使用fileupload实现文件上传

最新推荐文章于 2023-05-24 20:15:00 发布

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本文介绍如何使用Java和Apache Commons FileUpload解析HTTP请求中的文件上传表单，并将上传的文件保存到服务器指定目录。通过创建解析工厂、判断是否为文件上传表单、解析请求获取文件项、遍历文件项并保存文件等步骤，实现文件上传功能。

package cn.itcast.servlet;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.List;

import javax.servlet.ServletException;
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;

public class Servlet1 extends HttpServlet {

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

		// 获得表单参数   name=zhangsan&password=123
		// 1. 创建解析工厂
		DiskFileItemFactory factory = new DiskFileItemFactory();
		
		// 2. 创建用于解析request的FileUpload
		ServletFileUpload upload = new ServletFileUpload(factory);
		
		// 3. 判断一下是否是文件上传表单
		if(!upload.isMultipartContent(request)) {
			request.setAttribute("message", "不是文件上传表单");
			request.getRequestDispatcher("/message.jsp").forward(request, response);
			return;
		}
		
		// 4. 解析
		List<FileItem> fileitems = null;
		try {
			fileitems = upload.parseRequest(request);
		} catch (FileUploadException e) {
			throw new RuntimeException(e);
		}
		
		
		// 5. 遍历
		for(FileItem item : fileitems) {
			// 判断是否为普通字段
			if(item.isFormField()) {
				// 获得字段的name和value
				String name = item.getFieldName();
				String value = item.getString();
				System.out.println(name + "=" + value);
			} else {
				// 上传字段
				// 获得字段名
				String name = item.getFieldName();
				// 获得文件名
				String filename = item.getName();
				System.out.println("before: " + filename);
				filename = filename.substring(filename.lastIndexOf("\\")+1);
				System.out.println("after: " + filename);
				
				// 约定一个文件的存放目录   获得目录绝对路径
				String dirPath = getServletContext().getRealPath("/upload");
				File dir = new File(dirPath);
				//　创建必要的文件夹
				dir.mkdirs();
				// 创建文件对象
				File file = new File(dir, filename);
				// 创建文件
				file.createNewFile();
				// 获得流
				InputStream in = item.getInputStream();
				OutputStream out = new FileOutputStream(file);
				// 流的对拷
				int len;
				byte[] buffer = new byte[1024];
				while((len=in.read(buffer))>0)
					out.write(buffer, 0, len);
				
				out.close();
			}
		}
		
	}

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

		doGet(request, response);
	}

}