从java中的html文件下载excel文件。

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DownloadServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 设置响应的内容类型为Excel文件
        response.setContentType("application/vnd.ms-excel");
        
        // 创建Excel文件并填充数据
        File excelFile = createExcelFile();
        
        // 设置响应的头信息，告诉浏览器要下载的文件名
        response.setHeader("Content-Disposition", "attachment; filename=example.xlsx");
        
        // 将Excel文件的内容写入响应的输出流中
        FileInputStream fileInputStream = new FileInputStream(excelFile);
        int bytesRead;
        while ((bytesRead = fileInputStream.read()) != -1) {
            response.getOutputStream().write(bytesRead);
        }
        fileInputStream.close();
    }
    
    private File createExcelFile() {
        // 使用Apache POI库创建Excel文件并填充数据
        // 这里省略具体的代码
        
        // 假设Excel文件保存在服务器的临时目录中
        File excelFile = new File("/tmp/example.xlsx");
        return excelFile;
    }
}