From 85ccf57a9ca45c3f53cf7e5a31734da160573f63 Mon Sep 17 00:00:00 2001
From: Yegor Bugayenko <yegor256@gmail.com>
Date: Thu, 3 Nov 2022 12:38:44 +0300
Subject: [PATCH] #185 extra synchronization

---
 src/main/java/com/jcabi/xml/XSLDocument.java  | 24 +++++++++++--------
 .../java/com/jcabi/xml/XSLDocumentTest.java   |  3 ++-
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/main/java/com/jcabi/xml/XSLDocument.java b/src/main/java/com/jcabi/xml/XSLDocument.java
index d7855be..14eec80 100644
--- a/src/main/java/com/jcabi/xml/XSLDocument.java
+++ b/src/main/java/com/jcabi/xml/XSLDocument.java
@@ -357,7 +357,9 @@ public String toString() {
     public XML transform(final XML xml) {
         final DocumentBuilder builder;
         try {
-            builder = XSLDocument.DFACTORY.newDocumentBuilder();
+            synchronized (XSLDocument.DFACTORY) {
+                builder = XSLDocument.DFACTORY.newDocumentBuilder();
+            }
         } catch (final ParserConfigurationException ex) {
             throw new IllegalArgumentException(
                 String.format(
@@ -397,7 +399,7 @@ public String applyTo(final XML xml) {
      * @param xml XML
      * @param result Result
      * @since 0.11
-     * @link https://stackoverflow.com/questions/4695489/capture-xslmessage-output-in-java
+     * @link <a href="https://stackoverflow.com/questions/4695489">Relevant SO question</a>
      */
     private void transformInto(final XML xml, final Result result) {
         final Transformer trans = this.transformer();
@@ -405,7 +407,9 @@ private void transformInto(final XML xml, final Result result) {
         trans.setErrorListener(errors);
         final long start = System.nanoTime();
         try {
-            trans.transform(new DOMSource(xml.node()), result);
+            synchronized (XSLDocument.DFACTORY) {
+                trans.transform(new DOMSource(xml.node()), result);
+            }
         } catch (final TransformerException ex) {
             throw new IllegalArgumentException(
                 String.format(
@@ -431,10 +435,10 @@ private void transformInto(final XML xml, final Result result) {
      * @return The transformer
      */
     private Transformer transformer() {
-        if (this.cached.get() == null) {
-            final Transformer trans;
-            synchronized (XSLDocument.TFACTORY) {
+        synchronized (XSLDocument.TFACTORY) {
+            if (this.cached.get() == null) {
                 XSLDocument.TFACTORY.setURIResolver(this.sources);
+                final Transformer trans;
                 try {
                     trans = XSLDocument.TFACTORY.newTransformer(
                         new StreamSource(new StringReader(this.xsl), this.sid)
@@ -448,11 +452,11 @@ private Transformer transformer() {
                         ex
                     );
                 }
+                for (final Map.Entry<String, Object> ent : this.params.entrySet()) {
+                    trans.setParameter(ent.getKey(), ent.getValue());
+                }
+                this.cached.set(XSLDocument.forSaxon(trans));
             }
-            for (final Map.Entry<String, Object> ent : this.params.entrySet()) {
-                trans.setParameter(ent.getKey(), ent.getValue());
-            }
-            this.cached.set(XSLDocument.forSaxon(trans));
         }
         return this.cached.get();
     }
diff --git a/src/test/java/com/jcabi/xml/XSLDocumentTest.java b/src/test/java/com/jcabi/xml/XSLDocumentTest.java
index 1154ab0..b406a13 100644
--- a/src/test/java/com/jcabi/xml/XSLDocumentTest.java
+++ b/src/test/java/com/jcabi/xml/XSLDocumentTest.java
@@ -230,13 +230,14 @@ void transformsInManyThreads() throws Exception {
         );
         final AtomicInteger done = new AtomicInteger(0);
         final CountDownLatch latch = new CountDownLatch(1);
-        final int total = 10;
+        final int total = 50;
         final ExecutorService exec = Executors.newFixedThreadPool(total);
         for (int task = 0; task < total; ++task) {
             exec.submit(
                 () -> {
                     latch.await();
                     xsl.transform(xml);
+                    xsl.transform(xml);
                     done.incrementAndGet();
                     return 0;
                 }