216 fix issue where pyjnius is loaded from global context

src/omotes_simulator_core/entities/assets/ates_cluster.py

@@ -32,21 +32,12 @@
 from omotes_simulator_core.entities.assets.asset_defaults import ATES_DEFAULTS
 
 from omotes_simulator_core.entities.assets.esdl_asset_object import EsdlAssetObject
+from omotes_simulator_core.entities.assets.pyjnius_loader import PyjniusLoader
 from omotes_simulator_core.solver.network.assets.production_asset import ProductionAsset
 from omotes_simulator_core.entities.assets.utils import (
     heat_demand_and_temperature_to_mass_flow,
 )
 
-path = os.path.dirname(__file__)
-import jnius_config  # noqa
-
-jnius_config.add_classpath(os.path.join(path, "bin/jfxrt.jar"))
-jnius_config.add_classpath(os.path.join(path, "bin/rosim-batch-0.4.2.jar"))
-from jnius import autoclass  # noqa
-
-javaioFile = autoclass("java.io.File")
-RosimSequential = autoclass("tno.calc.RosimSequential")
-
 
 class AtesCluster(AssetAbstract):
     """A AtesCluster represents an asset that consumes heat and produces heat."""
@@ -93,6 +84,8 @@ def __init__(self, asset_name: str, asset_id: str, port_ids: list[str]):
         # Output list
         self.output: list = []
 
+        self.pyjnius_loader = PyjniusLoader.get_loader()
+
     def _calculate_massflowrate(self) -> None:
         """Calculate mass flowrate of the asset."""
         self.mass_flowrate = heat_demand_and_temperature_to_mass_flow(
@@ -208,6 +201,7 @@ def write_to_output(self) -> None:
 
     def _init_rosim(self) -> None:
         """Function to initailized Rosim from XML file."""
+        path = os.path.dirname(__file__)
         xmlfile = os.path.join(path, "bin/sequentialTemplate_v0.4.2_template.xml")
         with open(xmlfile, "r") as fd:
             xml_str = fd.read()
@@ -251,6 +245,8 @@ def _init_rosim(self) -> None:
         with open(temp_xmlfile_path, "w") as temp_xmlfile:
             temp_xmlfile.write(xml_str)
 
+        javaioFile = self.pyjnius_loader.load_class("java.io.File")
+        RosimSequential = self.pyjnius_loader.load_class("tno.calc.RosimSequential")
         xmlfilejava = javaioFile(temp_xmlfile_path)
         self.rosim = RosimSequential(xmlfilejava, False, 2)
 

src/omotes_simulator_core/entities/assets/pyjnius_loader.py

@@ -0,0 +1,74 @@
+#  Copyright (c) 2023. Deltares & TNO
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+"""Binding to Rosim through Pyjnius."""
+
+import os
+from typing import Dict, Callable
+
+JavaClass = Callable
+
+
+class PyjniusLoader:
+    """Class to load Pyjnius and connect to Rosim.
+
+    This is a singleton and you should only use PyjniusLoader.get_loader() instead of
+    constructing this class directly.
+
+    Also ensure that after loading this class, the process is not forked into a subprocess
+    as this will destroy the connection to Pyjnius and may lead to an indefinite hang when using
+    Java code.
+    """
+
+    INSTANCE = None
+    loaded_classes: Dict[str, JavaClass]
+
+    def __init__(self) -> None:
+        """Create an instance of PyjniusLoader.
+
+        This function should only be called ONCE. Do not use construct this class directly
+        but rather use `PyjniusLoader.get_loader`.
+        """
+        path = os.path.dirname(__file__)
+        import jnius_config  # noqa
+
+        jnius_config.add_classpath(os.path.join(path, "bin/jfxrt.jar"))
+        jnius_config.add_classpath(os.path.join(path, "bin/rosim-batch-0.4.2.jar"))
+
+        self.loaded_classes = {}
+
+    def load_class(self, classpath: str) -> JavaClass:
+        """Load a Java class.
+
+        If it has been loaded previously, the reference to the class will be laoded from cache.
+        Otherwise, it is loaded through pyjnius.
+
+        """
+        from jnius import autoclass  # noqa
+        if classpath not in self.loaded_classes:
+            self.loaded_classes[classpath] = autoclass(classpath)
+
+        return self.loaded_classes[classpath]
+
+    @staticmethod
+    def get_loader() -> 'PyjniusLoader':
+        """Get the global instance of the PyjniusLoader.
+
+        This loader allows to load Java classes. This is the preferred method of retrieving
+        a reference to the PyjniusLoader.
+        """
+        if PyjniusLoader.INSTANCE is None:
+            PyjniusLoader.INSTANCE = PyjniusLoader()
+        return PyjniusLoader.INSTANCE