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calling a servlet which does not return anything...from a jsp while loading

I need to call a servlet during a page load(abc.jsp). The Servlet would not return anything.It just makes some updates to a database.
If I use href to call the servlet, abc.jsp does not get loaded as the servlet does not return anything.
If I use form submit(empty form with no fields) to call the servlet and call it during onload event of the abc.jsp, that does makes a call to the servlet but abc.jsp will not be loaded.
What is the best way to call the servlet which does not return anything and still load abc.jsp ?
Thanks

Use jQuery Ajax request during page loade time:
$(document).ready(function(){
$.get( "myServlet" );
});

Maybe you should use Filter. As Specification says:
Filters differ from web components in that filters usually do not themselves create a response. Instead, a filter provides functionality that can be “attached” to any kind of web resource. Consequently, a filter should not have any dependencies on a web resource for which it is acting as a filter; this way, it can be composed with more than one type of web resource.

Where does getRequestDispatcher("path") look?

Using embedded tomcat, this code:
System.out.println("getServletPath: " + request.getServletPath());
System.out.println("getServletContext: " + request.getServletContext().getContextPath());
System.out.println("getServerName: " + request.getServerName());
System.out.println("getServerPort: " + request.getServerPort());
Prints out:
getServletPath: /example
getServletContext:
getServerName: localhost
getServerPort: 9090
Does that mean that:
request.getRequestDispatcher("/example/read.jsp").forward(request, response);
Will look at this URL to forward(request, response) to the JSP:
http://localhost:9090/example/read.jsp?
Is there a way to print out what absolute URL getRequestDispatcher("relativePath") is addressing?

The Servlet Specification explains this
The getRequestDispatcher method takes a String argument describing a
path within the scope of the ServletContext. This path must be
relative to the root of the ServletContext and begin with a ‘/’, or
be empty. The method uses the path to look up a servlet, using the
servlet path matching rules in Chapter 12, “Mapping Requests to
Servlets”, wraps it with a RequestDispatcher object, and returns the
resulting object. If no servlet can be resolved based on the given
path, a RequestDispatcher is provided that returns the content for
that path.
Those rules are the following
The container will try to find an exact match of the path of the request to the path of the servlet. A successful match selects the
servlet.
The container will recursively try to match the longest path-prefix. This is done by stepping down the path tree a directory
at a time, using the ’/’ character as a path separator. The longest
match determines the servlet selected.
If the last segment in the URL path contains an extension (e.g. .jsp), the servlet container will try to match a servlet that handles
requests for the extension. An extension is defined as the part of
the last segment after the last ’.’ character.
If neither of the previous three rules result in a servlet match, the container will attempt to serve content appropriate for the
resource requested. If a "default" servlet is defined for the
application, it will be used. Many containers provide an implicit
default servlet for serving content.
You ask
Does that mean that:
request.getRequestDispatcher("/example/display.jsp").forward(request,
response); Will look at this URL to forward(request, response) to the
JSP:
http://localhost:9090/example/display.jsp?
No, it doesn't send an HTTP request, so the path has nothing to do with a URI. It's more of an internal path that the Servlet container will try to match with its various url-mappings for Servlets.
You also ask
Is there a way to print out what absolute URL getRequestDispatcher("relativePath") is addressing?
No. And it isn't exactly an absolute URL. It's a path that can be handled by some resource in the web application context.
After your edit, you addWebapp to your Tomcat instance.
tomcat.addWebapp(null, "/view2/example2", new File("src/com/example/view/example").getAbsolutePath());
You then send a request to
/view2/example2/read.jsp
I'm going to assume that read.jsp is in
src/com/example/view/example/
I believe it's in the publicly accessible part of the web application and therefore the Servlet container can render it and respond with it.
You've also added a webapp with addContext which seems to be similar to addWebapp
context = tomcat.addContext("", base.getAbsolutePath());
and added servlet mappings to this context.
Tomcat.addServlet(context, "example", new ExampleController());
context.addServletMapping("/example/*", "example");
I was wrong about the /example/* not being able to handle /example.
When you send a request to
/example
since the context path is "", the Context above will be used and the mapping will match the ExampleController registered above. Your Servlet code will execute and reach
request.getRequestDispatcher("/view2/example2/read.jsp").forward(request, response);
Note the javadoc of ServletRequest#getRequestDispatcher(String)
The pathname specified may be relative, although it cannot extend
outside the current servlet context.
In other words, this Servlet, ExampleController was registered in the ServletContext mapped to the context path "", ie. root. The path /view2/example2/read.jsp is referring to another context. Since this context doesn't have a mapping for it, it responds with 404.
You can get a reference to another web applications in a different context. You have to use ServletContext#getContext(String). For example
ServletContext otherContext = request.getServletContext().getContext("/view2/example2");
Now that you have the ServletContext, you can get a RequestDispatcher for a resource in that context.
otherContext.getRequestDispatcher("/read.jsp").forward(request, response);
since ServletContext#getRequestDispatcher(String) states
The pathname must begin with a / and is interpreted as relative to the current context root.
Final Answer:
getRequestDispatcher("path") will look at the directory set in the addWebapp method when referencing a JSP file. If a blank page or NullPointerException is displayed, ensure that you have done the following:
Remove all the addWebapp definitions.
Run addContext then addWebApp like this so they both point to ROOT:
File base = new File("src/com/example/view");
context = tomcat.addContext("", base.getAbsolutePath());
tomcat.addWebapp(null, "/", base.getAbsolutePath());
In the servlet point to the jsp using request.getRequestDispatcher("/example/read.jsp").forward(request, response); provided that the directory /example exists in "src/com/example/view".

Are Servlet Init parameters accessible in whole servlet container

I have this question as i did not find any correct results when searching in Web.
Does Servlet Init Parameters y default accessible in whole container without making any configaration.I mean servlet A has some property x,If another servlet B ,in the same container(may be or may not be in same Application) access it? If so can anyone please show me with an example.
Thanks in Avance.

No, init parameters are servlet-scoped, context-param are application scoped.
There's no other wider scope (e.g. between two applications)

As servlet config, The init parameters of a servlet can only be accessed by that servlet
here is link http://tutorials.jenkov.com/java-servlets/web-xml.html#initParams

Simple servlet with annotations in java (image folder)

i have a folder with images on webContent/images.
I Just wanna to know how to provide this folder on the web.
In my project i have just one servlet with annotations:
#WebServlet(urlPatterns = { "/" })
public class IndexCtrl extends HttpServlet {
Every time i try to get a image this servlet get priority and send a index page.
How can I provide images folder on the web?
What I'm doing wrong?

Just don't map the servlet to /. That makes it the default servlet, which catches all the requests. Map it to the URL it must handle (like /index.html for example).

Call servlet on window.open in javascript

How can I call servlet using window.open()?
My code is:
onclick='window.open("/PDFServlet", "popupWindowName",
"dependent=yes, menubar=no, scrollbars=yes, resizable=1, toolbar=no,width800,height=600")'

This should work, if your application is deployed as the ROOT context. If not, you have to specify /context/PDFServlet/