文件上传的基本操作

 

文件上传的基本操作

1、      表单属性enctype的设置

multipart/form-data和application/x-www-form-urlencoded的区别

FORM元素的enctype属性指定了表单数据向服务器提交时所采用的编码类型，默认的缺省值是“application/x-www-form-urlencoded”。

然而，在向服务器发送大量的文本、包含非ASCII字符的文本或二进制数据时这种编码方式效率很低。

在文件上载时，所使用的编码类型应当是“multipart/form-data”，它既可以发送文本数据，也支持二进制数据上载。

Browser端<form>表单的ENCTYPE属性值为multipart/form-data，它告诉我们传输的数据要用到多媒体传输协议，由于多媒体传输的都是大量的数据，所以规定上传文件必须是post方法，<input>的type属性必须是file。

2、      实现代码

///////////////////////////servlet层////////////////////////////////////////

package cn.class3g.servlet;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.PrintWriter;import java.util.List;import java.util.UUID;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.FileUploadBase.FileSizeLimitExceededException;import org.apache.commons.fileupload.FileUploadException;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;public class UserServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {try {//1 建立工厂对象DiskFileItemFactory factory = new DiskFileItemFactory();factory.setRepository(new File("d:\\temp"));//上传文件到缓存文件夹//2 得到上传文件解析器ServletFileUpload upload = new ServletFileUpload(factory);upload.setHeaderEncoding("utf-8"); //处理上传文件的乱码//设定上传文件尺寸upload.setFileSizeMax(1024*1024);//3 进行解析  得到存放FileItem的List对象List<FileItem> list = upload.parseRequest(request);//4 对List进行迭代处理for(FileItem item : list){if(item.isFormField()){//表单普通输入项String paramName = item.getFieldName();//String paramValue = item.getString();String paramValue = item.getString("utf-8");System.out.println("普通输入项" +paramName +"=" +paramValue);}else{//上传文件处理//获取上传文件名String fileName = item.getName();//如果文件名中有目录  则去掉目录部分  只保留文件名fileName = fileName.substring(fileName.lastIndexOf("\\")+1);System.out.println(fileName);if(!fileName.equals("")){fileName =refactorFileName(fileName) ;System.out.println("filename = " + fileName);InputStream in = item.getInputStream();File file = new File("d:\\" +fileName);FileOutputStream fos = new FileOutputStream(file);byte[] buffer = new byte[1024];int len = 0;while((len = in.read(buffer))>0){fos.write(buffer,0,len);}fos.flush();fos.close();in.close();request.setAttribute("message", "文件上传成功");}}}} catch(FileSizeLimitExceededException e1){e1.printStackTrace();request.setAttribute("message", "上传文件尺寸太大！！！");}catch (FileUploadException e) {// TODO Auto-generated catch blocke.printStackTrace();request.setAttribute("message", "文件上传失败");}request.getRequestDispatcher("/message.jsp").forward(request, response);}public String refactorFileName(String fileName){return UUID.randomUUID().toString() + "_" + fileName;}}

 

/////////////////jsp层/////////////////////

   

<form action="${pageContext.request.contextPath }/servlet/UploadServlet2" method="post" enctype="multipart/form-data">    用户名：<input type="text" name="username"/><br>    文件1：<input type="file" name="file1"/><br>    文件2：<input type="file" name="file2"/><br>    <input type="submit" value="上传"/><br></form>