Make driver-, session- and transaction config serializable.

driver/src/main/java/org/neo4j/driver/Config.java

@@ -19,6 +19,7 @@
 package org.neo4j.driver;
 
 import java.io.File;
+import java.io.Serializable;
 import java.net.InetAddress;
 import java.util.Objects;
 import java.util.concurrent.TimeUnit;
@@ -64,8 +65,10 @@
  * @since 1.0
  */
 @Immutable
-public class Config
+public class Config implements Serializable
 {
+    private static final long serialVersionUID = -4496545746399601108L;
+
     private static final Config EMPTY = builder().build();
 
     /** User defined logging */
@@ -780,8 +783,10 @@ public Config build()
     /**
      * Control how the driver determines if it can trust the encryption certificates provided by the Neo4j instance it is connected to.
      */
-    public static class TrustStrategy
+    public static class TrustStrategy implements Serializable
     {
+        private static final long serialVersionUID = -1631888096243987740L;
+
         /**
          * The trust strategy that the driver supports
          */

driver/src/main/java/org/neo4j/driver/SessionConfig.java

@@ -20,6 +20,7 @@
 
 import org.reactivestreams.Subscription;
 
+import java.io.Serializable;
 import java.util.Arrays;
 import java.util.Objects;
 import java.util.Optional;
@@ -33,14 +34,16 @@
 /**
  * The session configurations used to configure a session.
  */
-public class SessionConfig
+public class SessionConfig implements Serializable
 {
+    private static final long serialVersionUID = 5773462156979050657L;
+
     private static final SessionConfig EMPTY = builder().build();
 
     private final Iterable<Bookmark> bookmarks;
     private final AccessMode defaultAccessMode;
     private final String database;
-    private final Optional<Long> fetchSize;
+    private final Long fetchSize;
     private final String impersonatedUser;
 
     private SessionConfig( Builder builder )
@@ -123,7 +126,7 @@ public Optional<String> database()
      */
     public Optional<Long> fetchSize()
     {
-        return fetchSize;
+        return Optional.ofNullable( fetchSize );
     }
 
     /**
@@ -170,7 +173,7 @@ public String toString()
      */
     public static class Builder
     {
-        private Optional<Long> fetchSize = Optional.empty();
+        private Long fetchSize = null;
         private Iterable<Bookmark> bookmarks = null;
         private AccessMode defaultAccessMode = AccessMode.WRITE;
         private String database = null;
@@ -278,7 +281,7 @@ public Builder withDatabase( String database )
          */
         public Builder withFetchSize( long size )
         {
-            this.fetchSize = Optional.of( assertValidFetchSize( size ) );
+            this.fetchSize = assertValidFetchSize( size );
             return this;
         }
 

driver/src/main/java/org/neo4j/driver/TransactionConfig.java

@@ -18,7 +18,9 @@
  */
 package org.neo4j.driver;
 
+import java.io.Serializable;
 import java.time.Duration;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 
@@ -61,17 +63,22 @@
  *
  * @see Session
  */
-public class TransactionConfig
+public class TransactionConfig implements Serializable
 {
+    private static final long serialVersionUID = -7954949878657177280L;
+
     private static final TransactionConfig EMPTY = builder().build();
 
     private final Duration timeout;
-    private final Map<String,Value> metadata;
+    private final Map<String,Object> metadata;
+
+    // Values are not serializable, hence, we keep a transient volatile map of them around
+    private transient volatile Map<String, Value> convertedMetadata;
 
     private TransactionConfig( Builder builder )
     {
         this.timeout = builder.timeout;
-        this.metadata = unmodifiableMap( builder.metadata );
+        this.metadata = builder.metadata;
     }
 
     /**
@@ -111,7 +118,20 @@ public Duration timeout()
      */
     public Map<String,Value> metadata()
     {
-        return metadata;
+        Map<String,Value> result = this.convertedMetadata;
+        if ( result == null )
+        {
+            synchronized ( this )
+            {
+                result = this.convertedMetadata;
+                if ( result == null )
+                {
+                    this.convertedMetadata = unmodifiableMap( Extract.mapOfValues( this.metadata ) );
+                    result = this.convertedMetadata;
+                }
+            }
+        }
+        return result;
     }
 
     /**
@@ -161,7 +181,7 @@ public String toString()
     public static class Builder
     {
         private Duration timeout;
-        private Map<String,Value> metadata = emptyMap();
+        private Map<String,Object> metadata = emptyMap();
 
         private Builder()
         {
@@ -202,7 +222,8 @@ public Builder withTimeout( Duration timeout )
         public Builder withMetadata( Map<String,Object> metadata )
         {
             requireNonNull( metadata, "Transaction metadata should not be null" );
-            this.metadata = Extract.mapOfValues( metadata );
+            metadata.values().forEach( Extract::assertParameter ); // Just assert valid parameters but don't create a value map yet
+            this.metadata = new HashMap<>( metadata ); // Create a defensive copy
             return this;
         }
 

driver/src/main/java/org/neo4j/driver/internal/InternalBookmark.java

@@ -18,6 +18,7 @@
  */
 package org.neo4j.driver.internal;
 
+import java.io.Serializable;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.Objects;
@@ -28,8 +29,10 @@
 
 import static java.util.Objects.requireNonNull;
 
-public final class InternalBookmark implements Bookmark
+public final class InternalBookmark implements Bookmark, Serializable
 {
+    private static final long serialVersionUID = 8196096018245038950L;
+
     private static final InternalBookmark EMPTY = new InternalBookmark( Collections.emptySet() );
 
     private final Set<String> values;

driver/src/main/java/org/neo4j/driver/internal/SecuritySettings.java

@@ -19,6 +19,7 @@
 package org.neo4j.driver.internal;
 
 import java.io.IOException;
+import java.io.Serializable;
 import java.security.GeneralSecurityException;
 
 import org.neo4j.driver.Config;
@@ -30,8 +31,10 @@
 import static org.neo4j.driver.internal.Scheme.isSecurityScheme;
 import static org.neo4j.driver.internal.security.SecurityPlanImpl.insecure;
 
-public class SecuritySettings
+public class SecuritySettings implements Serializable
 {
+    private static final long serialVersionUID = 4494615367164106576L;
+
     private static final boolean DEFAULT_ENCRYPTED = false;
     private static final Config.TrustStrategy DEFAULT_TRUST_STRATEGY = Config.TrustStrategy.trustSystemCertificates();
     private static final SecuritySettings DEFAULT = new SecuritySettings( DEFAULT_ENCRYPTED, DEFAULT_TRUST_STRATEGY );

driver/src/main/java/org/neo4j/driver/internal/logging/ConsoleLogging.java

@@ -19,6 +19,7 @@
 package org.neo4j.driver.internal.logging;
 
 import java.io.PrintWriter;
+import java.io.Serializable;
 import java.io.StringWriter;
 import java.time.LocalDateTime;
 import java.util.Objects;
@@ -39,8 +40,10 @@
  *
  * @see Logging#console(Level)
  */
-public class ConsoleLogging implements Logging
+public class ConsoleLogging implements Logging, Serializable
 {
+    private static final long serialVersionUID = 9205935204074879150L;
+
     private final Level level;
 
     public ConsoleLogging( Level level )

driver/src/main/java/org/neo4j/driver/internal/logging/DevNullLogging.java

@@ -18,11 +18,15 @@
  */
 package org.neo4j.driver.internal.logging;
 
+import java.io.Serializable;
+
 import org.neo4j.driver.Logger;
 import org.neo4j.driver.Logging;
 
-public class DevNullLogging implements Logging
+public class DevNullLogging implements Logging, Serializable
 {
+    private static final long serialVersionUID = -2632752338512373821L;
+
     public static final Logging DEV_NULL_LOGGING = new DevNullLogging();
 
     private DevNullLogging()
@@ -34,4 +38,14 @@ public Logger getLog( String name )
     {
         return DevNullLogger.DEV_NULL_LOGGER;
     }
+
+    // Don't remove that apparently unused method.
+    // It is involved during deserialization after readObject on the new object.
+    // The returned value replaces the object read.
+    // An enum would be preferable, but would not be API compatible.
+    // Reference: https://docs.oracle.com/en/java/javase/17/docs/specs/serialization/input.html#the-readresolve-method andJoshua Bloch, Effective Java 3rd edition
+    private Object readResolve()
+    {
+        return DEV_NULL_LOGGING;
+    }
 }

driver/src/main/java/org/neo4j/driver/internal/logging/JULogging.java

@@ -18,6 +18,7 @@
  */
 package org.neo4j.driver.internal.logging;
 
+import java.io.Serializable;
 import java.util.logging.Level;
 
 import org.neo4j.driver.Logger;
@@ -29,8 +30,10 @@
  *
  * @see Logging#javaUtilLogging(Level)
  */
-public class JULogging implements Logging
+public class JULogging implements Logging, Serializable
 {
+    private static final long serialVersionUID = -1145576859241657833L;
+
     private final Level loggingLevel;
 
     public JULogging( Level loggingLevel )

driver/src/main/java/org/neo4j/driver/internal/logging/Slf4jLogging.java

@@ -20,6 +20,8 @@
 
 import org.slf4j.LoggerFactory;
 
+import java.io.Serializable;
+
 import org.neo4j.driver.Logger;
 import org.neo4j.driver.Logging;
 
@@ -29,8 +31,10 @@
  *
  * @see Logging#slf4j()
  */
-public class Slf4jLogging implements Logging
+public class Slf4jLogging implements Logging, Serializable
 {
+    private static final long serialVersionUID = 4120390028025944991L;
+
     @Override
     public Logger getLog( String name )
     {

driver/src/main/java/org/neo4j/driver/internal/retry/RetrySettings.java

@@ -18,8 +18,12 @@
  */
 package org.neo4j.driver.internal.retry;
 
-public final class RetrySettings
+import java.io.Serializable;
+
+public final class RetrySettings implements Serializable
 {
+    private static final long serialVersionUID = -2895062473220745239L;
+
     public static final RetrySettings DEFAULT =
             new RetrySettings( ExponentialBackoffRetryLogic.DEFAULT_MAX_RETRY_TIME_MS );