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

The following servlet read the configuration.properties file from the /WEB-INF directory in our web application. The configuration.properties file is just a regular text file with the following contents.

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

Here is our ReadTextFileServlet servlet class.

package org.kodejava.example.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;

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 + "</br>");
            }
        }
    }
}

After creating the servlet class we need to register our servlet and create a servlet-mapping in the web.xml file.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app
        PUBLIC
        "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
        "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
    <display-name>Servlet Examples</display-name>
    <servlet>
        <servlet-name>ReadTextFileServlet</servlet-name>
        <servlet-class>org.kodejava.example.servlet.ReadTextFileServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ReadTextFileServlet</servlet-name>
        <url-pattern>/readTextFileServlet</url-pattern>
    </servlet-mapping>
</web-app>

To access the servlet you can type http://localhost:8080/readTextFileServlet in your browser URL textbox..