J2EE Archives - Coddicted

Servlet’s Life…

Apr

15

2013

Initializing… When the Web Container is started the container loads the servlet class and create the instance of the servlet. The container calls the no-argument init() method (called only once) on the servlet instance after the servlet instance is created but before the servlet can service any request. Servicing… 1. When a user clicks a ...

Servlet’s Life moment Listeners

Apr

15

2013

Scenario Listener interface Event type You want to know if an attribute in a web app context has been added, removed, or replaced. javax.servlet.ServletContextAttributeListener attributeAdded attributeRemoved attributeReplaced ServletContextAttributeEvent You want to know how many concurrent users there are. In other words, you want to track the active sessions. (We cover sessions in detail in the ...

RequestProcessor Class

Apr

15

2013

RequestProcessor Class is the actual place where the request processing takes place in a Struts controller environmentStruts Documentation When the request object first reaches the actionservlet class ,it invokes the process method of the underlying RequestProcessor Class. This process method then looks into the struts-config.xml file and tries to locate the name of the action that has come with ...

RequestDispatcher

Apr

15

2013

A RequestDispatcher object can forward a client’s request to a resource or include the resource itself in the response back to the client. A resource can be another servlet, or an HTML file, or a JSP file, etc. You can also think of a RequestDispatcher object as a wrapper for the resource located at a given path ...

JSP include standard action and include directive

Apr

15

2013

S.No. include directive JSP include <jsp:include page="..." ></jsp:include>.......... 1. Content of the file specified in the attribute “file” of the include directive will be pasted as it is at tranlation time , where include directive is used in the jsp At runtime, the includED file will be executed and the response will be included in the includING ...

Jsp Implicit Objects and EL implicit Variables

Apr

15

2013

Jsp Implicit Objects EL Implicit Variables 1. JspWriter out 2. HttpServletRequest request 3. HttpServletResponse response 4. HttpSession session 5. ServletContext application 6. Servlet config 7. Throwable exception 8. PageContext pageContext 9. Object page 1. cookie 2. pageContext 3. header 4. headerValues 5. param 6. paramValues 7. initParam 8. applicationScope 9. requestScope 10. sessionScope 11. pageScope

Invalid Statements

Apr

15

2013

1. Using the method isUserInRole(), overrides any declarative authorization related to method in which it is invoked – isUserInRole() method itself doesn’t do any authorization. 2. name - value attribute is mandatory for 3. Benefits of the JSP precompilation is , it avoids initialization on the first request. 4. java.lang.Error /error.html - valid value ...

forward and sendRedirect

Apr

5

2013

Whenever there is a request from the client (or browser) to the server, the server container creates two objects 1. request 2. response and pass these objects to the servlet along with other parameters if needed. S.No. RequestDispatcher.forward HttpServletResponse.sendRedirect 1. the request is forwarded to other resource(say B) in the same context, B does some ...

flushing buffer means?

Apr

5

2013

Flushing means the data processed so far can go to the client even if the rest of the page isn’t done yet. It’s useful when you have a lot of data to send like in a download. flush=true : means send to client flush=false : means wait.

Attributes and Parameters in Servlets

Apr

5

2013

Attributes Parameters Types 1. Application/context 2. Request 3. Session 1. Application/context init parameters 2. Request parameters 3. Servlet init parameters Method to set setAttribute(String name, Object value) You CANNOT set Application and Servlet init parameters—they’re set in the DD, Return type Object String Method to get getAttribute(String name) return type of the method is Object getInitParameter(String name) ...