文件上传FileUpload

Posted 2020-09-18 MrPeng

从上面可以看出，如果我们想上传文件，需要对表单提交过来的内容进行解析，每一个文件项.

java 核心代码

jar 包

 

 

文件上传代码

package cn.ecit.servlet;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
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.FileItemFactory;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

public class FileUploadServlet extends HttpServlet{

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		//初始化文件工厂
		FileItemFactory fileItemFactory = new DiskFileItemFactory();
		ServletFileUpload up = new ServletFileUpload(fileItemFactory);
		up.setFileSizeMax(50*1024*1024);                
		up.setSizeMax(10*1024*1024);	
		up.setHeaderEncoding("UTF-8");
		if(up.isMultipartContent(req)){
			try {
				List<FileItem> list = up.parseRequest(req);
				for(FileItem item:list){
					if(item.isFormField()){
						String fieldName = item.getFieldName();
						String fieldValue = item.getString("UTF-8");
						System.out.println(fieldName+" "+fieldValue);
					}else{
						String fileName = item.getName();
						String path = getServletContext().getRealPath("/upload");
						File file = new File(path,fileName);
						item.write(file);
						item.delete();
					}
				}
			} catch (FileUploadException e) {
				e.printStackTrace();
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		this.doGet(req, resp);
	}
	
}

　　文件上传总结：　　　　　

　　1.创建文件临时工厂

　　FileItemFactory factory = new DiskFileItemFactory();
　　ServletFileUpload up = new ServletFileUpload(factory);

　　2.配置工厂参数

　　up.setFileSizeMax(30*1024*1024);
　　up.setSizeMax(80*1024*1024);
　　up.setHeaderEncoding("UTF-8");

　　3.判断是否为文件上传（由前台提交表单属性决定）

　　up.isMultipartContent(req)

　　4.得到 FileItem （可以是多文件上传）

　　List<FileItem> list = up.parseRequest(req);

　　一个list 代表一个文件项目，如上图所示

　　5.遍历文件项

　　for(FileItem item:list)

　　6.判断 item.isFormField() 是否为普通文本框

　　7. 得到文件上传路径 getServletContext().getRealPath("/upload");

　　8.写入文件 item.write(file);

　　9.item.delete(); 删除临时文件