使用servlet下载文件-优快云博客

本文链接：https://blog.youkuaiyun.com/weiluo12/article/details/7366670

本文介绍了一个用于文件上传下载功能的Servlet实现。该Servlet通过POST请求处理文件下载，从数据库中读取文件数据并返回给客户端。文章详细展示了如何设置HTTP响应头以支持不同类型的文件下载，并更新数据库中的下载次数。

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package upload_download.servlet;

import java.io.ByteArrayOutputStream;
import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import upload_download.dao.UploadDownloadDAO;
import upload_download.vo.UploadDownload;

public class UploadDownloadDownServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		this.doPost(request, response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		// 获取id
		String id = request.getParameter("id");

		UploadDownload uploadDownload = UploadDownloadDAO.findOneById(id);
		
		//UploadDownloadDAO.downloadTimesAdd(id);

		this.glsEnclosureDownload(request, response, uploadDownload);
	}

	/**
	 * 下载文件。
	 */
	public void glsEnclosureDownload(HttpServletRequest request,
			HttpServletResponse response, UploadDownload uploadDownload)
			throws ServletException, IOException {

		ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

		outputStream.write(uploadDownload.getFile_data());

		// 文件名称
		String filename = uploadDownload.getFile_name().substring(0,
				uploadDownload.getFile_name().lastIndexOf("."));
		// 文件类型
		String file_type = uploadDownload.getFile_name().substring(
				uploadDownload.getFile_name().lastIndexOf("."));

		response
				.addHeader("Content-Disposition", "attachment; filename="
						+ new String(filename.getBytes("gbk"), "iso8859-1")
						+ file_type);
		// response.setHeader("Content-Disposition", "inline; filename=" + new
		// String(rewardPunish.getFile_name().getBytes("gbk"),"iso8859-1"));
		response.setContentType("application/octet-stream");
		response.setContentLength(outputStream.size());
		ServletOutputStream out = response.getOutputStream();
		outputStream.writeTo(out);
		out.flush();
		out.close();
		UploadDownloadDAO.downloadTimesAdd(uploadDownload.getId()+"");
	}

}