参考链接：https://www.runoob.com/servlet/servlet-file-uploading.html
功能介绍：
利用 Servlet 和表单提交，选择本地文件上传到服务器。上传的文件可以是文本文件或图像文件或任何文档，不能是文件夹。
需要引入的 jar 文件：commons-fileupload-1.3.2、commons-io-2.5.jar。
下载链接：
- commons-fileupload.x.x.jar 文件：http://commons.apache.org/proper/commons-fileupload/
- commons-io-x.x.jar 文件： http://commons.apache.org/proper/commons-io/ 下载。
将下载好的jar包复制到项目/WebContent/WEB-INF/lib 文件夹下：
实现代码：
fileUpload.jsp:文件上传的界面页
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>文件上传</title>
</head>
<body>
<h1>文件上传</h1>
<form action="/JavaEE17ToolDemo/file-upload-servlet" method="post" enctype="multipart/form-data">
选择一个文件：
<input type="file" name="file" value="" />
<br/>
<input type="submit" value="上传">
</form>
</body>
</html>
FileUploadServlet.java:文件上传处理
package com.company.project.servlet.fileupload;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
@WebServlet("/file-upload-servlet")
public class FileUploadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
// 文件上传的存储路径
private static final String SAVE_PATH = "file-upload";
// 上传配置
// 配置内存临界值
private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3; // 3MB
// 配置最大文件大小
private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB
// 配置请求大小
private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50; // 50MB
public FileUploadServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 检测是否为多媒体文件
if (!ServletFileUpload.isMultipartContent(request)) {
// 如果不是则停止
PrintWriter out = response.getWriter();
out.println("表单必须包含 enctype=multipart/form-data");
out.flush();
out.close();
return;
}
// 配置上传参数
DiskFileItemFactory factory = new DiskFileItemFactory();
// 设置内存临界值 - 超过后将产生临时文件并存储于临时目录中
factory.setSizeThreshold(MEMORY_THRESHOLD);
ServletFileUpload upload = new ServletFileUpload(factory);
// 设置上传文件最大值
upload.setFileSizeMax(MAX_FILE_SIZE);
// 设置最大请求值(包含文件和表单数据)
upload.setSizeMax(MAX_REQUEST_SIZE);
// 中文处理
upload.setHeaderEncoding("UTF-8");
// 创建保存路径
String uploadPath = request.getServletContext().getRealPath("./") + File.separator + SAVE_PATH;
// 如果路径不存在则创建
File uploadDir = new File(uploadPath);
if (!uploadDir.exists()) {
uploadDir.mkdir();
}
try {
@SuppressWarnings("unchecked")
List<FileItem> formItems = upload.parseRequest(request);
if (formItems != null && formItems.size() > 0) {
//迭代表单数据
for (FileItem fileItem : formItems) {
//处理不在表单的字段
if(!fileItem.isFormField()) {
String fileName = new File(fileItem.getName()).getName();
String filePath = uploadPath + File.separator + fileName;
File storeFile = new File(filePath);
// 在控制台输出文件的上传路径
System.out.println(filePath);
// 保存文件到硬盘
fileItem.write(storeFile);
request.setAttribute("message",
"文件上传成功!");
}
}
}
} catch (FileUploadException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
request.setAttribute("message",
"错误信息: " + e.getMessage());
}
//文件上传完成跳转
request.getServletContext().getRequestDispatcher("/page/UploadMes.jsp").forward(request, response);
}
}
UploadMes.jsp:文件传输完成跳转页
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>文件上传结果</title>
</head>
<body>
<center>
<h2>${message }</h2>
</center>
</body>
</html>
效果图：
网友评论