Register NullRequestCache When Disabled

Fixes: gh-6102

config/src/main/java/org/springframework/security/config/annotation/web/configurers/RequestCacheConfigurer.java

@@ -23,6 +23,7 @@ import org.springframework.http.MediaType;
 import org.springframework.security.config.annotation.web.HttpSecurityBuilder;
 import org.springframework.security.config.annotation.web.builders.HttpSecurity;
 import org.springframework.security.web.savedrequest.HttpSessionRequestCache;
+import org.springframework.security.web.savedrequest.NullRequestCache;
 import org.springframework.security.web.savedrequest.RequestCache;
 import org.springframework.security.web.savedrequest.RequestCacheAwareFilter;
 import org.springframework.security.web.util.matcher.AndRequestMatcher;
@@ -85,6 +86,12 @@ public final class RequestCacheConfigurer<H extends HttpSecurityBuilder<H>> exte
 		return this;
 	}
 
+	@Override
+	public H disable() {
+		getBuilder().setSharedObject(RequestCache.class, new NullRequestCache());
+		return super.disable();
+	}
+
 	@Override
 	public void init(H http) throws Exception {
 		http.setSharedObject(RequestCache.class, getRequestCache(http));

config/src/test/java/org/springframework/security/config/annotation/web/configurers/RequestCacheConfigurerTests.java

@@ -236,6 +236,28 @@ public class RequestCacheConfigurerTests {
 		}
 	}
 
+	// gh-6102
+	@Test
+	public void getWhenRequestCacheIsDisabledThenExceptionTranslationFilterDoesNotStoreRequest() throws Exception {
+		this.spring.register(RequestCacheDisabledConfig.class, DefaultSecurityConfig.class).autowire();
+
+		MockHttpSession session = (MockHttpSession)
+				this.mvc.perform(get("/bob"))
+						.andReturn().getRequest().getSession();
+
+		this.mvc.perform(formLogin(session))
+				.andExpect(redirectedUrl("/"));
+	}
+
+	@EnableWebSecurity
+	static class RequestCacheDisabledConfig extends WebSecurityConfigurerAdapter {
+		@Override
+		protected void configure(HttpSecurity http) throws Exception {
+			super.configure(http);
+			http.requestCache().disable();
+		}
+	}
+
 	@EnableWebSecurity
 	static class DefaultSecurityConfig {