Home > Articles > Programming > Java

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

Customizing Authentication

There are two aspects to authentication: challenging principals for usernames and passwords and authenticating usernames and passwords. The servlet specification requires servlet containers to allow customization of the former with form-based authentication, as discussed in "Form-Based Authentication" on page 260. The servlet specification does not require servlet containers to allow customization of the latter, but most servlet containers let you do so.

Because the servlet specification does not provide a standard mechanism for customizing authentication of usernames and passwords, that kind of customization is inherently nonportable. This section describes how to customize authentication with Resin and Tomcat and should give you a good idea of what to look for if you are using a different servlet container.


Resin authenticates usernames and passwords with authenticators, which are classes that implement the Resin Authenticator interface.

The default Resin authenticator will authenticate any combination of username and password—a useful feature if you are using Resin in combination with Apache or IIS, because you can rely on the web server's authentication. If you are using Resin in stand-alone mode, then you need to implement an authenticator for basic authentication.

Figure 9-4 shows a basic authentication example with Resin.

Figure 9-4 Customizing Basic Authentication with Resin

The protected page shown in Figure 9-4 is listed in Example 9-3.a.

Example 9-3.a /protected-page.jsp

 <html><head><title>A Protected Page</title></head> 

 <%@ include file='show-security.jsp' %></p> 
 <% if(request.isUserInRole("resin-user")) { %> 
   You are in <i>resin-user</i> role<br/> 
 <% } else {%> 
   You are <b>not</b> in <i>resin-user</i> role<br/> 
 <% } %> 

The JSP page listed in Example 9-3.a relies on the show-security JSP page to print security information; see "Basic Authentication" on page 256 for more information about that page. The JSP page listed in Example 9-3.a also verifies the user's role.

Example 9-3.b lists the deployment descriptor for the application shown in Figure 9-4.

Example 9-3.b /WEB-INF/web.xml

 <?xml version="1.0" encoding="ISO-8859-1"?> 

 <!DOCTYPE web-app 
  PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" 

    <!-- web resources that are protected --> 
      <web-resource-name>A Protected Page</web-resource-name> 


    <realm-name>Basic Authentication Example</realm-name> 
 		<!-- The authenticator tag is Resin-specific --> 
 		<authenticator id='beans.SimpleAuthenticator'/> 

The deployment descriptor listed in Example 9-3.b restricts access to /protected-page.jsp to principals in the role of resin-user and specifies BASIC as the authentication method. That deployment descriptor also contains a Resin-specific authenticator tag that specifies the authenticator to use for this authentication. That authenticator is listed in Example 9-3.c.

Example 9-3.c /WEB-INF/classes/beans/SimpleAuthenticator.java

 package beans; 

 import com.caucho.server.http.AbstractAuthenticator; 
 import com.caucho.server.http.BasicPrincipal; 
 import java.security.Principal; 

 public class SimpleAuthenticator extends AbstractAuthenticator { 
   public Principal authenticate(String user, String password) { 
    boolean valid = password != null &&  
            password.equals("resin") && 
            user != null && user.equals("resin"); 

    if(valid) return new BasicPrincipal(user); 
    else    return null; 
   public boolean isUserInRole(Principal user, String role) { 
    return user.getName().equals("resin") &&  

The authenticator listed in Example 9-3.c extends the Resin AbstractAuthenticator class and overrides the authenticate and isUserInRole methods, both of which are defined in the Authenticator interface and given default implementations in AbstractAuthenticator.

The authenticate method returns an instance of BasicPrincipal, which is a Resin-specific class from com.caucho.server.http, if the username and password are authentic; otherwise, the method returns null.

Tomcat 4.0

Tomcat 4.0 uses realms, which are similar in principle to Resin's authenticators, to authenticate usernames and passwords. Unlike Resin, Tomcat does not require special tags in /WEB-INF/web.xml; instead, Tomcat specifies a realm in $TOMCAT_HOME/conf/server.xml, like this:

 <!-- From $TOMCAT_HOME/conf/server.xml --> 
 <!-- Example Server Configuration File --> 
 <!-- Note that component elements are nested corresponding to their 
    parent-child relationships with each other --> 

 <Server port="8005" shutdown="SHUTDOWN" debug="0"> 
   <!-- Because this Realm is here, an instance will be  
 		shared globally  
   <Realm className="org.apache.catalina.realm.MemoryRealm" /> 
   <Realm className="CustomRealm"/> 

Just inside the Server start tag, Tomcat specifies a default realm—org.apache.catalina.realm.MemoryRealm—which is shared by all contexts.4 To replace the default realm, comment out the default and insert your own, as listed above.

Tomcat custom realms typically extend the Tomcat RealmBase abstract class, which implements the Realm interface. RealmBase defines three abstract methods that extensions must implement. Those methods are listed in Table 9-4.

Table 9-4 Tomcat 4.0 RealmBase Abstract Methods



boolean hasRole(Principal principal, String role)

Returns true if a role is suitable for a principal

String getPassword(String user)

Returns a password associated with a user

Principal getPrincipal(String user)

Returns a principal associated with a user

The CustomRealm class referred to in the server.xml file listed above is listed in Example 9-4.

Example 9-4 A Tomcat Custom Realm

 import java.security.Principal; 
 import org.apache.catalina.realm.RealmBase; 

 public class CustomRealm extends RealmBase { 
   public boolean hasRole(Principal principal, String role) { 
    String name = principal.getName(); 

      return role.equals("tomcat"); 

      return role.equals("role1"); 

      return role.equals("tomcat") || role.equals("role1"); 

    return false; 
   protected String getPassword(String username) { 
    return "tomcat"; 
   protected Principal getPrincipal(String username) { 
    return new CustomPrincipal(username); 
   class CustomPrincipal implements Principal { 
    private final String name; 

    public CustomPrincipal(String name) { 
      this.name = name; 
    public String getName() { 
      return name; 
    public String toString() { 
      return getName(); 

The custom realm listed in Example 9-4 is designed to work with the default entries from $TOMCAT_HOME/conf/tomcat-users.xml, which is listed in Example 9-1.d on page 258. For example, hasRole returns true if the principal and role correspond to those specified in tomcat-users.xml. The getPassword method returns tomcat, which is the password used for all of the users defined in tomcat-users.xml. The getPrincipal method returns a custom principal, which is a simple implementation of the java.security.Principal interface.

Custom realms must be made available to Tomcat at startup, which requires that custom realm classes reside in a JAR file in $TOMCAT_HOME/server. So, for the example listed above to work, CustomRealm.java is compiled, yielding two class files. Those class files are placed in a JAR file and copied to $TOMCAT_HOME/server.


The code in this section is based on a beta version of Tomcat 4.0, so that code may need to be modified by the time you read this.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020