12 Important Key points about Servlet | Adv Java Servlet programming Tutorial advance java tutorial

#Key #points #about #Servlet: #Adv #Java #Servlet #programming #Tutorial #advance #java #tutorial - Our Servlet class must be public in order to make it visible to servlet-container for instantiation of life cycle methods.

- We never execute servlet program manually, because the servlet container takes care of this execution.(From birth to death)

- For every request coming to our servlet program the servlet container calls one set of request, response objects & calls service (-,-) method having these request, response objects as arguments.

- Programmer receives servlet container supplied request, response objects as parameters of service(-,-) & uses them for request processing & response generation.

- res.setContentType("text/html");
Gives instruction to browser window through web server to become ready to display html code as text based web page on the browser.

- PrintWriter pw=res.getWriter();
Gets PrintWriter stream object from Response, pointing to "res" object. "res" object contains built in stream object called PrintWriter object.

Stream object can point files/objects & can perform read/write operations on those files/objects.
PrintWriter "pw" stream object can be used to write messages to "res" object.

- pw.println("Date & Time is "+s);
pw.println(-) sends given message to "res" (Response) object. This "res" object sends received messages to web server. This web server sends received message to browser window as response connection.

(Note:- pw.println()/print() methods generated messages comes to browser window as the web page. Whereas System.out.println(-) statement generated messages goes to server console as debugging/configuration message.)

- The modification done in source code of servlet program (DateServ.java) belonging to deployed web application will be reflected only after the recompilation of the servlet program and reloading of the web application.

for Recompilation:
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J:\1-Andi-java-Classess\Java\2Servlet\1Workspace\1DateApp\WEB-INF\classes\javac DateServ.java

for Reloading:
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Tomcat homepage------Tomcat manager ----- submit username and password---- 1DateApp ---- Reload