feat: implement eager close ResultSet mode (enabled by default)

ojp-server/src/main/java/org/openjproxy/grpc/server/ServerConfiguration.java

@@ -81,6 +81,9 @@ public class ServerConfiguration {
     private static final String TELEMETRY_POOL_METRICS_ENABLED_KEY = "ojp.telemetry.pool.metrics.enabled";
     private static final String TELEMETRY_CACHE_METRICS_ENABLED_KEY = "ojp.telemetry.cache.metrics.enabled";
 
+    // Eager Close ResultSet mode configuration key
+    private static final String EAGER_CLOSE_ENABLED_KEY = "ojp.resultset.eagerClose.enabled";
+
     // TLS configuration keys
     private static final String TLS_ENABLED_KEY = "ojp.server.tls.enabled";
     private static final String TLS_KEYSTORE_PATH_KEY = "ojp.server.tls.keystore.path";
@@ -155,6 +158,9 @@ public class ServerConfiguration {
     public static final boolean DEFAULT_TELEMETRY_POOL_METRICS_ENABLED = true; // Enabled by default when OpenTelemetry is enabled
     public static final boolean DEFAULT_TELEMETRY_CACHE_METRICS_ENABLED = true; // Enabled by default when OpenTelemetry is enabled
 
+    // Eager Close ResultSet mode default values
+    public static final boolean DEFAULT_EAGER_CLOSE_ENABLED = true; // Enabled by default
+
     // TLS default values
     public static final boolean DEFAULT_TLS_ENABLED = false; // Disabled by default for backwards compatibility
     public static final boolean DEFAULT_TLS_CLIENT_AUTH_REQUIRED = false; // mTLS disabled by default
@@ -247,6 +253,9 @@ public class ServerConfiguration {
     private final String tlsTruststoreType;
     private final boolean tlsClientAuthRequired;
 
+    // Eager Close ResultSet mode configuration
+    private final boolean eagerCloseEnabled;
+
     // ResultSet streaming configuration
     private final int resultsetRowsPerBlock;
 
@@ -316,6 +325,9 @@ public ServerConfiguration() {
         this.tlsTruststoreType = getStringProperty(TLS_TRUSTSTORE_TYPE_KEY, "JKS");
         this.tlsClientAuthRequired = getBooleanProperty(TLS_CLIENT_AUTH_REQUIRED_KEY, DEFAULT_TLS_CLIENT_AUTH_REQUIRED);
 
+        // Eager Close ResultSet mode configuration
+        this.eagerCloseEnabled = getBooleanProperty(EAGER_CLOSE_ENABLED_KEY, DEFAULT_EAGER_CLOSE_ENABLED);
+
         // Tracing configuration
         this.tracingEnabled = getBooleanProperty(TRACING_ENABLED_KEY, DEFAULT_TRACING_ENABLED);
         this.tracingEndpoint = getStringProperty(TRACING_ENDPOINT_KEY, DEFAULT_TRACING_ENDPOINT);
@@ -497,6 +509,8 @@ private void logConfigurationSummary() {
             logger.info("  TLS Keystore Type: {}", tlsKeystoreType);
             logger.info("  TLS Truststore Type: {}", tlsTruststoreType);
         }
+        logger.info("Eager Close ResultSet Mode:");
+        logger.info("  Eager Close Enabled: {}", eagerCloseEnabled);
         logger.info("Tracing Configuration:");
         logger.info("  Tracing Enabled: {}", tracingEnabled);
         if (tracingEnabled) {
@@ -781,6 +795,10 @@ public boolean isTelemetryCacheMetricsEnabled() {
         return telemetryCacheMetricsEnabled;
     }
 
+    public boolean isEagerCloseEnabled() {
+        return eagerCloseEnabled;
+    }
+
     public int getResultsetRowsPerBlock() {
         return resultsetRowsPerBlock;
     }

ojp-server/src/main/java/org/openjproxy/grpc/server/SessionManagerImpl.java

@@ -117,7 +117,8 @@ public String registerResultSet(SessionInfo sessionInfo, ResultSet rs) {
 
     @Override
     public ResultSet getResultSet(SessionInfo sessionInfo, String uuid) {
-        return this.sessionMap.get(sessionInfo.getSessionUUID()).getResultSet(uuid);
+        Session session = this.sessionMap.get(sessionInfo.getSessionUUID());
+        return session != null ? session.getResultSet(uuid) : null;
     }
 
     @Override
@@ -129,7 +130,8 @@ public String registerStatement(SessionInfo sessionInfo, Statement stmt) {
 
     @Override
     public Statement getStatement(SessionInfo sessionInfo, String uuid) {
-        return this.sessionMap.get(sessionInfo.getSessionUUID()).getStatement(uuid);
+        Session session = this.sessionMap.get(sessionInfo.getSessionUUID());
+        return session != null ? session.getStatement(uuid) : null;
     }
 
     @Override
@@ -141,7 +143,8 @@ public String registerPreparedStatement(SessionInfo sessionInfo, PreparedStateme
 
     @Override
     public PreparedStatement getPreparedStatement(SessionInfo sessionInfo, String uuid) {
-        return this.sessionMap.get(sessionInfo.getSessionUUID()).getPreparedStatement(uuid);
+        Session session = this.sessionMap.get(sessionInfo.getSessionUUID());
+        return session != null ? session.getPreparedStatement(uuid) : null;
     }
 
     @Override
@@ -153,7 +156,8 @@ public String registerCallableStatement(SessionInfo sessionInfo, CallableStateme
 
     @Override
     public CallableStatement getCallableStatement(SessionInfo sessionInfo, String uuid) {
-        return this.sessionMap.get(sessionInfo.getSessionUUID()).getCallableStatement(uuid);
+        Session session = this.sessionMap.get(sessionInfo.getSessionUUID());
+        return session != null ? session.getCallableStatement(uuid) : null;
     }
 
     @Override
@@ -235,13 +239,15 @@ public void waitLobStreamsConsumption(SessionInfo sessionInfo) {
     @Override
     public void registerAttr(SessionInfo sessionInfo, String key, Object value) {
         Session session = this.sessionMap.get(sessionInfo.getSessionUUID());
-        session.addAttr(key, value);
+        if (session != null) {
+            session.addAttr(key, value);
+        }
     }
 
     @Override
     public Object getAttr(SessionInfo sessionInfo, String key) {
         Session session = this.sessionMap.get(sessionInfo.getSessionUUID());
-        return session.getAttr(key);
+        return session != null ? session.getAttr(key) : null;
     }
 
     @Override

ojp-server/src/main/java/org/openjproxy/grpc/server/action/resource/CallResourceAction.java

@@ -176,6 +176,17 @@ public void execute(ActionContext context, CallResourceRequest request, StreamOb
                 responseBuilder.setSession(request.getSession());
             }
 
+            // If the session was eagerly terminated (e.g., after a fully-read ResultSet with no LOBs
+            // outside a transaction), the resource may be null. Return an empty success response so
+            // that close() calls from the JDBC driver do not surface as errors to the application.
+            if (resource == null) {
+                log.debug("Resource not found for session {} (session may have been eagerly closed) - returning empty success",
+                        request.getSession().getSessionUUID());
+                responseObserver.onNext(responseBuilder.build());
+                responseObserver.onCompleted();
+                return;
+            }
+
             List<Object> paramsReceived = (request.getTarget().getParamsCount() > 0) ?
                     ProtoConverter.parameterValuesToObjectList(request.getTarget().getParamsList()) : EMPTY_LIST;
             Class<?> clazz = resource.getClass();

ojp-server/src/main/java/org/openjproxy/grpc/server/action/session/ResultSetHelper.java

@@ -16,6 +16,7 @@
 import org.openjproxy.grpc.server.utils.DateTimeUtils;
 
 import java.sql.Clob;
+import java.sql.Connection;
 import java.sql.Date;
 import java.sql.ResultSet;
 import java.sql.SQLException;
@@ -97,9 +98,19 @@ public static void handleResultSet(ActionContext context, SessionInfo session, S
         String resultSetMode = "";
         boolean resultSetMetadataCollected = false;
 
+        boolean eagerCloseEnabled = context.getServerConfiguration().isEagerCloseEnabled();
+        if (eagerCloseEnabled) {
+            // Snapshot metadata early so it survives RS closure.
+            collectResultSetMetadata(context, session, resultSetUUID, rs);
+            resultSetMetadataCollected = true;
+        }
+
         while (rs.next()) {
+            // DB2 requires metadata to be captured before LOBs can move the cursor;
+            // skip if already collected (e.g., by eager-close pre-loop snapshot above).
             if (DbName.DB2.equals(dbName) && !resultSetMetadataCollected) {
                 collectResultSetMetadata(context, session, resultSetUUID, rs);
+                resultSetMetadataCollected = true;
             }
             justSent = false;
             row++;
@@ -223,6 +234,50 @@ public static void handleResultSet(ActionContext context, SessionInfo session, S
 
         responseObserver.onCompleted();
 
+        if (shouldEagerClose(context, session, dbName, resultSetMode, eagerCloseEnabled)) {
+            Connection connForCheck = context.getSessionManager().getConnection(session);
+            if (connForCheck != null && connForCheck.getAutoCommit()
+                    && rs.getType() == ResultSet.TYPE_FORWARD_ONLY) {
+                try {
+                    rs.close();
+                    log.debug("Eager close: closed forward-only ResultSet {} (no LOBs, auto-commit, non-XA)",
+                            resultSetUUID);
+                } catch (SQLException e) {
+                    log.debug("Eager close: error closing ResultSet: {}", e.getMessage());
+                }
+            }
+        }
+    }
+
+    /**
+     * Returns {@code true} when the preconditions for eagerly closing the ResultSet cursor are met.
+     * <p>
+     * All five conditions must hold:
+     * <ol>
+     *   <li>The eager close feature is enabled.</li>
+     *   <li>The database is not DB2 (DB2 requires post-iteration metadata access via a session attribute).</li>
+     *   <li>The result set was not in row-by-row (LOB) mode for SQL Server / DB2.</li>
+     *   <li>No LOBs or binary streams were registered in the session during row processing.</li>
+     *   <li>The session is not an XA session (XA lifecycle is managed separately).</li>
+     * </ol>
+     * Two additional guards are applied by the caller:
+     * <ul>
+     *   <li><b>auto-commit check</b> — the session must not be inside an active transaction.</li>
+     *   <li><b>forward-only check</b> — only {@link ResultSet#TYPE_FORWARD_ONLY} result sets are
+     *       closed early; scrollable result sets must stay open so the client can call navigation
+     *       methods such as {@code first()}, {@code last()}, and {@code absolute()} after the stream
+     *       completes.</li>
+     * </ul>
+     * The session and its Statement are intentionally left alive after the RS cursor is freed so that
+     * the JDBC connection can be reused for subsequent statements without interruption.
+     */
+    private static boolean shouldEagerClose(ActionContext context, SessionInfo session, DbName dbName,
+            String resultSetMode, boolean eagerCloseEnabled) {
+        return eagerCloseEnabled
+                && !DbName.DB2.equals(dbName)
+                && resultSetMode.isEmpty()
+                && context.getSessionManager().getLobs(session).isEmpty()
+                && !session.getIsXA();
     }
 
     /**