Propagate TestSecurityContextHolder to SecurityContextHolder

Create SecurityMockMvcResultHandlers to define security related MockMvc ResultHandlers
Create a method to allow copying the SecurityContext from the TestSecurityContextHolder to SecurityContextHolder

Closes gh-9565

docs/manual/src/docs/asciidoc/_includes/servlet/test/mockmvc.adoc

@@ -1889,3 +1889,65 @@ mvc
     }
 ----
 ====
+
+=== SecurityMockMvcResultHandlers
+
+Spring Security provides a few ``ResultHandler``s implementations.
+In order to use Spring Security's ``ResultHandler``s implementations ensure the following static import is used:
+
+[source,java]
+----
+import static org.springframework.security.test.web.servlet.response.SecurityMockMvcResultHandlers.*;
+----
+
+==== Exporting the SecurityContext
+
+Often times we want to query a repository to see if some `MockMvc` request actually persisted in the database.
+In some cases our repository query uses the <<data,Spring Data Integration>> to filter the results based on current user's username or any other property.
+Let's see an example:
+
+A repository interface:
+[source,java]
+----
+private interface MessageRepository extends JpaRepository<Message, Long> {
+	@Query("SELECT m.content FROM Message m WHERE m.sentBy = ?#{ principal?.name }")
+	List<String> findAllUserMessages();
+}
+----
+
+Our test scenario:
+
+[source,java]
+----
+mvc
+	.perform(post("/message")
+		.content("New Message")
+		.contentType(MediaType.TEXT_PLAIN)
+	)
+	.andExpect(status().isOk());
+
+List<String> userMessages = messageRepository.findAllUserMessages();
+assertThat(userMessages).hasSize(1);
+----
+
+This test won't pass because after our request finishes, the `SecurityContextHolder` will be cleared out by the filter chain.
+We can then export the `TestSecurityContextHolder` to our `SecurityContextHolder` and use it as we want:
+
+[source,java]
+----
+mvc
+	.perform(post("/message")
+		.content("New Message")
+		.contentType(MediaType.TEXT_PLAIN)
+	)
+	.andDo(exportTestSecurityContext())
+	.andExpect(status().isOk());
+
+List<String> userMessages = messageRepository.findAllUserMessages();
+assertThat(userMessages).hasSize(1);
+----
+
+[NOTE]
+====
+Remember to clear the `SecurityContextHolder` between your tests, or it may leak amongst them
+====

etc/checkstyle/checkstyle.xml

@@ -14,6 +14,7 @@
 	<module name="io.spring.javaformat.checkstyle.SpringChecks">
 		<property name="excludes" value="io.spring.javaformat.checkstyle.check.SpringHeaderCheck" />
 		<property name="avoidStaticImportExcludes" value="org.springframework.security.test.web.reactive.server.SecurityMockServerConfigurers.*" />
+		<property name="avoidStaticImportExcludes" value="org.springframework.security.test.web.servlet.response.SecurityMockMvcResultHandlers.*" />
 	</module>
 	<module name="com.puppycrawl.tools.checkstyle.TreeWalker">
  		<module name="com.puppycrawl.tools.checkstyle.checks.regexp.RegexpSinglelineJavaCheck">

test/src/main/java/org/springframework/security/test/web/servlet/response/SecurityMockMvcResultHandlers.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2002-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.test.web.servlet.response;
+
+import org.springframework.security.core.context.SecurityContext;
+import org.springframework.security.core.context.SecurityContextHolder;
+import org.springframework.security.test.context.TestSecurityContextHolder;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.MvcResult;
+import org.springframework.test.web.servlet.ResultHandler;
+
+/**
+ * Security related {@link MockMvc} {@link ResultHandler}s
+ *
+ * @author Marcus da Coregio
+ * @since 5.6
+ */
+public final class SecurityMockMvcResultHandlers {
+
+	private SecurityMockMvcResultHandlers() {
+	}
+
+	/**
+	 * Exports the {@link SecurityContext} from {@link TestSecurityContextHolder} to
+	 * {@link SecurityContextHolder}
+	 */
+	public static ResultHandler exportTestSecurityContext() {
+		return new ExportTestSecurityContextHandler();
+	}
+
+	/**
+	 * A {@link ResultHandler} that copies the {@link SecurityContext} from
+	 * {@link TestSecurityContextHolder} to {@link SecurityContextHolder}
+	 *
+	 * @author Marcus da Coregio
+	 * @since 5.6
+	 */
+	private static class ExportTestSecurityContextHandler implements ResultHandler {
+
+		@Override
+		public void handle(MvcResult result) {
+			SecurityContextHolder.setContext(TestSecurityContextHolder.getContext());
+		}
+
+	}
+
+}

test/src/test/java/org/springframework/security/test/web/servlet/response/SecurityMockMvcResultHandlersTest.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright 2002-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.test.web.servlet.response;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.core.context.SecurityContextHolder;
+import org.springframework.security.test.context.support.WithMockUser;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.springframework.test.context.web.WebAppConfiguration;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.context.WebApplicationContext;
+import org.springframework.web.servlet.config.annotation.EnableWebMvc;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.security.test.web.servlet.response.SecurityMockMvcResultHandlers.exportTestSecurityContext;
+import static org.springframework.security.test.web.servlet.setup.SecurityMockMvcConfigurers.springSecurity;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration(classes = SecurityMockMvcResultHandlersTest.Config.class)
+@WebAppConfiguration
+public class SecurityMockMvcResultHandlersTest {
+
+	@Autowired
+	private WebApplicationContext context;
+
+	private MockMvc mockMvc;
+
+	@BeforeEach
+	public void setup() {
+		// @formatter:off
+		this.mockMvc = MockMvcBuilders
+				.webAppContextSetup(this.context)
+				.apply(springSecurity())
+				.build();
+		// @formatter:on
+	}
+
+	@AfterEach
+	public void tearDown() {
+		SecurityContextHolder.clearContext();
+	}
+
+	@Test
+	@WithMockUser
+	public void withTestSecurityContextCopiedToSecurityContextHolder() throws Exception {
+		this.mockMvc.perform(get("/")).andDo(exportTestSecurityContext());
+
+		Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
+
+		assertThat(authentication.getName()).isEqualTo("user");
+		assertThat(authentication.getAuthorities()).hasSize(1).first().hasToString("ROLE_USER");
+	}
+
+	@Test
+	@WithMockUser
+	public void withTestSecurityContextNotCopiedToSecurityContextHolder() throws Exception {
+		this.mockMvc.perform(get("/"));
+
+		Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
+
+		assertThat(authentication).isNull();
+	}
+
+	@EnableWebSecurity
+	@EnableWebMvc
+	static class Config {
+
+		@RestController
+		static class Controller {
+
+			@RequestMapping("/")
+			String ok() {
+				return "ok";
+			}
+
+		}
+
+	}
+
+}