文件上传

package com.ding.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.annotation.WebServlet;
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;

@WebServlet("/upload")
public class FileServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) 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(request)){
            return;//终止方法运行，说明这是一个普通的表单，直接返回
        }

        //创建上传文件的保存路径，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 uploadFile = new File(uploadPath);
        if (uploadFile.exists()){//.exists()取反
            uploadFile.mkdir();//创建这个目录
        }

        //缓存，临时文件
        //临时路径，加入文件超过了预期的大小，我们就把它放到一个临时文件中，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/upload");
        File file = new File(tmpPath);
        if (file.exists()){//.exists()取反
            file.mkdir();//创建这个临时目录
        }

        // 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 {
            // 创建DiskFileItemFactory对象，处理文件路径或者大小限制
            DiskFileItemFactory factory = getDiskFileItemFactory(file);
            /*
             * //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
             */

            // 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, request, uploadPath);

            // Servlet请求转发消息
            System.out.println(msg);
            if(msg.equals("文件上传成功!")) {
                // Servlet请求转发消息
                request.setAttribute("msg",msg);
                request.getRequestDispatcher("info.jsp").forward(request, response);
            }else {
                msg ="请上传文件";
                request.setAttribute("msg",msg);
                request.getRequestDispatcher("info.jsp").forward(request, response);
            }

        } catch (FileUploadException e) {
            e.printStackTrace();
        }
    }

    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,将他放到临时文件中;
        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);
        // 监听上传进度
        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);
                System.out.println("path:"+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 doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<form action="/upload" method="post" enctype="multipart/form-data">
    上传用户: <input type="text" name="username"><br>
    <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>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${msg}
</body>
</html>

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>javaweb-upload</artifactId>
    <version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
<dependencies>
    <dependency>
        <groupId>commons-fileupload</groupId>
        <artifactId>commons-fileupload</artifactId>
        <version>1.4</version>
    </dependency>

    <dependency>
        <groupId>commons-io</groupId>
        <artifactId>commons-io</artifactId>
        <version>2.6</version>
    </dependency>
    <!-- servlet3.0规范的坐标 -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
        <scope>provided</scope>
    </dependency>
    <!--jsp坐标-->
    <dependency>
        <groupId>javax.servlet.jsp</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.1</version>
        <scope>provided</scope>
    </dependency>

    <!-- JSTL表达式的依赖 -->
    <dependency>
        <groupId>javax.servlet.jsp.jstl</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>
</dependencies>


</project>