ServletContextAttributeListener doesn't receive attributeRemoved() notification

[Faisal Ahmad]

I've the following ServletContextAttributeListener:

package com.example.servlets;

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

public class MyContextAttributeListener implements ServletContextAttributeListener{
	public void attributeAdded(ServletContextAttributeEvent scae){
		scae.getServletContext().log("MyContextAttributeListener.attributeAdded():"+scae.getName()+","+scae.getValue());
	}

	public void attributeRemoved(ServletContextAttributeEvent scae){
		scae.getServletContext().log("MyContextAttributeListener.attributeRemoved():"+scae.getName()+","+scae.getValue());
	}

	public void attributeReplaced(ServletContextAttributeEvent scae){
		scae.getServletContext().log("MyContextAttributeListener.attributeReplaced():"+scae.getName()+","+scae.getValue());
	}
}

And here is my servlet:

package com.example.servlets;

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.example.model.Dog;

public class TestServlet extends HttpServlet{
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException{
		response.setContentType("text/html");
		PrintWriter rWriter = response.getWriter();//Working. Can see the output in browser as well as log file.
		Dog dog = (Dog) this.getServletContext().getAttribute("dog");
		this.getServletContext().log(dog.getBreed());
		//PrintWriter rWriter = response.getWriter();//Can see the output only in log file. Browser shows nothing.
		rWriter.println(dog.getBreed());

		this.getServletContext().setAttribute("author","faisal");
		this.getSerlvetContext().removeAttribute("dog");
	}
}

The last line of doGet() removes an attribute. But, MyContextAttributeListener is not notified about this event. Why?

[Niiraj Patel]

Faisal Ahmad wrote:The last line of doGet() removes an attribute. But, MyContextAttributeListener is not notified about this event. Why?

It has a Typo mistake. Notice the getSerlvetContext instead of getServletContext.

your last line of doGet is :

this.getSerlvetContext().removeAttribute("dog"); 

It should be :

this.[b]getServletContext[/b]().removeAttribute("dog"); 

You should get compilation error for this.

Regards,
Niraj

[Faisal Ahmad]

Thanks a lot lot Niraj! I overlooked the compilation error. How silly!

[Niiraj Patel]

Faisal,

While preparing for exam, the best practice is the Notepad.

Please manually compile and deploy classes.

Regards,
Niraj

[Faisal Ahmad]

Yes, you are right. I use a better notepad - TextPad. However, I am using a batch script (make.bat) that I wrote exclusively for practicing exercises. Unfortunately, it lacks the mechanism to stop upon compilation error. I just overlooked the error. I'll have to modify the script.

Thanks again!