fix exception when sending email has special chars (#1383)

Co-authored-by: Carpe-Wang <wangcarpe@126.com>

alerter/src/main/java/org/dromara/hertzbeat/alert/util/AlertTemplateUtil.java

@@ -44,14 +44,14 @@ public static String render(String template, Map<String, Object> replaceData) {
         }
         try {
             Matcher matcher = PATTERN.matcher(template);
-            StringBuilder buffer = new StringBuilder();
+            StringBuilder builder = new StringBuilder();
             while (matcher.find()) {
                 Object objectValue = replaceData.getOrDefault(matcher.group(1), "NullValue");
                 String value = objectValue.toString();
-                matcher.appendReplacement(buffer, value);
+                matcher.appendReplacement(builder, Matcher.quoteReplacement(value));
             }
-            matcher.appendTail(buffer);
-            return buffer.toString();
+            matcher.appendTail(builder);
+            return builder.toString();
         } catch (Exception e) {
             log.error(e.getMessage(), e);
             return template;

alerter/src/test/java/org/dromara/hertzbeat/alert/util/AlertTemplateUtilTest.java

@@ -62,4 +62,17 @@ void render() {
         template = "${key1} ${key2} ${key3}";
         assertEquals(AlertTemplateUtil.render(template, param), "Just for testing");
     }
+
+    @Test
+    void renderSpecialCharacters() {
+        Map<String, Object> param = new HashMap<>();
+        param.put("valueWithDollar", "$100");
+        param.put("valueWithBackslash", "C:\\Users");
+
+        String template = "The price is ${valueWithDollar} and the path is ${valueWithBackslash}";
+
+        // Expected to handle the dollar sign and backslash correctly without throwing an exception
+        String expectedResult = "The price is $100 and the path is C:\\Users";
+        assertEquals(expectedResult, AlertTemplateUtil.render(template, param));
+    }
 }