Null safety via JSpecify spring-security-kerberos-test

Closes gh-18551

kerberos/kerberos-test/spring-security-kerberos-test.gradle

@@ -1,6 +1,7 @@
 plugins {
 	id 'io.spring.convention.spring-module'
 	id 'javadoc-warnings-error'
+	id 'security-nullability'
 }
 
 description = 'Spring Security Kerberos Test'

kerberos/kerberos-test/src/main/java/org/springframework/security/kerberos/test/KerberosSecurityTestcase.java

@@ -19,6 +19,7 @@ package org.springframework.security.kerberos.test;
 import java.io.File;
 import java.util.Properties;
 
+import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 
@@ -35,17 +36,23 @@ import org.junit.jupiter.api.BeforeEach;
  */
 public class KerberosSecurityTestcase {
 
-	private MiniKdc kdc;
+	private @Nullable MiniKdc kdc;
 
-	private File workDir;
+	private @Nullable File workDir;
 
-	private Properties conf;
+	private @Nullable Properties conf;
 
 	@BeforeEach
 	public void startMiniKdc() throws Exception {
 		createTestDir();
 		createMiniKdcConf();
 
+		if (this.conf == null) {
+			throw new IllegalStateException("conf must be initialized");
+		}
+		if (this.workDir == null) {
+			throw new IllegalStateException("workDir must be initialized");
+		}
 		this.kdc = new MiniKdc(this.conf, this.workDir);
 		this.kdc.start();
 	}
@@ -73,15 +80,15 @@ public class KerberosSecurityTestcase {
 		}
 	}
 
-	public MiniKdc getKdc() {
+	public @Nullable MiniKdc getKdc() {
 		return this.kdc;
 	}
 
-	public File getWorkDir() {
+	public @Nullable File getWorkDir() {
 		return this.workDir;
 	}
 
-	public Properties getConf() {
+	public @Nullable Properties getConf() {
 		return this.conf;
 	}
 

kerberos/kerberos-test/src/main/java/org/springframework/security/kerberos/test/MiniKdc.java

@@ -34,6 +34,7 @@ import org.apache.kerby.kerberos.kerb.server.KdcConfigKey;
 import org.apache.kerby.kerberos.kerb.server.SimpleKdcServer;
 import org.apache.kerby.util.IOUtil;
 import org.apache.kerby.util.NetworkUtil;
+import org.jspecify.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -197,7 +198,7 @@ public class MiniKdc {
 
 	private Properties conf;
 
-	private SimpleKdcServer simpleKdc;
+	private @Nullable SimpleKdcServer simpleKdc;
 
 	private int port;
 
@@ -205,9 +206,9 @@ public class MiniKdc {
 
 	private File workDir;
 
-	private File krb5conf;
+	private @Nullable File krb5conf;
 
-	private String transport;
+	private @Nullable String transport;
 
 	private boolean krb5Debug;
 
@@ -300,6 +301,9 @@ public class MiniKdc {
 
 	private void prepareKdcServer() throws Exception {
 		// transport
+		if (this.simpleKdc == null) {
+			throw new IllegalStateException("simpleKdc must be initialized");
+		}
 		this.simpleKdc.setWorkDir(this.workDir);
 		this.simpleKdc.setKdcHost(getHost());
 		this.simpleKdc.setKdcRealm(this.realm);
@@ -395,6 +399,9 @@ public class MiniKdc {
 	 * @throws Exception thrown if the principal could not be created.
 	 */
 	public synchronized void createPrincipal(String principal, String password) throws Exception {
+		if (this.simpleKdc == null) {
+			throw new IllegalStateException("MiniKdc must be started before creating principals");
+		}
 		this.simpleKdc.createPrincipal(principal, password);
 	}
 
@@ -405,6 +412,9 @@ public class MiniKdc {
 	 * @throws Exception thrown if the principals or the keytab file could not be created.
 	 */
 	public synchronized void createPrincipal(File keytabFile, String... principals) throws Exception {
+		if (this.simpleKdc == null) {
+			throw new IllegalStateException("MiniKdc must be started before creating principals");
+		}
 		this.simpleKdc.createPrincipals(principals);
 		if (keytabFile.exists() && !keytabFile.delete()) {
 			LOG.error("Failed to delete keytab file: " + keytabFile);

kerberos/kerberos-test/src/main/java/org/springframework/security/kerberos/test/package-info.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2004-present 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.
+ */
+
+@NullMarked
+package org.springframework.security.kerberos.test;
+
+import org.jspecify.annotations.NullMarked;