文件上传异常

来源：互联网发布：windows cmd关机命令编辑：程序博客网时间：2024/06/07 19:34

原因：引起异常的原因是没有设置MIME的编码，不能完整的传递文本数据！！！

工程中使用到以下两个jar包：

commons-fileupload-1.2.1.jar

commons-io-1.4.jar

upload.jsp:

在form标签中没有加入entype="multipart/form-data"之前：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>       <title>My JSP 'upload.jsp' starting page</title>     </head>  <body>  <!-- entype="multipart/form-data" -->    <form action="${pageContext.request.contextPath}/UploadServlet"  method="post">    上传用户：<input type="text" name="username"><br/>    上传文件1：<input type="file" name="filed1"><br/>    上传文件2：<input type="file" name="filed2"><br/>    <input type="submit" value="上传">    </form>  </body></html>

UploadServlet:

package cn.lsh.servlet;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.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;@SuppressWarnings("serial")public class UploadServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {try {//创建解析工厂DiskFileItemFactory factory = new DiskFileItemFactory();//创建解析器ServletFileUpload file = new ServletFileUpload(factory);//调用解析器解析request，得到保存了所有上传数据的listList<FileItem> list = file.parseRequest(request);//迭代list集合，拿到封装每个输入项数据的filenamefor(FileItem item: list){//判断item类型，如果是普通字段，则直接获取，如果为上传文件，则调用流获取数据写到硬盘if(item.isFormField()){String inputName = item.getFieldName();String inputValue = item.getString();System.out.println(inputName+"="+inputValue);}else{//item封装的是上传文件String filename = item.getName().substring(item.getName().lastIndexOf("\\")+1);InputStream in = item.getInputStream();int len = 0;byte [] by = new byte[1024];FileOutputStream out = new FileOutputStream("c:\\"+filename);while((len=in.read())>0){out.write(by,0,len);}in.close();out.close();}}} catch (Exception e) {throw new RuntimeException(e);}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

浏览器输出提示：服务器500异常。

type Exception report

message org.apache.commons.fileupload.FileUploadBase$InvalidContentTypeException: the request doesn't contain a multipart/form-data or multipart/mixed stream, content type header is application/x-www-form-urlencoded

description The server encountered an internal error that prevented it from fulfilling this request.

exception

java.lang.RuntimeException: org.apache.commons.fileupload.FileUploadBase$InvalidContentTypeException: the request doesn't contain a multipart/form-data or multipart/mixed stream, content type header is application/x-www-form-urlencodedcn.lsh.servlet.UploadServlet.doGet(UploadServlet.java:51)cn.lsh.servlet.UploadServlet.doPost(UploadServlet.java:57)javax.servlet.http.HttpServlet.service(HttpServlet.java:643)javax.servlet.http.HttpServlet.service(HttpServlet.java:723)

application/x-www-form-urlencoded： 窗体数据被编码为名称/值对。这是标准的编码格式。multipart/form-data： 窗体数据被编码为一条消息，页上的每个控件对应消息中的一个部分，上传附件用到text/plain： 窗体数据以纯文本形式进行编码，其中不含任何控件或格式字符。enctype="multipart/form-data是设置表单的MIME编码。默认情况，这个编码格式是application/x-www-form-urlencoded，不能用于文件上传；只有使用了multipart/form- data，才能完整的传递文件数据，进行下面的操作.

总结：

引起异常的原因是：当你在提交form表单的数据，他默认的编码格式是application/x-www-form-urlencoded，这个是不能用于上传文件的，所以要设置表单的MIME编码，当设置表单的MIME编码enctype="multipart/form-data才能完整的传递文件数据。

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