From db8eb922a8d63e6565cd6a9933d716541f129d50 Mon Sep 17 00:00:00 2001
From: HenryNebula <22852427+HenryNebula@users.noreply.github.com>
Date: Sun, 26 Apr 2026 12:05:22 -0400
Subject: [PATCH] Add jvm_args parameter to connect() for custom JVM arguments
 (fixes #90)

Users can now pass custom JVM arguments (e.g., -Duser.timezone,
-Dfile.encoding=UTF-8) via the jvm_args parameter. These are applied
on the first connect() call when the JVM starts.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 jaydebeapiarrow/__init__.py | 14 +++++++++++---
 test/test_integration.py    | 28 ++++++++++++++++++++++++++++
 test/test_mock.py           | 15 ++++++++++++++-
 3 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/jaydebeapiarrow/__init__.py b/jaydebeapiarrow/__init__.py
index 9b1f8053..67760721 100644
--- a/jaydebeapiarrow/__init__.py
+++ b/jaydebeapiarrow/__init__.py
@@ -128,9 +128,12 @@ def _handle_sql_exception_jpype():
         
     reraise(exc_type, exc_info[1], exc_info[2])
 
-def _jdbc_connect_jpype(jclassname, url, driver_args, jars, libs):
+def _jdbc_connect_jpype(jclassname, url, driver_args, jars, libs, jvm_args=None):
     import jpype
     if not _is_jvm_started():
+        args = []
+        if jvm_args:
+            args.extend(jvm_args)
         class_path = []
         if jars:
             class_path.extend(jars)
@@ -379,7 +382,7 @@ def TimestampFromTicks(ticks):
     return Timestamp(*time.localtime(ticks)[:6])
 
 # DB-API 2.0 Module Interface connect constructor
-def connect(jclassname, url, driver_args=None, jars=None, libs=None):
+def connect(jclassname, url, driver_args=None, jars=None, libs=None, jvm_args=None):
     """Open a connection to a database using a JDBC driver and return
     a Connection instance.
 
@@ -395,6 +398,11 @@ def connect(jclassname, url, driver_args=None, jars=None, libs=None):
     jars: Jar filename or sequence of filenames for the JDBC driver
     libs: Dll/so filenames or sequence of dlls/sos used as shared
           library by the JDBC driver
+    jvm_args: Sequence of additional JVM arguments (e.g.
+           ['-Duser.timezone=America/Toronto',
+            '-Dfile.encoding=UTF-8']). Only used on the first
+           connect() call when the JVM is started. Ignored on
+           subsequent calls since the JVM cannot be restarted.
     """
     if isinstance(driver_args, str):
         driver_args = [ driver_args ]
@@ -410,7 +418,7 @@ def connect(jclassname, url, driver_args=None, jars=None, libs=None):
             libs = [ libs ]
     else:
         libs = []
-    jconn = _jdbc_connect(jclassname, url, driver_args, jars, libs)
+    jconn = _jdbc_connect(jclassname, url, driver_args, jars, libs, jvm_args)
     return Connection(jconn, jclassname)
 
 # DB-API 2.0 Connection Object
diff --git a/test/test_integration.py b/test/test_integration.py
index c9242f0d..3f369f4e 100644
--- a/test/test_integration.py
+++ b/test/test_integration.py
@@ -2007,3 +2007,31 @@ def test_hsqldb_jar_path_with_spaces(self):
             )
             self.assertTrue(result.stdout.strip().startswith('OK'),
                             f'Connection failed: {result.stdout}\n{result.stderr}')
+
+
+class JvmArgsTest(unittest.TestCase):
+    """Test that jvm_args parameter passes custom JVM arguments on first connect."""
+
+    _TEST_PROP = 'jaydebeapiarrow.test.jvmargs'
+
+    def setUp(self):
+        import jpype
+        if jpype.isJVMStarted():
+            self.skipTest("JVM already started; jvm_args only takes effect on first connect")
+
+    def test_jvm_args_sets_system_property(self):
+        """jvm_args should set JVM system properties during startup."""
+        import jpype
+        import glob
+        mock_jars = glob.glob(os.path.join(_THIS_DIR, 'mock-jars', 'mockdriver*.jar'))
+        c = jaydebeapiarrow.connect(
+            'org.jaydebeapi.mockdriver.MockDriver',
+            'jdbc:jaydebeapi://dummyurl',
+            jars=mock_jars,
+            jvm_args=[f'-D{self._TEST_PROP}=hello_from_jvm_args']
+        )
+        try:
+            prop_value = jpype.java.lang.System.getProperty(self._TEST_PROP)
+            self.assertEqual(prop_value, 'hello_from_jvm_args')
+        finally:
+            c.close()
diff --git a/test/test_mock.py b/test/test_mock.py
index c45843d4..f2daea38 100644
--- a/test/test_mock.py
+++ b/test/test_mock.py
@@ -1248,7 +1248,6 @@ def test_rollback_called_when_autocommit_disabled(self):
         self.conn.jconn.mockAutoCommit(False)
         self.conn.rollback()
 
-
     def test_lastrowid_exists_and_is_none(self):
         """PEP-249: lastrowid attribute must exist on cursor (fixes #84)."""
         with self.conn.cursor() as cursor:
@@ -1273,6 +1272,20 @@ def test_lastrowid_none_after_executemany(self):
         """lastrowid should be None after executemany (mock driver limitation: skip)."""
         self.skipTest("Mock driver executeBatch returns None; covered by integration test")
 
+    # --- JVM args parameter test (issue #90) ---
+
+    def test_connect_accepts_jvm_args(self):
+        """connect() should accept jvm_args parameter without error."""
+        import jpype
+        # The JVM is already started by setUp, so jvm_args won't take effect,
+        # but the parameter should be accepted without raising TypeError.
+        conn = jaydebeapiarrow.connect(
+            'org.jaydebeapi.mockdriver.MockDriver',
+            'jdbc:jaydebeapi://dummyurl',
+            jvm_args=['-Duser.timezone=UTC']
+        )
+        conn.close()
+
 
 class JarPathSpacesTest(unittest.TestCase):
     """Tests for JAR file paths containing spaces (issue #86).