文章目录
文件上传与下载
-
文件上传是项目开发中最常见的功能之一 ,springMVC 可以很好的支持文件上传,但是SpringMVC上下文中默认没有装配MultipartResolver,因此默认情况下其不能处理文件上传工作。如果想使用Spring的文件上传功能,则需要在上下文中配置MultipartResolver。
-
前端表单要求:为了能上传文件,必须将表单的method设置为POST,并将enctype设置为multipart/form-data。只有在这样的情况下,浏览器才会把用户选择的文件以二进制数据发送给服务器;
对表单中的 enctype 属性做个详细的说明:
- application/x-www=form-urlencoded:默认方式,只处理表单域中的 value 属性值,采用这种编码方式的表单会将表单域中的值处理成 URL 编码方式。
- multipart/form-data:这种编码方式会以二进制流的方式来处理表单数据,这种编码方式会把文件域指定文件的内容也封装到请求参数中,不会对字符编码。
- text/plain:除了把空格转换为 “+” 号外,其他字符都不做编码处理,这种方式适用直接通过表单发送邮件。
<form action="" enctype="multipart/form-data" method="post">
<input type="file" name="file"/>
<input type="submit">
</form>
实现文件上传
- 导入文件上传的jar包,commons-fileupload , Maven会自动帮我们导入他的依赖包 commons-io包;
<!--文件上传-->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.3</version>
</dependency>
<!--servlet-api导入高版本的-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
-
- 配置bean:multipartResolver
【注意!!!这个bena的id必须为:multipartResolver , 否则上传文件会报400的错误!在这里栽过坑,教训!】
<!--文件上传配置-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<!-- 请求的编码格式,必须和jSP的pageEncoding属性一致,以便正确读取表单的内容,默认为ISO-8859-1 -->
<property name="defaultEncoding" value="utf-8"/>
<!-- 上传文件大小上限,单位为字节(10485760=10M) -->
<property name="maxUploadSize" value="10485760"/>
<property name="maxInMemorySize" value="40960"/>
</bean>
CommonsMultipartFile 的 常用方法:
- String getOriginalFilename():获取上传文件的原名
- InputStream getInputStream():获取文件流
- void transferTo(File dest):将上传文件保存到一个目录文件中
前端表单
<p>文件上传</p>
<form action="${pageContext.request.contextPath}/f3" enctype="multipart/form-data" method="post">
<input type="file" name="file"/>
<input type="submit" value="上传">
</form>
后端Conroller
//@RequestParam("file") 将name=file控件得到的文件封装成CommonsMultipartFile 对象
//批量上传CommonsMultipartFile则为数组即可
//方式一
@RequestMapping("f2")
public String upload(Model model, @RequestParam("file")CommonsMultipartFile file,
HttpServletRequest request) throws IOException {
//获取文件名
String fileName = file.getOriginalFilename();
if (fileName == null || "".equals(fileName)) {
//说明没有文件
return "redirect:/index.jsp";
}
System.out.println("[DEBUG]" + fileName);
//设置上传文件的保存路径
String filePath = request.getServletContext().getRealPath("/upload");
File uploadFile = new File(filePath);
if (!uploadFile.exists()) {
uploadFile.mkdirs();
}
InputStream inputStream = file.getInputStream();
FileOutputStream fileOutputStream = new FileOutputStream(new File(filePath + "/" + fileName));
byte[] buffer = new byte[1024];
int len = 0;
while ((len = inputStream.read(buffer)) != -1) {
fileOutputStream.write(buffer,0, len);
fileOutputStream.flush();
}
//关闭流对象
fileOutputStream.close();
inputStream.close();
model.addAttribute("msg", "上传成功: " + fileName);
return "file";
}
//实现文件上传方式二
@RequestMapping("/f3")
public String upload2(Model model, @RequestParam("file") CommonsMultipartFile file,
HttpServletRequest request) throws IOException {
String uploadFileName = file.getOriginalFilename();
if (uploadFileName == null || "".equals(uploadFileName)) {
return "redirect:/index.jsp";
}
System.out.println("[DEBUG]" + uploadFileName);
//下载文件
String uploadPath = request.getServletContext().getRealPath("/upload");
File uploadFile = new File(uploadPath);
if (!uploadFile.exists()) {
uploadFile.mkdirs();
}
file.transferTo(new File(uploadPath + "/" + uploadFileName));
model.addAttribute("msg", "上传成功: " + uploadFileName);
return "file";
}
文件下载
文件下载步骤:
1、判断文件是否已经上传
2、设置 response 响应头
3、读取文件 – InputStream
4、写出文件 – OutputStream
5、执行操作
6、关闭流 (先开后关)
前端表单
<%--
Created by IntelliJ IDEA.
User: Huawei
Date: 2020/11/8
Time: 14:34
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>文件上传和下载</title>
<script src="https://s3.pstatp.com/cdn/expire-1-M/jquery/3.3.1/jquery.min.js"></script>
<script>
function show() {
$.ajax({
url:"${pageContext.request.contextPath}/f4",
method:"POST",
success:function (data) {
let html = "";
for (let i = 0; i < data.length; i++) {
html += "( " + data[i] + " )"
}
$("#sp").html(html)
}
});
}
</script>
</head>
<body>
<p>文件上传</p>
<form action="${pageContext.request.contextPath}/f3" enctype="multipart/form-data" method="post">
<input type="file" name="file"/>
<input type="submit" value="上传">
</form>
<p>==============================</p>
<p>文件下载</p>
<input type="button" name="but" value="文件名加载" onclick="show()"> <span id="sp"></span>
<form action="${pageContext.request.contextPath}/f5" method="post">
<p></p>
<span>请输入文件下载名字:</span><input type="text" name="filename"/>
<input type="submit" value="下载">
</form>
</body>
</html>
controller
//判断文件是否已经上传
@RequestMapping("/f4")
@ResponseBody
public List<String> getNames(HttpServletRequest request) {
List<String> list = new ArrayList<>();
String path = request.getServletContext().getRealPath("/upload");
File file = new File(path);
if (!file.exists()) {
list.add("没有文件!!");
return list;
}
File[] files = file.listFiles();
if (files == null ||files.length == 0) {
list.add("没有文件!!");
return list;
}
for (File f : files
) {
list.add(f.getName());
}
return list;
}
//实现文件下载
@RequestMapping("/f5")
public String down(Model model, HttpServletRequest request, HttpServletResponse response) throws IOException {
request.setCharacterEncoding("UTF-8");
//获得需要下载的文件名
String fileName = request.getParameter("filename").trim();
System.out.println("[DEBUG]" + fileName);
List<String> list = getNames(request);
//判断有没有这个文件
String target = "";
for (String s : list) {
int index = s.lastIndexOf('.');
if (index == -1) {
model.addAttribute("msg", "还没有文件");
return "file";
}
if (fileName.equalsIgnoreCase(s)) {
target = s;
break;
}
String s1 = s.substring(0, index);
if (fileName.equalsIgnoreCase(s1)) {
target = s;
break;
}
}
if (target.equals("")) {
//说明没有文件
model.addAttribute("msg", "请输入正确文件名");
return "file";
}
//设置response响应头
response.reset(); //清空缓存
response.setCharacterEncoding("UTF-8"); //设置字符编码
response.setContentType("multipart/form-data"); //设置二进制传输数据
//设置响应头
response.setHeader("Content-Disposition",
"attachment;fileName="+ URLEncoder.encode(fileName, "UTF-8"));
//获得所需的文件
String path = request.getServletContext().getRealPath("/upload") + "/" + target;
File file = new File(path);
//下载文件
InputStream inputStream = new FileInputStream(file);
OutputStream outputStream = response.getOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while ((len = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, len);
outputStream.flush();
}
//关闭流对象
outputStream.close();
inputStream.close();
model.addAttribute("msg", "下载成功");
return "file";
}
本文地址:https://blog.csdn.net/Shangxingya/article/details/109562739
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