看看Java Web怎么上传文件到服务器

news2024/9/24 23:33:12

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 stub
		response.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。