第一種：

直接讀取固定路徑下的檔案，上傳到工程下的file檔案。

import ch.qos.logback.core.util.FileUtil;
import org.apache.tomcat.util.http.fileupload.FileItem;
import org.apache.tomcat.util.http.fileupload.FileUploadException;
import org.apache.tomcat.util.http.fileupload.disk.DiskFileItemFactory;
import org.apache.tomcat.util.http.fileupload.servlet.ServletFileUpload;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.util.ResourceUtils;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;

import javax.servlet.http.HttpServletRequest;
import java.io.*;
import java.util.List;

@RestController
public class UpdateFileController {

    public static void main(String[] args) {
        String relativelyPath=System.getProperty("user.dir");
        System.out.println("relativelyPath=="+relativelyPath);
        //需要複製的目標檔案或目標資料夾
        String pathname = "C:/Users/duxt/Desktop/11.xls";
        File file = new File(pathname);
        //複製到的位置
        String topathname = "./file/";
        File toFile = new File(topathname);
        try {
            copy(file, toFile);
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public static void copy(File file, File toFile) throws Exception {
        byte[] b = new byte[1024];
        int a;
        FileInputStream fis;
        FileOutputStream fos;
        if (file.isDirectory()) {
            String filepath = file.getAbsolutePath();
            filepath=filepath.replaceAll("\\\\", "/");
            String toFilepath = toFile.getAbsolutePath();
            toFilepath=toFilepath.replaceAll("\\\\", "/");
            int lastIndexOf = filepath.lastIndexOf("/");
            toFilepath = toFilepath + filepath.substring(lastIndexOf ,filepath.length());
            File copy=new File(toFilepath);
            //複製資料夾
            if (!copy.exists()) {
                copy.mkdir();
            }
            //遍歷資料夾
            for (File f : file.listFiles()) {
                copy(f, copy);
            }
        } else {
            if (toFile.isDirectory()) {
                String filepath = file.getAbsolutePath();
                filepath=filepath.replaceAll("\\\\", "/");
                String toFilepath = toFile.getAbsolutePath();
                toFilepath=toFilepath.replaceAll("\\\\", "/");
                int lastIndexOf = filepath.lastIndexOf("/");
                toFilepath = toFilepath + filepath.substring(lastIndexOf ,filepath.length());

                //寫檔案
                File newFile = new File(toFilepath);
                fis = new FileInputStream(file);
                fos = new FileOutputStream(newFile);
                while ((a = fis.read(b)) != -1) {
                    fos.write(b, 0, a);
                }
            } else {
                //寫檔案
                fis = new FileInputStream(file);
                fos = new FileOutputStream(toFile);
                while ((a = fis.read(b)) != -1) {
                    fos.write(b, 0, a);
                }
            }

        }
    }
}
 

第二種：

有頁面，好除錯版本

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;

import java.io.*;

@Controller
public class UpdateFileController {
    /*
     * 獲取file.html頁面
     */
    @RequestMapping("file")
    public String file(){
        return "/file";
    }
    /**
     * 實現檔案上傳
     * */
    @RequestMapping("fileUpload")
    @ResponseBody
    public String fileUpload(@RequestParam("fileName") MultipartFile file){
        if(file.isEmpty()){
            return "false";
        }
        String fileName = file.getOriginalFilename();
        int size = (int) file.getSize();
        System.out.println(fileName + "-->" + size);

//        String path = "D:/" ;
        String path = "./file/";
        File dest = new File(path + "/" + fileName);
        if(!dest.getParentFile().exists()){ //判斷檔案父目錄是否存在
            dest.getParentFile().mkdir();
        }
        try {
            file.transferTo(dest); //儲存檔案
            return "true";
        } catch (IllegalStateException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return "false";
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return "false";
        }
    }
 

<html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org"
      xmlns:sec="http://www.thymeleaf.org/thymeleaf-extras-springsecurity3">
<head>
    <meta charset="UTF-8" />
    <title>Insert title here</title>
</head>
<body>
<h1 th:inlines="text">檔案上傳</h1>
<form action="fileUpload" method="post" enctype="multipart/form-data">
    <p>選擇檔案: <input type="file" name="fileName"/></p>
    <p><input type="submit" value="提交"/></p>
</form>

</body>
</html>