How to read text file in Servlet?

This example show you how to read a text file using a Servlet. Use ServletContext.getResourceAsStream() will enable you to read a file whether the web application is deployed in an exploded format or in a war file archive.

package com.javacoderanch.example.servlet;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ReadTextFileServlet extends HttpServlet {
 protected void doGet(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {
  
  response.setContentType("text/html");
  
  //
  // We are going to read a file called configuration.properties. This
  // file is placed under the WEB-INF directory.
  //
  String filename = "/WEB-INF/configuration.properties";
  
  ServletContext context = getServletContext();
  
  //
  // First get the file InputStream using ServletContext.getResourceAsStream()
  // method.
  //
  InputStream is = context.getResourceAsStream(filename);
  if (is != null) {
   InputStreamReader isr = new InputStreamReader(is);
   BufferedReader reader = new BufferedReader(isr);
   PrintWriter writer = response.getWriter();
   String text = "";
   
   //
   // We read the file line by line and later will be displayed on the 
   // browser page.
   //
   while ((text = reader.readLine()) != null) {
    writer.println(text);
   }
  }
 }

 protected void doPost(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {
 }
}

The configuration.properties file is just a regular text file. Below is an example of the configuration we are going to read.

app.appname=Servlet Examples
app.version=1.0
app.copyright=2007