Basic Authentication using servlets example

In this post, I am going to explain basic authentication using servlets.

I am going to develop below API that is secured by basic authentication.

{Server_URL}/dataContainer/api/userDetails

HTTP Method	Server URL	Description
GET	{Server_URL}/dataContainer/api/userDetails	Get all the users information
POST	{Server_URL}/dataContainer/api/userDetails	Create new user.

Below snippet reads the user credentials from ‘Authorization’ header.

private static Credentials getCredentials(HttpServletRequest req) {
  String authHeader = req.getHeader("Authorization");

  if (authHeader == null)
   return null;

  StringTokenizer st = new StringTokenizer(authHeader);
  if (st.hasMoreTokens()) {
   String basic = st.nextToken();

   if (basic.equalsIgnoreCase("Basic")) {
    try {
     String credentials = new String(Base64.getDecoder().decode(st.nextToken()), "UTF-8");
     int p = credentials.indexOf(":");
     if (p != -1) {
      String login = credentials.substring(0, p).trim();
      String password = credentials.substring(p + 1).trim();

      return new Credentials(login, password);
     }
    } catch (UnsupportedEncodingException e) {
     return null;
    }
   }
  }

Below snippet checks user credentials and create session for valid user, else send 403 response.

 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
   throws IOException, ServletException {
  HttpServletRequest req = (HttpServletRequest) request;
  HttpSession session = req.getSession(false);

  if (session == null) {
   Credentials credentials = getCredentials(req);
   if (credentials == null) {
    ((HttpServletResponse) response).sendError(403);
    return;
   }
   if ("admin".equals(credentials.getUserName()) && "password".equals(credentials.getPassword())) {
    session = req.getSession();
    session.setAttribute("sessionCreated", true);
   } else {
    ((HttpServletResponse) response).sendError(403);
    return;
   }

  }
  chain.doFilter(request, response);
 }

Find the below working application.

AuthFilter.java

package com.sample.filters;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Base64;
import java.util.StringTokenizer;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.sample.model.Credentials;

public class AuthFilter implements Filter {

 public AuthFilter() {
 }

 public void destroy() {

 }

 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
   throws IOException, ServletException {
  HttpServletRequest req = (HttpServletRequest) request;
  HttpSession session = req.getSession(false);

  if (session == null) {
   Credentials credentials = getCredentials(req);
   if (credentials == null) {
    ((HttpServletResponse) response).sendError(403);
    return;
   }
   if ("admin".equals(credentials.getUserName()) && "password".equals(credentials.getPassword())) {
    session = req.getSession();
    session.setAttribute("sessionCreated", true);
   } else {
    ((HttpServletResponse) response).sendError(403);
    return;
   }

  }
  chain.doFilter(request, response);
 }

 private static Credentials getCredentials(HttpServletRequest req) {
  String authHeader = req.getHeader("Authorization");

  if (authHeader == null)
   return null;

  StringTokenizer st = new StringTokenizer(authHeader);
  if (st.hasMoreTokens()) {
   String basic = st.nextToken();

   if (basic.equalsIgnoreCase("Basic")) {
    try {
     String credentials = new String(Base64.getDecoder().decode(st.nextToken()), "UTF-8");
     int p = credentials.indexOf(":");
     if (p != -1) {
      String login = credentials.substring(0, p).trim();
      String password = credentials.substring(p + 1).trim();

      return new Credentials(login, password);
     }
    } catch (UnsupportedEncodingException e) {
     return null;
    }
   }
  }

  return null;

 }

 @Override
 public void init(FilterConfig filterConfig) throws ServletException {
  // TODO Auto-generated method stub

 }

}

Credentials.java

package com.sample.model;

public class Credentials {
 private String userName;
 private String password;

 public Credentials(String userName, String password) {
  super();
  this.userName = userName;
  this.password = password;
 }

 public String getUserName() {
  return userName;
 }

 public void setUserName(String userName) {
  this.userName = userName;
 }

 public String getPassword() {
  return password;
 }

 public void setPassword(String password) {
  this.password = password;
 }

}

DataContainer.java

package com.sample.servlets;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

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

public class DataContainer extends HttpServlet {
 private static final long serialVersionUID = 1L;

 private static List<String> container = new ArrayList<>();

 public DataContainer() {
  super();

 }

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

  response.getWriter().write(container.toString());
 }

 protected void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  String data = getData(request.getInputStream());
  container.add(data);
  response.getWriter().write("Data written successfully");
 }

 private static String getData(InputStream is) throws IOException {
  StringBuilder sb = new StringBuilder();
  BufferedReader br = new BufferedReader(new InputStreamReader(is));
  String read;

  while ((read = br.readLine()) != null) {
   sb.append(read);
  }

  br.close();
  return sb.toString();
 }

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xmlns="http://xmlns.jcp.org/xml/ns/javaee"
 xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
 id="WebApp_ID" version="3.1">
 <display-name>dataContainer</display-name>
 <welcome-file-list>
  <welcome-file>index.html</welcome-file>
  <welcome-file>index.htm</welcome-file>
  <welcome-file>index.jsp</welcome-file>
  <welcome-file>default.html</welcome-file>
  <welcome-file>default.htm</welcome-file>
  <welcome-file>default.jsp</welcome-file>
 </welcome-file-list>

 <filter>
  <filter-name>authentication</filter-name>
  <filter-class>com.sample.filters.AuthFilter</filter-class>
 </filter>

 <filter-mapping>
  <filter-name>authentication</filter-name>
  <url-pattern>/api/*</url-pattern>
 </filter-mapping>

 <servlet>
  <servlet-name>userDetails</servlet-name>
  <servlet-class>com.sample.servlets.DataContainer</servlet-class>
 </servlet>

 <servlet-mapping>
  <servlet-name>userDetails</servlet-name>
  <url-pattern>/api/userDetails</url-pattern>
 </servlet-mapping>

</web-app>

index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
 <h1>Hello World</h1>
</body>
</html>

Complete project structure looks like below.

Run the application ‘dataContainer’ in application server.

Use any rest client like postman and hit below request.

Method: POST

URL: http://localhost:8080/dataContainer/api/userDetails

Body:

{

"name" : "Krishna",

"age" : 29

}

Set the authorization header.

Hit the request.

Hit below request to get the user details.

Method: GET

URL: http://localhost:8080/dataContainer/api/userDetails

You can download complete application from below github link.

https://github.com/harikrishna553/webApplications.git

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