From fa8957d81af625dd45d459661ce5564b0b701a8c Mon Sep 17 00:00:00 2001
From: Nico Piel <nico.piel@hotmail.de>
Date: Thu, 20 Nov 2025 01:17:58 +0100
Subject: [PATCH] Replace SimpleDateFormat with DateTimeFormatter

Replace usages of the non-thread-safe date formatter with java.time's DateTimeFormatter and related APIs to improve thread-safety and correctness when parsing/formatting dates and time zones. Update calendar parameter conversion to use ZonedDateTime/Instant and adapt log timestamp formatting to use DateTimeFormatter.

Removes unused imports and modernizes date handling to avoid concurrency issues introduced by SimpleDateFormat.

Collectively decided to use `DateTimeFormatter` instead of `FastDateTime`.

Signed-off-by: Nico Piel <nico.piel@hotmail.de>
---
 .../CalendarParamConverterProvider.java       | 41 +++++++++++++------
 .../plugins/serverlog/ServerLogItem.java      |  8 ++--
 2 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/server/src/com/mirth/connect/client/core/api/providers/CalendarParamConverterProvider.java b/server/src/com/mirth/connect/client/core/api/providers/CalendarParamConverterProvider.java
index 9436bbcb62..f194439702 100644
--- a/server/src/com/mirth/connect/client/core/api/providers/CalendarParamConverterProvider.java
+++ b/server/src/com/mirth/connect/client/core/api/providers/CalendarParamConverterProvider.java
@@ -9,23 +9,24 @@
 
 package com.mirth.connect.client.core.api.providers;
 
-import java.lang.annotation.Annotation;
-import java.lang.reflect.Type;
-import java.text.ParseException;
-import java.text.SimpleDateFormat;
-import java.util.Calendar;
-
 import javax.inject.Singleton;
 import javax.ws.rs.ProcessingException;
 import javax.ws.rs.ext.ParamConverter;
 import javax.ws.rs.ext.ParamConverterProvider;
 import javax.ws.rs.ext.Provider;
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Type;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeParseException;
+import java.util.Calendar;
 
 @Provider
 @Singleton
 public class CalendarParamConverterProvider implements ParamConverterProvider {
-
-    private static final SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
+    private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
 
     @Override
     public <T> ParamConverter<T> getConverter(Class<T> rawType, Type genericType, Annotation[] annotations) {
@@ -38,10 +39,16 @@ public T fromString(String value) {
                     }
 
                     try {
-                        Calendar date = Calendar.getInstance();
-                        date.setTime(format.parse(value));
-                        return (T) date;
-                    } catch (ParseException e) {
+                        // Parse the incoming string as a ZonedDateTime using the given pattern
+                        ZonedDateTime zdt = ZonedDateTime.parse(value, FORMATTER);
+
+                        Calendar calendar = Calendar.getInstance(java.util.TimeZone.getTimeZone(zdt.getZone()));
+                        calendar.setTimeInMillis(zdt.toInstant().toEpochMilli());
+
+                        @SuppressWarnings("unchecked")
+                        T result = (T) calendar;
+                        return result;
+                    } catch (DateTimeParseException e) {
                         throw new ProcessingException(e);
                     }
                 }
@@ -51,7 +58,15 @@ public String toString(T value) {
                     if (value == null) {
                         return null;
                     }
-                    return format.format(((Calendar) value).getTime());
+
+                    Calendar calendar = (Calendar) value;
+
+                    // Build a ZonedDateTime from the Calendar (date/time + time zone)
+                    Instant instant = calendar.toInstant();
+                    ZoneId zoneId = calendar.getTimeZone().toZoneId();
+                    ZonedDateTime zdt = ZonedDateTime.ofInstant(instant, zoneId);
+
+                    return FORMATTER.format(zdt);
                 }
             };
         }
diff --git a/server/src/com/mirth/connect/plugins/serverlog/ServerLogItem.java b/server/src/com/mirth/connect/plugins/serverlog/ServerLogItem.java
index a88bdf3f9a..0008fa8a26 100644
--- a/server/src/com/mirth/connect/plugins/serverlog/ServerLogItem.java
+++ b/server/src/com/mirth/connect/plugins/serverlog/ServerLogItem.java
@@ -10,14 +10,16 @@
 package com.mirth.connect.plugins.serverlog;
 
 import java.io.Serializable;
-import java.text.SimpleDateFormat;
+
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
 import java.util.Date;
 
 import org.apache.commons.lang3.StringUtils;
 
 public class ServerLogItem implements Serializable {
 
-    public static SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
+    public static DateTimeFormatter DATE_FORMAT = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS").withZone(ZoneId.systemDefault());
 
     private String serverId;
     private Long id;
@@ -123,7 +125,7 @@ public void setThrowableInformation(String throwableInformation) {
     public String toString() {
         if (id != null) {
             StringBuilder builder = new StringBuilder();
-            builder.append('[').append(DATE_FORMAT.format(date)).append("]  ");
+            builder.append('[').append(DATE_FORMAT.format(date.toInstant())).append("]  ");
             builder.append(level);
             builder.append("  (").append(category);
             if (StringUtils.isNotBlank(lineNumber)) {