manually clear the inputstream on various XMLInputFactory objects to …

…allow gc. Make the code more uniform.

A reference to the last inputstream is kept by the factory, and we keep the factory
in a static reference.

Signed-off-by: HARPER Jon <jon.harper87@gmail.com>

cgmes/cgmes-model/src/main/java/com/powsybl/cgmes/model/FullModel.java

@@ -6,6 +6,8 @@
  */
 package com.powsybl.cgmes.model;
 
+import com.google.common.base.Supplier;
+import com.google.common.base.Suppliers;
 import com.powsybl.commons.PowsyblException;
 import com.powsybl.commons.exceptions.UncheckedXmlStreamException;
 import com.powsybl.commons.xml.XmlUtil;
@@ -24,6 +26,8 @@
  */
 public class FullModel {
 
+    private static final Supplier<XMLInputFactory> XML_INPUT_FACTORY_SUPPLIER = Suppliers.memoize(XMLInputFactory::newInstance);
+
     private final String id;
 
     private final ZonedDateTime scenarioTime;
@@ -138,7 +142,7 @@ public static FullModel parse(Reader reader) {
             factory.setProperty(XMLConstants.ACCESS_EXTERNAL_DTD, "");
             factory.setProperty(XMLConstants.ACCESS_EXTERNAL_SCHEMA, "");
 
-            XMLStreamReader xmlReader = factory.createXMLStreamReader(reader);
+            XMLStreamReader xmlReader = XML_INPUT_FACTORY_SUPPLIER.get().createXMLStreamReader(reader);
             try {
                 XmlUtil.readUntilStartElement(new String[] {"/", CgmesNames.RDF, CgmesNames.FULL_MODEL}, xmlReader, () -> {
                     context.id = xmlReader.getAttributeValue(CgmesNamespace.RDF_NAMESPACE, CgmesNames.ABOUT);
@@ -176,6 +180,7 @@ public static FullModel parse(Reader reader) {
                 });
             } finally {
                 xmlReader.close();
+                XmlUtil.gcXmlInputFactory(XML_INPUT_FACTORY_SUPPLIER.get());
             }
         } catch (XMLStreamException e) {
             throw new UncheckedXmlStreamException(e);

cgmes/cgmes-model/src/main/java/com/powsybl/cgmes/model/NamespaceReader.java

@@ -9,6 +9,7 @@
 
 import com.google.common.base.Supplier;
 import com.google.common.base.Suppliers;
+import com.powsybl.commons.xml.XmlUtil;
 
 import javax.xml.stream.XMLInputFactory;
 import javax.xml.stream.XMLStreamConstants;
@@ -50,6 +51,7 @@ public static Set<String> namespaces1(InputStream is) throws XMLStreamException
             }
         } finally {
             xmlsr.close();
+            XmlUtil.gcXmlInputFactory(XML_INPUT_FACTORY_SUPPLIER.get());
         }
         return found;
     }

commons/src/main/java/com/powsybl/commons/xml/XmlUtil.java

@@ -12,6 +12,9 @@
 import javanet.staxutils.IndentingXMLStreamWriter;
 
 import javax.xml.stream.*;
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.Writer;
 import java.nio.charset.StandardCharsets;
@@ -20,11 +23,16 @@
 import java.util.function.IntConsumer;
 import java.util.function.Supplier;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 /**
  * @author Geoffroy Jamgotchian <geoffroy.jamgotchian at rte-france.com>
  */
 public final class XmlUtil {
 
+    private static final Logger LOGGER = LoggerFactory.getLogger(XmlUtil.class);
+
     private static final Supplier<XMLOutputFactory> XML_OUTPUT_FACTORY_SUPPLIER = Suppliers.memoize(XMLOutputFactory::newFactory);
 
     private XmlUtil() {
@@ -284,4 +292,17 @@ private static XMLStreamWriter initializeWriter(boolean indent, String indentStr
         xmlWriter.writeStartDocument(StandardCharsets.UTF_8.toString(), "1.0");
         return xmlWriter;
     }
+
+    public static void gcXmlInputFactory(XMLInputFactory xmlInputFactory) {
+        // Workaround: Manually force XMLInputFactory and XmlStreamReader to clear the reference to the last inputstream.
+        // jdk xerces XmlInputFactory keeps a ref to the last created XmlStreamReader (so that the factory
+        // can optionally reuse it. But the XmlStreamReader keeps a ref to it's inputstream. There is
+        // no public API in XmlStreamReader to clear the previous input stream, close doesn't do it).
+        try (InputStream is = new ByteArrayInputStream(new byte[] {})) {
+            XMLStreamReader xmlsr = xmlInputFactory.createXMLStreamReader(is);
+            xmlsr.close();
+        } catch (XMLStreamException | IOException e) {
+            LOGGER.error(e.toString(), e);
+        }
+    }
 }

iidm/iidm-xml-converter/src/main/java/com/powsybl/iidm/xml/NetworkXml.java

@@ -504,6 +504,8 @@ public static Network read(InputStream is, ImportOptions config, Anonymizer anon
             checkExtensionsNotFound(context, extensionNamesNotFound);
 
             context.getEndTasks().forEach(Runnable::run);
+            reader.close();
+            XmlUtil.gcXmlInputFactory(XML_INPUT_FACTORY_SUPPLIER.get());
             return network;
         } catch (XMLStreamException e) {
             throw new UncheckedXmlStreamException(e);

iidm/iidm-xml-converter/src/main/java/com/powsybl/iidm/xml/XMLImporter.java

@@ -16,6 +16,7 @@
 import com.powsybl.commons.config.PlatformConfig;
 import com.powsybl.commons.datasource.DataSource;
 import com.powsybl.commons.datasource.ReadOnlyDataSource;
+import com.powsybl.commons.xml.XmlUtil;
 import com.powsybl.iidm.import_.ImportOptions;
 import com.powsybl.iidm.import_.Importer;
 import com.powsybl.iidm.network.Network;
@@ -131,6 +132,7 @@ private boolean exists(ReadOnlyDataSource dataSource, String ext) throws IOExcep
                     } finally {
                         try {
                             xmlsr.close();
+                            XmlUtil.gcXmlInputFactory(XML_INPUT_FACTORY_SUPPLIER.get());
                         } catch (XMLStreamException e) {
                             LOGGER.error(e.toString(), e);
                         }