Need to an OutputStream or Writer to write in a file

Question

Hello,
I my java class, I need to an OutputStream or a Writer to write in a file. The problem is that I am in a webapp.
To get an inputStream, I use this :
InputStream is = this.getClass().getResourceAsStream("RELATIVE_PATH_IN_WEBAPP");
But it doesn't exist a correspondance for the outputstream.
With this code :
Writer writer = new FileWriter("RELATIVE�_PATH_IN_WEBAPP");
I cannot find the file because it looks for my application server relative path.

Answer 1

Ok but I think it doesn't help me.
To explain : I have a servlet that calls a service in a Java class :
public class MyServlet extends HttpServlet{
public void init(){
MyService service = new MyService();
String file = "RELATIVE_PATH_IN_WEBAPP//myfile.xml";
service.createFile(file);
In MyService class :
public void createFile(String file){
XMLWriter writer = new XMLWriter( //dom4j API
new FileWriter(file) );
writer.write( document );
But this doesn't looks for my file in the relative path of the webapp.