Problem in making Beer Expert app from Head First Servlet Book

[Shadab Alam]

Hii friends I m new to the Servlet world. I am going through the Head First Servlet book and facing difficulty in Chapter 3 while making the Beer Expert web app.

I need to compile the model class -

package com.example.model;
import java.util.*;

public class BeerExpert{
 public List getBrands(String color){
  List brands=new ArrayList();
  if(color.equals("amber")){
   brands.add("Jack Amber");
   brands.add("Red Moose");
  }
  else{
   brands.add("Jail Pale Ale");
   brands.add("Gout Stout");
  }
  return(brands);
 }
}

When I compile the above class on Windows the command prompt says -

"Note: src\com\example\model\BeerExpert.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details."

However the class is compiled. After that the book says me to compile Servlet version 2 -

package com.example.web;

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

public class BeerSelect extends HttpServlet{
 public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException{
  
  String c=request.getParameter("color");
  BeerExpert be=new BeerExpert();
  List result=be.getBrands(c);

  response.setContentType("text/html");
  PrintWriter out=response.getWriter();
  out.println("Beer Selection Advice<br>");
  
  Iterator it=result.iterator();
  
  while(it.hasNext()){
   out.println("<br>try: " +it.next());
  }

 }
}

When I compile the Servlet Vertion two the command prompt gives three errors-

src\com\example\web\BeerSelect.java:3: package com.example.model does not exist
import com.example.model.*;
^
src\com\example\web\BeerSelect.java:13: cannot find symbol
symbol : class BeerExpert
location: class com.example.web.BeerSelect
BeerExpert be=new BeerExpert();
^
src\com\example\web\BeerSelect.java:13: cannot find symbol
symbol : class BeerExpert
location: class com.example.web.BeerSelect
BeerExpert be=new BeerExpert();
^
3 errors


Please help me out

[Devaka Cooray]

Howdy, Shadab,
Welcome to JavaRanch

Please UseCodeTags when you post a code. It's unnecessarily hard to read the code otherwise. Please edit your post to add code tags by clicking the button.

This problem is just about packaging and importing - it has nothing to do with servlets. Can you show us the way which you used to compile these classes?

[Charles 'King]

The compiler can't find your classes or package you're attempting to import. Are you using an IDE or compiling from the command line? If the latter, post your command.

[Shadab Alam]

Thanks for reply. Sorry I joined JavaRanch today, so I was not aware of the rules.

My model class is in "D:\MyProjects\beerV1\src\com\example\model" directory
and the Servlet is in "D:\MyProjects\beerV1\src\com\example\web" directory.
My current working directory on Windows command prompt is "D:\MyProjects\beerV1".

To compile the model class I typed on the command prompt
javac -d classes src\com\example\model\BeerExpert.java

The class is compiled but I got the warnings that I mentioned in the first post.

Now to compile the servlet, from the current working directory, i.e "D:\MyProjects\beerV1" I type the following on the command prompt
javac -classpath C:\Program Files\Apache Software Foundation\Tomcat 5.5\common\lib\servlet-api.jar;classes:. -d classes src\com\example\web\BeerSelect.java

And I got the errors that I wrote in my first post. Please help

[Mark E Hansen]

Shadab Alam wrote:Now to compile the servlet, from the current working directory, i.e "D:\MyProjects\beerV1" I type the following on the command prompt
javac -classpath C:\Program Files\Apache Software Foundation\Tomcat 5.5\common\lib\servlet-api.jar;classes:. -d classes src\com\example\web\BeerSelect.java

And I got the errors that I wrote in my first post. Please help

Have a look at your classpath entry for your servlet compilation. You must realize that command-line parameters are separated by spaces.
You need to enclose that classpath value in double quotes. Also, what is the second value? It looks like classes:.
That is, "classes" then a colon, then a period. Perhaps you meant to use a semicolon?

[Bear Bibeault]

Moved to beginning Java as this has less to do with servlets than with learning how to compile Java classes.

[Mark Vermette]

Shadab says:

When I compile the above class on Windows the command prompt says -

"Note: src\com\example\model\BeerExpert.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details."

However the class is compiled.

Shadab - Later versions of Java will generate that error because, unlike previous versions, the Collection
classes now work with generics, and can enforce the object type that they contain. Your program builds
a List of Strings. Replace the line that creates the brands list with the following, and your warnings should
go away:

List<String> brands = new ArrayList <String>();

What this does is to declare that your new List will only accept String objects. A compile-time error
will be thrown if you try to put any other type of object in the list.