Set "rolePrefix" in ReactiveMethodSecurityConfiguration

Currently, `GrantedAuthorityDefaults` is not considered in
`ReactiveMethodSecurityConfiguration`.
This commit updates the configuration to be aware of
`GrantedAuthorityDefaults` and update `rolePrefix` when the bean is
available.

Also, use the same instance of `DefaultMethodSecurityExpressionHandler`
when constructing `ExpressionBasedAnnotationAttributeFactory`.

config/src/test/java/org/springframework/security/config/annotation/method/configuration/ReactiveMethodSecurityConfigurationTests.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright 2002-2019 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.config.annotation.method.configuration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.expression.EvaluationContext;
+import org.springframework.security.access.expression.SecurityExpressionRoot;
+import org.springframework.security.access.expression.method.DefaultMethodSecurityExpressionHandler;
+import org.springframework.security.access.intercept.method.MockMethodInvocation;
+import org.springframework.security.authentication.TestingAuthenticationToken;
+import org.springframework.security.config.core.GrantedAuthorityDefaults;
+import org.springframework.security.config.test.SpringTestRule;
+
+/**
+ * @author Tadaya Tsuyukubo
+ */
+public class ReactiveMethodSecurityConfigurationTests {
+
+	@Rule
+	public final SpringTestRule spring = new SpringTestRule();
+
+	@Autowired
+	DefaultMethodSecurityExpressionHandler methodSecurityExpressionHandler;
+
+	@Test
+	public void rolePrefixWithGrantedAuthorityDefaults() {
+		this.spring.register(WithRolePrefixConfiguration.class).autowire();
+
+		TestingAuthenticationToken authentication = new TestingAuthenticationToken(
+				"principal", "credential", "CUSTOM_ABC");
+		MockMethodInvocation methodInvocation = mock(MockMethodInvocation.class);
+
+		EvaluationContext context = this.methodSecurityExpressionHandler
+				.createEvaluationContext(authentication, methodInvocation);
+		SecurityExpressionRoot root = (SecurityExpressionRoot) context.getRootObject()
+				.getValue();
+
+		assertThat(root.hasRole("ROLE_ABC")).isFalse();
+		assertThat(root.hasRole("ROLE_CUSTOM_ABC")).isFalse();
+		assertThat(root.hasRole("CUSTOM_ABC")).isTrue();
+		assertThat(root.hasRole("ABC")).isTrue();
+	}
+
+	@Test
+	public void rolePrefixWithDefaultConfig() {
+		this.spring.register(ReactiveMethodSecurityConfiguration.class).autowire();
+
+		TestingAuthenticationToken authentication = new TestingAuthenticationToken(
+				"principal", "credential", "ROLE_ABC");
+		MockMethodInvocation methodInvocation = mock(MockMethodInvocation.class);
+
+		EvaluationContext context = this.methodSecurityExpressionHandler
+				.createEvaluationContext(authentication, methodInvocation);
+		SecurityExpressionRoot root = (SecurityExpressionRoot) context.getRootObject()
+				.getValue();
+
+		assertThat(root.hasRole("ROLE_ABC")).isTrue();
+		assertThat(root.hasRole("ABC")).isTrue();
+	}
+
+	@Configuration
+	@EnableReactiveMethodSecurity // this imports ReactiveMethodSecurityConfiguration
+	static class WithRolePrefixConfiguration {
+		@Bean
+		GrantedAuthorityDefaults grantedAuthorityDefaults() {
+			return new GrantedAuthorityDefaults("CUSTOM_");
+		}
+	}
+
+}