How can I Locate the correct filepath in a jsp page?

Question

In http://localhost:8080/myweb/a.jsp, I will call a java bean file which is locate in http://localhost:8080/myweb/WEB-INF/classes/haha/DBConnection.class. This java file requires to read an external file which locates in http://localhost:8080/myweb/WEB-INF/classes/haha/db.txt
My question is how can I get the correct filepath in this environment?
inputStream = new BufferedReader(new FileReader(????????));
Only this will work
inputStream = new BufferedReader(new FileReader("D:\Program Files\Apache Software Foundation\Tomcat 5.5\db.txt"));
But no one will place the file here, and it is impossible to do this when upload to 3rd party hosting.
Any suggestion? thx.

Answer 1

Thx all, in a jsp page, calling this method is fine.
ServletContext s = getServletContext();
String a = s.getRealPath("/");
In a Servlet file, below method is ready to use:
String b = getServletConfig().getServletContext().getRealPath("/");
My problem is, I have a jsp page, which initialize a java bean , this java file is responsible for Database Connection, which will read the external text file to get the login, password and database name. So I won't need to recompile this file every time when I place in different platform with different configuration. I only need to edit the text file is ok.
But How can I get the absolute file path when that jsp page initialize that java bean file? Below is my error, any suggestions are thx.
package sql;
import java.sql.*;
import java.util.ArrayList;
import java.io.FileReader;
import java.io.BufferedReader;
import javax.servlet.*;
import javax.servlet.http.*;
public class DBConnection extends HttpServlet{
public String sql = null;
public Connection con = null;
public Statement statement = null;
public ResultSet rs = null;
private BufferedReader inputStream = null;
private static ArrayList<String> arr = new ArrayList<String>();
  public DBConnection(){
    String fs = System.getProperty("file.separator");
    ServletContext s = getServletContext();
    String realpath = s.getRealPath("/");
    String filepath = realpath + "WEB-INF"+fs+"Properties"+fs+"db.txt";
    try{
      inputStream = new BufferedReader(new FileReader(filepath));
      String l;
      while ((l = inputStream.readLine()) != null) {
        arr.add(l);
      Class.forName("com.mysql.jdbc.Driver");
      this.con = DriverManager.getConnection("jdbc:mysql://localhost:3306/"+arr.get(0)+"?user=" +arr.get(1)+ "&password="+arr.get(2)+"&useUnicode=true&characterEncoding=utf-8");
      this.statement = this.con.createStatement();
    }catch (Exception e){
      System.err.println(e.getMessage());
    }finally{
}java.lang.NullPointerException
     javax.servlet.GenericServlet.getServletContext(GenericServlet.java:159)
     sql.DBConnection.<init>(DBConnection.java:20)
     html.ShowCategory.<init>(ShowCategory.java:17)
     org.apache.jsp.left_jsp._jspService(left_jsp.java:66)
     org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
     javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
     org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:334)
     org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
     org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
     javax.servlet.http.HttpServlet.service(HttpServlet.java:802)