TbDate isoDateFormat is ThreadLocal instead synchronization

common/script/script-api/src/main/java/org/thingsboard/script/api/tbel/TbDate.java

@@ -35,7 +35,8 @@ public class TbDate extends Date {
     private static final DateTimeFormatter isoDateFormatter = DateTimeFormatter.ofPattern(
             "yyyy-MM-dd[[ ]['T']HH:mm[:ss[.SSS]][ ][XXX][Z][z][VV][O]]").withZone(ZoneId.systemDefault());
 
-    private static final DateFormat isoDateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
+    private static final ThreadLocal<DateFormat> isoDateFormat = ThreadLocal.withInitial(() ->
+            new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ"));
 
     public TbDate() {
         super();
@@ -73,9 +74,7 @@ public class TbDate extends Date {
     }
 
     public String toISOString() {
-        synchronized (TbDate.class) {
-            return isoDateFormat.format(this);
-        }
+        return isoDateFormat.get().format(this);
     }
 
     public String toLocaleString(String locale) {

common/script/script-api/src/test/java/org/thingsboard/script/api/tbel/TbDateTest.java

@@ -25,6 +25,7 @@ import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 
 import java.util.ArrayList;
+import java.util.Calendar;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;
@@ -32,6 +33,8 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 
+import static org.assertj.core.api.Assertions.assertThat;
+
 @Slf4j
 class TbDateTest {
 
@@ -99,4 +102,26 @@ class TbDateTest {
             future.get(30, TimeUnit.SECONDS);
         }
     }
-}
+
+    @Test
+    void testToISOStringThreadLocalStaticFormatter() throws ExecutionException, InterruptedException, TimeoutException {
+        executor = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(1));
+        long ts = 1709217342987L; //Thu Feb 29 2024 14:35:42.987 GMT+0000
+        int offset = Calendar.getInstance().get(Calendar.ZONE_OFFSET); // for example 3600000 for GMT + 1
+        TbDate tbDate = new TbDate(ts - offset);
+        String datePrefix = "2024-02-29T14:35:42.987"; //without time zone
+        assertThat(tbDate.toISOString())
+                .as("format in main thread")
+                .startsWith(datePrefix);
+        assertThat(executor.submit(tbDate::toISOString).get(30, TimeUnit.SECONDS))
+                .as("format in executor thread")
+                .startsWith(datePrefix);
+        assertThat(new TbDate(ts - offset).toISOString())
+                .as("new instance format in main thread")
+                .startsWith(datePrefix);
+        assertThat(executor.submit(() -> new TbDate(ts - offset).toISOString()).get(30, TimeUnit.SECONDS))
+                .as("new instance format in executor thread")
+                .startsWith(datePrefix);
+    }
+
+}