Namespace configuration has been available since version 2.0 of the Spring framework. It allows you to supplement the traditional Spring beans application context syntax with elements from additional XML schema. You can find more information in the Spring Reference Documentation. A namespace element can be used simply to allow a more concise way of configuring an individual bean or, more powerfully, to define an alternative configuration syntax which more closely matches the problem domain and hides the underlying complexity from the user. A simple element may conceal the fact that multiple beans and processing steps are being added to the application context. For example, adding the following element from the security namespace to an application context will start up an embedded LDAP server for testing use within the application: ]]> This is much simpler than wiring up the equivalent Apache Directory Server beans. The most common alternative configuration requirements are supported by attributes on the ldap-server element and the user is isolated from worrying about which beans they need create and what the bean property names are. You can find out more about the use of the ldap-server element in the chapter on LDAP.. Use of a good XML editor while editing the application context file should provide information on the attributes and elements that are available. We would recommend that you try out the SpringSource Tool Suite as it has special features for working with standard Spring namespaces. To start using the security namespace in your application context, all you need to do is add the schema declaration to your application context file: ... ]]> In many of the examples you will see (and in the sample) applications, we will often use "security" as the default namespace rather than "beans", which means we can omit the prefix on all the security namespace elements, making the content easier to read. You may also want to do this if you have your application context divided up into separate files and have most of your security configuration in one of them. Your security application context file would then start like this ... ]]> We'll assume this syntax is being used from now on in this chapter.

The namespace is designed to capture the most common uses of the framework and provide a simplified and concise syntax for enabling them within an application. The design is based around the large-scale dependencies within the framework, and can be divided up into the following areas: Web/HTTP Security - the most complex part. Sets up the filters and related service beans used to apply the framework authentication mechanisms, to secure URLs, render login and error pages and much more. Business Object (Method) Security - options for securing the service layer. AuthenticationManager - handles authentication requests from other parts of the framework. AccessDecisionManager - provides access decisions for web and method security. A default one will be registered, but you can also choose to use a custom one, declared using normal Spring bean syntax. AuthenticationProviders - mechanisms against which the authentication manager authenticates users. The namespace provides supports for several standard options and also a means of adding custom beans declared using a traditional syntax. UserDetailsService - closely related to authentication providers, but often also required by other beans. We'll see how these work together in the following sections.

In this section, we'll look at how you can build up a namespace configuration to use some of the main features of the framework. Let's assume you initially want to get up and running as quickly as possible and add authentication support and access control to an existing web application, with a few test logins. Then we'll look at how to change over to authenticating against a database or other security information repository. In later sections we'll introduce more advanced namespace configuration options.

The first thing you need to do is add the following filter declaration to your web.xml file: springSecurityFilterChain org.springframework.web.filter.DelegatingFilterProxy springSecurityFilterChain /* ]]> This provides a hook into the Spring Security web infrastructure. DelegatingFilterProxy is a Spring Framework class which delegates to a filter implementation which is defined as a Spring bean in your application context. In this case, the bean is named springSecurityFilterChain, which is an internal infrastructure bean created by the namespace to handle web security. Note that you should not use this bean name yourself. Once you've added this to your web.xml, you're ready to start editing your application context file. Web security services are configured using the <http> element.

All you need to enable web security to begin with is ]]> Which says that we want all URLs within our application to be secured, requiring the role ROLE_USER to access them. You can use multiple <intercept-url> elements to define different access requirements for different sets of URLs, but they will be evaluated in the order listed and the first match will be used. So you must put the most specific matches at the top. To add some users, you can define a set of test data directly in the namespace: ]]> If you are familiar with pre-namespace versions of the framework, you can probably already guess roughly what's going on here. The <http> element is responsible for creating a FilterChainProxy and the filter beans which it uses. Common issues like incorrect filter ordering are no longer an issue as the filter positions are predefined. The <authentication-provider> element creates a DaoAuthenticationProvider bean and the <user-service> element creates an InMemoryDaoImpl. All authentication-provider elements must be within the authentication-manager element, which creates a ProviderManager and registers the authentication providers with it. You can find more detailed information on the beans that are created in the namespace appendix. It's worth cross-checking this if you want to start understanding what the important classes in the framework are and how they are used, particularly if you want to customise things later. The configuration above defines two users, their passwords and their roles within the application (which will be used for access control). It is also possible to load user information from a standard properties file using the properties attribute on user-service. See the section on in-memory authentication for more details on the file format. Using the <authentication-provider> element means that the user information will be used by the authentication manager to process authentication requests. You can have multiple <authentication-provider> elements to define different authentication sources and each will be consulted in turn. At this point you should be able to start up your application and you will be required to log in to proceed. Try it out, or try experimenting with the tutorial sample application that comes with the project. The above configuration actually adds quite a few services to the application because we have used the auto-config attribute. For example, form-based login processing is automatically enabled.

The auto-config attribute, as we have used it above, is just a shorthand syntax for: ]]> These other elements are responsible for setting up form-login, basic authentication and logout handling services respectively In versions prior to 3.0, this list also included remember-me functionality. This could cause some confusing errors with some configurations and was removed in 3.0. In 3.0, the addition of an AnonymousAuthenticationFilter is part of the default <http> configuration, so the <anonymous /> element is added regardless of whether auto-config is enabled. . They each have attributes which can be used to alter their behaviour.

You might be wondering where the login form came from when you were prompted to log in, since we made no mention of any HTML files or JSPs. In fact, since we didn't explicitly set a URL for the login page, Spring Security generates one automatically, based on the features that are enabled and using standard values for the URL which processes the submitted login, the default target URL the user will be sent to after loggin in and so on. However, the namespace offers plenty of support to allow you to customize these options. For example, if you want to supply your own login page, you could use: ]]> Note that you can still use auto-config. The form-login element just overrides the default settings. Also note that we've added an extra intercept-url element to say that any requests for the login page should be available to anonymous users See the chapter on anonymous authentication for more details.. Otherwise the request would be matched by the pattern /** and it wouldn't be possible to access the login page itself! This is a common configuration error and will result in an infinite loop in the application. Spring Security will emit a warning in the log if your login page appears to be secured. It is also possible to have all requests matching a particular pattern bypass the security filter chain completely: ]]> Note that these requests will be completely oblivious to Spring Security, so you will not be able to access information on the current user or call secured methods during the request. If you want to use basic authentication instead of form login, then change the configuration to ]]> Basic authentication will then take precedence and will be used to prompt for a login when a user attempts to access a protected resource. Form login is still available in this configuration if you wish to use it, for example through a login form embedded in another web page.

If a form login isn't prompted by an attempt to access a protected resource, the default-target-url option comes into play. This is the URL the user will be taken to after logging in, and defaults to "/". You can also configure things so that they user always ends up at this page (regardless of whether the login was "on-demand" or they explicitly chose to log in) by setting the always-use-default-target attribute to "true". This is useful if your application always requires that the user starts at a "home" page, for example: ]]>

In practice you will need a more scalable source of user information than a few names added to the application context file. Most likely you will want to store your user information in something like a database or an LDAP server. LDAP namespace configuration is dealt with in the LDAP chapter, so we won't cover it here. If you have a custom implementation of Spring Security's UserDetailsService, called "myUserDetailsService" in your application context, then you can authenticate against this using ]]> If you want to use a database, then you can use ]]> Where "securityDataSource" is the name of a DataSource bean in the application context, pointing at a database containing the standard Spring Security user data tables. Alternatively, you could configure a Spring Security JdbcDaoImpl bean and point at that using the user-service-ref attribute: ]]> You can also use standard AuthenticationProvider beans as follows ]]> where myAuthenticationProvider is the name of a bean in your application context which implements AuthenticationProvider. See for more on information on how the Spring Security AuthenticationManager is configured using the namespace.

Often your password data will be encoded using a hashing algorithm. This is supported by the <password-encoder> element. With SHA encoded passwords, the original authentication provider configuration would look like this: ]]> When using hashed passwords, it's also a good idea to use a salt value to protect against dictionary attacks and Spring Security supports this too. Ideally you would want to use a randomly generated salt value for each user, but you can use any property of the UserDetails object which is loaded by your UserDetailsService. For example, to use the username property, you would use ]]> You can use a custom password encoder bean by using the ref attribute of password-encoder. This should contain the name of a bean in the application context which is an instance of Spring Security's PasswordEncoder interface.

See the separate Remember-Me chapter for information on remember-me namespace configuration.

If your application supports both HTTP and HTTPS, and you require that particular URLs can only be accessed over HTTPS, then this is directly supported using the requires-channel attribute on <intercept-url>: ... ]]> With this configuration in place, if a user attempts to access anything matching the "/secure/**" pattern using HTTP, they will first be redirected to an HTTPS URL. The available options are "http", "https" or "any". Using the value "any" means that either HTTP or HTTPS can be used. If your application uses non-standard ports for HTTP and/or HTTPS, you can specify a list of port mappings as follows: ... ]]>

You can configure Spring Security to detect the submission of an invalid session ID and redirect the user to an appropriate URL. This is achieved through the session-management element: ... ]]>

If you wish to place constraints on a single user's ability to log in to your application, Spring Security supports this out of the box with the following simple additions. First you need to add the following listener to your web.xml file to keep Spring Security updated about session lifecycle events: org.springframework.security.web.session.HttpSessionEventPublisher ]]> Then add the following lines to your application context: ... ]]> This will prevent a user from logging in multiple times - a second login will cause the first to be invalidated. Often you would prefer to prevent a second login, in which case you can use ... ]]> The second login will then be rejected. By rejected, we mean that the user will be sent to the authentication-failure-url if form-based login is being used. If the second authentication takes place through another non-interactive mechanism, such as remember-me, an unauthorized (402) error will be sent to the client. If instead you want to use an error page, you can add the attribute session-authentication-error-url to the session-management element. If you are using a customized authentication filter for form-based login, then you have to configure concurrent session control support explicitly. More details can be found in the Session Management chapter.

Session fixation attacks are a potential risk where it is possible for a malicious attacker to create a session by accessing a site, then persuade another user to log in with the same session (by sending them a link containing the session identifier as a parameter, for example). Spring Security protects against this automatically by creating a new session when a user logs in. If you don't require this protection, or it conflicts with some other requirement, you can control the behaviour using the session-fixation-protection attribute on <session-management>, which has three options migrateSession - creates a new session and copies the existing session attributes to the new session. This is the default.none - Don't do anything. The original session will be retained.newSession - Create a new "clean" session, without copying the existing session data.

The namespace supports OpenID login either instead of, or in addition to normal form-based login, with a simple change: ]]> You should then register yourself with an OpenID provider (such as myopenid.com), and add the user information to your in-memory <user-service>: ]]> You should be able to login using the myopenid.com site to authenticate. It is also possible to select a specific UserDetailsService bean for use OpenID by setting the user-service-ref attribute on the openid-login element. See the previous section on authentication providers for more information.

If you've used Spring Security before, you'll know that the framework maintains a chain of filters in order to apply its services. You may want to add your own filters to the stack at particular locations or use a Spring Security filter for which there isn't currently a namespace configuration option (CAS, for example). Or you might want to use a customized version of a standard namespace filter, such as the UsernamePasswordAuthenticationFilter which is created by the <form-login> element, taking advantage of some of the extra configuration options which are available by using the bean explicitly. How can you do this with namespace configuration, since the filter chain is not directly exposed? The order of the filters is always strictly enforced when using the namespace. When the application context is being created, the filter beans are sorted by the namespace handling code and the standard Spring Security filters each have an alias in the namespace and a well-known position.In previous versions, the sorting took place after the filter instances had been created, during post-processing of the application context. In version 3.0+ the sorting is now done at the bean metadata level, before the classes have been instantiated. This has implications for how you add your own filters to the stack as the entire filter list must be known during the parsing of the <http> element, so the syntax has changed slightly in 3.0.The filters, aliases and namespace elements/attributes which create the filters are shown in . The filters are listed in the order in which they occur in the filter chain. AliasFilter ClassNamespace Element or Attribute CHANNEL_FILTERChannelProcessingFilterhttp/intercept-url@requires-channel CONCURRENT_SESSION_FILTERConcurrentSessionFilter session-management/concurrency-control SECURITY_CONTEXT_FILTERSecurityContextPersistenceFilterhttp LOGOUT_FILTER LogoutFilterhttp/logout X509_FILTER X509AuthenticationFilterhttp/x509 PRE_AUTH_FILTER AstractPreAuthenticatedProcessingFilter SubclassesN/A CAS_FILTER CasAuthenticationFilterN/A FORM_LOGIN_FILTER UsernamePasswordAuthenticationFilterhttp/form-login BASIC_AUTH_FILTER BasicAuthenticationFilterhttp/http-basic SERVLET_API_SUPPORT_FILTERSecurityContextHolderAwareFilterhttp/@servlet-api-provision REMEMBER_ME_FILTER RememberMeAuthenticationFilterhttp/remember-me ANONYMOUS_FILTER AnonymousAuthenticationFilterhttp/anonymous SESSION_MANAGEMENT_FILTERSessionManagementFiltersession-managementEXCEPTION_TRANSLATION_FILTER ExceptionTranslationFilterhttp FILTER_SECURITY_INTERCEPTOR FilterSecurityInterceptorhttp SWITCH_USER_FILTER SwitchUserFilterN/A You can add your own filter to the stack, using the custom-filter element and one of these names to specify the position your filter should appear at: ]]> You can also use the after or before attributes if you want your filter to be inserted before or after another filter in the stack. The names "FIRST" and "LAST" can be used with the position attribute to indicate that you want your filter to appear before or after the entire stack, respectively. If you are inserting a custom filter which may occupy the same position as one of the standard filters created by the namespace then it's important that you don't include the namespace versions by mistake. Avoid using the auto-config attribute and remove any elements which create filters whose functionality you want to replace. Note that you can't replace filters which are created by the use of the <http> element itself - SecurityContextPersistenceFilter, ExceptionTranslationFilter or FilterSecurityInterceptor. If you're replacing a namespace filter which requires an authentication entry point (i.e. where the authentication process is triggered by an attempt by an unauthenticated user to access to a secured resource), you will need to add a custom entry point bean too.

If you aren't using form login, OpenID or basic authentication through the namespace, you may want to define an authentication filter and entry point using a traditional bean syntax and link them into the namespace, as we've just seen. The corresponding AuthenticationEntryPoint can be set using the entry-point-ref attribute on the <http> element. The CAS sample application is a good example of the use of custom beans with the namespace, including this syntax. If you aren't familiar with authentication entry points, they are discussed in the technical overview chapter.

From version 2.0 onwards Spring Security has improved support substantially for adding security to your service layer methods. It provides support for JSR-250 security as well as the framework's original @Secured annotation. From 3.0 you can also make use of new expression-based annotations. You can apply security to a single bean, using the intercept-methods element to decorate the bean declaration, or you can secure multiple beans across the entire service layer using the AspectJ style pointcuts.

This element is used to enable annotation-based security in your application (by setting the appropriate attributes on the element), and also to group together security pointcut declarations which will be applied across your entire application context. You should only declare one <global-method-security> element. The following declaration would enable support for both Spring Security's @Secured, and JSR-250 annotations: ]]> Adding an annotation to a method (on an class or interface) would then limit the access to that method accordingly. Spring Security's native annotation support defines a set of attributes for the method. These will be passed to the AccessDecisionManager for it to make the actual decision: public interface BankService { @Secured("IS_AUTHENTICATED_ANONYMOUSLY") public Account readAccount(Long id); @Secured("IS_AUTHENTICATED_ANONYMOUSLY") public Account[] findAccounts(); @Secured("ROLE_TELLER") public Account post(Account account, double amount); } To use the new expression-based syntax, you would use ]]>and the equivalent Java code would be public interface BankService { @PreAuthorize("isAnonymous()") public Account readAccount(Long id); @PreAuthorize("isAnonymous()") public Account[] findAccounts(); @PreAuthorize("hasAuthority('ROLE_TELLER')") public Account post(Account account, double amount); }

The use of protect-pointcut is particularly powerful, as it allows you to apply security to many beans with only a simple declaration. Consider the following example: ]]> This will protect all methods on beans declared in the application context whose classes are in the com.mycompany package and whose class names end in "Service". Only users with the ROLE_USER role will be able to invoke these methods. As with URL matching, the most specific matches must come first in the list of pointcuts, as the first matching expression will be used.

This section assumes you have some knowledge of the underlying architecture for access-control within Spring Security. If you don't you can skip it and come back to it later, as this section is only really relevant for people who need to do some customization in order to use more than simple role based security. When you use a namespace configuration, a default instance of AccessDecisionManager is automatically registered for you and will be used for making access decisions for method invocations and web URL access, based on the access attributes you specify in your intercept-url and protect-pointcut declarations (and in annotations if you are using annotation secured methods). The default strategy is to use an AffirmativeBased AccessDecisionManager with a RoleVoter and an AuthenticatedVoter.

If you need to use a more complicated access control strategy then it is easy to set an alternative for both method and web security. For method security, you do this by setting the access-decision-manager-ref attribute on global-method-security to the Id of the appropriate AccessDecisionManager bean in the application context: ... ]]> The syntax for web security is the same, but on the http element: ... ]]>

The main interface which provides authentication services in Spring Security is the AuthenticationManager. This is usually an instance of Spring Security's ProviderManager class, which you may already be familiar with if you've used the framework before. If not, it will be covered later, in . The bean instance is registered using the authentication-manager namespace element. You can't use a custom AuthenticationManager if you are using either HTTP or method security through the namespace, but this should not be a problem as you have full control over the AuthenticationProviders that are used. You may want to register additional AuthenticationProvider beans with the ProviderManager and you can do this using the <authentication-provider> element with the ref attribute, where the value of the attribute is the name of the provider bean you want to add. For example: ... ]]> Another common requirement is that another bean in the context may require a reference to the AuthenticationManager. There is a special element which lets you register an alias for the AuthenticationManager and you can then use this name elsewhere in your application context. ... ... ]]>