[CSV-318] CSVPrinter.printRecord(Stream) hangs if given a parallel

garydgregory · garydgregory · commit 410175c3d014 · 2025-05-06T17:46:14.000-04:00
stream
diff --git a/src/changes/changes.xml b/src/changes/changes.xml
@@ -42,6 +42,7 @@
   <body>
     <release version="1.14.1" date="YYYY-MM-DD" description="This is a feature and maintenance release. Java 8 or later is required.">
       <!-- FIX -->
+      <action type="fix" issue="CSV-318" dev="ggregory" due-to="Joseph Shraibman, Gary Gregory">CSVPrinter.printRecord(Stream) hangs if given a parallel stream.</action>
       <!-- ADD -->
       <!-- UPDATE -->
       <action type="update" dev="ggregory" due-to="Gary Gregory">Bump commons-io:commons-io from 2.18.0 to 2.19.0.</action>
diff --git a/src/main/java/org/apache/commons/csv/CSVPrinter.java b/src/main/java/org/apache/commons/csv/CSVPrinter.java
@@ -35,6 +35,7 @@
 import java.sql.Statement;
 import java.util.Arrays;
 import java.util.Objects;
+import java.util.concurrent.locks.ReentrantLock;
 import java.util.stream.Stream;
 
 import org.apache.commons.io.function.IOStream;
@@ -87,6 +88,8 @@ public final class CSVPrinter implements Flushable, Closeable {
     private boolean newRecord = true;
 
     private long recordCount;
+    
+    private ReentrantLock lock = new ReentrantLock();
 
     /**
      * Creates a printer that will print values to the given stream following the CSVFormat.
@@ -326,9 +329,14 @@ public void printRecord(final Object... values) throws IOException {
      * @since 1.10.0
      */
     @SuppressWarnings("resource") // caller closes.
-    public synchronized void printRecord(final Stream<?> values) throws IOException {
-        IOStream.adapt(values).forEachOrdered(this::print);
-        endOfRecord();
+    public void printRecord(final Stream<?> values) throws IOException {
+        lock.lock();
+        try {
+            IOStream.adapt(values).forEachOrdered(this::print);
+            endOfRecord();
+        } finally {
+            lock.unlock();
+        }
     }
 
     private void printRecordObject(final Object value) throws IOException {
diff --git a/src/test/java/org/apache/commons/csv/JiraCsv318Test.java b/src/test/java/org/apache/commons/csv/JiraCsv318Test.java
@@ -31,7 +31,6 @@
 import org.apache.commons.io.function.IOConsumer;
 import org.apache.commons.io.function.IOStream;
 import org.apache.commons.lang3.ArrayUtils;
-import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 
 /**
@@ -67,10 +66,6 @@ private Stream<String> newStream() {
         return Stream.of("col a", "col b", "col c");
     }
 
-    public synchronized void printRecord(final Stream<?> values) throws IOException {
-        // IOStream.adapt(values).forEachOrdered(this::print);
-    }
-
     @Test
     void testDefaultStream() throws IOException {
         final ByteArrayOutputStream baos = new ByteArrayOutputStream();
@@ -91,20 +86,6 @@ void testParallelIOStream() throws IOException {
         checkOutput(baos);
     }
 
-    @SuppressWarnings("resource")
-    @Test
-    @Disabled("Deadlock because CSVPrinter.print(Object) is synchronized")
-    void testParallelIOStreamSynchronizedPrinter() throws IOException {
-        final ByteArrayOutputStream baos = new ByteArrayOutputStream();
-        try (CSVPrinter printer = newPrinter(baos)) {
-            synchronized (printer) {
-                IOStream.adapt(newParallelStream()).forEachOrdered(printer::print);
-            }
-        }
-        // No EOR marker in this test intentionally, so checkOutput will trim.
-        checkOutput(baos);
-    }
-
     @SuppressWarnings("resource")
     @Test
     void testParallelIOStreamSynchronizedPrinterNotUsed() throws IOException {
@@ -125,7 +106,6 @@ void testParallelIOStreamSynchronizedPrinterNotUsed() throws IOException {
     }
 
     @Test
-    @Disabled("Deadlock because CSVPrinter.print(Object) is synchronized")
     void testParallelStream() throws IOException {
         final ByteArrayOutputStream baos = new ByteArrayOutputStream();
         try (CSVPrinter printer = newPrinter(baos)) {
