【javaweb】form表单的文件上传demo

1.基础知识

2.demo如下

package indi.fileupload;

import java.io.File;
import java.io.FileOutputStream;
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.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.IOUtils;

public class Fileuploadservlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//1.第一步新建一个磁盘文件项工厂
		String path_temp=this.getServletContext().getRealPath("temp");
		//第一个参数是设置缓存文件的大小(也就是要多大才缓存)，第二个参数是设置缓存的地址
		//DiskFileItemFactory factory=new DiskFileItemFactory(1024*1024, new File(path_temp));
		//当然也可以这样设置
		DiskFileItemFactory factory=new DiskFileItemFactory();
		factory.setSizeThreshold(1024*1024);//设置缓存大小为1M
		factory.setRepository(new File(path_temp));
		
		//2.第二步新建一个文件上传的核心类
		ServletFileUpload upload=new ServletFileUpload(factory);
		//3.判断是否是一个文件上传的表单，即判断是否是enctype="multipart/form-data"
		boolean multipartContent = ServletFileUpload.isMultipartContent(request);
		if(multipartContent) {
			//是文件上传类表单
			//4.设置上传文件名的编码方式,目的是解决文件名为中文的乱码问题
			upload.setHeaderEncoding("UTF-8");
			//5.解析request获得表单项的集合,设置设置泛型为FileItem
			List<FileItem> parseRequest=null;
			try {
				parseRequest = upload.parseRequest(request);
			} catch (FileUploadException e) {
				e.printStackTrace();
			}
			//6.遍历文件项集合
			for(FileItem item:parseRequest) {
				//7.判断是否是普通表单项
				boolean formField = item.isFormField();
				if(formField) {
					//普通表单项
					//获得表单的name属性值
					String fieldName=item.getFieldName();
					String fieldValue=item.getString("UTF-8");//参数表示对普通表单项的内容进行UTF-8编码，防止中文乱码，若非中文直接getString()
					System.out.println(fieldName+"----"+fieldValue);
				}else {
					//文件上传项
					//获得文件上传的内容
					String fileName=item.getName();
					//获得上传文件的输入流
					InputStream in = item.getInputStream();
					//将输入流的数据copy至服务器上
					String path_store=this.getServletContext().getRealPath("upload");
					//新建一个输出流
					FileOutputStream out = new FileOutputStream(new File(path_store+"/"+fileName));//当然也可以直接path_store+"/"+fileName
					int len=0;
					byte[] buffer = new byte[1024];
					while((len=in.read(buffer))>0) {
						out.write(buffer, 0, len);
					}
					//当然上面的操作可以通过IO工具简化书写，其它步骤相同
					//IOUtils.copy(in, out);
					in.close();
					out.close();
					//8.删除临时文件
					item.delete();
				}
			}
		}else {
			//是传统表单
			//那么就用传统的request.getAttribute(arg0)就行
			
		}
		
		
	}

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