Added null checks and tests to constructors

RequestKey, JaasGrantedAuthority, and SwitchUserGrantedAuthority
assume certain final members are non-null.

Issue: gh-6892

core/src/main/java/org/springframework/security/authentication/jaas/JaasGrantedAuthority.java

@@ -18,6 +18,7 @@ package org.springframework.security.authentication.jaas;
 
 import org.springframework.security.core.GrantedAuthority;
 import org.springframework.security.core.SpringSecurityCoreVersion;
+import org.springframework.util.Assert;
 
 import java.security.Principal;
 
@@ -37,6 +38,8 @@ public final class JaasGrantedAuthority implements GrantedAuthority {
 	private final Principal principal;
 
 	public JaasGrantedAuthority(String role, Principal principal) {
+		Assert.notNull(role, "role cannot be null");
+		Assert.notNull(principal, "principal cannot be null");
 		this.role = role;
 		this.principal = principal;
 	}

core/src/test/java/org/springframework/security/authentication/jaas/JaasGrantedAuthorityTests.java

@@ -0,0 +1,50 @@
+/*
+ * 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.authentication.jaas;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import org.springframework.security.authentication.jaas.JaasGrantedAuthority;
+
+/**
+ *
+ * @author Clement Ng
+ *
+ */
+public class JaasGrantedAuthorityTests {
+
+	/**
+	 * @throws Exception
+	 */
+	@Test
+	public void authorityWithNullRoleFailsAssertion() throws Exception {
+		assertThatThrownBy(() -> new JaasGrantedAuthority(null, null))
+				.isInstanceOf(IllegalArgumentException.class)
+				.hasMessageContaining("role cannot be null");
+	}
+
+	/**
+	 * @throws Exception
+	 */
+	@Test
+	public void authorityWithNullPrincipleFailsAssertion() throws Exception {
+		assertThatThrownBy(() -> new JaasGrantedAuthority("role", null))
+				.isInstanceOf(IllegalArgumentException.class)
+				.hasMessageContaining("principal cannot be null");
+	}
+}