
[[jc]]
= Java Configuration

General support for https://docs.spring.io/spring/docs/3.1.x/spring-framework-reference/html/beans.html#beans-java[Java configuration] was added to Spring Framework in Spring 3.1.
Spring Security 3.2 introduced Java configuration to let users configure Spring Security without the use of any XML.

If you are familiar with the xref:servlet/configuration/xml-namespace.adoc#ns-config[Security Namespace Configuration], you should find quite a few similarities between it and Spring Security Java configuration.

[NOTE]
====
Spring Security provides https://github.com/spring-projects/spring-security-samples/tree/main/servlet/java-configuration[lots of sample applications] to demonstrate the use of Spring Security Java Configuration.
====

[[jc-hello-wsca]]
== Hello Web Security Java Configuration

The first step is to create our Spring Security Java Configuration.
The configuration creates a Servlet Filter known as the `springSecurityFilterChain`, which is responsible for all the security (protecting the application URLs, validating submitted username and passwords, redirecting to the log in form, and so on) within your application.
The following example shows the most basic example of a Spring Security Java Configuration:

====
[source,java]
----
import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.context.annotation.*;
import org.springframework.security.config.annotation.authentication.builders.*;
import org.springframework.security.config.annotation.web.configuration.*;

@Configuration
@EnableWebSecurity
public class WebSecurityConfig {

	@Bean
	public UserDetailsService userDetailsService() {
		InMemoryUserDetailsManager manager = new InMemoryUserDetailsManager();
		manager.createUser(User.withDefaultPasswordEncoder().username("user").password("password").roles("USER").build());
		return manager;
	}
}
----
====

This configuration is not complex or extensive, but it does a lot:

* Require authentication to every URL in your application
* Generate a login form for you
* Let the user with a *Username* of `user` and a *Password* of `password` authenticate with form based authentication
* Let the user logout
* https://en.wikipedia.org/wiki/Cross-site_request_forgery[CSRF attack] prevention
* https://en.wikipedia.org/wiki/Session_fixation[Session Fixation] protection
* Security Header integration:
** https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security[HTTP Strict Transport Security] for secure requests
** https://msdn.microsoft.com/en-us/library/ie/gg622941(v=vs.85).aspx[X-Content-Type-Options] integration
** Cache Control (which you can override later in your application to allow caching of your static resources)
** https://msdn.microsoft.com/en-us/library/dd565647(v=vs.85).aspx[X-XSS-Protection] integration
** X-Frame-Options integration to help prevent https://en.wikipedia.org/wiki/Clickjacking[Clickjacking]
* Integration with the following Servlet API methods:
** https://docs.oracle.com/javaee/6/api/javax/servlet/http/HttpServletRequest.html#getRemoteUser()[`HttpServletRequest#getRemoteUser()`]
** https://docs.oracle.com/javaee/6/api/javax/servlet/http/HttpServletRequest.html#getUserPrincipal()[`HttpServletRequest#getUserPrincipal()`]
** https://docs.oracle.com/javaee/6/api/javax/servlet/http/HttpServletRequest.html#isUserInRole(java.lang.String)[`HttpServletRequest#isUserInRole(java.lang.String)`]
** https://docs.oracle.com/javaee/6/api/javax/servlet/http/HttpServletRequest.html#login(java.lang.String,%20java.lang.String)[`HttpServletRequest#login(java.lang.String, java.lang.String)`]
** https://docs.oracle.com/javaee/6/api/javax/servlet/http/HttpServletRequest.html#logout()[`HttpServletRequest#logout()`]

=== AbstractSecurityWebApplicationInitializer

The next step is to register the `springSecurityFilterChain` with the WAR file.
You can do so in Java configuration with https://docs.spring.io/spring/docs/3.2.x/spring-framework-reference/html/mvc.html#mvc-container-config[Spring's `WebApplicationInitializer` support] in a Servlet 3.0+ environment.
Not surprisingly, Spring Security provides a base class (`AbstractSecurityWebApplicationInitializer`) to ensure that the `springSecurityFilterChain` gets registered for you.
The way in which we use `AbstractSecurityWebApplicationInitializer` differs depending on if we are already using Spring or if Spring Security is the only Spring component in our application.

* <<abstractsecuritywebapplicationinitializer-without-existing-spring>> - Use these instructions if you are not already using Spring
* <<abstractsecuritywebapplicationinitializer-with-spring-mvc>> - Use these instructions if you are already using Spring

[[abstractsecuritywebapplicationinitializer-without-existing-spring]]
=== AbstractSecurityWebApplicationInitializer without Existing Spring

If you are not using Spring or Spring MVC, you need to pass the `WebSecurityConfig` to the superclass to ensure the configuration is picked up:

====
[source,java]
----
import org.springframework.security.web.context.*;

public class SecurityWebApplicationInitializer
	extends AbstractSecurityWebApplicationInitializer {

	public SecurityWebApplicationInitializer() {
		super(WebSecurityConfig.class);
	}
}
----
====

The `SecurityWebApplicationInitializer`:

* Automatically registers the `springSecurityFilterChain` Filter for every URL in your application.
* Add a `ContextLoaderListener` that loads the <<jc-hello-wsca,WebSecurityConfig>>.

[[abstractsecuritywebapplicationinitializer-with-spring-mvc]]
=== AbstractSecurityWebApplicationInitializer with Spring MVC

If we use Spring elsewhere in our application, we probably already have a `WebApplicationInitializer` that is loading our Spring Configuration.
If we use the previous configuration, we would get an error.
Instead, we should register Spring Security with the existing `ApplicationContext`.
For example, if we use Spring MVC, our `SecurityWebApplicationInitializer` could look something like the following:

====
[source,java]
----
import org.springframework.security.web.context.*;

public class SecurityWebApplicationInitializer
	extends AbstractSecurityWebApplicationInitializer {

}
----
====

This onlys register the `springSecurityFilterChain` for every URL in your application.
After that, we need to ensure that `WebSecurityConfig` was loaded in our existing `ApplicationInitializer`.
For example, if we use Spring MVC it is added in the `getRootConfigClasses()`:

[[message-web-application-inititializer-java]]
====
[source,java]
----
public class MvcWebApplicationInitializer extends
		AbstractAnnotationConfigDispatcherServletInitializer {

	@Override
	protected Class<?>[] getRootConfigClasses() {
		return new Class[] { WebSecurityConfig.class };
	}

	// ... other overrides ...
}
----
====

[[jc-httpsecurity]]
== HttpSecurity

Thus far, our <<jc-hello-wsca,`WebSecurityConfig`>> contains only information about how to authenticate our users.
How does Spring Security know that we want to require all users to be authenticated?
How does Spring Security know we want to support form-based authentication?
Actually, there is a configuration class (called `SecurityFilterChain`) that is being invoked behind the scenes.
It is configured with the following default implementation:

====
[source,java]
----
@Bean
public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
	http
		.authorizeRequests(authorize -> authorize
			.anyRequest().authenticated()
		)
		.formLogin(withDefaults())
		.httpBasic(withDefaults());
	return http.build();
}
----
====

The default configuration (shown in the preceding example):

* Ensures that any request to our application requires the user to be authenticated
* Lets users authenticate with form based login
* Lets users authenticate with HTTP Basic authentication

Note that this configuration is parallels the XML Namespace configuration:

====
[source,xml]
----
<http>
	<intercept-url pattern="/**" access="authenticated"/>
	<form-login />
	<http-basic />
</http>
----
====

== Multiple HttpSecurity Instances

We can configure multiple `HttpSecurity` instances just as we can have multiple `<http>` blocks in XML.
The key is to register multiple `SecurityFilterChain` ``@Bean``s.
The following example has a different configuration for URL's that start with `/api/`.

====
[source,java]
----
@Configuration
@EnableWebSecurity
public class MultiHttpSecurityConfig {
	@Bean                                                             <1>
	public UserDetailsService userDetailsService() throws Exception {
		// ensure the passwords are encoded properly
		UserBuilder users = User.withDefaultPasswordEncoder();
		InMemoryUserDetailsManager manager = new InMemoryUserDetailsManager();
		manager.createUser(users.username("user").password("password").roles("USER").build());
		manager.createUser(users.username("admin").password("password").roles("USER","ADMIN").build());
		return manager;
	}

	@Bean
	@Order(1)                                                        <2>
	public SecurityFilterChain apiFilterChain(HttpSecurity http) throws Exception {
		http
			.antMatcher("/api/**")                                   <3>
			.authorizeHttpRequests(authorize -> authorize
				.anyRequest().hasRole("ADMIN")
			)
			.httpBasic(withDefaults());
		return http.build();
	}

	@Bean                                                            <4>
	public SecurityFilterChain formLoginFilterChain(HttpSecurity http) throws Exception {
		http
			.authorizeHttpRequests(authorize -> authorize
				.anyRequest().authenticated()
			)
			.formLogin(withDefaults());
		return http.build();
	}
}
----
<1> Configure Authentication as usual.
<2> Create an instance of `SecurityFilterChain` that contains `@Order` to specify which `SecurityFilterChain` should be considered first.
<3> The `http.antMatcher` states that this `HttpSecurity` is applicable only to URLs that start with `/api/`.
<4> Create another instance of `SecurityFilterChain`.
If the URL does not start with `/api/`, this configuration is used.
This configuration is considered after `apiFilterChain`, since it has an `@Order` value after `1` (no `@Order` defaults to last).
====

[[jc-custom-dsls]]
== Custom DSLs

You can provide your own custom DSLs in Spring Security:

====
[source,java]
----
public class MyCustomDsl extends AbstractHttpConfigurer<MyCustomDsl, HttpSecurity> {
	private boolean flag;

	@Override
	public void init(HttpSecurity http) throws Exception {
		// any method that adds another configurer
		// must be done in the init method
		http.csrf().disable();
	}

	@Override
	public void configure(HttpSecurity http) throws Exception {
		ApplicationContext context = http.getSharedObject(ApplicationContext.class);

		// here we lookup from the ApplicationContext. You can also just create a new instance.
		MyFilter myFilter = context.getBean(MyFilter.class);
		myFilter.setFlag(flag);
		http.addFilterBefore(myFilter, UsernamePasswordAuthenticationFilter.class);
	}

	public MyCustomDsl flag(boolean value) {
		this.flag = value;
		return this;
	}

	public static MyCustomDsl customDsl() {
		return new MyCustomDsl();
	}
}
----
====

[NOTE]
====
This is actually how methods like `HttpSecurity.authorizeRequests()` are implemented.
====

You can then use the custom DSL:

====
[source,java]
----
@Configuration
@EnableWebSecurity
public class Config {
	@Bean
	public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
		http
			.apply(customDsl())
				.flag(true)
				.and()
			...;
		return http.build();
	}
}
----
====

The code is invoked in the following order:

* Code in the `Config.configure` method is invoked
* Code in the `MyCustomDsl.init` method is invoked
* Code in the `MyCustomDsl.configure` method is invoked

If you want, you can have `HttpSecurity` add `MyCustomDsl` by default by using `SpringFactories`.
For example, you can create a resource on the classpath named `META-INF/spring.factories` with the following contents:

.META-INF/spring.factories
====
[source]
----
org.springframework.security.config.annotation.web.configurers.AbstractHttpConfigurer = sample.MyCustomDsl
----
====

You can also explicit disable the default:

====
[source,java]
----
@EnableWebSecurity
public class Config {
	@Bean
	public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
		http
			.apply(customDsl()).disable()
			...;
		return http.build();
	}
}
----
====

[[post-processing-configured-objects]]
== Post Processing Configured Objects

Spring Security's Java configuration does not expose every property of every object that it configures.
This simplifies the configuration for a majority of users.
After all, if every property were exposed, users could use standard bean configuration.

While there are good reasons to not directly expose every property, users may still need more advanced configuration options.
To address this issue, Spring Security introduces the concept of an `ObjectPostProcessor`, which can be used to modify or replace many of the `Object` instances created by the Java Configuration.
For example, to configure the `filterSecurityPublishAuthorizationSuccess` property on `FilterSecurityInterceptor`, you can use the following:

====
[source,java]
----
@Bean
public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
	http
		.authorizeRequests(authorize -> authorize
			.anyRequest().authenticated()
			.withObjectPostProcessor(new ObjectPostProcessor<FilterSecurityInterceptor>() {
				public <O extends FilterSecurityInterceptor> O postProcess(
						O fsi) {
					fsi.setPublishAuthorizationSuccess(true);
					return fsi;
				}
			})
		);
	return http.build();
}
----
====
