I am writing a Java Servlet, and I am struggling to get a simple HelloWorld example to work properly.

The HelloWorld.java class is:

package crunch; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloWorld extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); out.println("Hello World"); } }

I am running Tomcat v7.0, and have already read similar questions, with responses referring to changing the invoker servlet-mapping section in web.xml. This section actually doesn't exist in mine, and when I added it the same problem still occurred.

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7 Answers

Try this (if the Java EE V6)

package crunch; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; @WebServlet(name="hello",urlPatterns={"/hello"}) // added this line public class HelloWorld extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); out.println("Hello World"); } }

now reach the servlet by

where 8080 is default Tomcat port, and yourapp is the context name of your applciation

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You definitely need to map your servlet onto some URL. If you use Java EE 6 (that means at least Servlet API 3.0) then you can annotate your servlet like 

@WebServlet(name="helloServlet", urlPatterns={"/hello"}) public class HelloWorld extends HttpServlet { //rest of the class

Then you can just go to the localhost:8080/yourApp/hello and the value should be displayed. In case you can't use Servlet 3.0 API than you need to register this servlet into web.xml file like

<servlet> <servlet-name>helloServlet</servlet-name> <servlet-class>crunch.HelloWorld</servlet-class> </servlet> <servlet-mapping> <servlet-name>helloServlet</servlet-name> <url-pattern>/hello</url-pattern> </servlet-mapping>

Writing Java servlets is easy if you use Java EE 7

@WebServlet("/hello-world") public class HelloWorld extends HttpServlet { @Override public void doGet(HttpServletRequest request, HttpServletResponse response) { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println("Hello World"); out.flush(); } }

Since servlet 3.0

The good news is the deployment descriptor is no longer required!

Read the tutorial for Java Servlets.

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this is may be due to the thing that you have created your .jsp or the .html file in the WEB-INF instead of the WebContent folder.

Solution: Just replace the files that are there in the WEB-INF folder to the Webcontent folder and try executing the same - You will get the appropriate output

For those stuck with "The requested resource is not available" in Java EE 7 and dynamic web module 3.x, maybe this could help: the "Create Servlet" wizard in Eclipse (tested in Mars) doesn't create the @Path annotation for the servlet class, but I had to include it to access successfuly to the public methods exposed.

You have to user ../../projectName/Filename.jsp in your action attr. or href

../ = contains current folder simple(demo.project.filename.jsp)

Servlet can only be called with 1 slash forward to your project name..

My problem was in web.xml file. In one <servlet-mapping> there was an error inside <url-pattern>: I forgot to add / before url.