test

common/src/main/java/stirling/software/common/service/CustomPDFDocumentFactory.java

@@ -83,7 +83,7 @@ public class CustomPDFDocumentFactory {
      */
     public PDDocument load(File file, boolean readOnly) throws IOException {
         if (file == null) {
-            throw new IllegalArgumentException("File cannot be null");
+            throw ExceptionUtils.createNullArgumentException("File");
         }
 
         long fileSize = file.length();
@@ -110,7 +110,7 @@ public class CustomPDFDocumentFactory {
      */
     public PDDocument load(Path path, boolean readOnly) throws IOException {
         if (path == null) {
-            throw new IllegalArgumentException("File cannot be null");
+            throw ExceptionUtils.createNullArgumentException("File");
         }
 
         long fileSize = Files.size(path);
@@ -131,7 +131,7 @@ public class CustomPDFDocumentFactory {
     /** Load a PDF from byte array with automatic optimization and read-only option. */
     public PDDocument load(byte[] input, boolean readOnly) throws IOException {
         if (input == null) {
-            throw new IllegalArgumentException("Input bytes cannot be null");
+            throw ExceptionUtils.createNullArgumentException("Input bytes");
         }
 
         long dataSize = input.length;
@@ -152,7 +152,7 @@ public class CustomPDFDocumentFactory {
     /** Load a PDF from InputStream with automatic optimization and read-only option. */
     public PDDocument load(InputStream input, boolean readOnly) throws IOException {
         if (input == null) {
-            throw new IllegalArgumentException("InputStream cannot be null");
+            throw ExceptionUtils.createNullArgumentException("InputStream");
         }
 
         // Since we don't know the size upfront, buffer to a temp file
@@ -175,7 +175,7 @@ public class CustomPDFDocumentFactory {
     public PDDocument load(InputStream input, String password, boolean readOnly)
             throws IOException {
         if (input == null) {
-            throw new IllegalArgumentException("InputStream cannot be null");
+            throw ExceptionUtils.createNullArgumentException("InputStream");
         }
 
         // Since we don't know the size upfront, buffer to a temp file

common/src/main/java/stirling/software/common/util/ExceptionUtils.java

@@ -137,6 +137,23 @@ public class ExceptionUtils {
         return new TranslatableException(message, messageKey, args);
     }
 
+    /** Create common validation exceptions with translation support. */
+    public static IllegalArgumentException createInvalidArgumentException(String argumentName) {
+        return createIllegalArgumentException(
+                "error.invalidArgument", "Invalid argument: {0}", argumentName);
+    }
+
+    public static IllegalArgumentException createInvalidArgumentException(
+            String argumentName, String value) {
+        return createIllegalArgumentException(
+                "error.invalidFormat", "Invalid {0} format: {1}", argumentName, value);
+    }
+
+    public static IllegalArgumentException createNullArgumentException(String argumentName) {
+        return createIllegalArgumentException(
+                "error.argumentRequired", "{0} must not be null", argumentName);
+    }
+
     /** Create file validation exceptions. */
     public static IllegalArgumentException createHtmlFileRequiredException() {
         return createIllegalArgumentException(

common/src/main/java/stirling/software/common/util/PdfUtils.java

@@ -571,8 +571,7 @@ public class PdfUtils {
             case "less":
                 return actualPageCount < pageCount;
             default:
-                throw new IllegalArgumentException(
-                        "Invalid comparator. Only 'greater', 'equal', and 'less' are supported.");
+                throw ExceptionUtils.createInvalidArgumentException("comparator", comparator);
         }
     }
 

stirling-pdf/src/main/java/stirling/software/SPDF/controller/api/filters/FilterController.java

@@ -25,6 +25,7 @@ import stirling.software.SPDF.model.api.filter.FileSizeRequest;
 import stirling.software.SPDF.model.api.filter.PageRotationRequest;
 import stirling.software.SPDF.model.api.filter.PageSizeRequest;
 import stirling.software.common.service.CustomPDFDocumentFactory;
+import stirling.software.common.util.ExceptionUtils;
 import stirling.software.common.util.PdfUtils;
 import stirling.software.common.util.WebResponseUtils;
 
@@ -96,7 +97,7 @@ public class FilterController {
                 valid = actualPageCount < pageCount;
                 break;
             default:
-                throw new IllegalArgumentException("Invalid comparator: " + comparator);
+                throw ExceptionUtils.createInvalidArgumentException("comparator", comparator);
         }
 
         if (valid) return WebResponseUtils.multiPartFileToWebResponse(inputFile);
@@ -139,7 +140,7 @@ public class FilterController {
                 valid = actualArea < standardArea;
                 break;
             default:
-                throw new IllegalArgumentException("Invalid comparator: " + comparator);
+                throw ExceptionUtils.createInvalidArgumentException("comparator", comparator);
         }
 
         if (valid) return WebResponseUtils.multiPartFileToWebResponse(inputFile);
@@ -172,7 +173,7 @@ public class FilterController {
                 valid = actualFileSize < fileSize;
                 break;
             default:
-                throw new IllegalArgumentException("Invalid comparator: " + comparator);
+                throw ExceptionUtils.createInvalidArgumentException("comparator", comparator);
         }
 
         if (valid) return WebResponseUtils.multiPartFileToWebResponse(inputFile);
@@ -208,7 +209,7 @@ public class FilterController {
                 valid = actualRotation < rotation;
                 break;
             default:
-                throw new IllegalArgumentException("Invalid comparator: " + comparator);
+                throw ExceptionUtils.createInvalidArgumentException("comparator", comparator);
         }
 
         if (valid) return WebResponseUtils.multiPartFileToWebResponse(inputFile);

stirling-pdf/src/main/resources/messages_en_GB.properties

@@ -225,6 +225,7 @@ error.pathTraversalDetected=Path traversal detected for security reasons.
 
 # Validation messages
 error.invalidArgument=Invalid argument: {0}
+error.argumentRequired={0} must not be null
 error.operationFailed=Operation failed: {0}
 error.angleNotMultipleOf90=Angle must be a multiple of 90
 error.pdfBookmarksNotFound=No PDF bookmarks/outline found in document

stirling-pdf/src/main/resources/static/js/downloader.js

@@ -348,19 +348,13 @@
     // Handle structured error response with translation support
     let displayMessage = json.message;
     
-    // If translation info is available, use it to translate the message
-    if (json.translationKey && window.stirlingPDF && window.stirlingPDF.translations) {
-      const translatedTemplate = window.stirlingPDF.translations[json.translationKey];
-      if (translatedTemplate) {
-        displayMessage = translatedTemplate;
-        
-        // Replace placeholders with args if available
-        if (json.translationArgs && Array.isArray(json.translationArgs)) {
-          json.translationArgs.forEach((arg, index) => {
-            displayMessage = displayMessage.replace(`{${index}}`, arg);
-          });
-        }
-      }
+    // If translation info is available, use MessageFormatter to translate
+    if (json.translationKey && window.MessageFormatter) {
+      displayMessage = window.MessageFormatter.translate(
+        json.translationKey, 
+        json.translationArgs, 
+        json.message // fallback to original message
+      );
     }
     
     showErrorBanner((json.error || 'Error') + ': ' + displayMessage, json.trace || '');

stirling-pdf/src/main/resources/static/js/messageFormatter.js

@@ -0,0 +1,66 @@
+/**
+ * Utility for formatting internationalized messages with placeholder replacement.
+ * Supports the {0}, {1}, {2}... placeholder format used by Java MessageFormat.
+ */
+window.MessageFormatter = (function() {
+  'use strict';
+
+  /**
+   * Format a message template by replacing {0}, {1}, etc. placeholders with provided arguments.
+   * 
+   * @param {string} template - The message template with {0}, {1}, etc. placeholders
+   * @param {Array|string} args - Arguments to replace placeholders with. Can be array or individual arguments
+   * @returns {string} The formatted message with placeholders replaced
+   * 
+   * @example
+   * formatMessage("Hello {0}, you have {1} messages", ["John", 5])
+   * // Returns: "Hello John, you have 5 messages"
+   * 
+   * formatMessage("Error {0}: {1}", "404", "Not Found") 
+   * // Returns: "Error 404: Not Found"
+   */
+  function formatMessage(template, ...args) {
+    if (!template || typeof template !== 'string') {
+      return template || '';
+    }
+
+    // Handle case where first argument is an array
+    const argumentArray = Array.isArray(args[0]) ? args[0] : args;
+    
+    // Replace {0}, {1}, {2}, etc. with corresponding arguments
+    return template.replace(/\{(\d+)\}/g, function(match, index) {
+      const argIndex = parseInt(index, 10);
+      return argumentArray[argIndex] !== undefined && argumentArray[argIndex] !== null 
+        ? String(argumentArray[argIndex]) 
+        : match; // Keep original placeholder if no argument provided
+    });
+  }
+
+  /**
+   * Translate and format an error message using the global translation object.
+   * Falls back to the provided fallback message if translation not found.
+   * 
+   * @param {string} translationKey - The translation key (e.g., "error.dpiExceedsLimit")
+   * @param {Array} translationArgs - Arguments for placeholder replacement
+   * @param {string} fallbackMessage - Fallback message if translation not found
+   * @returns {string} The translated and formatted message
+   */
+  function translateAndFormat(translationKey, translationArgs, fallbackMessage) {
+    if (!window.stirlingPDF || !window.stirlingPDF.translations) {
+      return fallbackMessage || translationKey;
+    }
+
+    const template = window.stirlingPDF.translations[translationKey];
+    if (!template) {
+      return fallbackMessage || translationKey;
+    }
+
+    return formatMessage(template, translationArgs || []);
+  }
+
+  // Public API
+  return {
+    format: formatMessage,
+    translate: translateAndFormat
+  };
+})();

stirling-pdf/src/main/resources/templates/fragments/common.html

@@ -86,6 +86,7 @@
   <script th:src="@{'/js/tab-container.js'}"></script>
   <script th:src="@{'/js/darkmode.js'}"></script>
   <script th:src="@{'/js/csrf.js'}"></script>
+  <script th:src="@{'/js/messageFormatter.js'}"></script>
   <script th:inline="javascript">
 
     function UpdatePosthogConsent(){