maven
<!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.11.0</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>servlet-api</artifactId>
<version>2.5</version>
</dependency>
servlet
public class FileServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//判断上传表单是普通表单还是带文件的表单
if (!ServletFileUpload.isMultipartContent(req)){
return; //终止方法运行，说明是一个普通表单
}
//创建上传文件的保存路径 ，建议保存在WEB-INF路径下，安全，用户无法直接访问
String realPath = this.getServletContext().getRealPath("/WEB-INF/upload");
File updateFile = new File(realPath);
if (!updateFile.exists()){
updateFile.mkdir();//创建这个目录
}
//缓存，临时文件，假设文件放到了链式文件中，过几天自动删除
String tmpPath = this.getServletContext().getRealPath("/WEB-INF/tmp");
File tmpFile = new File(tmpPath);
if (!tmpFile.exists()){
updateFile.mkdir();//创建这个临时目录
}
//处理上传的文件，一般需要流来获取，我们可以使用request.getInputStream() ,原生态文件上传流获取，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 他需要依赖于common-io组件
try {
//1.创建 DiskFileItemFactory 对象，处理文件上传路径或者大小限制
DiskFileItemFactory factory = getDiskFileItemFactory(tmpFile);
//2.获取servletFileUpload
ServletFileUpload upload = getServletFileUpload(factory);
//3.处理上传文件
String msg = uploadParseRequest(upload, req, realPath);
// Servlet请求转发消息
System.out.println(msg);
if(msg == "文件上传成功!") {
// 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 (Exception e) {
e.printStackTrace();
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
public static DiskFileItemFactory getDiskFileItemFactory(File file){
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，将它放到临时文件
factory.setSizeThreshold(1024*1024); //缓冲区大小为 1M;
factory.setRepository(file); //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
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;
}
}
index.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<!--<h1>首页</h1>-->
<!--通过表单上传文件
1、get:上传文件大小有限制
2、post：上传文件没有限制-->
<form action=" ${pageContext.request.contextPath}/upload.do" method="post" enctype="multipart/form-data">
<p>上传用户：<input type="text" name="username"></p><br>
<p><input type="file" name="filename" ></p><br>
<p> <input type="submit"> | <input type="reset"></p>
</form>
/body>
</html>
web.xml
<?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>FileServlet</servlet-name>
<servlet-class>com.wukong.servlet.FileServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FileServlet</servlet-name>
<url-pattern>/upload.do</url-pattern>
</servlet-mapping>
</web-app>
info.jsp
${msg}
