use atomic booleans to track closed state

ocfl-java-core/src/main/java/edu/wisc/library/ocfl/core/DefaultOcflRepository.java

@@ -76,6 +76,7 @@
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Consumer;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
@@ -105,7 +106,7 @@ public class DefaultOcflRepository implements OcflRepository {
 
     private Clock clock;
 
-    private boolean closed = false;
+    private final AtomicBoolean closed = new AtomicBoolean(false);
 
     /**
      * @see OcflRepositoryBuilder
@@ -550,8 +551,9 @@ public void importObject(Path objectPath, OcflOption... options) {
     public void close() {
         LOG.debug("Close OCFL repository");
 
-        closed = true;
-        storage.close();
+        if (closed.compareAndSet(false, true)) {
+            storage.close();
+        }
     }
 
     /**
@@ -875,7 +877,7 @@ protected OffsetDateTime now(VersionInfo versionInfo) {
     }
 
     protected void ensureOpen() {
-        if (closed) {
+        if (closed.get()) {
             throw new OcflStateException(DefaultOcflRepository.class.getName() + " is closed.");
         }
     }

ocfl-java-core/src/main/java/edu/wisc/library/ocfl/core/storage/AbstractOcflStorage.java

@@ -30,17 +30,18 @@
 import edu.wisc.library.ocfl.core.extension.ExtensionSupportEvaluator;
 import edu.wisc.library.ocfl.core.extension.OcflExtensionConfig;
 import edu.wisc.library.ocfl.core.inventory.InventoryMapper;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 /**
  * OcflStorage abstract implementation that handles managing the repository's state, initialized, open, close.
  */
 public abstract class AbstractOcflStorage implements OcflStorage {
 
+    private final AtomicBoolean closed = new AtomicBoolean(false);
+    private final AtomicBoolean initialized = new AtomicBoolean(false);
+
     protected InventoryMapper inventoryMapper;
     protected ExtensionSupportEvaluator supportEvaluator;
-
-    private boolean closed = false;
-    private boolean initialized = false;
     private RepositoryConfig repositoryConfig;
 
     /**
@@ -52,15 +53,15 @@ public synchronized RepositoryConfig initializeStorage(
             OcflExtensionConfig layoutConfig,
             InventoryMapper inventoryMapper,
             ExtensionSupportEvaluator supportEvaluator) {
-        if (this.initialized) {
+        if (this.initialized.get()) {
             return this.repositoryConfig;
         }
 
         this.inventoryMapper = Enforce.notNull(inventoryMapper, "inventoryMapper cannot be null");
         this.supportEvaluator = Enforce.notNull(supportEvaluator, "supportEvaluator cannot be null");
 
         this.repositoryConfig = doInitialize(ocflVersion, layoutConfig);
-        this.initialized = true;
+        this.initialized.set(true);
         return repositoryConfig;
     }
 
@@ -69,7 +70,7 @@ public synchronized RepositoryConfig initializeStorage(
      */
     @Override
     public void close() {
-        closed = true;
+        closed.set(true);
     }
 
     /**
@@ -100,11 +101,11 @@ public void invalidateCache() {
      * Throws an exception if the repository has not been initialized or is closed
      */
     protected void ensureOpen() {
-        if (closed) {
+        if (closed.get()) {
             throw new OcflStateException(this.getClass().getName() + " is closed.");
         }
 
-        if (!initialized) {
+        if (!initialized.get()) {
             throw new OcflStateException(this.getClass().getName() + " must be initialized before it can be used.");
         }
     }