准备工作
对于文件上传，浏览器在上传的过程中是将文件以流的形式提交到服务器端的。
一般采用Apache的开源工具common-fileupload这个文件上传组件。
common-fileupload是依赖于common-io这个包的，所以还需要下载这个包。
使用类介绍
文件上传注意事项
- 为保证服务器的安全，上传的文件应放在外界无法访问的目录下，如WEB-INF。
- 为防止同名文件产生覆盖现象，要为文件指定一个唯一的文件名。
- 要对上传文件的大小进行限制。
-
限制上传文件的类型，收到文件时，判断文件名是否合法。
需要用到的类详解
ServletFileUpload类
ServletFileUpload负责处理上传的文件数据，并将表单中的每个输入项封装成一个FileItem对象，在使用ServletFileUpload对象解析请求时需要DiskFileItemFactory对象。所以，我们需要在进行解析工作前构造好DiskFileItemFactory对象，通过ServletFileItem对象的构造方法或setFileItemFactory()设置ServletFileUpload对象的fileItemFactory属性。
FileItem类
在HTML页面中input必须要有name：<input type="file" name="fileName">
上传文件表单中如果包含一个文件上传项的话，这个表单的entype属性必须设置为multipart/form-data
浏览器的表单类型为multipart/form-data的话，服务器想获取数据就要通过流。
常用方法介绍
编写代码
maven库下载依赖包并引入
commons-fileupload-1.4.jar
commons-io-2.8.0.jar
出现问题提示：打包时不会打入lib目录下的jar，点击fix处理
处理成功
配置Tomcat
在gitee创建远程仓库并关联
创建远程仓库
创建本地仓库
Administrator@L87Y12K91TH8M2R MINGW64 /d/code/fileUpAndDown
$ git init
Initialized empty Git repository in D:/code/fileUpAndDown/.git/
Administrator@L87Y12K91TH8M2R MINGW64 /d/code/fileUpAndDown (main)
$ ll -a
total 24
drwxr-xr-x 1 Administrator 197121 0 Jun 2 23:25 ./
drwxr-xr-x 1 Administrator 197121 0 May 27 08:48 ../
drwxr-xr-x 1 Administrator 197121 0 Jun 2 23:25 .git/
drwxr-xr-x 1 Administrator 197121 0 Jun 2 23:26 .idea/
-rw-r--r-- 1 Administrator 197121 968 May 15 00:03 fileUpAndDown.iml
drwxr-xr-x 1 Administrator 197121 0 May 15 00:01 lib/
drwxr-xr-x 1 Administrator 197121 0 May 24 23:33 out/
drwxr-xr-x 1 Administrator 197121 0 May 14 23:56 src/
drwxr-xr-x 1 Administrator 197121 0 May 15 00:04 web/
Administrator@L87Y12K91TH8M2R MINGW64 /d/code/fileUpAndDown (main)
关联远程仓库，并拉取远程仓库文件
Administrator@L87Y12K91TH8M2R MINGW64 /d/code/fileUpAndDown (main)
$ git remote add origin git@gitee.com:wl3pbzhyq/fileUpAndDown.git
Administrator@L87Y12K91TH8M2R MINGW64 /d/code/fileUpAndDown (main)
$ git pull origin master
remote: Enumerating objects: 5, done.
remote: Counting objects: 100% (5/5), done.
remote: Compressing objects: 100% (5/5), done.
remote: Total 5 (delta 0), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (5/5), 1.42 KiB | 7.00 KiB/s, done.
From gitee.com:wl3pbzhyq/fileUpAndDown
* branch master -> FETCH_HEAD
* [new branch] master -> origin/master
Administrator@L87Y12K91TH8M2R MINGW64 /d/code/fileUpAndDown (main)
配置忽略文件
# target
target/
# idea
.idea/
*.iml
提交main分支到远程仓库
D:\code\fileUpAndDown>git add .
warning: LF will be replaced by CRLF in out/artifacts/fileUpAndDown_war_exploded/WEB-INF/web.xml.
The file will have its original line endings in your working directory
warning: LF will be replaced by CRLF in out/artifacts/fileUpAndDown_war_exploded/index.jsp.
The file will have its original line endings in your working directory
warning: LF will be replaced by CRLF in web/WEB-INF/web.xml.
The file will have its original line endings in your working directory
warning: LF will be replaced by CRLF in web/index.jsp.
The file will have its original line endings in your working directory
D:\code\fileUpAndDown>git status
On branch main
Changes to be committed:
(use "git restore --staged <file>..." to unstage)
modified: .gitignore
new file: .idea/vcs.xml
new file: lib/commons-fileupload-1.4.jar
new file: lib/commons-io-2.8.0.jar
D:\code\fileUpAndDown>git commit -m "初始化"
[main 0680e1f] 初始化
31 files changed, 105 insertions(+)
create mode 100644 .idea/vcs.xml
create mode 100644 lib/commons-fileupload-1.4.jar
create mode 100644 lib/commons-io-2.8.0.jar
D:\code\fileUpAndDown>git push --set-upstream origin main
Enumerating objects: 38, done.
Counting objects: 100% (38/38), done.
Delta compression using up to 4 threads
Compressing objects: 100% (27/27), done.
Writing objects: 100% (36/36), 662.53 KiB | 5.22 MiB/s, done.
Total 36 (delta 1), reused 0 (delta 0), pack-reused 0
remote: Powered by GITEE.COM [GNK-5.0]
remote: Create a pull request for 'main' on Gitee by visiting:
remote: https://gitee.com/wl3pbzhyq/fileUpAndDown/pull/new/wl3pbzhyq:main...wl3pbzhyq:master
To gitee.com:wl3pbzhyq/fileUpAndDown.git
* [new branch] main -> main
Branch 'main' set up to track remote branch 'main' from 'origin'.
D:\code\fileUpAndDown>
编写表单
input必须要有name：<input type="file" name="fileName">
表单中如果包含文件上传项的话，这个表单的entype属性必须设置为multipart/form-data
浏览器的表单类型为multipart/form-data的话，服务器想获取数据就要通过流。
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<%--
通过表单上传文件
get：上传文件大小有限制
post：上传文件大小没有限制
表单中如果包含文件上传项的话，这个表单的entype属性必须设置为multipart/form-data
浏览器的表单类型为multipart/form-data的话，服务器想获取数据就要通过流
--%>
<%--${pageContext.request.contextPath}获取服务器路径--%>
<form action="${pageContext.request.contextPath}/upload.do" method="post" enctype="multipart/form-data">
<p>上传用户：<input type="text" name="username"></p>
<p><input type="file" name="file1"></p>
<p><input type="file" name="file2"></p>
<p><input type="submit"> | <input type="reset"></p>
</form>
</body>
</html>
编写文件上传Servlet，web.xml中注册
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<servlet>
<servlet-name>FileUploadServlet</servlet-name>
<servlet-class>com.qing.servlet.FileUploadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FileUploadServlet</servlet-name>
<url-pattern>/upload.do</url-pattern>
</servlet-mapping>
</web-app>
package com.qing.servlet;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.ProgressListener;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.time.LocalDate;
import java.util.List;
import java.util.UUID;
public class FileUploadServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) {
// 判断上传的表单是普通表单还是带文件的表单
if (! ServletFileUpload.isMultipartContent(request)) {
return; // 终止方法运行，这是一个普通表单
}
// 创建上传文件的保存目录，建议在WEB-INF路径下，安全，用户无法直接访问上传的文件
String uploadPath = this.getServletContext().getRealPath("/WEB-INF/upload");
File uploadDir = new File(uploadPath);
if (! uploadDir.exists()) {
uploadDir.mkdir(); // 创建文件上传目录
}
// 缓存，临时文件
// 临时路径，假如文件超过了预期的大小，我们就把它放到一个临时目录中，过几天自动删除或者提醒用户转存为永久
String tmpPath = this.getServletContext().getRealPath("/WEB-INF/tmp");
File tmpDir = new File(tmpPath);
if (! tmpDir.exists()) {
tmpDir.mkdir(); // 创建临时目录
}
/*
处理上传的文件，一般都需要通过流来获取，可以使用request.getInputStream()，原生态的文件上传流获取，十分麻烦
建议使用Apache的文件上传组件来实现，common-fileupload，它需要依赖common-io组件
*/
// 1.创建DiskFileItemFactory对象，负责处理文件上传路径或者大小限制
DiskFileItemFactory factory = getDiskFileItemFactory(tmpDir);
// 2.获取ServletFileUpload
ServletFileUpload upload = getServletFileUpload(factory);
// 3.处理上传的文件
try {
String msg = uploadParseRequest(request, uploadPath, upload);
// Servlet请求转发消息
request.setAttribute("msg",msg);
request.getRequestDispatcher("info.jsp").forward(request,response);
} catch (IOException e) {
e.printStackTrace();
} catch (FileUploadException e) {
e.printStackTrace();
} catch (ServletException e) {
e.printStackTrace();
}
}
/**
* 处理上传的文件
* @param request
* @param uploadPath
* @param upload
* @return
* @throws IOException
*/
private String uploadParseRequest(HttpServletRequest request, String uploadPath, ServletFileUpload upload) throws IOException, FileUploadException {
StringBuilder msg = new StringBuilder();
// 把前端请求解析，封装成一个FileItem对象(表单对象)
List<FileItem> fileItems = upload.parseRequest(request);
for (FileItem fileItem : fileItems) {
// 判断表单是普通表单还是文件表单，普通表单返回true，文件表单返回false
if (fileItem.isFormField()) {
String name = fileItem.getFieldName();
String vlaue = fileItem.getString("UTF-8");// 处理乱码
System.out.println(name + ":" + vlaue);
} else {
System.out.println("=================处理文件==============================");
String name = fileItem.getFieldName();
String fileName = fileItem.getName();
System.out.println(name + ":" + fileName);
// 过滤文件名不合法的文件
if (fileName == null || "".equals(fileName.trim())) {
continue;
}
// 获取文件后缀名，如果文件后缀名不是我们需要的文件类型，就直接return，告诉用户文件类型错误
String fileExtName = fileName.substring(fileName.lastIndexOf(".") + 1);
System.out.println("=================文件存放地址==============================");
// 生成日期目录
String datePath = LocalDate.now().toString();
// 生成唯一目录
String uuidPath = UUID.randomUUID().toString();
// 组成文件实际路径
String realPath = uploadPath + "/" + datePath + "/" + uuidPath;
File realDir = new File(realPath);
if (! realDir.exists()) {
// 注：创建多层目录使用mkdirs，mkdir只能创建一层目录
realDir.mkdirs();// 创建文件实际路径
}
System.out.println("=================文件传输==============================");
// 获取文件上传输入流
InputStream inputStream = fileItem.getInputStream();
// 创建文件输出流
FileOutputStream fos = new FileOutputStream(realPath + "/" + fileName);
// 创建缓冲区
byte[] buffer = new byte[1024 * 1024];
// 判断是否读取完毕
int len = 0;
// 如果大于0，说明还存在数据
while ((len = inputStream.read(buffer)) > 0) {
fos.write(buffer,0,len);
}
// 关闭流
fos.close();
inputStream.close();
msg.append(fileName).append("文件上传成功！");
fileItem.delete(); // 上传成功，清除临时文件
}
}
return msg.toString();
}
/**
* 获取ServletFileUpload
* @param factory
* @return
*/
private ServletFileUpload getServletFileUpload(DiskFileItemFactory factory) {
ServletFileUpload upload = new ServletFileUpload(factory);
// 监听文件上传进度
upload.setProgressListener(new ProgressListener() {
@Override
public void update(long read, long total, int i) {
// read 已读取的文件大小
// total 文件总大小
System.out.println("总大小：" + total + "，已上传：" + read);
}
});
// 处理乱码问题
upload.setHeaderEncoding("UTF-8");
// 设置单个文件的最大值
upload.setFileSizeMax(1024 * 1024 * 10); // 10M
// 设置总共能够上传文件的大小
upload.setSizeMax(1024 * 1024 * 1000); // 1000M
return upload;
}
/**
* 创建DiskFileItemFactory对象，负责处理文件上传路径或者大小限制
* @param tmpDir
* @return
*/
private DiskFileItemFactory getDiskFileItemFactory(File tmpDir) {
DiskFileItemFactory factory = new DiskFileItemFactory();
// 通过工厂设置一个缓冲区，当上传的文件大于缓冲区的时候，将它放到临时目录
factory.setSizeThreshold(1024 * 1024); // 缓冲区大小为1M
factory.setRepository(tmpDir); // 设置临时目录
return factory;
}
}
编写转发页面
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
${msg}
</body>
</html>
