一：配置springBoot上传文件限制

spring:
  servlet:
    multipart:
      max-file-size: 100MB  #单个文件大小
      max-request-size: 1024MB #总文件大小

二：代码

import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.support.StandardMultipartHttpServletRequest;

import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Base64;
import java.util.Locale;
import java.util.UUID;

@RestController
@RequestMapping("upload")
public class UploadController {

    /**
     * 上传方式一，从请求体中获取文件信息
     * @param request
     * @return
     * @throws IOException
     */
    @PostMapping("method1")
    public String upload1(HttpServletRequest request) throws IOException {

        MultipartFile file = ((StandardMultipartHttpServletRequest) request).getFile("file");
        String fileName = file.getOriginalFilename();
        String newName=UUID.randomUUID().toString()+fileName.substring(fileName.indexOf("."));

        // 获取当前操作系统
        String osName = System.getProperties().get("os.name").toString().toLowerCase(Locale.ROOT);
        String path="";

        if(osName.startsWith("win")){
            path="D:\\Test\\";
        }else{
            path="/mnt/test";
        }
        File saveFile=new File(path+newName);
        if(!saveFile.getParentFile().exists()){
            saveFile.getParentFile().mkdirs();
        }
        // 设置文件权限时需先创建文件
        // saveFile.createNewFile();
        file.transferTo(saveFile);
        // 文件权限 
        // fileAuth(saveFile.toPath());
        return saveFile.getPath();
    }

    /**
     * 上传方式2 MultipartFile 上传
     * @param file
     * @return
     * @throws IOException
     */
    @PostMapping("method2")
    public String upload2(@RequestParam("file") MultipartFile file) throws IOException {
        String fileName = file.getOriginalFilename();
        String newName=UUID.randomUUID().toString()+fileName.substring(fileName.indexOf("."));
        // 获取当前操作系统
        String osName = System.getProperties().get("os.name").toString().toLowerCase(Locale.ROOT);
        String path="";

        if(osName.startsWith("win")){
            path="D:\\Test\\";
        }else{
            path="/mnt/test";
        }
        File saveFile=new File(path+newName);
        if(!saveFile.getParentFile().exists()){
            saveFile.getParentFile().mkdirs();
        }
        file.transferTo(saveFile);
        return saveFile.getPath();
    }

    /**
     * base64 图片上传
     * @param base64
     * @return
     */
    @PostMapping("method3")
    public String upload3(@RequestParam("base64")String base64){
        String base64Data = base64.split(",")[1];
        Base64.Decoder decoder = Base64.getDecoder();
        byte[] bytes = decoder.decode(base64Data);
        // 获取当前操作系统
        String osName = System.getProperties().get("os.name").toString().toLowerCase(Locale.ROOT);
        String path="";

        if(osName.startsWith("win")){
            path="D:\\Test\\";
        }else{
            path="/mnt/test";
        }
        String newName=UUID.randomUUID().toString()+".png";
        File saveFile=new File(path+newName);
        if(!saveFile.getParentFile().exists()){
            saveFile.getParentFile().mkdirs();
        }
        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(saveFile);
            fos.write(bytes);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return saveFile.getPath();
    }

	/**
     * 文件上传到linux权限处理
     * @throws Exception
     */
    private static void fileAuth(Path path) throws Exception {
        Set perms = Files.readAttributes(path, PosixFileAttributes.class).permissions();
        // 当前用户权限
        /*perms.add(PosixFilePermission.OWNER_WRITE);
        perms.add(PosixFilePermission.OWNER_READ);
        perms.add(PosixFilePermission.OWNER_EXECUTE);
        // 组权限
        perms.add(PosixFilePermission.GROUP_WRITE);
        perms.add(PosixFilePermission.GROUP_READ);
        perms.add(PosixFilePermission.GROUP_EXECUTE);*/
        // 其它权限
        perms.add(PosixFilePermission.OTHERS_WRITE);
        perms.add(PosixFilePermission.OTHERS_READ);
        perms.add(PosixFilePermission.OTHERS_EXECUTE);
        Files.setPosixFilePermissions(path, perms);
    }

    public static void main(String[] args) {
        String data = "data:image/png;base64,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";
    }
}