文件上传
文件上传
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee
https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd"
version="5.0">
</web-app>
<dependencies>
<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.6</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.4</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.3</version>
</dependency>
</dependencies>
注意事项
- 上传文件需要放在外界无法直接访问的目录,例如
WEB-INF目录; - 上传文件的文件名一定要保持唯一性; -时间戳 -
uuid- - 限制文件上传的最大值
- 可以限制上传文件的类型，在收到上传文件时，判断后缀名是否合法；
package com.jezer.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.util.List;
import java.util.UUID;
/**
* @author Jay_Soul
*/
public class FileServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//判断上传的文件是普通表单还是带文件的表单
if (!ServletFileUpload.isMultipartContent(req)){
return; //终止方法运行，说明这是一个普通的表单，直接返回
}
//上传文件需要放在外界无法直接访问的目录,例如WEB-INF目录;
String uploadPath = this.getServletContext().getRealPath("/WEB-INF/upload");
File uploadFile = new File(uploadPath);
if (!uploadFile.exists()){
boolean mkdir = uploadFile.mkdir();//创建目录
System.out.println(mkdir);
}
//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文件，过几天自动删除，或者提醒用户转存为永久
String tempPath = this.getServletContext().getRealPath("/WEB-INF/temp");
File tempFile = new File(tempPath);
if (!tempFile.exists()){
tempFile.mkdir();//创建目录
}
// 处理上传的文件,一般都需要通过流来获取,我们可以使用 request.getInputstream(),原生态的文件上传流获取,十分麻烦
// 但是我们都建议使用 Apache的文件上传组件来实现, common-fileupload,它需要依赖于commons-io组件;
try {
//1. 创建DiskFileItemFactory对象，处理文件路径或者大小限制
/*
* 通过这个工厂设置一个缓冲区,当上传的文件大于这个缓冲区的时候,将他放到临时文件 factory.setSizeThreshold(1024 * 1024);
* 缓存区大小为1M factory.setRepository (file);
* 临时目录的保存目录,需要一个File
*/
DiskFileItemFactory factory = getDiskFileItemFactory(tempFile);
// 2、获取ServletFileUpload
ServletFileUpload upload = getServletFileUpload(factory);
// 3、处理上传文件
// 把前端请求解析，封装成FileItem对象，需要从ServletFileUpload对象中获取
String msg = uploadParseRequest(upload, req, uploadPath);
// Servlet请求转发消息
System.out.println(msg);
if("文件上传成功!".equals(msg)) {
// Servlet请求转发消息
req.setAttribute("msg",msg);
req.getRequestDispatcher("info.jsp").forward(req, resp);
}else {
msg ="请上传文件";
req.setAttribute("msg",msg);
req.getRequestDispatcher("info.jsp").forward(req, resp);
}
} catch (FileUploadException e) {
e.printStackTrace();
}
}
public static DiskFileItemFactory getDiskFileItemFactory(File tempFile) {
DiskFileItemFactory factory = new DiskFileItemFactory();
/* 通过这个工厂设置一个缓冲区,当上传的文件大于这个缓冲区的时候,将他放到临时文件中; */
factory.setSizeThreshold(1024 * 1024);// 缓冲区大小为1M
factory.setRepository(tempFile);// 临时目录的保存目录,需要一个file
return factory;
}
public static ServletFileUpload getServletFileUpload(DiskFileItemFactory factory) {
ServletFileUpload upload = new ServletFileUpload(factory);
// 监听长传进度
upload.setProgressListener(new ProgressListener() {
// pBYtesRead:已读取到的文件大小
// pContextLength:文件大小
@Override
public void update(long pBytesRead, long pContentLength, int pItems) {
System.out.println("总大小：" + pContentLength + "已上传：" + pBytesRead);
}
});
// 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);
// 设置总共能够上传文件的大小
// 1024 = 1kb * 1024 = 1M * 10 = 10м
return upload;
}
public static String uploadParseRequest(ServletFileUpload upload, HttpServletRequest request, String uploadPath) throws FileUploadException, IOException {
String msg = "";
// 把前端请求解析，封装成FileItem对象
List<FileItem> fileItems = upload.parseRequest(request);
for (FileItem fileItem : fileItems) {
if (fileItem.isFormField()) {// 判断上传的文件是普通的表单还是带文件的表单
// getFieldName指的是前端表单控件的name;
String name = fileItem.getFieldName();
String value = fileItem.getString("UTF-8"); // 处理乱码
System.out.println(name + ": " + value);
} else {// 判断它是上传的文件
// ============处理文件==============
// 拿到文件名
String uploadFileName = fileItem.getName();
System.out.println("上传的文件名: " + uploadFileName);
if (uploadFileName.trim().equals("") || uploadFileName == null) {
continue;
}
// 获得上传的文件名/images/girl/paojie.png
String fileName = uploadFileName.substring(uploadFileName.lastIndexOf("/") + 1);
// 获得文件的后缀名
String fileExtName = uploadFileName.substring(uploadFileName.lastIndexOf(".") + 1);
/*
* 如果文件后缀名fileExtName不是我们所需要的 就直按return.不处理,告诉用户文件类型不对。
*/
System.out.println("文件信息[件名: " + fileName + " ---文件类型" + fileExtName + "]");
// 可以使用UID（唯一识别的通用码),保证文件名唯
// 0UID. randomUUID(),随机生一个唯一识别的通用码;
String uuidPath = UUID.randomUUID().toString();
// ================处理文件完毕==============
// 存到哪? uploadPath
// 文件真实存在的路径realPath
String realPath = uploadPath + "/" + uuidPath;
// 给每个文件创建一个对应的文件夹
File realPathFile = new File(realPath);
if (!realPathFile.exists()) {
realPathFile.mkdir();
}
// ==============存放地址完毕==============
// 获得文件上传的流
InputStream inputStream = fileItem.getInputStream();
// 创建一个文件输出流
// realPath =真实的文件夹;
// 差了一个文件;加上翰出文件的名产"/"+uuidFileName
FileOutputStream fos = new FileOutputStream(realPath + "/" + fileName);
// 创建一个缓冲区
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 = "文件上传成功!";
fileItem.delete(); // 上传成功,清除临时文件
//=============文件传输完成=============
}
}
return msg;
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
<!-- servlet注册-->
<servlet>
<servlet-name>FileServlet</servlet-name>
<servlet-class>com.jezer.servlet.FileServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FileServlet</servlet-name>
<url-pattern>/upload.do</url-pattern>
</servlet-mapping>
<%--index.jsp--%>
<%@ 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；
--%>
<form action="${pageContext.request.contextPath}/ upload.do" enctype="multipart/form-data" method = "post">
上传用户：<input type="text" name = "username"><br/>
<p><input type="file" name = "upload"></p>
<p><input type="submit"> | <input type="reset"></p>
</form>
</body>
</html>
<%--info.jsp--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
${msg}
</body>
</html>
课后巩固：
UUID
native
序列化接口
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