验证Excel URL。检查每个URL是否有效，特别是检查代码失败的URL。在浏览器中打开它。检查URL格式。例如，它们应以“http”或“https”开头。确保从Excel文件读取的URL正确。打印它以验证其值。
验证URL的有效性和格式后，您可以创建一个URL对象，并使用openConnection（）打开连接并读取输入流。
使用apache poi库执行此操作的代码段

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>4.1.2</version>
</dependency>

FileInputStream inputStream = new FileInputStream(new File("path/to/excel/file.xlsx"));
Workbook workbook = WorkbookFactory.create(inputStream);
Sheet sheet = workbook.getSheetAt(0);

for (Row row : sheet) {
    for (Cell cell : row) {
        if (cell.getCellType() == CellType.STRING) {
            String urlString = cell.getStringCellValue();
            URL url = new URL(urlString);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            InputStream imageInputStream = connection.getInputStream();
            // Do something with the input stream, such as saving the image to a file
        }
    }
}

String urlString = "http://www.example.com/images/image.jpg";
URL url = new URL(urlString);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
InputStream inputStream = connection.getInputStream();