pseudo code
service(..){
//httpclient get http://www.facebook.com
}
the above is pseudo code for java servlet, when user call this servlet service(..) from browser repeatly
for instance
1. call http://localhost:8080/callService?url=facebook.com/index.php
2. call http://localhost:8080/callService?url=facebook.com/editprofile.php
can these subsequent request using the same "session" ?
Checkout HttpState class to handle cookie and session. Here is the sample code.
Related
I want to send values from jsp1.jsp to jsp2.jsp but redirect jsp1.jsp to jsp3.jsp . I used the following code in servlet for jsp1
response.sendRedirect("welcome1.jsp");
request.setAttribute("usern",user);
RequestDispatcher rd = request.getRequestDispatcher("afterlogin.jsp");
rd.forward(request,response);
but it keeps on giving this error "org.apache.jasper.JasperException: PWC6033: Error in Javac compilation for JSP".
you can use the possiblites of sessions in those case so you can access the parameter in jsp2 and redirect the jsp 1 to 3
https://www.javatpoint.com/servlet-http-session-login-and-logout-example
http://java.candidjava.com/tutorial/Servlet-Jsp-HttpSession-Login-logout-example.htm
You can use a HttpSession object as a user session, or use the ServletContext object for sharing global application information. Then use methods getAttribute (String attb) and setAttribute (String attb, String value) for sharing information within JSPs. The issue when you use a request is that the domain of the request is constraining you to use this information only when you receive this request.
You can also use JavaBeans to share information within JSPs
EDIT: Have you included your Java code inside a scriptlet? Using <% your code here %>
when you are using the sendRedirect function it will immediately redirect to that page it will not read next line code.
So according to your code your compiler is smart enough to check it so it is giving you an error.
please see below
1) SendRedirect ():
This method is declared in HttpServletResponse Interface.
Signature: void sendRedirect(String url)
1)In case of sendRedirect request is transfer to another resource to different domain or different server for further processing.
2)When you use SendRedirect container transfers the request to client or browser so URL given inside the sendRedirect method is visible as a new request to the client.
3)In case of SendRedirect call old request and response object is lost because it’s treated as new request by the browser.
4)SendRedirect is slower because one extra round trip is required because completely new request is created and old request object is lost.Two browser request required.
5)But in sendRedirect if we want to use we have to store the data in session or pass along with the URL.
2) Forward():
This method is declared in RequestDispatcher Interface.
Signature: forward(ServletRequest request, ServletResponse response)
1)When we use forward method request is transfer to other resource within the same server for further processing.
2)In case of forward Web container handle all process internally and client or browser is not involved.
3)When forward is called on requestdispather object we pass request and response object so our old request object is present on new resource which is going to process our request
4)Using forward () method is faster then send redirect.
5)When we redirect using forward and we want to use same data in new resource we can use request. setAttribute() as we have request object available.
more in : https://www.javatpoint.com/q/3577/difference-between-requestdispatcher-and-sendredirect
I'm working with servlets in java; I'm trying to forward from one servlet to another servlet.
I also want to pass an attribute to that other servlet.
When i want to forward to a JSP, it works fine. i do
request.setAttribute("attrName", attribute)
request.getRequestDispatcher("forward.jsp").forward(request, response);
But When I do the same with a servlet:
request.setAttribute("attrName", attribute)
request.getRequestDispatcher("TheServlet").forward(request, response);
My server freaks out and I get the following error:
javax.servlet.ServletRequestWrapper.isAsyncStarted(ServletRequestWrapper.java:395)
I know I can use the following line to redirect to a servlet:
response.sendRedirect("TheServlet");
But for some reason the set Attribute doesn't work when I redirect instead of forward.
redirect is a HTTP response sent to the browser requesting it to submit a new request to the specified URL. Since it results in issuing an entirely new request previous request attributes you set wont be available in the new request.
In terms of forwarding to a servlet, did you check your web.xml configuration. Is it setup so that the forwarded servlet is seeing forwarded requests ?
You could save the attribute to the session in the first servlet and access it from the second.
Use http://docs.oracle.com/javaee/6/api/javax/servlet/http/HttpServletRequest.html#getSession()
Also you could pass the attribute value in the URL query string in the redirect. So your redirect URL would look like 'myRedirectUrl?attributeName=attributeValue'
Also additionally try using 'include' method rather than 'forward'.
i am new to service and java.i will explain my workflow.
Client will call one synchronous service to service 1. service 1 do some operation and will delegate the session to service 2.then service 1 become free and ready to do some other work.service 2 do some operation and response back to client. is this possible like delegate the work to some other service and reply back to client. below Diagram makes you more clear.
in servlet we can redirect the response (response.sendredirect(url)) to some url like service or html page.but i think that response just redirect to some different url not the session right. so i want to know whether above workflow is possible ? if its possible please give some piece of code or ref link .
You can use RequestDispatcher class to forward the request to service 2;
RequestDispatcher rd = context_object.getRequestDispatcher('url to service 2');
rd.forward(request, response);
Inside service 2, you can use
request_object.getSession();
to get the original session object
Hi I was just curious when is the doPut() method in a servlet called. I know that if the form on a jsp/html page has a "post" method then the doPost() is called otherwise if it has a "GET" then the doGet() is called.When is the doPut() called ??
When an HTTP PUT request is received, naturally.
Can a page do a PUT request by code?
The only valid method attribute values of a <form> are get and post, according to the HTML5 spec. I assume that's what you're asking.
The doPut() method handles requests send by using the HTTP PUT method. The PUT method allows a client to store information on the server. For an example, you can use it to post an image file to the server. As the above answer says, goGet() and doPost() are in use, mostly. In my case, I use only these two, and I am getting only get requests, so I simply transfer the get request to doPost() and do my job easily.
if you want to send some confidential values in url via form you must use the post method, If you will use the get method for the form like login the values parameters like userid and password will be visible in url and anyone can hack that thing. So better to use post method in forms. By default it will call get method.
in get the url is like http://url?method=methodname&userid=123&password=123
so if you use post method the url will be like this http://url/methodname.do
How is it possible to call doGet() method from RequestDispatcher?
RequestDispatcher rd = sc.getRequestDispatcher("/CartServlet");
rd.forward(request, response);
This code calls doPost() as the default action.
It calls doPost() because your original request used POST method.
Generally servlets cannot "call" each other. They just can forward or redirect request. In both cases the same HTTP method that was used in original request is used.
If you want to call doGet() of other servlet it is the time to refactor your application, i.e. separate the logic implemented in doGet(), put it to other class and call this class from both servlets.
Check out below link, using HttpURLConnection to send request internally by POST or GET methods. I had felt the need for this for a long long time.
Java - sending HTTP parameters via POST method easily