follow a standard API.  Servlets are extensible. Java Server Pages (JSP) build on top of the Servlet API.  A servlet is a server resource, providing access to other server resources, such as other servlets, EJBs, JSPs, JDBC, and so on.
  3. 3. Method Description GET The client requests information from the given URL. HEAD Similar to GET, except the body is not retrieved. POST Client adds info to URI (HTML forms) PUT Used to place documents on the Server. DELETE Client deletes resource of URI.
  4. 4. Status Code Category 100s 200s 300s 400s 500s Informational Successful Redirection Request Error Server Error
  5. 5.   The Servlet API defines a standard interface for handling request and response between the browser and the Web server. The Servlet API is composed of two packages:  javax.servlet - javax.servlet.GenericServlet  javax.servlet.http - javax.servlet.HttpServlet
  6. 6. A generic servlet handling a request
  7. 7. An HTTP servlet handling GET and POST requests
  8. 8. Can use ServletOutputStream or PrintWriter to send data back to the client. 1. reference the stream from the Response parameter: ServletOutputStream out =response.getOutputStream(); 2. get a reference to the writer from the Response parameter: PrintWriter out = response.getWriter(); 3. Then write the output to the stream: out.println(“<HTML>Inside HTML</HTML>”); 4. Finally, close the writer: out.close();
  9. 9.   MIME – Multiple Internet Mail Extension Identifies extension of each file in the HTTPResponse response.setContentType(“text/html”); PrintWriter out = response.getWriter();
  10. 10. import*; import javax.servlet.*; import javax.servlet.http.*; public class srvltJust extends HttpServlet { protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { res.setContentType(“text/html”); PrintWriter out = res.getWriter(); out.println(“<HTML>”); out.println(“<HEAD><TITLE>Servlet</TITLE></HEAD>”); out.println(“<BODY>”); out.println(“<H1>This is a just a Servlet!</H1>”); out.println(“</BODY></HTML>”); out.close();
  11. 11. Parameters  public String getParameter(String name)  public Enumeration getParameterNames()  public String[] getParameterValues(String name) Content  public int getContentLength() - returns the length, in bytes. -1 is returned if the length is not known.  getContentType() - returns the request’s MIME type of the content (null if it’s not known).  getCharacterEncoding() - returns the name character encoding style of the request.
  12. 12. Header Methods  setDateHeader()  setIntHeader()  setContentType()  setContentLength()  addCookie()  sendError()
  13. 13. Ways to manage session,  Hidden form fields  URL rewriting  Persistent cookies  Session tracking API
  14. 14. <input type=”hidden” name=”pageid” value=”5”>  public String getParameter(String name)  public Enumeration getParameterNames()  public String[] getParameterValues(String name)
  15. 15. http://myServer/servlets/srvltEmp?EMPID=1009& DEPID=200
  16. 16. API for persistent cookie is, javax.servlet.http.Cookie To create a new cookie,  Cookie cookie(String name, String value)  Eg: Cookie cookie = new Cookie("ID", "123"); To get all available cookies,  req.getCookies() To send back the cookie name  response.addCookie(cookie_name)
  17. 17.  A servlet with getSession( ) method retrieves the current HttpSession object Eg: public HttpSession HttpServletRequest.getSession(boolean )  Set properties by, public void HttpSession.setAttribute(String name, Object value) Eg: session.setAttribute(“name”, id);  Get properties by, public void HttpSession.setMaxInactiveInterval(int secs)
  18. 18.  Get current session id by, public String getId()  Whether it is a new cookie or referenced, public boolean isNew  Start of a session public long getCreationTime()  Last session activity public long getLastAccessedTime  Session invalidating by, public void invalidate()  Removing attribute by, public void removeAttribute(String name)
  19. 19. import*; import*; import java.util.*; import javax.servlet.*; import javax.servlet.http.*; public class srvltHoldAppID extends HttpServlet {public void service(HttpServletRequest req, HttpServletResponse res) throws IOException, ServletException { resp.setContentType(“text/html”); PrintWriter out = res.getWriter(); String sAPPID` = “undefined”; String[] sAPPID = req.getParameter(“APPID”); if(sAPPID != null && sAPPID.length > 0) { // Create session: HttpSession session = req.getSession(); session.setAttribute(“APPID”, sAPPID); }}}
  20. 20. ServletContext sc = this.getServletContext(); RequestDispatcher rd = sc.getRequestDispatcher(“/srvltComplete”); if (rd !=null) { try { rd.forward(req, res); } catch (Exception e) { // Handle Exception } }
  21. 21. Connection conn = null; Statement stmt = null; ResultSet rs = null; String sSQL = “……….” InitialContext ic = new InitialContext() //Get a reference to the datasource String dsName = “java:comp/env/jdbc/emplphone” DataSource ds = (DataSource) ic.lookup(dsName) conn = ds.getConnection() // Get a Connection stmt = conn.createStatement() rs = stmt.executeQuery(sSQL) while( {out.println(rs.getString(1))}