看看Java Web怎么上传文件到服务器-编程知识

看看Java Web怎么上传文件到服务器

旁白不多说了直接上主题了。

1、新建上传文件夹

在eclipse中，在我们前面文章中用到的项目HelloJSP，在webapp目录下新建uploadfiles文件夹，如下所示：

2、修改HelloWorld.jsp文件

<body><h1>文件上传</h1><form action="upload" method="post" enctype="multipart/form-data"><input type="file" name="file"><input type="submit" value="上传"></form>
</body>

3、新建servlet

上面表单action里面新建名为upload的servlet文件，然后修改dopost方法如下：

package com.servlet;import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;/*** Servlet implementation class Upload*/
@WebServlet("/Upload")
@MultipartConfig
public class Upload extends HttpServlet {private static final long serialVersionUID = 1L;/*** @see HttpServlet#HttpServlet()*/public Upload() {super();// TODO Auto-generated constructor stub}/*** @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)*/protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubresponse.getWriter().append("Served at: ").append(request.getContextPath());}/*** @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)*/protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stub//doGet(request, response);// 获取上传的文件Part filePart = request.getPart("file");String fileName = Paths.get(filePart.getSubmittedFileName()).getFileName().toString();String uploadPath = getServletContext().getRealPath("") + File.separator + "uploadfiles";System.out.println(uploadPath);File uploadDir = new File(uploadPath);if (!uploadDir.exists()) {uploadDir.mkdir();}// 保存文件到服务器InputStream inputStream = filePart.getInputStream();Path filePath = Paths.get(uploadPath, fileName);Files.copy(inputStream, filePath);inputStream.close();// 返回成功信息response.setContentType("text/html;charset=UTF-8");response.getWriter().println("文件上传成功！");}}

注意：记得要添加@MultipartConfig注释，否则上传文件会报错。

@MultipartConfig 是一个Java注解，用于在Java Servlet中配置支持文件上传的功能。它通常与标签的enctype属性值设置为"multipart/form-data"一起使用。

当你在Servlet中使用@MultipartConfig注解时，它告诉容器该Servlet可以接收以多部分（multipart）形式发送的请求。多部分请求通常用于上传文件，因为文件的二进制数据需要以多部分形式进行传输。