利用javaweb如何实现一个文件上传功能？针对这个问题，这篇文章详细介绍了相对应的分析和解答，希望可以帮助更多想解决这个问题的小伙伴找到更简单易行的方法。
具体内容如下
文件上传示例
注意：jsp页面编码为"UTF-8"
文件上传的必要条件
1.form表单，必须为POST方式提交
2.enctype="multipart/form-data"
3.必须有<input type="file" />
前端jsp页面
<%@ 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>
<base href="<%=basePath%>" rel="external nofollow" >
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css" rel="external nofollow" >
-->
</head>
<script type="text/javascript">
function addFile(){
var div1=document.getElementById("div1");
div1.innerHTML+="<div><input type='file' /><input type='button' value='删除' onclick='deleteFile(this)' /> <br/></div>";
}
function deleteFile(div){
//他的爷爷删除他的爸爸
div.parentNode.parentNode.removeChild(div.parentNode);
}
</script>
<body>
<form action="${pageContext.request.contextPath }/servlet/upLoadServlet" method="post" enctype="multipart/form-data">
文件的描述：<input type="text" name ="description" /><br/>
<div id="div1">
<div>
<input type="file" name ="file" /><input type="button" value="添加" onclick="addFile()" /><br/>
</div>
</div>
<input type="submit" />
</form>
</body>
</html>实现文件上传的servlet
package com.learning.servlet;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import java.util.UUID;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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;
/**
* Servlet implementation class UpLoadServlet
*/
@WebServlet("/servlet/upLoadServlet")
public class UpLoadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//文件上传
//判断是否支持文件上传
boolean isMultipartContent = ServletFileUpload
.isMultipartContent(request);
if (!isMultipartContent) {
throw new RuntimeException("不支持");
}
// 创建一个DiskFileItemfactory工厂类
DiskFileItemFactory diskFileItemFactory=new DiskFileItemFactory();
// 创建一个ServletFileUpload核心对象
ServletFileUpload fileUpload=new ServletFileUpload(diskFileItemFactory);
//设置中文乱码
fileUpload.setHeaderEncoding("UTF-8");
//设置一个文件大小
fileUpload.setFileSizeMax(1024*1024*3); //大小为3M
//设置总文件大小
//fileUpload.setSizeMax(1024*1024*10);//大小为10M
try {
//fileload解析request请求，返回list<FileItem>集合
List<FileItem> fileItems = fileUpload.parseRequest(request);
for (FileItem fileItem : fileItems) {
if (fileItem.isFormField()) {
//是文本域 (处理文本域的函数)
processFormField(fileItem);
}else {
//文件域 (处理文件域的函数)
processUpLoadField1(fileItem);
}
}
} catch (FileUploadException e) {
e.printStackTrace();
}
}
/**
* @param fileItem
*
*/
private void processUpLoadField1(FileItem fileItem) {
try {
//获得文件读取流
InputStream inputStream = fileItem.getInputStream();
//获得文件名
String fileName = fileItem.getName();
//对文件名处理
if (fileName!=null) {
fileName.substring(fileName.lastIndexOf(File.separator)+1);
}else {
throw new RuntimeException("文件名不存在");
}
//对文件名重复处理
// fileName=new String(fileName.getBytes("ISO-8859-1"),"UTF-8");
fileName=UUID.randomUUID()+"_"+fileName;
//日期分类
SimpleDateFormat simpleDateFormat=new SimpleDateFormat("yyyy-MM-dd");
String date = simpleDateFormat.format(new Date());
//创建目录
File parent=new File(this.getServletContext().getRealPath("/WEB-INF/upload/"+date));
if (!parent.exists()) {
parent.mkdirs();
}
//上传文件
fileItem.write(new File(parent, fileName));
//删除临时文件（如果上传文件过大，会产生.tmp的临时文件）
fileItem.delete();
} catch (IOException e) {
System.out.println("上传失败");
e.printStackTrace();
} catch (Exception e) {
}
}
/**
* @param fileItem
*/
//文件域
private void processUpLoadField(FileItem fileItem) {
try {
//获得文件输入流
InputStream inputStream = fileItem.getInputStream();
//获得是文件名字
String filename = fileItem.getName();
//对文件名字处理
if (filename!=null) {
// filename.substring(filename.lastIndexOf(File.separator)+1);
filename = FilenameUtils.getName(filename);
}
//获得路径，创建目录来存放文件
String realPath = this.getServletContext().getRealPath("/WEB-INF/load");
File storeDirectory=new File(realPath);//既代表文件又代表目录
//创建指定目录
if (!storeDirectory.exists()) {
storeDirectory.mkdirs();
}
//防止文件名一样
filename=UUID.randomUUID()+"_"+filename;
//目录打散 防止同一目录文件下文件太多，不好查找
//按照日期分类存放上传的文件
//storeDirectory = makeChildDirectory(storeDirectory);
//多级目录存放上传的文件
storeDirectory = makeChildDirectory(storeDirectory,filename);
FileOutputStream fileOutputStream=new FileOutputStream(new File(storeDirectory, filename));
//读取文件，输出到指定的目录中
int len=1;
byte[] b=new byte[1024];
while((len=inputStream.read(b))!=-1){
fileOutputStream.write(b, 0, len);
}
//关闭流
fileOutputStream.close();
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
//按照日期来分类
private File makeChildDirectory(File storeDirectory) {
SimpleDateFormat simpleDateFormat=new SimpleDateFormat("yyyy-MM-dd");
String date = simpleDateFormat.format(new Date());
//创建目录
File childDirectory=new File(storeDirectory, date);
if (!childDirectory.exists()) {
childDirectory.mkdirs();
}
return childDirectory;
}
//多级目录
private File makeChildDirectory(File storeDirectory, String filename) {
filename=filename.replaceAll("-", "");
File childDirectory =new File(storeDirectory, filename.charAt(0)+File.separator+filename.charAt(1));
if (!childDirectory.exists()) {
childDirectory.mkdirs();
}
return childDirectory;
}
//文本域
private void processFormField(FileItem fileItem) {
//对于文本域的中文乱码，可以用new String()方式解决
try {
String fieldName = fileItem.getFieldName();//表单中字段名name，如description
String fieldValue = fileItem.getString("UTF-8");//description中value
// fieldValue=new String(fieldValue.getBytes("ISO-8859-1"),"UTF-8");
System.out.println(fieldName +":"+fieldValue);
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}关于利用javaweb如何实现一个文件上传功能问题的解答就分享到这里了，希望以上内容可以对大家有一定的帮助，如果你还有很多疑惑没有解开，可以关注亿速云行业资讯频道了解更多相关知识。
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