1。文件上传的必要前提:
a、表单的method必须是post
b、表单的enctype属性必须是multipart/form-data类型的。
enctype默认值:application/x-www-form-urlencoded
作用:告知服务器,请求正文的MIME类型
c、表单中提供type=”file”类型的上传组件
2。文件上传原理。
3。文件上传案例1:
a.导包:
commons-fileupload-1.3.1.jar
commons-io-2.2.jar
b. upload.jsp文件:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>文件上传</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/servlet/UploadServlet2" method="post" enctype="multipart/form-data">
name:<input name="name"/><br>
file1:<input type="file" name="f1"/><br>
file2:<input type="file" name="f2"/><br>
<input type="submit" value="上传">
</form>
</body>
</html>
c. web.xml文件:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<servlet>
<servlet-name>UploadServlet2</servlet-name>
<servlet-class>com.itheima.servlet.UploadServlet2</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>UploadServlet2</servlet-name>
<url-pattern>/servlet/UploadServlet2</url-pattern>
</servlet-mapping>
</web-app>
d. UploadServlet2.java文件:
package com.itheima.servlet;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
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.FilenameUtils;
//借助commons-fileupload实现文件上传的简单案例
public class UploadServlet2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
//判断用户提交的正文类型是不是multipart/form-data
boolean isMultipart = ServletFileUpload.isMultipartContent(request);
if(!isMultipart){
throw new RuntimeException("请检查您的表单的enctype属性,确定是multipart/form-data");
}
//创建DiskFileItemFactory
DiskFileItemFactory dfif = new DiskFileItemFactory();
dfif.setRepository(new File("d:/"));
ServletFileUpload parser = new ServletFileUpload(dfif);
List<FileItem> items = null;
//解析请求内容
try {
items = parser.parseRequest(request);
} catch (FileUploadException e) {
throw new RuntimeException("解析上传内容失败,请重新试一下");
}
//处理请求内容
if(items!=null){
for(FileItem item:items){
if(item.isFormField()){
//普通表单字段
processFormField(item);
}else{
//上传字段
processUploadField(item);
}
}
}
out.write("上传成功!");
}
//上传字段
private void processUploadField(FileItem item) {
try {
InputStream in = item.getInputStream();//输入流
String fileName = item.getName();//上传文件的文件名 C:\Users\wzhting\Desktop\a.txt a.txt
//截取文件名
// fileName = fileName.substring(fileName.lastIndexOf("\\")+1);
if(fileName!=null){
fileName = FilenameUtils.getName(fileName);
}
//把文件存到服务器的某个目录中
String storeDirectoryPath = getServletContext().getRealPath("/files");
File storeDirectory = new File(storeDirectoryPath);
if(!storeDirectory.exists()){
storeDirectory.mkdirs();
}
//构建输出流
// OutputStream out = new FileOutputStream(storeDirectoryPath+File.separator+fileName);
// int len = -1;
// byte b[] = new byte[1024];
// while((len=in.read(b))!=-1){
// out.write(b, 0, len);
// }
// in.close();
// out.close();
// item.delete();//删除临时文件
item.write(new File(storeDirectoryPath+File.separator+fileName));
} catch (Exception e) {
throw new RuntimeException("上传失败,请重试");
}
}
//普通表单字段
private void processFormField(FileItem item) {
String fieldName = item.getFieldName();//字段名
String fieldValue = item.getString();
System.out.println(fieldName+"="+fieldValue);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}