支持附件以链接的形式发送

ruoyi-oa/src/main/java/com/ruoyi/oa/utils/EmailUtil.java

@@ -355,4 +355,22 @@ public class EmailUtil {
         
         return processedHtml;
     }
+
+    /**
+     * 下载网络文件到本地临时文件
+     * @param url 文件的http/https链接
+     * @return 本地临时文件
+     */
+    public static File downloadUrlToTempFile(String url) throws Exception {
+        File tempFile = File.createTempFile("mail_attach_", null);
+        try (java.io.InputStream in = new java.net.URL(url).openStream();
+             java.io.OutputStream out = new java.io.FileOutputStream(tempFile)) {
+            byte[] buffer = new byte[8192];
+            int bytesRead;
+            while ((bytesRead = in.read(buffer)) != -1) {
+                out.write(buffer, 0, bytesRead);
+            }
+        }
+        return tempFile;
+    }
 }