Can a client can explicitly destroy the servlet?

A servlet will get destroyed after its purpose is served or timed out or server was shut down. Is there any possibility for the client to destroy the servlet explicity?

Not really no. Why would you want to? A servlet object is maybe 16 or 32 bytes of memory (unless you are putting fields in it, which is usually a no-no.) Or do you mean unmap the servlet so it is no longer accessible?

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How can I get the servlet Context from a WebService Implementation?

I have made a webservice endpoint, using the conventional way (WSDL->wsimport->Java interface->implementation) . I need to get the servlet context below the implementation class. I haven't found any way to get the servletContext though. Any clues? Any help will be greatly appreciated.

yes i can found the words's unicode form Cmaps where may be at the type of tounicde and another Cmaps table just like "Adobe-GB1-GBK-EUC" ,but when the word dont have either of them how can i do? when i write a chinese word "一",it just the winansi encoding , there is not Cmap for me to use to change the "G208f" to the word "一"'s unicode value.
best wishes thank you very much

Can't find the servlets package when compiling

Hi,
My problem is that when I compiling my servlets so can't the compiler find the two packages javax.servlet and javax.servlet.http.
Why?
Please can someone help me with this problem!
HelloServlet.java:2: package javax.servlet does not exist
import javax.servlet.*;
^
HelloServlet.java:3: package javax.servlet.http does not exist
import javax.servlet.http.*;

OK,
It seems like it will work with your proposal to. But now I have a new problem that you maybe can solve for me. That is when I try to test the following (from the book More Servlets and JavaServer Pages):
Test 3: A Servlet That Uses Packages and Utilities
The final servlet you should test to verify the configuration of your server and development environment is one that uses both packages and utility classes. HelloServlet3.java is a servlet in the moreservlets package that uses the ServletUtilities class to simplify the generation of the DOCTYPE (specifies the HTML version--useful when using HTML validators) and HEAD (specifies the title) portions of the HTML page. Those two parts of the page are useful (technically required, in fact), but are tedious to generate with servlet println statements.
Since both the servlet and the utility class are in the moreservlets package, they should go in the moreservlets directory. If you get compilation errors, go back and check your CLASSPATH settings--you most likely forgot to include the top-level development directory. I've said it before, but I'll say it again: your CLASSPATH must include the top-level directory of your package hierarchy before you can compile a packaged class that makes use of another class from the same package. This requirement is not particular to servlets; it is the way packages work on the Java platform in general. Nevertheless, many servlet developers are unaware of this fact, and it is one of the (perhaps the) most common errors beginning developers encounter.
Once you compile HelloServlet3.java (which will automatically cause ServletUtilities.java to be compiled), put HelloServlet3.class and ServletUtilities.class in install_dir/webapps/ROOT/WEB-INF/classes/moreservlets. Then, access the servlet with the URL http://localhost/servlet/moreservlets.HelloServlet3. You should get a simple HTML page that says "Hello (3)".
This works not for me! I will get this message when I try to compile HelloServlet3.java:
C:\Apache-Tomcat-4.1.27\ServletsDevel>javac HelloServlet3.java
HelloServlet3.java:23: cannot resolve symbol
symbol : variable ServletUtilities
location: class moreservlets.HelloServlet3
out.println(ServletUtilities.headWithTitle(title) +
^
1 error
Do you know what the problem is?

How can i do the servlet to servlet communicaion usingservlet context

public void doGet(HttpServletRequest request, HttpServletResponse response)
               throws ServletException, IOException {
          response.setContentType("text/html");
          //ServletContext context = null;
          PrintWriter out = response.getWriter();
          RequestDispatcher rd=request.getRequestDispatcher("/second");
          rd.forward(request,response);
          out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
          out.println("<HTML>");
          out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
          out.println(" <BODY>");
          /*out.print(" This is ");
          out.print(this.getClass());
          out.println(", using the GET method");*/
          out.println(" </BODY>");
          out.println("</HTML>");
          out.flush();
          out.close();
Here I have used request.getRequestDispatcher("/second ").. it wil cal the second servlet...
But how can i cal the second servlet using context.requestDispatcher(" ") inside the paranthesis what i wil give?
plz some one help me..

request.getRequestDispatcher("/second ") is the same as context.requestDispatcher("/second ") .
The requestDispatcher from the request object can take a relative path but if the path starts with a '/' it is interpreted as relative to the context root. The RequestDispatcher from the context can only take paths that start with '/' and are relative to the context root.
http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletRequest.html#getRequestDispatcher(java.lang.String)

Tomcat can't find the servlets!

Hi!
I've just installed tomcat tomcat-5.5.16 with apache. Tomcat runs ok. It shows some samples (delivered with tomcat) under www.mywebsite.com/servlets-example and also www.mywebsite.com/jsp-examples. JSP files work perfectly, but when I try the servlets it can't find them:
www.mywebsite.com/servlets-examples/servlet/RequestHeaderExample Object not found!my classpath lokks like this:
/opt/SUNWappserver/jdk/lib:/opt/apache-tomcat/common/lib/servlet-api.jar:/opt/apache-tomcat/bin:/opt/apache-tomcat/webapps/servlets-examples/WEB-INF/classes:/opt/apache-tomcat/webapps/ROOT/WEB-INF/classesand web.xml looks like this:
    <servlet>
        <servlet-name>invoker</servlet-name>
        <servlet-class>
          org.apache.catalina.servlets.InvokerServlet
        </servlet-class>
        <init-param>
            <param-name>debug</param-name>
            <param-value>0</param-value>
        </init-param>
        <load-on-startup>2</load-on-startup>
    </servlet>and
    
    <servlet-mapping>
        <servlet-name>default</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    
    <servlet-mapping>
        <servlet-name>invoker</servlet-name>
        <url-pattern>/servlet/*</url-pattern>
    </servlet-mapping>I changed the web.xml und conf and under WEB-INF.
I also changed server.xml to make tomcat work with apache on port 80.
What did I do wrong? What did I forget?
What is the difference between web.xml under conf and the ones under WEB-INF?
Thanks for any help.

opt/SUNWappserver/jdk/lib:/opt/apache-tomcat/common/lib/servlet-api.jar:/opt/apache-tomcat/bin:/opt/apache-tomcat/webapps/servlets-examples/WEB-INF/classes:/opt/apache-tomcat/webapps/ROOT/WEB-INF/classes
May be ur classpath will be wrong try the classpath like this
;C:\Tomcat5\common\lib\servlet-api.jar;C:\Tomcat5\common\lib\jsp-api.jar;C:\Tomcat5\common\lib\log4j-1.2.9.jar;C:\Tomcat5\common\lib\mysql-connector-java-3.1.8-bin.jar;hello
Check out all the enteries in the web-xml file and the path in the environment variable i your system.

Can I run the Servlet and Bean code on Sun ONE Webserver 6.1 SP5

Hi all.
My environment as below.
1) Windows 2000 Server SP4
2) Sun ONE Webserver 6.1 SP5
3) JRE1.5.0
The directory ( WEB-INF/classes) where is to create on. I have a Bean and Servlet code but I can't
to run it on. Another code Jsp, HTML can run.
How can I do?

Your question is somewhat vague, but I'll presume that you are asking how you can invoke your servlets.
If the servlet classes are correctly deployed, you can invoke them directly. i.e. http://host/<app>/servlet/<classname>. Or, you can create servlet mappings.
Java beans cannot be invoked the same way a servlet can. You can access beans from within servlets.
For more details, check out the servlet tutorials at http://java.sun.com

How can i know the servlet is running or not?

Hi all,
I have a doubt regarding servlet. I created one servlet and deployed in server. Now i called (RUN) the servlet from the browser. And it is running. Now can i know that the servlet is running or not in the server without seeing in the browser. Can we know the status of the servlet with its URL in the server whether it is running or not?
Let me explain my problem. In my servlet it will run continously read one table and do some operation depending on the entries in that table. Now i called the servlet from the browser. After some time i closed the browser. If browser is there i can know whether servlet is running or not. But now how can i know that servlet is running or not. Becoz eventhough we closed the browser the servlet will run in the background. How can i achieve this?
Thanks and Regards,
VJR.

Hi!
With first call, the servlet will be loaded, and it remains so until server-shutdown, but you need a timer-mechanism execute method calls continuously.
Regards,
Thomas

How can we destroy the instance of a singleton object?

I think by writing a method like getInstance and making null in that method will not the correct answer of this. Can someone tell me what should I do.

why do you need to destroy the singleton?
normally..it should live for the duration of the application.
most singleton i've worked with are used by sevarals different classes.
if you're singleton use by only one class...refactor your code to make the singleton an inner class. so the singleton will be destroy when that class is no longer references 9and gc kick in)
if the singleton is share among several class...you can have a destroy method...like destroyInstance() where you null the singleton. keep in mind about synchronization of the method as well as the instance ... example createInstance() and destroyInstance() get call at the same time.. Also, make sure you have condition to check to determine if your singleton class is null or not
example
MySingleton s = MySingleton.createInstance();
Object obj = s.getData(); // what happen when another thread call MySingleton.destroyInstance() you're s.getData would result in NullPointerException
so..it's not wise to destroy a singleton.
I think what is better for your app is an Object Pool that create new instance (if none exist) and hand it out to any requester...and recycle the object...or null it after use)

How can I find the servlet class name from inside a ServletFilter?

Ive implemented a servlet filter, but need to discover the class name of any servlet class that gets executed.
Ive dug through the spec and cant seem to find any path to do this.
Seems the methods needed to do this have been deprecated. (for security reasons?)
Is there any way to write a ServletFilter to grab this info?
If not, is there any other way to capture every servlet execution in the container, time its execution, and log the class name along with the execution time?
(***WITHOUT*** requiring a classpath over ride of any container provider classes)
Any help is much appreciated. Been banging my head against this for some time now :(

request.getServletPath() returns the part of the URL which refers to the servlet. It isn't the classname of the servlet but it should be a reasonable surrogate. If you log that, then you could write some code which reads your web.xml and uses the servlet-mapping elements to convert it to servlet class names later.

Can't invoke the Servlet............

Hi there!!
I'm trying to invoke my servlet from inside my simple Java Application.Though it shows me it has connected to the target URL but the servlet doesn't start its exceution,,here's my code...
System.out.println("========GOING FOR SERVLET=============");
URL url = new URL("http://localhost:8084/servlets-examples/servlet/HelloWorldExample");
URLConnection con = url.openConnection();
// inform the connection that we will send output and accept input
con.setDoInput(true);
con.setDoOutput(true);
con.setUseCaches (false);
con.setDefaultUseCaches (false);
con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
System.out.println("??????Connected to URL");
......urgent help reqd plz.......thanks in advance...

Thanks gimbal2 for your response but now I'm getting one more problem,,,I'm encountering an exception which is...........
java.io.IOException: Server returned HTTP response code: 405 for URL: http://localhost:8084/servlets-examples/servlet/HelloWorldExample
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1174)
hope you would respond,,,thanks in advance...

How can I judge the servlet directory?

hi there
I am learning web programming. I wonder when it comes the statement such as: "http://localhost/servlet/test", which directory is used? If I want to access a class file at, for example, e:\servlet, how can I do so? Anyone can give me a clue? Thanks.

You should post this in the Java ServerPages discussion forum, and you should also let people know what kind of application server you are using. And thirdly, you could just look at the documentation for your application server. Most tell you about the directory structure and where to put stuff.

I lost my Mac book air, how can I destroy the data?

Appreciate for any comment and solution

I believe if you have Find my PC/Phone/Ipad enabled thru Icloud you can quickly find it and by clicking on the right hand blue arrow next to it (as displayed on a map) you get the option to lock it down or trash it. I may be wrong...but I think thats right.
Rgds
Rod
Perth

Extra request reaching the servlet

Hi,
I have written a servlet which returns me some html code that I display in the browser. The servlet is working fine. My problem is with the HTML code that sends POST request to the servlet.
When the first POST request is send to the servlet, all the necessary parameters are passed and code works as expected.
Here is the bug: Sometimes after receiving the first POST request, a secong POST request is somehow send to the servlet. This second POST request is followed by a GET request to the servlet. This GET request doesn't carry all the expected parameters. Due to this my code fails.
I could not find the reason or the origin of these extra requests. The code is supposed to make only 1 POST request. But somwhow it is making extra requests (1 POST and 1 GET request).
Can anybody suggest a solution?
Has anybody come across a similar problem?
My client side code is similar to the one below:
<BODY id="MenuBody">
<FORM method="POST" name="MenuForm" action="/myServlet">
<input id="submitButton" type="button" style="left:585px; position:absolute" onclick="top.sendRequest();">
In the sendRequest() function, I submit the form as follows:
MenuForm.submit();
Thanks in advance...

Greetings,
Hi,
I have written a servlet which returns me some html
code that I display in the browser. The servlet is
working fine. My problem is with the HTML code that
sends POST request to the servlet. Are you sure the problem is in the client and not in the servlet itself?
When the first POST request is send to the servlet,
all the necessary parameters are passed and code works
as expected.
Here is the bug: Sometimes after receiving the first"Sometimes" implies intermittency of the problem... sure makes it tough to debug. ':) Are you able to (intentionally) duplicate the error? If so, what conditions are present when you can vs. when you can't? Are you doing all your own testing? Try a "hallway useability test" - "anonymous" third person and see if they can duplicate the problem...
POST request, a secong POST request is somehow send to
the servlet. This second POST request is followed by a
GET request to the servlet. This GET request doesn't
carry all the expected parameters. Due to this my code
fails.Are you actually seeing multiple requests being generated in the server logs?
I could not find the reason or the origin of these
extra requests. The code is supposed to make only 1
POST request. But somwhow it is making extra requests
(1 POST and 1 GET request).
Can anybody suggest a solution?
Has anybody come across a similar problem?
My client side code is similar to the one below:"Similar" but not the same? Sometimes, in trying to "paraphrase" code for presentation a crucial detail is left out... anyway...
<BODY id="MenuBody">
<FORM method="POST" name="MenuForm"
action="/myServlet">
<input id="submitButton" type="button"
style="left:585px; position:absolute"
onclick="top.sendRequest();">Have you tried this with a standard submit button input type? Does the error still persist? If not, then perhaps the error is in your browser's JavaScript handler.
In the sendRequest() function, I submit the form as
follows:
MenuForm.submit();
Thanks in advance...Regards,
Tony "Vee Schade" Cook

Preventing Tomcat from destroying a servlet

Hi,
I'm looking for a way to prevent Tomcat from destroying a servlet.
My problem is that I want to run parts of my application as a server that always needs to be running to receive requests from a legacy system. Is it possible to just start a thread from a dummy servlet that loads on startup and this thread will continue to run? Or will Tomcat destroy the servlet and the thread alongside?
Thanks for any answers.

I think it is one of the major weaknesses of the
J2EE that you cannot have your own server code
running in the same context.Huh? I' ve done that quite succesfully for years. Is there something that prevents it?
You can't start your own threads within an EJB container. That surely does suck IMHO. But by "Tomcat" you mean a web server, not an EJB container, don't you?
The last I read the Tomcat source, as far as I could figure, it destroyed servlet objects in exactly two situations: (1) when reloading a servlet when its code had changed, and (2) when shutting down the server. What I've done to prevent anything from being unloaded is put it in "library" jars; I don't think those are ever unloaded. AFAIK stuff loaded by the system class loader in particular is never unloaded. (I actually prefer to put servlets in CLASSPATH too, but that's ...controversial :-)

Urgent: how to run applet which connected to the servlet?

hi frends:
i have written an applet on the server side and it supposed to pass parameters to my servlet and retrieve some info from the servlet.
i put both applet and servlet under tomcat../WEB-INF/classes. but when i run the applet from the web browser, there is no response from the servlet.
could anyone help me to solve this problem?
one more thing is i know that applet is able to connect to servlet, but how about java application? is it able to do so? if yes, is it also using URLconnection as applet? and how to run it?
i will be very appreciate if anyone can help me... thanx a million.

You can connect to the servlet from an application.There's a URL class in java.net that has an openConnection method. Then cast the return to an HttpURLConnection and use setMethod to set up as a post request.This may be the default if you call setDoOutput(true) on the URLConnection. Then you'll need to get an OutputStream and write properly formatted form POST data to it. It's also possible to encode your data on the URL, even when using the POST method, and this may be easier when doing it programmatically from an application. To send a get request you can append the name-value pair at the end of the url.

Can a client can explicitly destroy the servlet?

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