12

I am creating simple servlet and deploying it in tomcat server but I am getting the following error:

HTTP Status 500 - Error instantiating servlet class pkg.coreServlet

File Structure on the tomcat server:

webapps     
| 
- aarya
  |
  - WEB-INF
    |
     -web.xml
     -src(folder)
       |
       -pkg
         |
         -coreServlet.class

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">


<servlet>
    <servlet-name>aaryaservlet</servlet-name>
    <servlet-class>pkg.coreServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>aaryaservlet</servlet-name>
        <url-pattern>/coreServlet</url-pattern>
    </servlet-mapping>
</web-app>

coreServlet.java:

package pkg;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*; 

public class coreServlet extends HttpServlet
{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;

public void doGet(HttpServletRequest req,HttpServletResponse res)
 throws ServletException,IOException


   {
        PrintWriter out = res.getWriter();
        res.setContentType("text/html");
        out.println("this is First servlet Example ");
    }
}

url I am giving is http://localhost:8080/aarya/coreServlet I try by restarting tomcat but I am getting same error. Where I am doing wrong?

pnuts
  • 58,317
  • 11
  • 87
  • 139
Anshul
  • 9,312
  • 11
  • 57
  • 74

10 Answers10

14

Do not put the src folder in the WEB-INF directory!!

javadev
  • 1,639
  • 2
  • 17
  • 35
  • I am doing with the help of http://www.mkyong.com/servlet/a-simple-servlet-example-write-deploy-run/ Is, that is wrong ? – Anshul Apr 10 '13 at 09:12
  • even in this, src is out side of WEB-INF – Ankit Apr 10 '13 at 09:13
  • Yeah. He is putting src folder just in the root directory. – javadev Apr 10 '13 at 09:13
  • @NickJ Does folder name really matters, I mean I am putting .class files in src, does it matters ? – Anshul Apr 10 '13 at 09:13
  • Step #5 shows the correct directly structure. I think you got your source and deployed directories mixed up – NickJ Apr 10 '13 at 09:14
  • yes, it does affect, otherwise container wont be able to find class files – Ankit Apr 10 '13 at 09:15
  • Ya in step#5 I changed classes into src, I am asking that name of folder is really matters ? – Anshul Apr 10 '13 at 09:16
  • 1
    @TechDon it is very important to get the directory names right. Tomcat will look for classes in a directory named classes, or jars in a directory called lib. It won't find them anywhere else. – NickJ Apr 10 '13 at 09:17
9

Change the

private static final long serialVersionUID = 1L;

to any other value like 

private static final long serialVersionUID = 102831973239L;

also you can generate it automatically in eclipse.

It is because each servlet in a app has a unique id.and tomcat causes problem with two servlets having same id...

Raunak Bhansali
  • 134
  • 1
  • 4
5

In my case missing private static final long serialVersionUID = 1L; line caused the same error. I added the line and it worked!

N D Thokare
  • 1,703
  • 6
  • 35
  • 57
4

Have you closed the < web-app > tag in your web.xml? From what you have posted, the closing tag seems to be missing.

N.M
  • 831
  • 9
  • 18
4

The servlet class should be in the WEB-INF/classes not WEB-INF/src.

2

The above error can occur for multiple cases during servlet startup / request. Hope you check the full stack trace of the server log, If you have tomcat, you can also see the exact causes in html preview of the 500 Internal Server Error page.

Weird thing is, if you try to hit the request url a second time, you would get 404 Not Found page.

You can also debug this issue, by placing breakpoints on all the classes constructor initialization block, whose objects are created during servlet startup/request.

In my case, I didn't had javaassist jar loaded for the Weld CDI injection to work. And it shown NoClassDefFound Error.

abitcode
  • 1,420
  • 17
  • 24
0

I had an issue with Servlet instantiation. I cleaned the project and it worked for me. In eclipse menu, Go to Project->Clean. It should work.

neeranzan
  • 131
  • 5
0

Try This:)

before:-

<servlet>
    <servlet-name>TestServlet</servlet-name>
    <servlet-class>TestServlet</servlet-class>  
</servlet>

After:-

 <servlet>
    <servlet-name>TestServlet</servlet-name>
    <servlet-class>operation.TestServlet</servlet-class>
 </servlet>
MAnoj Sarnaik
  • 1,592
  • 16
  • 16
0

Make sure the following:

  1. Proper "war" file structure i.e. WEB-INF & META-INF
  2. "web.xml" file is setup correct.
  3. Last and important: private static final long serialVersionUID = 1L; should be there in your class (<servlet-class>MyClass</servlet-class>).
Jawad Khan
  • 156
  • 1
  • 8
0

might be helpful for someone who seeks...

works for me.

  • keeping the servlet-name same as class name.
  • clean and rebuild (make sure your other projects are closed).
Umar
  • 49
  • 5