feat(target): Simplify xml document merging

pom.xml

@@ -58,6 +58,12 @@
             <artifactId>junit-jupiter</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>5.11.0</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <dependencyManagement>

src/main/java/com/github/olivergondza/saxeed/Saxeed.java

@@ -30,12 +30,11 @@
 public class Saxeed {
 
     private SAXParser saxParser;
-    private XMLOutputFactory xmlOutputFactory;
     private InputSource input;
     private final Map<TransformationBuilder, Target> transformations = new LinkedHashMap<>();
 
     public Saxeed() {
-        setXmlOutputFactory(null); // Initialize with defaults
+
     }
 
     public Saxeed setSaxParser(SAXParser saxParser) {
@@ -44,14 +43,6 @@ public Saxeed setSaxParser(SAXParser saxParser) {
         return this;
     }
 
-    public Saxeed setXmlOutputFactory(XMLOutputFactory xmlOutputFactory) {
-        this.xmlOutputFactory = xmlOutputFactory != null
-                ? xmlOutputFactory
-                : XMLOutputFactory.newInstance()
-        ;
-        return this;
-    }
-
     public Saxeed setInput(Path path) {
         input = new InputSource(path.toFile().toURI().toASCIIString());
         return this;
@@ -167,7 +158,7 @@ private MultiplexingHandler getSaxHandler() {
             Target target = trans.getValue();
             TransformationBuilder builder = trans.getKey();
 
-            return target.getHandler(builder, xmlOutputFactory);
+            return builder.build(this, target);
         }).collect(Collectors.toList());
         return new MultiplexingHandler(handlers);
     }

src/main/java/com/github/olivergondza/saxeed/Target.java

@@ -1,8 +1,8 @@
 package com.github.olivergondza.saxeed;
 
 import com.github.olivergondza.saxeed.ex.FailedWriting;
-import com.github.olivergondza.saxeed.internal.TransformationHandler;
 
+import javax.xml.stream.FactoryConfigurationError;
 import javax.xml.stream.XMLOutputFactory;
 import javax.xml.stream.XMLStreamException;
 import javax.xml.stream.XMLStreamWriter;
@@ -16,22 +16,29 @@
 /**
  * Target to write the resulting content into.
  */
-public interface Target {
+public abstract class Target implements AutoCloseable {
+
+    private AutoCloseable close = null;
 
     /**
      * Identify the target for the ease of debugging.
      *
      * Mostly used in error messages to identify the file/stream/etc.
      */
-    String getName();
+    public abstract String getName();
 
-    TransformationHandler getHandler(TransformationBuilder builder, XMLOutputFactory xmlOutputFactory);
+    /**
+     * Create new XMLStreamWriter for the transformation.
+     *
+     * If it is desirable to close any resource allocated, register it by {@link #registerClosable(AutoCloseable)}.
+     */
+    public abstract XMLStreamWriter getWriter(Saxeed saxeed);
 
-    default XMLStreamWriter create(XMLOutputFactory xmlOutputFactory, OutputStream os) {
+    public static XMLStreamWriter createXmlStreamWriter(OutputStream os) {
         try {
-            return xmlOutputFactory.createXMLStreamWriter(os);
-        } catch (XMLStreamException e) {
-            throw new FailedWriting("Unable to create XMLStreamWriter for " + getName(), e);
+            return XMLOutputFactory.newInstance().createXMLStreamWriter(os);
+        } catch (FactoryConfigurationError | XMLStreamException e) {
+            throw new FailedWriting("Unable to create XMLStreamWriter from " + objectId(os), e);
         }
     }
 
@@ -40,13 +47,39 @@ private static String objectId(Object obj) {
         return obj.getClass().getName() + "@" + Integer.toHexString(obj.hashCode());
     }
 
+    /**
+     * Register single resource for closing on {@link #close()}.
+     */
+    protected void registerClosable(AutoCloseable close) {
+        if (this.close != null) throw new IllegalStateException("Unclosed resource already present: " + this.close);
+
+        this.close = close;
+    }
+
+    /**
+     * Close method is called on target every time a transformation using a target is completed.
+     *
+     * It closes whatever resource was registered using {@link #registerClosable(AutoCloseable)}, or nothing if not set.
+     */
+    @Override
+    public void close() throws FailedWriting {
+        if (close != null) {
+            try {
+                close.close();
+                close = null;
+            } catch (Exception e) {
+                throw new FailedWriting("Failed closing target " + getName(), e);
+            }
+        }
+    }
+
     /**
      * Target for a file.
      *
      * The content is flush/closed once the transformation is over. It means that using same File target repeatedly will
      * overwrite its content.
      */
-    class FileTarget implements Target {
+    static class FileTarget extends Target {
         private final File file;
 
         public FileTarget(File file) {
@@ -63,12 +96,13 @@ public String getName() {
         }
 
         @Override
-        public TransformationHandler getHandler(TransformationBuilder builder, XMLOutputFactory xmlOutputFactory) {
+        public XMLStreamWriter getWriter(Saxeed saxeed) {
             OutputStream os = getOutputStream();
-            return builder.build(create(xmlOutputFactory, os), os);
+            registerClosable(os);
+            return createXmlStreamWriter(os);
         }
 
-        private OutputStream getOutputStream() throws FailedWriting {
+        protected /*for testing*/ OutputStream getOutputStream() throws FailedWriting {
             try {
                 return new BufferedOutputStream(new FileOutputStream(file));
             } catch (FileNotFoundException e) {
@@ -82,7 +116,7 @@ private OutputStream getOutputStream() throws FailedWriting {
      *
      * The stream is NOT closed.
      */
-    class OutputStreamTarget implements Target {
+    static class OutputStreamTarget extends Target {
         private final OutputStream os;
 
         public OutputStreamTarget(OutputStream os) {
@@ -95,12 +129,12 @@ public String getName() {
         }
 
         @Override
-        public TransformationHandler getHandler(TransformationBuilder builder, XMLOutputFactory xmlOutputFactory) {
-            return builder.build(create(xmlOutputFactory, os), null);
+        public XMLStreamWriter getWriter(Saxeed saxeed) {
+            return createXmlStreamWriter(os);
         }
     }
 
-    class DevNullTarget extends OutputStreamTarget {
+    static class DevNullTarget extends OutputStreamTarget {
 
         private static final OutputStream outputStream = new OutputStream() {
             @Override
@@ -119,7 +153,7 @@ public String getName() {
         }
     }
 
-    class XmlStreamWriterTarget implements Target {
+    static class XmlStreamWriterTarget extends Target {
 
         private final XMLStreamWriter writer;
 
@@ -133,8 +167,8 @@ public String getName() {
         }
 
         @Override
-        public TransformationHandler getHandler(TransformationBuilder builder, XMLOutputFactory __) {
-            return builder.build(writer, null);
+        public XMLStreamWriter getWriter(Saxeed saxeed) {
+            return writer;
         }
     }
 }

src/main/java/com/github/olivergondza/saxeed/TransformationBuilder.java

@@ -2,7 +2,6 @@
 
 import com.github.olivergondza.saxeed.internal.TransformationHandler;
 
-import javax.xml.stream.XMLStreamWriter;
 import java.util.Collection;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -37,7 +36,7 @@ public TransformationBuilder add(Subscribed subs, Collection<UpdatingVisitor> vi
         return this;
     }
 
-    public TransformationHandler build(XMLStreamWriter writer, AutoCloseable closeAction) {
-        return new TransformationHandler(visitors, writer, closeAction);
+    public TransformationHandler build(Saxeed saxeed, Target target) {
+        return new TransformationHandler(saxeed, target, visitors);
     }
 }

src/main/java/com/github/olivergondza/saxeed/internal/TransformationHandler.java

@@ -1,7 +1,9 @@
 package com.github.olivergondza.saxeed.internal;
 
+import com.github.olivergondza.saxeed.Saxeed;
 import com.github.olivergondza.saxeed.Subscribed;
 import com.github.olivergondza.saxeed.TagName;
+import com.github.olivergondza.saxeed.Target;
 import com.github.olivergondza.saxeed.UpdatingVisitor;
 import com.github.olivergondza.saxeed.ex.FailedTransforming;
 import com.github.olivergondza.saxeed.ex.FailedWriting;
@@ -36,8 +38,7 @@ public class TransformationHandler extends DefaultHandler implements AutoCloseab
     private final Map<TagName, List<UpdatingVisitor>> visitorCache = new HashMap<>();
 
     private final XMLStreamWriter writer;
-    // A resource to close once done. Can be null
-    private final AutoCloseable closeAction;
+    private final Target target;
 
     private TagImpl currentTag;
     private final CharChunk currentChars = new CharChunk();
@@ -49,13 +50,12 @@ public class TransformationHandler extends DefaultHandler implements AutoCloseab
     private final Map<String, AtomicInteger> writtenBookmarks = new HashMap<>();
 
     public TransformationHandler(
-            LinkedHashMap<UpdatingVisitor, Subscribed> visitors,
-            XMLStreamWriter writer,
-            AutoCloseable closeAction
+            Saxeed saxeed,
+            Target target, LinkedHashMap<UpdatingVisitor, Subscribed> visitors
     ) {
         this.visitors = visitors;
-        this.writer = writer;
-        this.closeAction = closeAction;
+        this.target = target;
+        this.writer = target.getWriter(saxeed);
     }
 
     @Override
@@ -328,19 +328,8 @@ public void endDocument() {
     @Override
     public void close() throws FailedWriting {
         try {
-            // Make sure the content is written to XMLStreamWriter, no matter if closing the target or not
             writer.flush();
-
-            // Closing XMLStreamWriter never close the target, but it will be un-writable afterward.
-            // So closing writer iff the target should be closed.
-            if (closeAction != null) {
-                // Hackish: Need to close 2 resources, and need to preserve both the eventual exceptions from close() - exactly what
-                // an empty try-with-resources would do. But, the XMLStreamWriter does not implement AutoClosable, so a compromise
-                // approach is needed.
-                try (closeAction) {
-                    writer.close();
-                }
-            }
+            target.close();
         } catch (Exception e) {
             throw new FailedWriting("Failed closing stream", e);
         }